miscutils/devmem.c

   1 /*
   2  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   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, mapped_size, offset_in_page;
  17         int fd;
  18         unsigned 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 fetch */
  54                 argv--;
  55         }
  56         if (errno)
  57                 bb_show_usage(); /* one of bb_strtouXX failed */
  58
  59         fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));
  60         mapped_size = page_size = getpagesize();
  61         offset_in_page = (unsigned)target & (page_size - 1);
  62         if (offset_in_page + width > page_size) {
  63                 /* This access spans pages.
  64                  * Must map two pages to make it possible: */
  65                 mapped_size *= 2;
  66         }
  67         map_base = mmap(NULL,
  68                         mapped_size,
  69                         argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
  70                         MAP_SHARED,
  71                         fd,
  72                         target & ~(off_t)(page_size - 1));
  73         if (map_base == MAP_FAILED)
  74                 bb_perror_msg_and_die("mmap");
  75
  76 //      printf("Memory mapped at address %p.\n", map_base);
  77
  78         virt_addr = (char*)map_base + offset_in_page;
  79
  80         if (!argv[3]) {
  81                 switch (width) {
  82                 case 8:
  83                         read_result = *(volatile uint8_t*)virt_addr;
  84                         break;
  85                 case 16:
  86                         read_result = *(volatile uint16_t*)virt_addr;
  87                         break;
  88                 case 32:
  89                         read_result = *(volatile uint32_t*)virt_addr;
  90                         break;
  91                 case 64:
  92                         read_result = *(volatile uint64_t*)virt_addr;
  93                         break;
  94                 default:
  95                         bb_error_msg_and_die("bad width");
  96                 }
  97 //              printf("Value at address 0x%"OFF_FMT"X (%p): 0x%llX\n",
  98 //                      target, virt_addr,
  99 //                      (unsigned long long)read_result);
 100                 /* Zero-padded output shows the width of access just done */
 101                 printf("0x%0*llX\n", (width >> 2), (unsigned long long)read_result);
 102         } else {
 103                 switch (width) {
 104                 case 8:
 105                         *(volatile uint8_t*)virt_addr = writeval;
 106 //                      read_result = *(volatile uint8_t*)virt_addr;
 107                         break;
 108                 case 16:
 109                         *(volatile uint16_t*)virt_addr = writeval;
 110 //                      read_result = *(volatile uint16_t*)virt_addr;
 111                         break;
 112                 case 32:
 113                         *(volatile uint32_t*)virt_addr = writeval;
 114 //                      read_result = *(volatile uint32_t*)virt_addr;
 115                         break;
 116                 case 64:
 117                         *(volatile uint64_t*)virt_addr = writeval;
 118 //                      read_result = *(volatile uint64_t*)virt_addr;
 119                         break;
 120                 default:
 121                         bb_error_msg_and_die("bad width");
 122                 }
 123 //              printf("Written 0x%llX; readback 0x%llX\n",
 124 //                              (unsigned long long)writeval,
 125 //                              (unsigned long long)read_result);
 126         }
 127
 128         if (ENABLE_FEATURE_CLEAN_UP) {
 129                 if (munmap(map_base, mapped_size) == -1)
 130                         bb_perror_msg_and_die("munmap");
 131                 close(fd);
 132         }
 133
 134         return EXIT_SUCCESS;
 135 }