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 via /dev/mem. 14 15 WIDTH is 1, 2, 4, or 8 bytes (default 4). 16 */ 17 18 #define FOR_devmem 19 #include "toys.h" 20 21 void devmem_main(void) 22 { 23 int writing = toys.optc == 3, page_size = getpagesize(), bytes = 4, fd; 24 unsigned long long addr = atolx(toys.optargs[0]), data = 0, map_off, map_len; 25 void *map, *p; 26 27 // WIDTH? 28 if (toys.optc>1) { 29 int i; 30 31 if (strlen(toys.optargs[1])!=1 || (i=stridx("1248", *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 fd = xopen("/dev/mem", (writing ? O_RDWR : O_RDONLY) | O_SYNC); 41 map_off = addr & ~(page_size - 1); 42 map_len = (addr+bytes-map_off); 43 map = xmmap(NULL, map_len, writing ? PROT_WRITE : PROT_READ, MAP_SHARED, fd, 44 map_off); 45 p = map + (addr & (page_size - 1)); 46 close(fd); 47 48 // Not using peek()/poke() because registers care about size of read/write 49 if (writing) { 50 if (bytes == 1) *(char *)p = data; 51 else if (bytes == 2) *(short *)p = data; 52 else if (bytes == 4) *(int *)p = data; 53 else if (bytes == 8) *(long long *)p = data; 54 } else { 55 if (bytes == 1) data = *(char *)p; 56 else if (bytes == 2) data = *(short *)p; 57 else if (bytes == 4) data = *(int *)p; 58 else if (bytes == 8) data = *(long long *)p; 59 printf("%#0*llx\n", bytes*2, data); 60 } 61 62 munmap(map, map_len); 63 } 64
