miscutils/devmem.c

   1 /*
   2  * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
   3  *  Copyright (C) 2000, Jan-Derk Bakker (J.D.Bakker@its.tudelft.nl)
   4  *  Copyright (C) 2008, BusyBox Team. -solar 4/26/08
   5  */
   6
   7 #include "libbb.h"
   8
   9 int devmem_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  10 int devmem_main(int argc UNUSED_PARAM, char **argv)
  11 {
  12         void *map_base, *virt_addr;
  13         uint64_t read_result;
  14         uint64_t writeval = writeval; /* for compiler */
  15         off_t target;
  16         unsigned page_size = getpagesize();
  17         int fd;
  18         int width = 8 * sizeof(int);
  19
  20         /* devmem ADDRESS [WIDTH [VALUE]] */
  21 // TODO: options?
  22 // -r: read and output only the value in hex, with 0x prefix
  23 // -w: write only, no reads before or after, and no output
  24 // or make this behavior default?
  25 // Let's try this and see how users react.
  26
  27         /* ADDRESS */
  28         if (!argv[1])
  29                 bb_show_usage();
  30         errno = 0;
  31         target = bb_strtoull(argv[1], NULL, 0); /* allows hex, oct etc */
  32
  33         /* WIDTH */
  34         if (argv[2]) {
  35                 if (isdigit(argv[2][0]) || argv[2][1])
  36                         width = xatou(argv[2]);
  37                 else {
  38                         static const char bhwl[] ALIGN1 = "bhwl";
  39                         static const uint8_t sizes[] ALIGN1 = {
  40                                 8 * sizeof(char),
  41                                 8 * sizeof(short),
  42                                 8 * sizeof(int),
  43                                 8 * sizeof(long),
  44                                 0 /* bad */
  45                         };
  46                         width = strchrnul(bhwl, (argv[2][0] | 0x20)) - bhwl;
  47                         width = sizes[width];
  48                 }
  49                 /* VALUE */
  50                 if (argv[3])
  51                         writeval = bb_strtoull(argv[3], NULL, 0);
  52         } else { /* argv[2] == NULL */
  53                 /* make argv[3] to be a valid thing to use */
  54                 argv--;
  55         }
  56         if (errno)
  57                 bb_show_usage(); /* bb_strtouXX failed */
  58
  59         fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));
  60         map_base = mmap(NULL,
  61                         page_size * 2 /* in case value spans page */,
  62                         argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
  63                         MAP_SHARED,
  64                         fd,
  65                         target & ~(off_t)(page_size - 1));
  66         if (map_base == MAP_FAILED)
  67                 bb_perror_msg_and_die("mmap");
  68
  69 //      printf("Memory mapped at address %p.\n", map_base);
  70
  71         virt_addr = (char*)map_base + (target & (page_size - 1));
  72
  73         if (!argv[3]) {
  74                 switch (width) {
  75                 case 8:
  76                         read_result = *(volatile uint8_t*)virt_addr;
  77                         break;
  78                 case 16:
  79                         read_result = *(volatile uint16_t*)virt_addr;
  80                         break;
  81                 case 32:
  82                         read_result = *(volatile uint32_t*)virt_addr;
  83                         break;
  84                 case 64:
  85                         read_result = *(volatile uint64_t*)virt_addr;
  86                         break;
  87                 default:
  88                         bb_error_msg_and_die("bad width");
  89                 }
  90 //              printf("Value at address 0x%"OFF_FMT"X (%p): 0x%llX\n",
  91 //                      target, virt_addr,
  92 //                      (unsigned long long)read_result);
  93                 /* Zero-padded output shows the width of access just done */
  94                 printf("0x%0*llX\n", (width >> 2), (unsigned long long)read_result);
  95         } else {
  96                 switch (width) {
  97                 case 8:
  98                         *(volatile uint8_t*)virt_addr = writeval;
  99 //                      read_result = *(volatile uint8_t*)virt_addr;
 100                         break;
 101                 case 16:
 102                         *(volatile uint16_t*)virt_addr = writeval;
 103 //                      read_result = *(volatile uint16_t*)virt_addr;
 104                         break;
 105                 case 32:
 106                         *(volatile uint32_t*)virt_addr = writeval;
 107 //                      read_result = *(volatile uint32_t*)virt_addr;
 108                         break;
 109                 case 64:
 110                         *(volatile uint64_t*)virt_addr = writeval;
 111 //                      read_result = *(volatile uint64_t*)virt_addr;
 112                         break;
 113                 default:
 114                         bb_error_msg_and_die("bad width");
 115                 }
 116 //              printf("Written 0x%llX; readback 0x%llX\n",
 117 //                              (unsigned long long)writeval,
 118 //                              (unsigned long long)read_result);
 119         }
 120
 121         if (ENABLE_FEATURE_CLEAN_UP) {
 122                 if (munmap(map_base, page_size * 2) == -1)
 123                         bb_perror_msg_and_die("munmap");
 124                 close(fd);
 125         }
 126
 127         return EXIT_SUCCESS;
 128 }