1#include <fcntl.h>
2#include <inttypes.h>
3#include <stdbool.h>
4#include <stdio.h>
5#include <stdlib.h>
6#include <string.h>
7#include <sys/mman.h>
8#include <unistd.h>
9
10#if __LP64__
11#define strtoptr strtoull
12#else
13#define strtoptr strtoul
14#endif
15
16static int usage()
17{
18    fprintf(stderr,"r [-b|-s] <address> [<value>]\n");
19    return -1;
20}
21
22int main(int argc, char *argv[])
23{
24    if(argc < 2) return usage();
25
26    int width = 4;
27    if(!strcmp(argv[1], "-b")) {
28        width = 1;
29        argc--;
30        argv++;
31    } else if(!strcmp(argv[1], "-s")) {
32        width = 2;
33        argc--;
34        argv++;
35    }
36
37    if(argc < 2) return usage();
38    uintptr_t addr = strtoptr(argv[1], 0, 16);
39
40    uintptr_t endaddr = 0;
41    char* end = strchr(argv[1], '-');
42    if (end)
43        endaddr = strtoptr(end + 1, 0, 16);
44
45    if (!endaddr)
46        endaddr = addr + width - 1;
47
48    if (endaddr <= addr) {
49        fprintf(stderr, "end address <= start address\n");
50        return -1;
51    }
52
53    bool set = false;
54    uint32_t value = 0;
55    if(argc > 2) {
56        set = true;
57        value = strtoul(argv[2], 0, 16);
58    }
59
60    int fd = open("/dev/mem", O_RDWR | O_SYNC);
61    if(fd < 0) {
62        fprintf(stderr,"cannot open /dev/mem\n");
63        return -1;
64    }
65
66    off64_t mmap_start = addr & ~(PAGE_SIZE - 1);
67    size_t mmap_size = endaddr - mmap_start + 1;
68    mmap_size = (mmap_size + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1);
69
70    void* page = mmap64(0, mmap_size, PROT_READ | PROT_WRITE,
71                        MAP_SHARED, fd, mmap_start);
72
73    if(page == MAP_FAILED){
74        fprintf(stderr,"cannot mmap region\n");
75        return -1;
76    }
77
78    while (addr <= endaddr) {
79        switch(width){
80        case 4: {
81            uint32_t* x = (uint32_t*) (((uintptr_t) page) + (addr & 4095));
82            if(set) *x = value;
83            fprintf(stderr,"%08"PRIxPTR": %08x\n", addr, *x);
84            break;
85        }
86        case 2: {
87            uint16_t* x = (uint16_t*) (((uintptr_t) page) + (addr & 4095));
88            if(set) *x = value;
89            fprintf(stderr,"%08"PRIxPTR": %04x\n", addr, *x);
90            break;
91        }
92        case 1: {
93            uint8_t* x = (uint8_t*) (((uintptr_t) page) + (addr & 4095));
94            if(set) *x = value;
95            fprintf(stderr,"%08"PRIxPTR": %02x\n", addr, *x);
96            break;
97        }
98        }
99        addr += width;
100    }
101    return 0;
102}
103