LXR toybox/toys/other/devmem.c

   1/* devmem.c - Access physical addresses
   2 *
   3 * Copyright 2019 The Android Open Source Project
   4
   5USE_DEVMEM(NEWTOY(devmem, "<1>3", TOYFLAG_USR|TOYFLAG_BIN))
   6
   7config 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
  21void 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