【linuxドライバ】組み込みLinuxによるメモリの直接読み書き(devmem)

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devmemツールソース

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define FATAL do { fprintf(stderr, "Error at line %d, file %s (%d) [%s]
", \
__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; unsigned long read_result, writeval; off_t target; int access_type = 'w'; if(argc < 2) { fprintf(stderr, "
Usage:\t%s { address } [ type [ data ] ]
"
"\taddress : memory address to act upon
"
"\ttype : access operation type : [b]yte, [h]alfword, [w]ord
"
"\tdata : data to be written

"
, argv[0]); exit(1); } target = strtoul(argv[1], 0, 0);// if(argc > 2) access_type = tolower(argv[2][0]);// if((fd = open("/dev/mem", O_RDWR | O_SYNC)) == -1) FATAL; printf("/dev/mem opened.
"
); fflush(stdout); /* Map one page */ // mmap map_base = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, target & ~MAP_MASK); if(map_base == (void *) -1) FATAL; printf("Memory mapped at address %p.
"
, map_base); fflush(stdout); virt_addr = map_base + (target & MAP_MASK); switch(access_type) { case 'b': read_result = *((unsigned char *) virt_addr); break; case 'h': read_result = *((unsigned short *) virt_addr); break; case 'w': read_result = *((unsigned long *) virt_addr); break; default: fprintf(stderr, "Illegal data type '%c'.
"
, access_type); exit(2); } printf("Value at address 0x%X (%p): 0x%X
"
, target, virt_addr, read_result); fflush(stdout); if(argc > 3) { writeval = strtoul(argv[3], 0, 0); switch(access_type) { case 'b': *((unsigned char *) virt_addr) = writeval; read_result = *((unsigned char *) virt_addr); break; case 'h': *((unsigned short *) virt_addr) = writeval; read_result = *((unsigned short *) virt_addr); break; case 'w': *((unsigned long *) virt_addr) = writeval; read_result = *((unsigned long *) virt_addr); break; } printf("Written 0x%X; readback 0x%X
"
, writeval, read_result); fflush(stdout); } if(munmap(map_base, MAP_SIZE) == -1) FATAL; close(fd); return 0; }

devmemの使用方法

root@myzr:~# ./devmem
Usage:  ./devmem { address } [ type [ data ] ]
    address : memory address to act upon
    type    : access operation type : [b]yte, [h]alfword, [w]ord
    data    : data to be written

レジスタアドレスの表示

root@myzr:~# ./devmem  0x20e05e0
/dev/mem opened.
Memory mapped at address 0x76f99000.
Value at address 0x20E05E0 (0x76f995e0): 0x1B8B1

ライトレジスタ

root@myzr:~# ./devmem 0x209c000 b 1
/dev/mem opened.
Memory mapped at address 0x76f25000.
Value at address 0x209C000 (0x76f25000): 0x5C
Written 0x1; readback 0x5C
root@myzr:~#