直接上代码，思路就是得到代码段的起始地址和结束地址，然后先将数据存在一个buffer中，最后写入文件。

kallsym.c

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

static char *path = NULL;
module_param(path, charp, S_IRUGO);

static int __write_to_file(char *buffer, int size)
{
	struct file *filep = NULL;
	loff_t pos = 0;
	int ret = 0;

	filep = filp_open(path, O_RDWR | O_CREAT, 0);
	if(filep == NULL) {
		printk("%s: Open file %s error\n", __func__, path);
		return 0;
	}

	ret = kernel_write(filep, buffer, size, &pos);
	if(ret < size) {
		printk("%s: Write file %s error\n", __func__, path);
		return 0;
	}

	filp_close(filep, NULL);

	return ret;
}

static int __init kallsyms_init(void)
{
	unsigned long stext, etext, size = 0;
	char *ptr = NULL;
	char *buffer = NULL;
	int i = 0;

	stext = kallsyms_lookup_name("_stext");
	etext = kallsyms_lookup_name("_etext");

	printk("%s: the _stext address is %lx\n", __func__, stext);
	printk("%s: the _stext address is %lx\n", __func__, etext);

	if(!stext || !etext) {
		printk("%s: Get text start end failed\n", __func__);
		return -EINVAL;
	}
	
	size = etext - stext;
	ptr = (char *)stext;

	buffer = vzalloc(size + 1024);
	if(buffer == NULL) {
		printk("%s: Alloc temp buffer memory failed\n", __func__);
		return 0;
	}

	for(i = 0; i < size; i++) {
		buffer[i] = ptr[i];
	}

	__write_to_file(buffer, size);

	vfree(buffer);
	return 0;
}

static void __exit kallsyms_exit(void)
{
	printk("%s: good bye\n", __func__);
}


module_init(kallsyms_init);
module_exit(kallsyms_exit);

MODULE_LICENSE("GPL");

Makefile:

obj-m += kallsym.o
KBUILD_CFLAGS += -g

all:
	make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) modules

clean:
	make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) clean

以下代码为dump指定内存地址，大小为offset；

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

static char *path = NULL;
static unsigned long base_addr = 0;
static unsigned int offset = 0;
module_param(path, charp, S_IRUGO);
module_param(base_addr, ulong, S_IRUGO);
module_param(offset, uint, S_IRUGO);

static int __write_to_file(char *buffer, int size)
{
	struct file *filep = NULL;
	loff_t pos = 0;
	int ret = 0;

	filep = filp_open(path, O_RDWR | O_CREAT, 0);
	if(filep == NULL) {
		printk("%s: Open file %s error\n", __func__, path);
		return 0;
	}

	ret = kernel_write(filep, buffer, size, &pos);
	if(ret < size) {
		printk("%s: Write file %s error\n", __func__, path);
		return 0;
	}

	filp_close(filep, NULL);

	return ret;
}

static int __init kallsyms_init(void)
{
	unsigned long stext, etext;
	char *ptr = NULL;
	char *buffer = NULL;
	int i = 0;

	stext = base_addr;
	etext = base_addr + offset;

	printk("%s: the _stext address is %lx\n", __func__, stext);
	printk("%s: the _stext address is %lx\n", __func__, etext);

	ptr = (char *)stext;

	buffer = vzalloc(offset + 100);
	if(buffer == NULL) {
		printk("%s: Alloc temp buffer memory failed\n", __func__);
		return 0;
	}

	for(i = 0; i < offset; i++) {
		buffer[i] = ptr[i];
	}

	__write_to_file(buffer, offset);

	vfree(buffer);
	return 0;
}

static void __exit kallsyms_exit(void)
{
	printk("%s: good bye\n", __func__);
}


module_init(kallsyms_init);
module_exit(kallsyms_exit);

MODULE_LICENSE("GPL");