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 //usage:#define devmem_trivial_usage
   8 //usage:        "ADDRESS [WIDTH [VALUE]]"
   9 //usage:#define devmem_full_usage "\n\n"
  10 //usage:       "Read/write from physical address\n"
  11 //usage:     "\n        ADDRESS Address to act upon"
  12 //usage:     "\n        WIDTH   Width (8/16/...)"
  13 //usage:     "\n        VALUE   Data to be written"
  14
  15 #include "libbb.h"
  16
  17 int devmem_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  18 int devmem_main(int argc UNUSED_PARAM, char **argv)
  19 {
  20         void *map_base, *virt_addr;
  21         uint64_t read_result;
  22         uint64_t writeval = writeval; /* for compiler */
  23         off_t target;
  24         unsigned page_size, mapped_size, offset_in_page;
  25         int fd;
  26         unsigned width = 8 * sizeof(int);
  27
  28         /* devmem ADDRESS [WIDTH [VALUE]] */
  29 // TODO: options?
  30 // -r: read and output only the value in hex, with 0x prefix
  31 // -w: write only, no reads before or after, and no output
  32 // or make this behavior default?
  33 // Let's try this and see how users react.
  34
  35         /* ADDRESS */
  36         if (!argv[1])
  37                 bb_show_usage();
  38         errno = 0;
  39         target = bb_strtoull(argv[1], NULL, 0); /* allows hex, oct etc */
  40
  41         /* WIDTH */
  42         if (argv[2]) {
  43                 if (isdigit(argv[2][0]) || argv[2][1])
  44                         width = xatou(argv[2]);
  45                 else {
  46                         static const char bhwl[] ALIGN1 = "bhwl";
  47                         static const uint8_t sizes[] ALIGN1 = {
  48                                 8 * sizeof(char),
  49                                 8 * sizeof(short),
  50                                 8 * sizeof(int),
  51                                 8 * sizeof(long),
  52                                 0 /* bad */
  53                         };
  54                         width = strchrnul(bhwl, (argv[2][0] | 0x20)) - bhwl;
  55                         width = sizes[width];
  56                 }
  57                 /* VALUE */
  58                 if (argv[3])
  59                         writeval = bb_strtoull(argv[3], NULL, 0);
  60         } else { /* argv[2] == NULL */
  61                 /* make argv[3] to be a valid thing to fetch */
  62                 argv--;
  63         }
  64         if (errno)
  65                 bb_show_usage(); /* one of bb_strtouXX failed */
  66
  67         fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));
  68         mapped_size = page_size = getpagesize();
  69         offset_in_page = (unsigned)target & (page_size - 1);
  70         if (offset_in_page + width > page_size) {
  71                 /* This access spans pages.
  72                  * Must map two pages to make it possible: */
  73                 mapped_size *= 2;
  74         }
  75         map_base = mmap(NULL,
  76                         mapped_size,
  77                         argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
  78                         MAP_SHARED,
  79                         fd,
  80                         target & ~(off_t)(page_size - 1));
  81         if (map_base == MAP_FAILED)
  82                 bb_perror_msg_and_die("mmap");
  83
  84 //      printf("Memory mapped at address %p.\n", map_base);
  85
  86         virt_addr = (char*)map_base + offset_in_page;
  87
  88         if (!argv[3]) {
  89                 switch (width) {
  90                 case 8:
  91                         read_result = *(volatile uint8_t*)virt_addr;
  92                         break;
  93                 case 16:
  94                         read_result = *(volatile uint16_t*)virt_addr;
  95                         break;
  96                 case 32:
  97                         read_result = *(volatile uint32_t*)virt_addr;
  98                         break;
  99                 case 64:
 100                         read_result = *(volatile uint64_t*)virt_addr;
 101                         break;
 102                 default:
 103                         bb_error_msg_and_die("bad width");
 104                 }
 105 //              printf("Value at address 0x%"OFF_FMT"X (%p): 0x%llX\n",
 106 //                      target, virt_addr,
 107 //                      (unsigned long long)read_result);
 108                 /* Zero-padded output shows the width of access just done */
 109                 printf("0x%0*llX\n", (width >> 2), (unsigned long long)read_result);
 110         } else {
 111                 switch (width) {
 112                 case 8:
 113                         *(volatile uint8_t*)virt_addr = writeval;
 114 //                      read_result = *(volatile uint8_t*)virt_addr;
 115                         break;
 116                 case 16:
 117                         *(volatile uint16_t*)virt_addr = writeval;
 118 //                      read_result = *(volatile uint16_t*)virt_addr;
 119                         break;
 120                 case 32:
 121                         *(volatile uint32_t*)virt_addr = writeval;
 122 //                      read_result = *(volatile uint32_t*)virt_addr;
 123                         break;
 124                 case 64:
 125                         *(volatile uint64_t*)virt_addr = writeval;
 126 //                      read_result = *(volatile uint64_t*)virt_addr;
 127                         break;
 128                 default:
 129                         bb_error_msg_and_die("bad width");
 130                 }
 131 //              printf("Written 0x%llX; readback 0x%llX\n",
 132 //                              (unsigned long long)writeval,
 133 //                              (unsigned long long)read_result);
 134         }
 135
 136         if (ENABLE_FEATURE_CLEAN_UP) {
 137                 if (munmap(map_base, mapped_size) == -1)
 138                         bb_perror_msg_and_die("munmap");
 139                 close(fd);
 140         }
 141
 142         return EXIT_SUCCESS;
 143 }