1 /* devmem.c - Access physical addresses
2 *
3 * Copyright 2019 The Android Open Source Project
4
5 USE_DEVMEM(NEWTOY(devmem, "<1>3", TOYFLAG_USR|TOYFLAG_BIN))
6
7 config DEVMEM
8 bool "devmem"
9 default y
10 help
11 usage: devmem ADDR [WIDTH [DATA]]
12
13 Read/write physical address. WIDTH is 1, 2, 4, or 8 bytes (default 4).
14 Prefix ADDR with 0x for hexadecimal, output is in same base as address.
15 */
16
17 #define FOR_devmem
18 #include "toys.h"
19
devmem_main(void)20 void devmem_main(void)
21 {
22 int writing = toys.optc == 3, page_size = sysconf(_SC_PAGESIZE), bytes = 4,fd;
23 unsigned long long data = 0, map_off, map_len;
24 unsigned long addr = atolx(*toys.optargs);
25 void *map, *p;
26
27 // WIDTH?
28 if (toys.optc>1) {
29 int i;
30
31 if ((i=stridx("1248", *toys.optargs[1]))==-1 || toys.optargs[1][1])
32 error_exit("bad width: %s", toys.optargs[1]);
33 bytes = 1<<i;
34 }
35
36 // DATA? Report out of range values as errors rather than truncating.
37 if (writing) data = atolx_range(toys.optargs[2], 0, (1ULL<<(8*bytes))-1);
38
39 // Map in just enough.
40 if (CFG_TOYBOX_FORK) {
41 fd = xopen("/dev/mem", (writing ? O_RDWR : O_RDONLY) | O_SYNC);
42
43 map_off = addr & ~(page_size - 1);
44 map_len = (addr+bytes-map_off);
45 map = xmmap(0, map_len, writing ? PROT_WRITE : PROT_READ, MAP_SHARED, fd,
46 map_off);
47 p = map + (addr & (page_size - 1));
48 close(fd);
49 } else p = (void *)addr;
50
51 // Not using peek()/poke() because registers care about size of read/write
52 if (writing) {
53 if (bytes == 1) *(unsigned char *)p = data;
54 else if (bytes == 2) *(unsigned short *)p = data;
55 else if (bytes == 4) *(unsigned int *)p = data;
56 else if (bytes == 8) *(unsigned long long *)p = data;
57 } else {
58 if (bytes == 1) data = *(unsigned char *)p;
59 else if (bytes == 2) data = *(unsigned short *)p;
60 else if (bytes == 4) data = *(unsigned int *)p;
61 else if (bytes == 8) data = *(unsigned long long *)p;
62 printf((!strchr(*toys.optargs, 'x')) ? "%0*lld\n" : "0x%0*llx\n",
63 bytes*2, data);
64 }
65
66 if (CFG_TOYBOX_FORK) munmap(map, map_len);
67 }
68