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 //config:config DEVMEM
   7 //config:       bool "devmem"
   8 //config:       default y
   9 //config:       help
  10 //config:         devmem is a small program that reads and writes from physical
  11 //config:         memory using /dev/mem.
  12
  13 //applet:IF_DEVMEM(APPLET(devmem, BB_DIR_SBIN, BB_SUID_DROP))
  14
  15 //kbuild:lib-$(CONFIG_DEVMEM) += devmem.o
  16
  17 //usage:#define devmem_trivial_usage
  18 //usage:        "ADDRESS [WIDTH [VALUE]]"
  19 //usage:#define devmem_full_usage "\n\n"
  20 //usage:       "Read/write from physical address\n"
  21 //usage:     "\n        ADDRESS Address to act upon"
  22 //usage:     "\n        WIDTH   Width (8/16/...)"
  23 //usage:     "\n        VALUE   Data to be written"
  24
  25 #include "libbb.h"
  26
  27 int devmem_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  28 int devmem_main(int argc UNUSED_PARAM, char **argv)
  29 {
  30         void *map_base, *virt_addr;
  31         uint64_t read_result;
  32         uint64_t writeval = writeval; /* for compiler */
  33         off_t target;
  34         unsigned page_size, mapped_size, offset_in_page;
  35         int fd;
  36         unsigned width = 8 * sizeof(int);
  37
  38         /* devmem ADDRESS [WIDTH [VALUE]] */
  39 // TODO: options?
  40 // -r: read and output only the value in hex, with 0x prefix
  41 // -w: write only, no reads before or after, and no output
  42 // or make this behavior default?
  43 // Let's try this and see how users react.
  44
  45         /* ADDRESS */
  46         if (!argv[1])
  47                 bb_show_usage();
  48         errno = 0;
  49         target = bb_strtoull(argv[1], NULL, 0); /* allows hex, oct etc */
  50
  51         /* WIDTH */
  52         if (argv[2]) {
  53                 if (isdigit(argv[2][0]) || argv[2][1])
  54                         width = xatou(argv[2]);
  55                 else {
  56                         static const char bhwl[] ALIGN1 = "bhwl";
  57                         static const uint8_t sizes[] ALIGN1 = {
  58                                 8 * sizeof(char),
  59                                 8 * sizeof(short),
  60                                 8 * sizeof(int),
  61                                 8 * sizeof(long),
  62                                 0 /* bad */
  63                         };
  64                         width = strchrnul(bhwl, (argv[2][0] | 0x20)) - bhwl;
  65                         width = sizes[width];
  66                 }
  67                 /* VALUE */
  68                 if (argv[3])
  69                         writeval = bb_strtoull(argv[3], NULL, 0);
  70         } else { /* argv[2] == NULL */
  71                 /* make argv[3] to be a valid thing to fetch */
  72                 argv--;
  73         }
  74         if (errno)
  75                 bb_show_usage(); /* one of bb_strtouXX failed */
  76
  77         fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));
  78         mapped_size = page_size = getpagesize();
  79         offset_in_page = (unsigned)target & (page_size - 1);
  80         if (offset_in_page + width > page_size) {
  81                 /* This access spans pages.
  82                  * Must map two pages to make it possible: */
  83                 mapped_size *= 2;
  84         }
  85         map_base = mmap(NULL,
  86                         mapped_size,
  87                         argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
  88                         MAP_SHARED,
  89                         fd,
  90                         target & ~(off_t)(page_size - 1));
  91         if (map_base == MAP_FAILED)
  92                 bb_perror_msg_and_die("mmap");
  93
  94 //      printf("Memory mapped at address %p.\n", map_base);
  95
  96         virt_addr = (char*)map_base + offset_in_page;
  97
  98         if (!argv[3]) {
  99                 switch (width) {
 100                 case 8:
 101                         read_result = *(volatile uint8_t*)virt_addr;
 102                         break;
 103                 case 16:
 104                         read_result = *(volatile uint16_t*)virt_addr;
 105                         break;
 106                 case 32:
 107                         read_result = *(volatile uint32_t*)virt_addr;
 108                         break;
 109                 case 64:
 110                         read_result = *(volatile uint64_t*)virt_addr;
 111                         break;
 112                 default:
 113                         bb_error_msg_and_die("bad width");
 114                 }
 115 //              printf("Value at address 0x%"OFF_FMT"X (%p): 0x%llX\n",
 116 //                      target, virt_addr,
 117 //                      (unsigned long long)read_result);
 118                 /* Zero-padded output shows the width of access just done */
 119                 printf("0x%0*llX\n", (width >> 2), (unsigned long long)read_result);
 120         } else {
 121                 switch (width) {
 122                 case 8:
 123                         *(volatile uint8_t*)virt_addr = writeval;
 124 //                      read_result = *(volatile uint8_t*)virt_addr;
 125                         break;
 126                 case 16:
 127                         *(volatile uint16_t*)virt_addr = writeval;
 128 //                      read_result = *(volatile uint16_t*)virt_addr;
 129                         break;
 130                 case 32:
 131                         *(volatile uint32_t*)virt_addr = writeval;
 132 //                      read_result = *(volatile uint32_t*)virt_addr;
 133                         break;
 134                 case 64:
 135                         *(volatile uint64_t*)virt_addr = writeval;
 136 //                      read_result = *(volatile uint64_t*)virt_addr;
 137                         break;
 138                 default:
 139                         bb_error_msg_and_die("bad width");
 140                 }
 141 //              printf("Written 0x%llX; readback 0x%llX\n",
 142 //                              (unsigned long long)writeval,
 143 //                              (unsigned long long)read_result);
 144         }
 145
 146         if (ENABLE_FEATURE_CLEAN_UP) {
 147                 if (munmap(map_base, mapped_size) == -1)
 148                         bb_perror_msg_and_die("munmap");
 149                 close(fd);
 150         }
 151
 152         return EXIT_SUCCESS;
 153 }