Linux 用户空间dump内存小工具

gcc dump_mem.c -o dump_mem

# 注意内存地址和大小必须是4K对齐
./dump_mem 0x80000000 0x1000

// 修改自开源的 devmem2.c :https://bootlin.com/pub/mirror/devmem2.c
// custom_devmem2 addr size
// 从addr开始，读取size个数据，并判断其值是否为feature_data

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <signal.h>
#include <fcntl.h>
#include <ctype.h>
#include <termios.h>
#include <sys/types.h>
#include <sys/mman.h>

#define FATAL do { fprintf(stderr, "Error at line %d, file %s (%d) [%s]\n", \
  __LINE__, __FILE__, errno, strerror(errno)); exit(1); } while(0)
 
#define MAP_SIZE 4096UL
#define MAP_MASK (MAP_SIZE - 1)

int main(int argc, char **argv) {
    int fd;
    void *map_base, *virt_addr; 
    //在arm64上，long代表8个字节
	unsigned long read_result, high32, low32;

	off_t target;
	int access_type = 'w';
    size_t size=0;
    int offset = 0;
    int i=0;


    printf("sizeof(unsigned long):%d\n",sizeof( unsigned long));
	
	if(argc < 2) {
		fprintf(stderr, "\nUsage:\t%s address  size\n"
			"\taddress : memory address to act upon\n"
			"\tsize    : size\n",
			argv[0]);
		exit(1);
	}
	target = strtoul(argv[1], 0, 0);

	if(argc > 2)
		size = strtoul(argv[2], 0, 0);
    
    //每次只能映射4K
    int map_time = size / 4096;
    int map_count = 0;

    printf("rmr addr:0x%llx size:0x%llx map_time:%d\n", target, size, map_time);
    if((fd = open("/dev/mem", O_RDWR | O_SYNC)) == -1) FATAL;
    printf("/dev/mem opened.\n"); 
    fflush(stdout);

    for(map_count = 0;map_count < map_time;map_count++) {
        // target = target+map_count*MAP_SIZE;
        printf("target:0x%llx %d/%d\r",target, map_count, map_time);
        offset=0;
        while(offset < MAP_SIZE){
            /* Map one page */
            //printf("Memory mapped pa:0x%llx at address %p.\n", target & ~MAP_MASK, map_base); 
            map_base = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, target & ~MAP_MASK);
            if(map_base == (void *) -1) FATAL;
            fflush(stdout);
            virt_addr = map_base + (target & MAP_MASK);
            read_result = *((unsigned long *) virt_addr);
            high32 = read_result >> 32;
            low32 = read_result & 0xFFFFFFFF;
            // printf("debug addr:0x%p value:0x%llx offset:0x%x high32:0x%llx low32:0x%llx \n",
            //     virt_addr, read_result, offset, high32,low32);
            for(i=0;i<sizeof(feature_data)/sizeof(unsigned long);i++){
                if (high32 == feature_data[i]){
                    printf("found feature_data:0x%llx at addr:0x%llx map_count:%d offset:0x%llx target:0x%llx\n",
                        feature_data[i], virt_addr, map_count, offset, target);
                }
                if (low32 == feature_data[i]){
                    printf("found feature_data:0x%llx at addr:0x%llx map_count:%d offset:0x%llx target:0x%llx\n",
                        feature_data[i], virt_addr, map_count, offset, target);
                }
            }
            offset+=8;
            target+=8;
            if(munmap(map_base, MAP_SIZE) == -1) FATAL;
        }
    }

    virt_addr = map_base + (target & MAP_MASK) + offset;
    read_result = *((unsigned long *) virt_addr);
    printf("Value at address 0x%X (%p): 0x%X\n", target, virt_addr, read_result); 
    fflush(stdout);
	
    close(fd);
    return 0;
}