cd BiscuitOS
make linux-5.0-i386_defconfig
make menuconfig

  [*] Package  --->
      [*] BiscuitOS Demo Code  --->
          [*] Kernel Demo Code on BiscuitOS  ---> 

make
cd BiscuitOS/output/linux-5.0-i386/package/BiscuitOS-kernel-0.0.1/

cd BiscuitOS/output/linux-5.0-i386/package/BiscuitOS-kernel-0.0.1/
make download
tree

make
make install
make pack
make run

obj-y += usage.o

1. 独立项目的功能
2. 独立代码在什么架构上验证的，内核版本号信息
3. 附件添加对应的源码
3. 开发者的介绍和联系邮箱

cd BiscuitOS
make linux-5.0-i386_defconfig
make menuconfig

  [*] Package  --->
      [*] BiscuitOS Demo Code  --->
          [*] Kernel Anywhere Demo Code on BiscuitOS  --->

make
cd BiscuitOS/output/linux-5.0-i386/package/BiscuitOS-kernel-any-0.0.1/

cd BiscuitOS/output/linux-5.0-i386/package/BiscuitOS-kernel-any-0.0.1/
make download
tree

make
make install
make pack
make run

int BiscuitOS_Demo(void) {}

1. 独立项目的功能
2. 独立代码在什么架构上验证的，内核版本号信息
3. 附件添加对应的源码
3. 开发者的介绍和联系邮箱

cd BiscuitOS
make linux-5.0-i386_defconfig
make menuconfig

  [*] Package  --->
      [*] BiscuitOS Demo Code  --->
          [*] Module Demo Code on BiscuitOS  --->
          [*] Module Project Demo on BiscuitOS  --->
make

cd BiscuitOS/output/linux-5.0-i386/package/BiscuitOS-modules-0.0.1/
make download
tree

make
make install
make pack
make run

#
# Module Common
#
# (C) 2020.03.14 BuddyZhang1 <buddy.zhang@aliyun.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.

ifneq ($(KERNELRELEASE),)

## Target
ifeq ("$(origin MODULE_NAME)", "command line")
MODULE_NAME		:= $(MODULE_NAME)
else
MODULE_NAME		:= BiscuitOS_mod
endif
obj-m			:= $(MODULE_NAME).o

## Source Code
$(MODULE_NAME)-m	+= usage.o

## CFlags
ccflags-y		+= -DCONFIG_BISCUITOS_MODULE 
## Header
ccflags-y		+= -I$(PWD)

else

## Parse argument
## Default support ARM32
ifeq ("$(origin BSROOT)", "command line")
BSROOT=$(BSROOT)
else
BSROOT=/xspace/OpenSource/BiscuitOS/BiscuitOS/output/linux-5.0-arm32
endif

ifeq ("$(origin ARCH)", "command line")
ARCH=$(ARCH)
else
ARCH=arm
endif

ifeq ("$(origin CROSS_TOOLS)", "command line")
CROSS_TOOLS=$(CROSS_TOOLS)
else
CROSS_TOOLS=arm-linux-gnueabi
endif

## Don't Edit
KERNELDIR=$(BSROOT)/linux/linux
CROSS_COMPILE_PATH=$(BSROOT)/$(CROSS_TOOLS)/$(CROSS_TOOLS)/bin
CROSS_COMPILE=$(CROSS_COMPILE_PATH)/$(CROSS_TOOLS)-
INCLUDEDIR=$(KERNELDIR)/include
ARCHINCLUDEDIR=$(KERNELDIR)/arch/$(ARCH)/include
INSTALLDIR=$(BSROOT)/rootfs/rootfs/

## X86/X64 Architecture
ifeq ($(ARCH), i386)
CROSS_COMPILE	:=
else ifeq ($(ARCH), x86_64)
CROSS_COMPILE	:=
endif

## Compile
AS		= $(CROSS_COMPILE)as
LD		= $(CROSS_COMPILE)ld
CC		= $(CROSS_COMPILE)gcc
CPP		= $(CC) -E
AR		= $(CROSS_COMPILE)ar
NM		= $(CROSS_COMPILE)nm
STRIP		= $(CROSS_COMPILE)strip
OBJCOPY		= $(CROSS_COMPILE)objcopy
OBJDUMP		= $(CROSS_COMPILE)objdump

# FLAGS
CFLAGS += -I$(INCLUDEDIR) -I$(ARCHINCLUDEDIR)

all: $(OBJS)
	make -C $(KERNELDIR) M=$(PWD) ARCH=$(ARCH) \
                CROSS_COMPILE=$(CROSS_COMPILE) modules

install:
	make -C $(KERNELDIR) M=$(PWD) ARCH=$(ARCH) \
		INSTALL_MOD_PATH=$(INSTALLDIR) modules_install

clean:
	@rm -rf *.ko *.o *.mod.o *.mod.c *.symvers *.order \
               .*.o.cmd .tmp_versions *.ko.cmd .*.ko.cmd

endif

1. 独立项目的功能
2. 独立代码在什么架构上验证的，内核版本号信息
3. 附件添加对应的源码
3. 开发者的介绍和联系邮箱

cd BiscuitOS
make linux-5.0-i386_defconfig
make menuconfig

  [*] Package  --->
      [*] BiscuitOS Demo Code  --->
          [*] Application Demo Code on BiscuitOS  --->
          [*] Application Project Demo on BiscuitOS  --->
make

cd BiscuitOS/output/linux-5.0-i386/package/BiscuitOS-Application-0.0.1/
make download
tree

make
make install
make pack
make run

#
# Application Project
#
# (C) 2020.02.02 BuddyZhang1 <buddy.zhang@aliyun.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.

## Target
ifeq ("$(origin TARGETA)", "command line")
TARGET			:= $(TARGETA)
else
TARGET			:= BiscuitOS_app
endif

## Source Code
SRC			+= usage.c

## CFlags
LCFLAGS			+= -DCONFIG_BISCUITOS_APP
## Header
LCFLAGS			+= -I./ -I$(PWD)/include

DOT			:= -
## X86/X64 Architecture
ifeq ($(ARCH), i386)
CROSS_COMPILE	=
LCFLAGS		+= -m32
DOT		:=
else ifeq ($(ARCH), x86_64)
CROSS_COMPILE   :=
DOT		:=
endif

# Compile
B_AS		= $(CROSS_COMPILE)$(DOT)as
B_LD		= $(CROSS_COMPILE)$(DOT)ld
B_CC		= $(CROSS_COMPILE)$(DOT)gcc
B_CPP		= $(CC) -E
B_AR		= $(CROSS_COMPILE)$(DOT)ar
B_NM		= $(CROSS_COMPILE)$(DOT)nm
B_STRIP		= $(CROSS_COMPILE)$(DOT)strip
B_OBJCOPY	= $(CROSS_COMPILE)$(DOT)objcopy
B_OBJDUMP	= $(CROSS_COMPILE)$(DOT)objdump

## Install PATH
ifeq ("$(origin INSPATH)", "command line")
INSTALL_PATH		:= $(INSPATH)
else
INSTALL_PATH		:= ./
endif

all:
	$(B_CC) $(LCFLAGS) -o $(TARGET) $(SRC)

install:
	@cp -rfa $(TARGET) $(INSTALL_PATH)

clean:
	@rm -rf $(TARGET) *.o

1. 独立项目的功能
2. 独立代码在什么架构上验证的，内核版本号信息
3. 附件添加对应的源码
3. 开发者的介绍和联系邮箱

cd BiscuitOS
make linux-5.0-i386_defconfig
make menuconfig

  [*] Package  --->
      [*] BiscuitOS Demo Code  --->
          [*] Module Demo Code on BiscuitOS  --->
          [*] Module Project Demo on BiscuitOS  --->
make

cd BiscuitOS/output/linux-5.0-i386/package/BiscuitOS-modules-0.0.1/
make download
tree

make
make install
make pack
make run

cd BiscuitOS
make linux-5.0-i386_defconfig
make menuconfig

  [*] Package  --->
      [*] BiscuitOS Demo Code  --->
          [*] Kernel Demo Code on BiscuitOS  --->

make
cd BiscuitOS/output/linux-5.0-i386/package/BiscuitOS-kernel-0.0.1/

cd BiscuitOS/output/linux-5.0-i386/package/BiscuitOS-kernel-0.0.1/
make download
tree

make
make install
make pack
make run

cd BiscuitOS
make linux-5.0-i386_defconfig
make menuconfig

  [*] Package  --->
      [*] BiscuitOS Demo Code  --->
          [*] Application Demo Code on BiscuitOS  --->
          [*] Application Project Demo on BiscuitOS  --->
make

cd BiscuitOS/output/linux-5.0-i386/package/BiscuitOS-Application-0.0.1/
make download
tree

make
make install
make pack
make run

[*] Package  --->
    [*] MMU Shrink  --->
        [*] kernel slab shrink Demo  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/kernel-slab-shrink-base-0.0.1

/*
 * BiscuitOS Kernel BiscuitOS Code
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/init.h>
#include <linux/kernel.h>

/* Shrink interface */
#include <linux/mm.h>
#include <linux/shrinker.h>

extern void drop_slab(void);
unsigned long BiscuitOS_free_pages = 0x1000;
unsigned long BiscuitOS_used_pages = 0x200;

static unsigned long
mmu_shrink_count_bs(struct shrinker *shrink, struct shrink_control *sc)
{
        printk("BiscuitOS Count...\n\n\n");
        return BiscuitOS_used_pages;
}

static unsigned long
mmu_shrink_scan_bs(struct shrinker *shrink, struct shrink_control *sc)
{
        printk("BiscuitOS Scan... \n\n\n");
        return BiscuitOS_free_pages;
}

static struct shrinker mmu_shrinker_bs = {
        .count_objects = mmu_shrink_count_bs,
        .scan_objects  = mmu_shrink_scan_bs,
        .seeks = DEFAULT_SEEKS * 10,
};

/* Shrink */
static int __init BiscuitOS_shrink_init(void)
{
        register_shrinker(&mmu_shrinker_bs);

        return 0;
}

/* kernel entry on initcall */
static int __init BiscuitOS_init(void)
{
        printk("Hello BiscuitOS on kernel.\n");

        drop_slab();

        /* unregister */
        unregister_shrinker(&mmu_shrinker_bs);
        return 0;
}

fs_initcall(BiscuitOS_shrink_init);
device_initcall(BiscuitOS_init);

Block layer SCSI generic (bsg) driver version 0.4 loaded (major 251)
io scheduler mq-deadline registered
io scheduler kyber registered
Hello BiscuitOS on kernel.
BiscuitOS Count...


input: Power Button as /devices/LNXSYSTM:00/LNXPWRBN:00/input/input0
ACPI: Power Button [PWRF]
Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
00:05: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
Non-volatile memory driver v1.3
Linux agpgart interface v0.103

[*] Package  --->
    [*] Assembly  --->
        [*] X86/i386/X64 Assembly  --->
            [*] RDMSR  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/rdmsr-x86-0.0.1/

/*
 * RDMSR [X86/i386/X86_64] -- Read from MSR register.
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

/*
 * Both i386 and x86_64 returns 64-bit value in edx:eax, but gcc's "A"
 * constraint has different meanings. For i386, "A" means exactly
 * edx:eax, while for x86_64 it doesn't mean rdx:rax or edx:eax. Instead
 * it means rax *or* rdx.
 */
#ifdef CONFIG_X86_64
#define DECLARE_ARGS(val, low, high)		unsigned low, high
#define EAX_EDX_VAL(val, low, high)		((low) | ((u64)(high) << 32))
#define EAX_EDX_ARGS(val, low, high)		"a" (low), "d" (high)
#define EAX_EDX_RET(val, low, high)		"=a" (low), "=d" (high)
#else
#define DECLARE_ARGS(val, low, high)		unsigned long long val
#define EAX_EDX_VAL(val, low, high)		(val)
#define EAX_EDX_ARGS(val, low, high)		"A" (val)
#define EAX_EDX_RET(val, low, high)		"=A" (val)
#endif

static inline unsigned long long native_read_msr_bs(unsigned int msr)
{
	DECLARE_ARGS(val, low, high);

	asm volatile("rdmsr"
		    : EAX_EDX_RET(val, low, high)
		    : "c" (msr));
	return EAX_EDX_VAL(val, low, high);
}

#define rdmsr_bs(msr, low, high)			\
do {							\
	u64 __val = native_read_msr_bs((msr));		\
	(void)((low) = (u32)__val);			\
	(void)((high) = (u32)(__val >> 32));		\
} while (0)

#define MSR_IA32_SYSENTER_CS		0x00000174

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
	unsigned int host_cs, junk;

	/* RDMSR */
	rdmsr_bs(MSR_IA32_SYSENTER_CS, host_cs, junk);
	printk("MSR_IA32_SYSENTER_CS: %#lx-%lx\n", host_cs, junk);

	return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Common Device driver on BiscuitOS");

cd /lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra # ls
rdmsr-x86-0.0.1.ko
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra # insmod rdmsr-x86-0.0.1.ko 
rdmsr_x86_0.0.1: loading out-of-tree module taints kernel.
MSR_IA32_SYSENTER_CS: 0x60-0
/lib/modules/5.0.0/extra #

[*] Package  --->
    [*] Assembly  --->
        [*] X86/i386/X64 Assembly  --->
            [*] WRMSR  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/wrmsr-x86-0.0.1/

/*
 * WRMSR [X86/X86_64] -- Write to Model Specific Register
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#define IA32_PQR_ASSOC		0x0c8f

static inline void wrmsr_bs(unsigned msr, unsigned low, unsigned high)
{
	asm volatile ("wrmsr"
		      :
		      : "c" (msr), "a" (low), "d" (high)
		      : "memory");
}

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
	printk("Hello modules on BiscuitOS\n");

	/* WRMSR */
	wrmsr_bs(IA32_PQR_ASSOC, 0, 0);

	return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Common Device driver on BiscuitOS");

cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
wrmsr-x86-0.0.1.ko
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra # insmod wrmsr-x86-0.0.1.ko 
wrmsr_x86_0.0.1: loading out-of-tree module taints kernel.
Hello modules on BiscuitOS
general protection fault: 0000 [#1] SMP
CPU: 1 PID: 1142 Comm: insmod Tainted: G           O      5.0.0 #61
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-0-ga698c8995f-p4
EIP: BiscuitOS_init+0x1b/0x1000 [wrmsr_x86_0.0.1]
Code: Bad RIP value.
EAX: 00000000 EBX: e0a5c000 ECX: 00000c8f EDX: 00000000
ESI: e0a5f000 EDI: cb59c0e0 EBP: cd3c9df8 ESP: cd3c9df4
DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010246
CR0: 80050033 CR2: e0a5eff1 CR3: 0ef54000 CR4: 001406d0
Call Trace:
 do_one_initcall+0x42/0x191
 ? call_usermodehelper_exec+0x87/0x170
 ? free_pcp_prepare+0x4f/0xa0
 ? _cond_resched+0x17/0x40
 ? kmem_cache_alloc_trace+0x35/0x160
 ? do_init_module+0x21/0x1e4
 do_init_module+0x50/0x1e4
 load_module+0x1d46/0x2280
 ? map_vm_area+0x2c/0x40
 sys_init_module+0x10d/0x150
 do_fast_syscall_32+0x7a/0x1c0
 entry_SYSENTER_32+0x6b/0xbe
EIP: 0xb7f3b871
Code: 8b 98 58 cd ff ff 85 d2 89 c8 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 14 24 c3 8b 1c6
EAX: ffffffda EBX: 09ab6390 ECX: 00000aec EDX: 0820dbd6
ESI: 00000003 EDI: 00000000 EBP: bf8b064c ESP: bf8b02e0
DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b EFLAGS: 00000246
Modules linked in: wrmsr_x86_0.0.1(O+)
---[ end trace f75e95a374ac04ef ]---
EIP: BiscuitOS_init+0x1b/0x1000 [wrmsr_x86_0.0.1]
Code: Bad RIP value.
EAX: 00000000 EBX: e0a5c000 ECX: 00000c8f EDX: 00000000
ESI: e0a5f000 EDI: cb59c0e0 EBP: cd3c9df8 ESP: dd06049c
DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010246
CR0: 80050033 CR2: e0a5eff1 CR3: 0ef54000 CR4: 001406d0
insmod (1142) used greatest stack depth: 6600 bytes left
Segmentation fault
/lib/modules/5.0.0/extra # 

[*] Package  --->
    [*] Notifier mechanism on Kernel  --->
        [*] Kernel notifier Base Demo  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/kernel-notifier-base-0.0.1

/*
 * Kernel notifier
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#define BISCUITOS_EVENT_A		0x01
#define BISCUITOS_EVENT_B		0x02
#define BISCUITOS_EVENT_C		0x03

static RAW_NOTIFIER_HEAD(BiscuitOS_chain);

int BiscuitOS_notifier_event(struct notifier_block *nb, 
					unsigned long event, void *v)
{
	switch (event) {
	case BISCUITOS_EVENT_A:
		printk("BiscuitOS notifier event A [%s]\n", (char *)v);
		break;
	case BISCUITOS_EVENT_B:
		printk("BiscuitOS notifier event B [%s]\n", (char *)v);
		break;
	default:
		break;
	}

	return NOTIFY_DONE;
}

static struct notifier_block BiscuitOS_notifier = {
	.notifier_call = BiscuitOS_notifier_event,
};

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
	printk("Hello modules on BiscuitOS\n");

	/* Register notifier */
	raw_notifier_chain_register(&BiscuitOS_chain, &BiscuitOS_notifier);

	/* Notifier */
	raw_notifier_call_chain(&BiscuitOS_chain, 
					BISCUITOS_EVENT_B, "BiscuitOS");
	raw_notifier_call_chain(&BiscuitOS_chain,
					BISCUITOS_EVENT_A, "Buddy");
	raw_notifier_call_chain(&BiscuitOS_chain,
					BISCUITOS_EVENT_C, "Memory");

	return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
	/* Unregister notifier */
	raw_notifier_chain_unregister(&BiscuitOS_chain, &BiscuitOS_notifier);
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Common Device driver on BiscuitOS");

cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra # ls
kernel-notifier-base-0.0.1.ko
/lib/modules/5.0.0/extra # insmod kernel-notifier-base-0.0.1.ko 
kernel_notifier_base_0.0.1: loading out-of-tree module taints kernel.
Hello modules on BiscuitOS
BiscuitOS notifier event B [BiscuitOS]
BiscuitOS notifier event A [Buddy]
/lib/modules/5.0.0/extra #

[*] Package  --->
    [*] CPUMASK mechanism on Kernel  --->
        [*] Kernel cpumask Base Demo  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/kernel-cpumask-base-0.0.1

/*
 * CPU mask mechanism
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mm.h>

/* CPUmask */
#include <linux/cpumask.h>

/* declear cpumask */
static cpumask_var_t BiscuitOS_cpumask;

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
	int cpu = raw_smp_processor_id();

	printk("BiscuitOS current cpu %d\n", cpu);
	/* alloc cpumask */
	zalloc_cpumask_var(&BiscuitOS_cpumask, GFP_KERNEL);

	/* test and set */
	if (!cpumask_test_cpu(cpu, BiscuitOS_cpumask)) {
		printk("CPUMASK set cpu %d\n", cpu);
		cpumask_set_cpu(cpu, BiscuitOS_cpumask);
	}

	/* test and clear */
	if (cpumask_test_cpu(cpu, BiscuitOS_cpumask)) {
		printk("CPUMASK clear cpu %d\n", cpu);
		cpumask_clear_cpu(cpu, BiscuitOS_cpumask);
	}

	return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
	/* free cpumask */
	free_cpumask_var(BiscuitOS_cpumask);
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Common Device driver on BiscuitOS");

cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
kernel-cpumask-base-0.0.1.ko
/lib/modules/5.0.0/extra # insmod kernel-cpumask-base-0.0.1.ko 
kernel_cpumask_base_0.0.1: loading out-of-tree module taints kernel.
BiscuitOS current cpu 0
CPUMASK set cpu 0
CPUMASK clear cpu 0
/lib/modules/5.0.0/extra #

/*
 * smp_call_function_single - Run a function on a specific CPU
 * @func: The function to run. This must be fast and non-blocking.
 * @info: An arbitrary pointer to pass to the function.
 * @wait: If true, wait until function has completed on other CPUs.
 *
 * Returns 0 on success, else a negative status code.
 */
int smp_call_function_single(int cpu, smp_call_func_t func, void *info, int wait)

[*] Package  --->
    [*] SMP  --->
        [*] smp_call_function_single  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/smp_call_function_single-0.0.1

/*
 * Run a function on a specific CPU
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

void BiscuitOS_smp(void *rtn)
{
	int cpu = raw_smp_processor_id();

	printk("SMP running on CPU%d - Default CPU%d\n", cpu, (int)rtn);
}

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
	int cpu = 0;
	int current_cpu = raw_smp_processor_id();

	/* Call function on specific CPU */
	smp_call_function_single(cpu, BiscuitOS_smp, (void *)current_cpu, 0);

	printk("Hello modules on BiscuitOS\n");

	return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Common Device driver on BiscuitOS");

cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
smp_call_function_single-0.0.1.ko
/lib/modules/5.0.0/extra # insmod smp_call_function_single-0.0.1.ko 
smp_call_function_single_0.0.1: loading out-of-tree module taints kernel.
SMP running on CPU0 - Default CPU1
Hello modules on BiscuitOS
/lib/modules/5.0.0/extra #

/*
 * Call a function on all processors.  May be used during early boot while
 * early_boot_irqs_disabled is set.  Use local_irq_save/restore() instead
 * of local_irq_disable/enable().
 */ 
int on_each_cpu(void (*func) (void *info), void *info, int wait)

[*] Package  --->
    [*] SMP  --->
        [*] on_each_cpu  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/on_each_cpu-0.0.1

/*
 * Call a function on all processors
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

void BiscuitOS_smp(void *info)
{
        int cpu = raw_smp_processor_id();

        printk("Current CPU%d Default CPU%d\n", cpu, (int)info);
}

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
        int cpu = raw_smp_processor_id();

        /* Call function on all processor */
        on_each_cpu(BiscuitOS_smp, (void *)cpu, 0);

        printk("Hello modules on BiscuitOS\n");

        return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Common Device driver on BiscuitOS");

cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
on_each_cpu-0.0.1.ko
/lib/modules/5.0.0/extra # insmod on_each_cpu-0.0.1.ko 
on_each_cpu_0.0.1: loading out-of-tree module taints kernel.
Current CPU1 Default CPU1
Current CPU0 Default CPU1
Hello modules on BiscuitOS
/lib/modules/5.0.0/extra #

[*] Package  --->
    [*] Notifier mechanism on Kernel  --->
        [*] Reboot notifier  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/reboot-notifier-0.0.1

/*
 * Reboot notifier
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

/* reboot notifier */
#include <linux/reboot.h>

static int BiscuitOS_reboot_notifier(struct notifier_block *notifier,
                                                unsigned long val, void *v)
{
        printk("Trigger reboot on BiscuitOS.\n");
        return 0;
}

static struct notifier_block BiscuitOS_reboot = {
        .notifier_call = BiscuitOS_reboot_notifier,
        .priority = 0,
};

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
        printk("Hello modules on BiscuitOS\n");

        /* Register reboot notifier */
        register_reboot_notifier(&BiscuitOS_reboot);

        return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
        unregister_reboot_notifier(&BiscuitOS_reboot);
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Common Device driver on BiscuitOS");

cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
reboot-notifier-0.0.1.ko
/lib/modules/5.0.0/extra # insmod reboot-notifier-0.0.1.ko 
reboot_notifier_0.0.1: loading out-of-tree module taints kernel.
Hello modules on BiscuitOS

~ # 
~ # reboot
~ # umount: devtmpfs busy - remounted read-only
EXT4-fs (ram0): re-mounted. Opts: (null)
The system is going down NOW!
Sent SIGTERM totelnetd (1129) used greatest stack depth: 6172 bytes left
 all processes
Sent SIGKILL to all processes
Requesting system reboot
sh (1131) used greatest stack depth: 6144 bytes left
Unregister pv shared memory for cpu 1
Unregister pv shared memory for cpu 0
Trigger reboot on BiscuitOS.
reboot: Restarting system
reboot: machine restart

[*] Package  --->
    [*] Power Manager  --->
        [*] Trigger Suspend Demo  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/suspend-base-0.0.1

/*
 * Syscore suspend/resume
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/syscore_ops.h>

static int BiscuitOS_suspend(void)
{
        printk("Trigger suspend on BiscuitOS\n");
        return 0;
}

static void BiscuitOS_resume(void)
{
        printk("Trigger resume on BiscuitOS.\n");
}

static struct syscore_ops BiscuitOS_syscore = {
        .suspend = BiscuitOS_suspend,
        .resume  = BiscuitOS_resume,
};

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
        printk("Hello modules on BiscuitOS\n");

        register_syscore_ops(&BiscuitOS_syscore);    

        return 0;
}

/* Module exit entry */ 
static void __exit BiscuitOS_exit(void)
{
        unregister_syscore_ops(&BiscuitOS_syscore);
}   

module_init(BiscuitOS_init); 
module_exit(BiscuitOS_exit);
    
MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Common Device driver on BiscuitOS");

~ # 
~ # cd /lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
reboot-notifier-0.0.1.ko  suspend-base-0.0.1.ko
/lib/modules/5.0.0/extra # insmod suspend-base-0.0.1.ko
suspend_base_0.0.1: loading out-of-tree module taints kernel.
Hello modules on BiscuitOS
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra # cd /sys/power/
/sys/power # echo disk > state
PM: hibernation entry
PM: Syncing filesystems ... 
PM: done.
Freezing user space processes ... (elapsed 0.001 seconds) done.
OOM killer disabled.
PM: Marking nosave pages: [mem 0x00000000-0x00000fff]
PM: Marking nosave pages: [mem 0x0009f000-0x000fffff]
PM: Basic memory bitmaps created
PM: Preallocating image memory... done (allocated 47593 pages)
PM: Allocated 190372 kbytes in 0.01 seconds (19037.20 MB/s)
Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
printk: Suspending console(s) (use no_console_suspend to debug)
ACPI: Preparing to enter system sleep state S4
PM: Saving platform NVS memory
Disabling non-boot CPUs ...
Unregister pv shared memory for cpu 1
smpboot: CPU 1 is now offline
Trigger suspend on BiscuitOS
PM: Creating hibernation image:
PM: Need to copy 47276 pages
PM: Normal pages needed: 47276 + 1024, available pages: 83650
PM: Hibernation image created (47276 pages copied)
kvm-clock: cpu 0, msr 1ba6b001, primary cpu clock, resume
PM: Restoring platform NVS memory
Trigger resume on BiscuitOS.
Enabling non-boot CPUs ...
x86: Booting SMP configuration:
smpboot: Booting Node 0 Processor 1 APIC 0x1
Initializing CPU#1
kvm-clock: cpu 1, msr 1ba6b041, secondary cpu clock
KVM setup async PF for cpu 1
kvm-stealtime: cpu 1, msr 1f78fa40
 cache: parent cpu1 should not be sleeping
CPU1 is up
ACPI: Waking up from system sleep state S4
PM: Cannot find swap device, try swapon -a
PM: Cannot get swap writer
PM: Basic memory bitmaps freed
OOM killer enabled.
Restarting tasks ... done.
PM: hibernation exit
sh: write error: No such device
/sys/power # ata2.01: NODEV after polling detection
e1000: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX

echo disk > /sys/power/state

1. freeze  冻结 I/O 设备, 将它们置于低功耗状态,使处理器进入空闲状态, 唤醒最快, 耗电比其它 standby、mem、disk 方式高
2. standby 除了冻结 I/O 设备外,还会暂停系统,唤醒较快,耗电比其它 mem、disk 方式高
3. mem     将运行状态数据存到内存, 并关闭外设, 进入等待模式, 唤醒较慢, 耗电比 disk 方式高
4. disk    将运行状态数据存到硬盘, 然后关机, 唤醒最慢

[*] Package  --->
    [*] Power Manager  --->
        [*] Trigger Resume Demo  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/resume-base-0.0.1

/*
 * Syscore suspend/resume
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/syscore_ops.h>

static int BiscuitOS_suspend(void)
{
        printk("Trigger suspend on BiscuitOS\n");
        return 0;
}

static void BiscuitOS_resume(void)
{
        printk("Trigger resume on BiscuitOS.\n");
}

static struct syscore_ops BiscuitOS_syscore = {
        .suspend = BiscuitOS_suspend,
        .resume  = BiscuitOS_resume,
};

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
        printk("Hello modules on BiscuitOS\n");

        register_syscore_ops(&BiscuitOS_syscore);    

        return 0;
}

/* Module exit entry */ 
static void __exit BiscuitOS_exit(void)
{
        unregister_syscore_ops(&BiscuitOS_syscore);
}   

module_init(BiscuitOS_init); 
module_exit(BiscuitOS_exit);
    
MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Common Device driver on BiscuitOS");

~ # 
~ # cd /lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
reboot-notifier-0.0.1.ko  suspend-base-0.0.1.ko
/lib/modules/5.0.0/extra # insmod suspend-base-0.0.1.ko
suspend_base_0.0.1: loading out-of-tree module taints kernel.
Hello modules on BiscuitOS
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra # cd /sys/power/
/sys/power # echo disk > state
PM: hibernation entry
PM: Syncing filesystems ... 
PM: done.
Freezing user space processes ... (elapsed 0.001 seconds) done.
OOM killer disabled.
PM: Marking nosave pages: [mem 0x00000000-0x00000fff]
PM: Marking nosave pages: [mem 0x0009f000-0x000fffff]
PM: Basic memory bitmaps created
PM: Preallocating image memory... done (allocated 47593 pages)
PM: Allocated 190372 kbytes in 0.01 seconds (19037.20 MB/s)
Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
printk: Suspending console(s) (use no_console_suspend to debug)
ACPI: Preparing to enter system sleep state S4
PM: Saving platform NVS memory
Disabling non-boot CPUs ...
Unregister pv shared memory for cpu 1
smpboot: CPU 1 is now offline
Trigger suspend on BiscuitOS
PM: Creating hibernation image:
PM: Need to copy 47276 pages
PM: Normal pages needed: 47276 + 1024, available pages: 83650
PM: Hibernation image created (47276 pages copied)
kvm-clock: cpu 0, msr 1ba6b001, primary cpu clock, resume
PM: Restoring platform NVS memory
Trigger resume on BiscuitOS.
Enabling non-boot CPUs ...
x86: Booting SMP configuration:
smpboot: Booting Node 0 Processor 1 APIC 0x1
Initializing CPU#1
kvm-clock: cpu 1, msr 1ba6b041, secondary cpu clock
KVM setup async PF for cpu 1
kvm-stealtime: cpu 1, msr 1f78fa40
 cache: parent cpu1 should not be sleeping
CPU1 is up
ACPI: Waking up from system sleep state S4
PM: Cannot find swap device, try swapon -a
PM: Cannot get swap writer
PM: Basic memory bitmaps freed
OOM killer enabled.
Restarting tasks ... done.
PM: hibernation exit
sh: write error: No such device
/sys/power # ata2.01: NODEV after polling detection
e1000: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX

echo disk > /sys/power/state

1. freeze  冻结 I/O 设备, 将它们置于低功耗状态,使处理器进入空闲状态, 唤醒最快, 耗电比其它 standby、mem、disk 方式高
2. standby 除了冻结 I/O 设备外,还会暂停系统,唤醒较快,耗电比其它 mem、disk 方式高
3. mem     将运行状态数据存到内存, 并关闭外设, 进入等待模式, 唤醒较慢, 耗电比 disk 方式高
4. disk    将运行状态数据存到硬盘, 然后关机, 唤醒最慢

[*] Package  --->
    [*] Assembly  --->
        [*] X86/i386/X64 Assembly  --->
            [*] RDTSC  --->
            [*] RDTSC on Userspace  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/rdtsc-x86-0.0.1
BiscuitOS/output/linux-XXX-YYY/package/rdtsc-app-x86-0.0.1

/*
 * RDTSC - Read Time-Stamp Counter [x86]
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

/* mdelay */
#include <linux/delay.h>

/*
 * both i386 and x86_64 returns 64-bit value in edx:eax, but gcc's "A"
 * constraint has different meanings. For i386, "A" means exactly
 * edx:eax, while for x86_64 it doesn't mean rdx:rax or edx:eax. Instead,
 * it means rax *or* rdx.
 */
#ifdef CONFIG_X86_64
#define DECLARE_ARGS(val, low, high)    unsigned low, high
#define EAX_EDX_VAL(val, low, high)     ((low) | ((u64)(high) << 32))
#define EAX_EDX_ARGS(val, low, high)    "a" (low), "d" (high)
#define EAX_EDX_RET(val, low, high)     "=a" (low), "=d" (high)
#else
#define DECLARE_ARGS(val, low, high)    unsigned long long val
#define EAX_EDX_VAL(val, low, high)     (val)
#define EAX_EDX_ARGS(val, low, high)    "A" (val)
#define EAX_EDX_RET(val, low, high)     "=A" (val)
#endif

static __always_inline unsigned long long __native_read_tsc(void)
{
        DECLARE_ARGS(val, low, high);

        asm volatile("rdtsc" : EAX_EDX_RET(val, low, high));

        return EAX_EDX_VAL(val, low, high);
}

#define rdtscl(low)     ((low) = (u32)__native_read_tsc())
#define rdtscll(val)    ((val) = __native_read_tsc())

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
        u64 tsc_u64;
        u32 tsc_low;
        u64 tsc_a, tsc_b, result, mod;

        /* Read TSC 64bit contents */
        rdtscll(tsc_u64);
        printk("TSC 64bit: %#llx\n", tsc_u64);
        /* Read TSC low-order 32bit contents */
        rdtscl(tsc_low);
        printk("TSC low-order 32bit: %#x\n", tsc_low);

        /* CPU frequency */
        rdtscll(tsc_a);
        mdelay(1000);
        rdtscll(tsc_b);
        result = tsc_b - tsc_a;
        /* 64bit div */
        mod = do_div(result, 1 * 1024 * 1024);

        printk("CPU %d.%d MHz\n", result, mod);
        printk("Hello modules on BiscuitOS\n");

        return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Common Device driver on BiscuitOS");

cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
rdtsc-x86-0.0.1.ko
/lib/modules/5.0.0/extra # insmod rdtsc-x86-0.0.1.ko 
rdtsc_x86_0.0.1: loading out-of-tree module taints kernel.
TSC 64bit: 0xbe7b729e4
TSC low-order 32bit: 0xe7cb5b2d
CPU 3141.0 MHz
Hello modules on BiscuitOS
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra # cat /proc/cpuinfo | grep model
model		: 60
model name	: Intel(R) Core(TM) i5-4590 CPU @ 3.30GHz
model		: 60
model name	: Intel(R) Core(TM) i5-4590 CPU @ 3.30GHz
/lib/modules/5.0.0/extra #

/*
 * RDTSC -- Read Time-Stamp Counter on userspace [x86]
 *
 * (C) 2020.02.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

/*
 * both i386 and x86_64 returns 64-bit value in edx:eax, but gcc's "A"
 * constraint has different meanings. For i386, "A" means exactly
 * edx:eax, while for x86_64 it doesn't mean rdx:rax or edx:eax. Instead,
 * it means rax *or* rdx.
 */
#ifdef CONFIG_X86_64
#define DECLARE_ARGS(val, low, high)    unsigned low, high
#define EAX_EDX_VAL(val, low, high)     ((low) | ((u64)(high) << 32))
#define EAX_EDX_ARGS(val, low, high)    "a" (low), "d" (high)
#define EAX_EDX_RET(val, low, high)     "=a" (low), "=d" (high)
#else
#define DECLARE_ARGS(val, low, high)    unsigned long long val
#define EAX_EDX_VAL(val, low, high)     (val)
#define EAX_EDX_ARGS(val, low, high)    "A" (val)
#define EAX_EDX_RET(val, low, high)     "=A" (val)
#endif

static __always_inline unsigned long long __native_read_tsc(void)
{
        DECLARE_ARGS(val, low, high);

        asm volatile("rdtsc" : EAX_EDX_RET(val, low, high));

        return EAX_EDX_VAL(val, low, high);
}

#define rdtscl(low)     ((low) = (u32)__native_read_tsc())
#define rdtscll(val)    ((val) = __native_read_tsc())

typedef unsigned long long u64;
typedef unsigned int u32;

int main()
{
        u64 tsc_u64;
        u32 tsc_low;
        u64 tsc_a, tsc_b;

        /* Read TSC 64bit contents */
        rdtscll(tsc_u64);
        printf("TSC 64bit: %#llx\n", tsc_u64);
        /* Read TSC low-order 32bit contents */
        rdtscl(tsc_low);
        printf("TSC low-order 32bit: %#x\n", tsc_low);

        /* CPU frequency */
        rdtscll(tsc_a);
        sleep(1);
        rdtscll(tsc_b);

        printf("CPU %lld MHz\n", (tsc_b - tsc_a) / 1000000);
        printf("Hello Application Demo on BiscuitOS.\n");
        return 0;
}

~ # 
~ # rdtsc-app-x86-0.0.1 
TSC 64bit: 0x670b3d3e8
TSC low-order 32bit: 0x70c2ce2d
CPU 3293 MHz
Hello Application Demo on BiscuitOS.
~ # cat /proc/cpuinfo | grep model
model		: 60
model name	: Intel(R) Core(TM) i5-4590 CPU @ 3.30GHz
model		: 60
model name	: Intel(R) Core(TM) i5-4590 CPU @ 3.30GHz
~ # 

[*] Package  --->
    [*] Notifier mechanism on Kernel  --->
        -*-   MMU notifier (Kernel Portion)  --->
        [*]   MMU notifier (Userspace Portion)  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/MMU-notifier-0.0.1
BiscuitOS/output/linux-XXX-YYY/package/MMU-userspace-notifier-0.0.1

/*
 * MMU notifier on BiscuitOS
 *
 * (C) 2020.10.06 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include <linux/sched/mm.h>
#include <linux/slab.h>
#include <linux/uaccess.h>

/* MMU notifier */
#include <linux/mmu_notifier.h>
/* Current */
#include <linux/sched.h>

/* DD Platform Name */
#define DEV_NAME                "BiscuitOS"

static struct mmu_notifier BiscuitOS_notifier;
static struct mmu_notifier_range BiscuitOS_range;

static void BiscuitOS_mmu_release(struct mmu_notifier *mn,
                                                struct mm_struct *mm)
{
        printk("BiscuitOS notifier: release\n");
}

static int BiscuitOS_mmu_clear_flush_young(struct mmu_notifier *mn,
                struct mm_struct *mm, unsigned long start, unsigned long end)
{
        printk("BiscuitOS notifier: clear_flush_young\n");
        return 0;
}

static int BiscuitOS_mmu_clear_young(struct mmu_notifier *mn,
                struct mm_struct *mm, unsigned long start, unsigned long end)
{
        printk("BiscuitOS notifier: clear_young\n");
        return 0;
}

static int BiscuitOS_mmu_test_young(struct mmu_notifier *mn,
                        struct mm_struct *mm, unsigned long address)
{   
        printk("BiscuitOS notifier: test_young\n");
        return 0;
}

static void BiscuitOS_mmu_change_pte(struct mmu_notifier *mn,
                struct mm_struct *mm, unsigned long address, pte_t pte)
{
        printk("BiscuitOS notifier: change_pte\n");
}

static int BiscuitOS_mmu_invalidate_range_start(struct mmu_notifier *mn,
                                const struct mmu_notifier_range *range)
{
        printk("BiscuitOS notifier: invalidate_range_start.\n");
        return 0;
}

static void BiscuitOS_mmu_invalidate_range_end(struct mmu_notifier *mn,
                                const struct mmu_notifier_range *range)
{
        printk("BiscuitOS notifier: invalidate_range_end.\n");
}

static void BiscuitOS_mmu_invalidate_range(struct mmu_notifier *mn,
                struct mm_struct *mm, unsigned long start, unsigned long end)
{
        printk("BiscuitOS notifier: invalidate_range.\n");
}

static const struct mmu_notifier_ops BiscuitOS_mmu_notifer_ops = {
        .release     = BiscuitOS_mmu_release,
        .clear_young = BiscuitOS_mmu_clear_young,
        .test_young  = BiscuitOS_mmu_test_young,
        .change_pte  = BiscuitOS_mmu_change_pte,
        .clear_flush_young = BiscuitOS_mmu_clear_flush_young,
        .invalidate_range  = BiscuitOS_mmu_invalidate_range,
        .invalidate_range_start = BiscuitOS_mmu_invalidate_range_start,
        .invalidate_range_end   = BiscuitOS_mmu_invalidate_range_end,
};

static int BiscuitOS_mmap(struct file *filp, struct vm_area_struct *vma)
{
        struct mm_struct *mm = filp->private_data;
        pte_t pte;

        /* Trigger invalidate range [range, start, end] */
        mmu_notifier_range_init(&BiscuitOS_range, mm,
                vma->vm_start & PAGE_MASK, vma->vm_end & PAGE_MASK);
        mmu_notifier_invalidate_range_start(&BiscuitOS_range);
        mmu_notifier_invalidate_range_end(&BiscuitOS_range);

        /* Trigger clear_flush_young */
        mmu_notifier_clear_flush_young(mm, vma->vm_start, vma->vm_end);

        /* Trigger clear_young */
        mmu_notifier_clear_young(mm, vma->vm_start, vma->vm_end);

        /* Trigger test_young */
        mmu_notifier_test_young(mm, vma->vm_start);

        /* Trigger change pte */
        mmu_notifier_change_pte(mm, vma->vm_start, pte);

        /* Trigger realease */
        mmu_notifier_release(mm);

        return 0;
}

static int BiscuitOS_open(struct inode *inode, struct file *file)
{
        struct mm_struct *mm = get_task_mm(current);

        file->private_data = mm;
        /* mmu notifier initialize */
        BiscuitOS_notifier.ops = &BiscuitOS_mmu_notifer_ops;
        /* mmu notifier register */
        mmu_notifier_register(&BiscuitOS_notifier, mm);

        return 0;
}

static int BiscuitOS_release(struct inode *inode, struct file *file)
{
        mmu_notifier_unregister(&BiscuitOS_notifier, current->mm);
        return 0;
}

/* file operations */
static struct file_operations BiscuitOS_fops = {
        .owner          = THIS_MODULE,
        .open           = BiscuitOS_open,
        .mmap           = BiscuitOS_mmap,
        .release        = BiscuitOS_release,
};

/* Misc device driver */
static struct miscdevice BiscuitOS_drv = {
        .minor  = MISC_DYNAMIC_MINOR,
        .name   = DEV_NAME,
        .fops   = &BiscuitOS_fops,
};

/* Module initialize entry */
static void __init BiscuitOS_init(void)
{
        /* Register Misc device */
        misc_register(&BiscuitOS_drv);

        printk("Hello modules on BiscuitOS\n");
}

device_initcall(BiscuitOS_init);

/*
 * BiscuitOS MMU notifier on Userspace
 *
 * (C) 2020.10.06 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>

/* PATH for device */
#define DEV_PATH                "/dev/BiscuitOS"

int main()
{
        char *memory;
        int fd;

        /* open device */
        fd = open(DEV_PATH, O_RDWR);
        if (fd < 0) {
                printf("ERROR: Can't open %s\n", DEV_PATH);
                return -1;
        }

        /* mmap */
        memory = mmap(NULL, 0x100000, PROT_READ | PROT_WRITE,
                                                MAP_SHARED, fd, 0);
        if (!memory) {
                printf("ERROR: mmap faied.\n");
                goto out;
        }

        /* un-mmap */
        munmap(memory, 0x100000);

        /* Normal ending */
        close(fd);
        return 0;
out:
        close(fd);
        return -1;
}

~ # MMU-userspace-notifier-0.0.1 
BiscuitOS notifier: invalidate_range_start.
BiscuitOS notifier: invalidate_range.
BiscuitOS notifier: invalidate_range_end.
BiscuitOS notifier: clear_flush_young
BiscuitOS notifier: clear_young
BiscuitOS notifier: test_young
BiscuitOS notifier: change_pte
BiscuitOS notifier: release
~ #

[*] Package  --->
    [*] Platofrm: Device Driver and Application  --->
        [*] Platform Simple Module  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/platform_simple_module-0.0.1

/*
 * Simple Platform Device Driver
 *
 * (C) 2019.10.01 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>

/* LDD Platform Name */
#define DEV_NAME        "BiscuitOS"

static struct platform_device *pdev;

/* Probe: (LDD) Initialize Device */
static int BiscuitOS_probe(struct platform_device *pdev)
{
        /* Device Probe Procedure */
        printk("BiscuitOS Porbeing...\n");

        return 0;
}

/* Remove: (LDD) Remove Device (Module) */
static int BiscuitOS_remove(struct platform_device *pdev)
{
        /* Device Remove Procedure */
        printk("BiscuitOS Removing...\n");

        return 0;
}

/* Platform Driver Information */
static struct platform_driver BiscuitOS_driver = {
        .probe    = BiscuitOS_probe,
        .remove   = BiscuitOS_remove,
        .driver = {
                .owner  = THIS_MODULE,
                .name   = DEV_NAME,
        },
};

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
        int ret;

        ret = platform_driver_register(&BiscuitOS_driver);
        if (ret) {
                printk("Error: Platform driver register.\n");
                return -EBUSY;
        }

        pdev = platform_device_register_simple(DEV_NAME, 1, NULL, 0);
        if (IS_ERR(pdev)) {
                printk("Error: Platform device register\n");
                return PTR_ERR(pdev);
        }
        return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
        platform_device_unregister(pdev);
        platform_driver_unregister(&BiscuitOS_driver);
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Simple Platform Device Driver");

cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
platform_simple_module-0.0.1.ko
/lib/modules/5.0.0/extra # insmod platform_simple_module-0.0.1.ko 
platform_simple_module_0.0.1: loading out-of-tree module taints kernel.
BiscuitOS Porbeing...
/lib/modules/5.0.0/extra # 
/sys/bus/platform # cd /sys/bus/platform/devices/BiscuitOS.1/
/sys/devices/platform/BiscuitOS.1 # 
/sys/devices/platform/BiscuitOS.1 # ls
driver           modalias         subsystem
driver_override  power            uevent
/sys/devices/platform/BiscuitOS.1 #

[*] Package  --->
    [*] Bitmap  --->
        [*] Emulate PID Allocating and Releasing  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/emulate-pid-0.0.1

/*
 * Bitmap: Emulate PID allocating and Releasing on BiscuitOS
 *
 * (C) 2020.10.11  Meijusan <20741602@qq.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include<linux/slab.h>
#include <linux/err.h>
#include <linux/file.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/atomic.h>
#include <linux/mm.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/kthread.h>
#include <linux/kernel.h>
#include <linux/syscalls.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>
#include <linux/mutex.h>
#include <linux/gfp.h>
#include <linux/pid.h>
#include <linux/delay.h>
#include <linux/random.h>

#define PID_BITMAP_MAX 4096

/*
 * pid range 0~4096,this is a example
 */

static DECLARE_BITMAP( pid_bitmap_mask, PID_BITMAP_MAX);
static DEFINE_MUTEX(pid_bitmap_lock);

int pid_produce_thread(void *arg)
{
        while (!kthread_should_stop())  {
                int pid;

                mutex_lock(&pid_bitmap_lock);
                if( bitmap_full(pid_bitmap_mask, PID_BITMAP_MAX) ) {
                        mutex_unlock(&pid_bitmap_lock);
                        msleep(1000);
                        continue;
                }

                pid = find_first_zero_bit(pid_bitmap_mask, PID_BITMAP_MAX);
                if ( pid >= PID_BITMAP_MAX) {
                        printk("bitmap is full\n");
                        mutex_unlock(&pid_bitmap_lock);
                        msleep(1000);
                        continue;
                }
                printk("threadid %d create  pid: %d \n",current->pid,  pid);
                set_bit(pid, pid_bitmap_mask);
                mutex_unlock(&pid_bitmap_lock);
        }
        return 0;
}

static int pid_consume_thread(void *dummy)
{
        while (!kthread_should_stop()) {

                /*range 0 ~PID_BITMAP_MAX*/
                int pid = prandom_u32()%(PID_BITMAP_MAX + 1) ;

                mutex_lock(&pid_bitmap_lock);
                clear_bit(pid, pid_bitmap_mask);
                mutex_unlock(&pid_bitmap_lock);
                printk("threadid %d remove  pid: %d \n",current->pid,  pid);
                msleep(1000);
        }
        return 0;
}

static struct task_struct *pid_produce_task = NULL;
static struct task_struct *pid_consume_task = NULL;


/* Module initialize entry */
static int __init pid_bitmap_demo_init(void)
{
        /* default all pid already exist */
        bitmap_fill(pid_bitmap_mask, PID_BITMAP_MAX);

        pid_produce_task = kthread_run(pid_produce_thread, NULL, "pidconsujme");
        if (IS_ERR(pid_produce_task)) {
                int err = PTR_ERR(pid_produce_task);
                printk("failed to start the kauditd thread (%d)\n", err);
        }

        pid_consume_task = kthread_run(pid_consume_thread, NULL, "testbitmap");
        if (IS_ERR(pid_consume_task)) {
                int err = PTR_ERR(pid_consume_task);
                printk("failed to start the kauditd thread (%d)\n", err);
        }

        return 0;
}

/* Module exit entry */
static void __exit pid_bitmap_demo_exit(void)
{
        if(pid_produce_task)
                kthread_stop(pid_produce_task);
        if(pid_consume_task)
                kthread_stop(pid_consume_task);
}

module_init(pid_bitmap_demo_init);
module_exit(pid_bitmap_demo_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Meijusan <20741602@qq.com>");
MODULE_DESCRIPTION("Emulate PID allocating and Releasing on BiscuitOS");

~ # cd lrandom: fast init done
~ # cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
emulate-pid-0.0.1.ko
/lib/modules/5.0.0/extra # insmod emulate-pid-0.0.1.ko 
emulate_pid_0.0.1: loading out-of-tree module taints kernel.
threadid 1140 remove  pid: 521 
/lib/modules/5.0.0/extra # threadid 1138 create  pid: 521 
threadid 1140 remove  pid: 4073 
threadid 1140 remove  pid: 3235 
threadid 1138 create  pid: 3235 
threadid 1138 create  pid: 4073 
threadid 1140 remove  pid: 960 
threadid 1138 create  pid: 960 
threadid 1140 remove  pid: 1575 
threadid 1138 create  pid: 1575 
threadid 1140 remove  pid: 286 
threadid 1138 create  pid: 286 
threadid 1140 remove  pid: 2280 
threadid 1138 create  pid: 2280 
threadid 1140 remove  pid: 4061 
threadid 1140 remove  pid: 435 
threadid 1138 create  pid: 435 
threadid 1138 create  pid: 4061 
threadid 1140 remove  pid: 2294

1.1 为了方便实验和更好的理解 trie, 本模块从路由 LC-trie 协议, 去除了路由
    规则, trie 的扩展/压缩等复杂模块简化而成
1.2 主要完成一个 32bits 的字典树 (网络搜索参考字典树的逻辑及下文的 "实例图解")
1.3 本模块功能包括: 插入节点, 移除节点和节点查找,节点可以附带具体业务对象数据
1.4 本模块包含基础插入/移除和查找 api, 以及一个使用实例

2. 调试环境信息: linux 5.0.0
3. 运行输出信息: 为了便于理解, 本模块在 init 函数中执行实例程序,并输出人性化
   的调试信息,如下 [运行输出信息]
4. 代码说明

   bits32_trie_new.c:    节点的创建, 内存分配, 本例分配内存统一使用
                         kmalloc/kfree, 如需优化,自行修改
   bits32_trie_debug.c:  调试信息输出, 针对trie结构体进行逐层打印
   bits32_trie_insert.c: 节点插入代码
   bits32_trie_lookup.c: 节点查找代码
   bits32_trie_remove.c: 节点删除代码
   bits32_trie.c:        模块初始化代码及测试实例

[*] Package  --->
    [*] Bitmap  --->
        [*] LC-trie Protocol  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/LC-trie-0.0.1

.
├── LC-trie-0.0.1
│   ├── bits32_trie.c
│   ├── bits32_trie_debug.c
│   ├── bits32_trie_debug.h
│   ├── bits32_trie.h
│   ├── bits32_trie_insert.c
│   ├── bits32_trie_insert.h
│   ├── bits32_trie_lookup.c
│   ├── bits32_trie_lookup.h
│   ├── bits32_trie_new.c
│   ├── bits32_trie_new.h
│   ├── bits32_trie_remove.c
│   ├── bits32_trie_remove.h
│   ├── Kconfig
│   ├── Makefile
│   └── readme.txt
├── Makefile
└── README.md

1 directory, 17 files

~ # cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
C-trie-0.0.1.ko
/lib/modules/5.0.0/extra # insmod C-trie-0.0.1.ko 
C_trie_0.0.1: loading out-of-tree module taints kernel.
bits32_trie_init:[16 - 4]
~~~~~~~~  start insert  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bits32_trie_init insert leaf[0x12345678] data[0x0]
bits32_trie_init insert leaf[0x87654321] data[0x1]
bits32_trie_init insert leaf[0x11111111] data[0x2]
bits32_trie_init insert leaf[0x22222222] data[0x3]
~~~~~~~~   end insert   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--------------------------------------------------------------
~~~~~~~~   now let's look the trie view ~~~~~~~~~~~~~~~~~
tnode[0x0]:pos[0x1f]bits[0x1]cindex[0x0]
- tnode[0x0]:pos[0x1d]bits[0x1]cindex[0x0]
- - tnode[0x10000000]:pos[0x19]bits[0x1]cindex[0x0]
- - - leaf[0x11111111]:pos[0x0]bits[0x0]data[0x2]cindex[0x0]
- - - leaf[0x12345678]:pos[0x0]bits[0x0]data[0x0]cindex[0x1]
- - leaf[0x22222222]:pos[0x0]bits[0x0]data[0x3]cindex[0x1]
- leaf[0x87654321]:pos[0x0]bits[0x0]data[0x1]cindex[0x1]
~~~~~~~~   trie view end, it's as what you think??  ~~~~~
--------------------------------------------------------------
~~~~~~~~   test lookup  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bits32_trie_init lookup[0x11111111]index[0x2]
bits32_trie_init it seems ok, found leaf->key[0x11111111]
~~~~~~~~  test remove  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bits32_trie_init remove[0x11111111]index[0x2]
bits32_trie_init it seems ok, found no leaf->key[0x11111111] after del
bits32_trie_init remove[12345678]index[0]
bits32_trie_init it seems ok, found no leaf->key[0x12345678] after del
~~~~~~~~  now let's check the trie if it same as what you think  ~~~~
tnode[0x0]:pos[0x1f]bits[0x1]cindex[0x0]
- tnode[0x0]:pos[0x1d]bits[0x1]cindex[0x0]
- - leaf[0x22222222]:pos[0x0]bits[0x0]data[0x3]cindex[0x1]
- leaf[0x87654321]:pos[0x0]bits[0x0]data[0x1]cindex[0x1]
bits32_trie_init finish
insmod (1137) used greatest stack depth: 6300 bytes left
/lib/modules/5.0.0/extra # 

             bit31  ->                      bit0
0x12345678   00010010 00110100 01010110 01111000
0x87654321   10000111 01100101 01000011 00100001
0x11111111   00010001 00010001 00010001 00010001
0x22222222   00100010 00100010 00100010 00100010


                       tp
                       |
                       v
              0x12345678
(00010010 00110100 01010110 01111000)

                                           tp
                                           |
                                           v
                       ------------------ 0x0 --------------------
                       |                                         |
                       v                                         v
              0x12345678                                0x87654321
(00010010 00110100 01010110 01111000)    (10000111 01100101 01000011 00100001)


                                                               tp
                                                               |
                                                               v
                                           ------------------ 0x0 --------------------
                                           |                                         |
                                           v                                         v
                                  0x10000000                                0x87654321
                    (00010000 00000000 00000000 00000000)    (10000111 01100101 01000011 00100001)
                                           |
                                           v
                       -------------------- ----------------------
                       |                                         |
                       v                                         v
              0x12345678                                0x11111111
(00010010 00110100 01010110 01111000)    (00010001 00010001 00010001 00010001)
                                                                                    tp
                                                                                    |
                                                                                    v
                                                                ------------------ 0x0 --------------------
                                                                |                                         |
                                                                v                                         v
                                                               0x0                                   0x87654321
                                                  (00000000 00000000 00000000 00000000)       (10000111 01100101 01000011 00100001)
                                                                |
                                                                v
                                           --------------------  ---------------------
                                           |                                         |
                                           v                                         v
                                     0x10000000                                 0x22222222
                    (00000001 00000000 00000000 00000000)    (00100010 00100010 00100010 00100010)
                                           |
                                           v
                       -------------------- ----------------------
                       |                                         |
                       v                                         v
                   0x11111111                                0x12345678
     (00010001 00010001 00010001 00010001)    (00010010 00110100 01010110 01111000)

[*] Package  --->
    [*] System Call  --->
        [*] sys_mmap2  --->
            [*] Anonymous mmap on Userspace  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/BiscuitOS-Anonymous-mmap-Userspace-0.0.1

/*
 * Anonymous mmap from Userspace on BiscuitOS
 *
 * (C) 2020.10.24 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/mman.h>

/* The size for anonymous mmap */
#define MMAP_SIZE               4096

int main()
{
        char *base;

        /* Anonymous mmap */
        base = mmap(NULL,
                    MMAP_SIZE,
                    PROT_READ | PROT_WRITE,
                    MAP_SHARED | MAP_ANONYMOUS,
                    -1,
                    0);
        if (!base) {
                printf("ERROR: Mmap anonymous failed.\n");
                return -1;
        }

        /* Use */
        sprintf(base, "BiscuitOS");
        printf("=> %s [%#lx]\n", base, (unsigned long)base);

        /* Un-mmap */
        munmap(base, MMAP_SIZE);

        return 0;
}

~ # BiscuitOS-Anonymous-mmap-Userspace-0.0.1 
=> BiscuitOS [0xb7d91000]
~ #

[*] Package  --->
    [*] System Call  --->
        [*] sys_mmap2  --->
            [*] Anonymous mmap on Kernel  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/BiscuitOS-Anonymous-mmap-Kernel-0.0.1

/*
 * Anonymous mmap from kernel on BiscuitOS
 *
 * (C) 2020.10.24 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/mman.h>

/* The size for mmaping */
#define MMAP_SIZE               PAGE_SIZE
/* The address fro mamping */
static char *mmap_base;

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
        /* Anonymous mmaping */
        mmap_base = (char *)vm_mmap(
                            NULL,
                            0,
                            MMAP_SIZE,
                            PROT_READ | PROT_WRITE,
                            MAP_SHARED | MAP_ANONYMOUS,
                            0);
        if (IS_ERR((void *)mmap_base)) {
                printk("ERROR: Anonymous mmap failed.\n");
                return -ENOMEM;
        }

        /* Use */
        sprintf(mmap_base, "BiscuitOS");
        printk("=> %s [%#lx]\n", mmap_base, (unsigned long)mmap_base);

        return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
        /* Un-mmap */
        vm_munmap((unsigned long)mmap_base, MMAP_SIZE);
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Anonymous kenrel mmap on BiscuitOS");

/lib/modules/5.0.0/extra # ls
BiscuitOS-Anonymous-mmap-Kernel-0.0.1.ko
/lib/modules/5.0.0/extra # insmod BiscuitOS-Anonymous-mmap-Kernel-0.0.1.ko 
BiscuitOS_Anonymous_mmap_Kernel_0.0.1: loading out-of-tree module taints kernel.
=> BiscuitOS [0xb7f08000]
/lib/modules/5.0.0/extra # 

[*] Package  --->
    [*] VFS (BiscuitOS+)  --->
        -*- Anonymous File (Kernel Part+)  --->
        [*] Anonymous file (Userspace Part+)  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/BiscuitOS-Anonymous-file-userspace-0.0.1
BiscuitOS/output/linux-XXX-YYY/package/BiscuitOS-Anonymous-file-kernel-0.0.1

/*
 * Anonymous file on BiscuitOS
 *
 * (C) 2020.10.06 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include <linux/anon_inodes.h>
#include <linux/errno.h>
#include <linux/file.h>

/* DD Platform Name */
#define DEV_NAME                "BiscuitOS"
/* IOCTL CMD */
#define BISCUITOS_IO            0xAE
#define BISCUITOS_SET           _IO(BISCUITOS_IO, 0x00)
#define BISCUITOS_GET           _IO(BISCUITOS_IO, 0x01)

/* File operation for anonymous file */
static struct file_operations BiscuitOS_anonymous_fops;

/* Create anonymous file */
static int BiscuitOS_anonymous_file(void)
{
        struct file *file;
        int fd;

        /* Get an unused fd */
        fd = get_unused_fd_flags(O_CLOEXEC);
        if (fd < 0) {
                printk("ERROR[%d]: Get unused fd failed.\n", fd);
                return fd;
        }

        /* Create anonymous file */
        file = anon_inode_getfile("BiscuitOS-anonymous",
                                &BiscuitOS_anonymous_fops, NULL, O_RDWR);
        if (IS_ERR(file)) {
                printk("ERROR[%ld]: Create anonymous file failed.\n",
                                                PTR_ERR(file));
                put_unused_fd(fd);
                return PTR_ERR(file);
        }

        /* Bind fd and file */
        fd_install(fd, file);
        return fd;
}

/* ioctl */
static long BiscuitOS_ioctl(struct file *filp,
                        unsigned int ioctl, unsigned long arg)
{
        switch (ioctl) {
        case BISCUITOS_SET:
                return BiscuitOS_anonymous_file();
        case BISCUITOS_GET:
                printk("IOCTL: BISCUITOS_GET.\n");
                break;
        default:
                break;
        }
        return 0;
}

/* file operations */
static struct file_operations BiscuitOS_fops = {
        .owner          = THIS_MODULE,
        .unlocked_ioctl = BiscuitOS_ioctl,
};

/* Misc device driver */
static struct miscdevice BiscuitOS_drv = {
        .minor  = MISC_DYNAMIC_MINOR,
        .name   = DEV_NAME,
        .fops   = &BiscuitOS_fops,
};

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
        /* Register Misc device */
        misc_register(&BiscuitOS_drv);
        return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
        /* Un-Register Misc device */
        misc_deregister(&BiscuitOS_drv);
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("BiscuitOS Anonymous file");

/*
 * Anonymous file on BiscuitOS (Userspace Part+)
 *
 * (C) 2020.10.24 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <linux/ioctl.h>
#include <sys/ioctl.h>
#include <sys/types.h>

/* PATH for devnode */
#define BISCUITOS_NODE          "/dev/BiscuitOS"
/* IOCTL CMD */
#define BISCUITOS_IO            0xAE
#define BISCUITOS_SET           _IO(BISCUITOS_IO, 0x00)
#define BISCUITOS_GET           _IO(BISCUITOS_IO, 0x01)

int main()
{
        int anonymous_fd;
        int fd;

        /* Open BiscuitOS node */
        fd = open(BISCUITOS_NODE, O_RDWR);
        if (fd < 0) {
                printf("ERROR[%d]: open %s failed.\n", fd, BISCUITOS_NODE);
                return fd;
        }

        /* Create Anonymous file by ioctl() */
        anonymous_fd = ioctl(fd, BISCUITOS_SET, (unsigned long)0);
        if (anonymous_fd < 0) {
                printf("ERROR[%d]: Anonymous file failed.\n", anonymous_fd);
                return anonymous_fd;
        }

        /* Anonymous fd */
        printf("Anonymous file-FD: %d\n", anonymous_fd);

        /* close */
        close(fd);

        return 0;
}

~ # 
~ # cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
BiscuitOS-Anonymous-file-kernel-0.0.1.ko
/lib/modules/5.0.0/extra # insmod BiscuitOS-Anonymous-file-kernel-0.0.1.ko 
BiscuitOS_Anonymous_file_kernel_0.0.1: loading out-of-tree module taints kernel.
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra # BiscuitOS-Anonymous-file-userspace-0.0.1 
Anonymous file-FD: 4
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra #

[*] Package  --->
    [*] VFS (BiscuitOS+)  --->
        [*] Kernel read Userspace file  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/BiscuitOS-Kernel-read-Userspace-file-0.0.1

/*
 * Kernel read Userspace file on BiscuitOS
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/fs.h>
#include <asm/uaccess.h>

/* The path for Userspace file */
#define BISCUITOS_FILE          "/proc/meminfo"
/* Buffer length */
#define MAX_BUFFER_SIZE         256

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
        char buffer[MAX_BUFFER_SIZE];
        struct file *filp = NULL;
        mm_segment_t fs;
        loff_t pos = 0;

        /* Open Userspace file */
        filp = filp_open(BISCUITOS_FILE, O_RDWR, 0644);
        if (IS_ERR(filp)) {
                printk("ERROR[%ld]: Open %s failed.\n", PTR_ERR(filp),
                                                        BISCUITOS_FILE);
                return PTR_ERR(filp);
        }

        fs = get_fs();
        set_fs(KERNEL_DS);

        /* Read from Userspace file */
        pos = 0;
        kernel_read(filp, buffer, sizeof(buffer), &pos);
        printk("BiscuitOS Read Contents:\n%s\n", buffer);

        /* Close Userspace file */
        filp_close(filp, NULL);
        set_fs(fs);

        return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Read Userspace file on BiscuitOS");

~ # cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra # ls
BiscuitOS-Kernel-read-Userspace-file-0.0.1.ko
/lib/modules/5.0.0/extra # insmod BiscuitOS-Kernel-read-Userspace-file-0.0.1.ko 
BiscuitOS_Kernel_read_Userspace_file_0.0.1: loading out-of-tree module taints kernel.
BiscuitOS Read Contents:
MemTotal:         504144 kB
MemFree:          334208 kB
MemAvailable:     331916 kB
Buffers:             112 kB
Cached:             1936 kB
SwapCached:            0 kB
Active:             1864 kB
Inactive:            312 kB
Active(anon):        136 kB

[*] Package  --->
    [*] VFS (BiscuitOS+)  --->
        [*] Kernel write Userspace file  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/BiscuitOS-Kernel-write-Userspace-file-0.0.1

/*
 * Kernel write to Userspace file on BiscuitOS
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/fs.h>
#include <asm/uaccess.h>

/* The path for Userspace file */
#define BISCUITOS_FILE          "/tmp/BiscuitOS.info"
/* Buffer length */
#define MAX_BUFFER_SIZE         256

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
        char buffer[MAX_BUFFER_SIZE];
        struct file *filp = NULL;
        mm_segment_t fs;
        loff_t pos = 0;

        /* Open Userspace file */
        filp = filp_open(BISCUITOS_FILE, O_RDWR | O_CREAT, 0644);
        if (IS_ERR(filp)) {
                printk("ERROR[%ld]: Open %s failed.\n", PTR_ERR(filp),
                                                        BISCUITOS_FILE);
                return PTR_ERR(filp);
        }

        fs = get_fs();
        set_fs(KERNEL_DS);

        /* Write data into Userspace file */
        sprintf(buffer, "BiscuitOS");
        buffer[strlen(buffer)] = '\n';
        pos = 0;
        kernel_write(filp, buffer, strlen(buffer) + 1, &pos);

        /* Close Userspace file */
        filp_close(filp, NULL);
        set_fs(fs);

        return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Write Userspace file on BiscuitOS");

~ # cd lib/modules/5.0.0/extra/
/lib/modules/5.0.0/extra # ls
BiscuitOS-Kernel-write-Userspace-file-0.0.1.ko
/lib/modules/5.0.0/extra # insmod BiscuitOS-Kernel-write-Userspace-file-0.0.1.ko
BiscuitOS_Kernel_write_Userspace_file_0.0.1: loading out-of-tree module taints kernel.
insmod (1184) used greatest stack depth: 6500 bytes left
/lib/modules/5.0.0/extra # 
/lib/modules/5.0.0/extra # cat /tmp/BiscuitOS.info 
BiscuitOS

  Memory Management options  --->
        Memory model (Sparse Memory)  --->
    [*] Allow for memory hot-add

[*] Package  --->
    [*] MMU (BiscuitOS+)  --->
        [*] Memory Hotplug in C  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/BiscuitOS-Memory-Hotplug-in-C-0.0.1

/*
 * Memory Hotplug in Code on BiscuitOS
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

/*
 * Memory region for Hotplugging.
 * BTW, The default Block size as 0x8000000, not 2 Gig.
 *
 * On Aarch, we reserved a memory region from 0x50000000 to 0x58000000 on
 * MEMBLOCK allocator that invoke "memblock_reserve(0x50000000, 0x8000000)"
 * on "arm64_memblock_init()".
 *
 * On x86_64, we can use "memmap=" on CMDLINE to reserved a memory
 * region. The range of memory region from 0x18000000 to 0x20000000, which 
 * descrbe as "memmap=0x128M$0x5000000".
 */

/* NUMA NODE */
static int nid = 0;

#ifdef __aarch64__
#define BISCUITOS_MEMORY_BASE           0x50000000
#else // X64
#define BISCUITOS_MEMORY_BASE           0x18000000
#endif
#define BISCUITOS_MEMORY_SIZE           0x8000000

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
#ifdef CONFIG_MEMORY_HOTPLUG
        /* Add into /sys/device/system/memory/memoryX */
        add_memory(nid, BISCUITOS_MEMORY_BASE, BISCUITOS_MEMORY_SIZE);
#endif
        printk("Hello BiscuitOS :)\n");
        return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Memory Hotplug in Code on BiscuitOS");

~ # cd /sys/devices/system/memory/
/sys/devices/system/memory # ls
auto_online_blocks  memory11            power
block_size_bytes    memory8             soft_offline_page
hard_offline_page   memory9             uevent
/sys/devices/system/memory # cat /proc/iomem 
40000000-4fffffff : System RAM
  40080000-41a1ffff : Kernel code
  41a20000-41baffff : reserved
  41bb0000-41e3cfff : Kernel data
  48000000-480fffff : reserved
58000000-5fffffff : System RAM
  5d600000-5d7fffff : reserved
  5d926000-5ddfffff : reserved
  5def7000-5def7fff : reserved
  5def8000-5df25fff : reserved
  5df28000-5df28fff : reserved
  5df29000-5df3bfff : reserved
  5df3c000-5df43fff : reserved
  5df44000-5fffffff : reserved
4010000000-401fffffff : PCI ECAM

/sys/devices/system/memory # 
/sys/devices/system/memory # insmod /lib/modules/5.0.0/extra/BiscuitOS-Memory-Ho
tplug-in-C-0.0.1.ko 
[   35.980429] BiscuitOS_Memory_Hotplug_in_C_0.0.1: loading out-of-tree module taints kernel.
[   36.019905] Hello BiscuitOS :)
/sys/devices/system/memory # 
/sys/devices/system/memory # ls
auto_online_blocks  memory10            memory9             uevent
block_size_bytes    memory11            power
hard_offline_page   memory8             soft_offline_page
/sys/devices/system/memory # 
/sys/devices/system/memory # cat /proc/iomem 
40000000-4fffffff : System RAM
  40080000-41a1ffff : Kernel code
  41a20000-41baffff : reserved
  41bb0000-41e3cfff : Kernel data
  48000000-480fffff : reserved
50000000-57ffffff : System RAM
58000000-5fffffff : System RAM
/sys/devices/system/memory #
/sys/devices/system/memory/memory11 # cat /proc/meminfo 
MemTotal:         355284 kB
MemFree:          316684 kB
/sys/devices/system/memory # cd memory10/
/sys/devices/system/memory/memory10 # ls
node0        phys_device  power        state        uevent
online       phys_index   removable    subsystem
/sys/devices/system/memory/memory10 # cat state 
offline
/sys/devices/system/memory/memory10 # echo online > state 
/sys/devices/system/memory/memory10 # cat /proc/meminfo 
MemTotal:         486356 kB
MemFree:          447520 kB

  Memory Management options  --->
        Memory model (Sparse Memory)  --->
    [*] Allow for memory hot-add

[*] Package  --->
    [*] MMU (BiscuitOS+)  --->
        [*] Memory Hotplug auto  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/BiscuitOS-Memory-Hotplug-auto-0.0.1

/*
 * Memory Hotplug in Code on BiscuitOS
 *
 * (C) 2020.10.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/fs.h>
#include <asm/uaccess.h>

/*
 * Memory region for Hotplugging.
 * BTW, The default Block size as 0x8000000, not 2 Gig.
 *
 * On Aarch, we reserved a memory region from 0x50000000 to 0x58000000 on
 * MEMBLOCK allocator that invoke "memblock_reserve(0x50000000, 0x8000000)"
 * on "arm64_memblock_init()".
 *
 * On x86_64, we can use "memmap=" on CMDLINE to reserved a memory
 * region. The range of memory region from 0x5000000 to 0xD000000, which 
 * descrbe as "memmap=0x128M$0x5000000".
 */

/* NUMA NODE */
static int nid = 0;

#ifdef __aarch64__
#define BISCUITOS_MEMORY_BASE   0x50000000
#define BISCUITOS_PATH          "/sys/devices/system/memory/memory10/state"
#else // X64
#define BISCUITOS_MEMORY_BASE   0x18000000
#define BISCUITOS_PATH          "/sys/devices/system/memory/memory3/state"
#endif
#define BISCUITOS_MEMORY_SIZE   0x8000000

/* Module initialize entry */
static int __init BiscuitOS_init(void)
{
        struct file *filp;
        mm_segment_t fs;
        loff_t pos = 0;

#ifdef CONFIG_MEMORY_HOTPLUG
        /* Add into /sys/device/system/memory/memoryX */
        add_memory(nid, BISCUITOS_MEMORY_BASE, BISCUITOS_MEMORY_SIZE);
#endif

        /* open file */
        filp = filp_open(BISCUITOS_PATH, O_RDWR, 0644);
        if (IS_ERR(filp)) {
                printk("ERROR[%ld]: open %s failed.\n", PTR_ERR(filp),
                                                        BISCUITOS_PATH);
                return PTR_ERR(filp);
        }

        fs = get_fs();
        set_fs(KERNEL_DS);

        /* Write */
        pos = 0;
        kernel_write(filp, "online", strlen("online"), &pos);

        /* Close */
        filp_close(filp, NULL);
        set_fs(fs);

        return 0;
}

/* Module exit entry */
static void __exit BiscuitOS_exit(void)
{
#ifdef CONFIG_MEMORY_HOTPLUG
        remove_memory(nid, BISCUITOS_MEMORY_BASE, BISCUITOS_MEMORY_SIZE);
#endif
}

module_init(BiscuitOS_init);
module_exit(BiscuitOS_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BiscuitOS <buddy.zhang@aliyun.com>");
MODULE_DESCRIPTION("Memory Hotplug in Code on BiscuitOS");

~ # 
~ # cd /sys/devices/system/memory/
/sys/devices/system/memory # ls
auto_online_blocks  memory11            power
block_size_bytes    memory8             soft_offline_page
hard_offline_page   memory9             uevent
/sys/devices/system/memory # cat /proc/iomem 
40000000-4fffffff : System RAM
  40080000-41a1ffff : Kernel code
  41a20000-41baffff : reserved
  41bb0000-41e3cfff : Kernel data
  48000000-480fffff : reserved
58000000-5fffffff : System RAM
  5d600000-5d7fffff : reserved
  5d926000-5ddfffff : reserved
  5def7000-5def7fff : reserved
  5def8000-5df25fff : reserved
  5df28000-5df28fff : reserved
  5df29000-5df3bfff : reserved
  5df3c000-5df43fff : reserved
  5df44000-5fffffff : reserved
4010000000-401fffffff : PCI ECAM
/sys/devices/system/memory # cat /proc/meminfo 
MemTotal:         355284 kB
MemFree:          319308 kB
/sys/devices/system/memory # insmod /lib/modules/5.0.0/extra/BiscuitOS-Memory-Ho
tplug-auto-0.0.1.ko
/sys/devices/system/memory # ls
auto_online_blocks  memory10            memory9             uevent
block_size_bytes    memory11            power
hard_offline_page   memory8             soft_offline_page
/sys/devices/system/memory # cat /proc/iomem 
40000000-4fffffff : System RAM
  40080000-41a1ffff : Kernel code
  41a20000-41baffff : reserved
  41bb0000-41e3cfff : Kernel data
  48000000-480fffff : reserved
50000000-57ffffff : System RAM
58000000-5fffffff : System RAM
  5d600000-5d7fffff : reserved
  5d926000-5ddfffff : reserved
  5def7000-5def7fff : reserved
  5def8000-5df25fff : reserved
  5df28000-5df28fff : reserved
  5df29000-5df3bfff : reserved
  5df3c000-5df43fff : reserved
  5df44000-5fffffff : reserved
4010000000-401fffffff : PCI ECAM
/sys/devices/system/memory # cat /proc/meminfo 
MemTotal:         486356 kB
MemFree:          447172 kB
/sys/devices/system/memory # cd memory10/
/sys/devices/system/memory/memory10 # cat state 
online

[*] Package  --->
    [*] Memory Mapping Mechanism  --->
        [*]  Anonymous Share mmap on Userspace

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/BiscuitOS-anonymous-share-mmap-userspace-default/

/*
 * Anonymout share mmap on Userspace
 *
 * (C) 2021.04.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>

#define BISCUITOS_MAP_SIZE      4096

int main()
{
        unsigned long *val;
        char *base;

        /* mmap */
        base = (char *)mmap(NULL,
                            BISCUITOS_MAP_SIZE,
                            PROT_READ | PROT_WRITE,
                            MAP_SHARED | MAP_ANONYMOUS,
                            -1,
                            0);
        if (base == MAP_FAILED) {
                printf("ERROR: mmap failed.\n");
                return -ENOMEM;
        }

        val = (unsigned long *)base;
        /* Trigger page fault */
        *val = 88520;
        printf("%#lx => %ld\n", (unsigned long)val, *val);

        /* unmap */
        munmap(base, BISCUITOS_MAP_SIZE);

        return 0;
}

[*] Package  --->
    [*] Memory Mapping Mechanism  --->
        [*]  Anonymous Private mmap on Userspace

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/BiscuitOS-anonymous-private-mmap-userspace-default/

/*
 * Anonymout private mmap on Userspace
 *
 * (C) 2021.04.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>

#define BISCUITOS_MAP_SIZE      4096

int main()
{
        unsigned long *val;
        char *base;

        /* mmap */
        base = (char *)mmap(NULL,
                            BISCUITOS_MAP_SIZE,
                            PROT_READ | PROT_WRITE,
                            MAP_PRIVATE | MAP_ANONYMOUS,
                            -1,
                            0);
        if (base == MAP_FAILED) {
                printf("ERROR: mmap failed.\n");
                return -ENOMEM;
        }

        val = (unsigned long *)base;
        /* Trigger page fault */
        *val = 88520;
        printf("%#lx => %ld\n", (unsigned long)val, *val);

        /* unmap */
        munmap(base, BISCUITOS_MAP_SIZE);

        return 0;
}

[*] Package  --->
    [*] Memory Mapping Mechanism  --->
        [*] File Share mmap on Userspace --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/BiscuitOS-file-share-mmap-userspace-default/

/*
 * File Share mmap on Userspace
 *
 * (C) 2021.04.02 BuddyZhang1 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>

#define BISCUITOS_FILE_PATH     "/BiscuitOS"
#define BISCUITOS_MAP_SIZE      4096

int main()
{
        unsigned long *val;
        char *base;
        int fd;

        /* Open */
        fd = open(BISCUITOS_FILE_PATH, O_RDWR);
        if (fd < 0) {
                printf("ERROR: Open %s failed.\n", BISCUITOS_FILE_PATH);
                return -EBUSY;
        }

        /* mmap */
        base = (char *)mmap(NULL,
                            BISCUITOS_MAP_SIZE,
                            PROT_READ | PROT_WRITE,
                            MAP_SHARED,
                            fd,
                            0);
        if (base == MAP_FAILED) {
                printf("ERROR: mmap failed.\n");
                close(fd);
                return -ENOMEM;
        }

        val = (unsigned long *)base;
        /* Trigger page fault */
        *val = 88520;
        printf("%#lx => %#lx\n", (unsigned long)val, *val);

        /* unmap */
        munmap(base, BISCUITOS_MAP_SIZE);
        close(fd);

        return 0;
}

[*] Package  --->
    [*] Assembly  --->

OUTPUT:
BiscuitOS/output/linux-XXX-YYY/package/