LXR busybox/miscutils/devmem.c

   1/*
   2 * Copyright (C) 2000, Jan-Derk Bakker (J.D.Bakker@its.tudelft.nl)
   3 * Copyright (C) 2008, BusyBox Team. -solar 4/26/08
   4 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   5 */
   6//config:config DEVMEM
   7//config:       bool "devmem (2.5 kb)"
   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
  27int devmem_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  28int 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}
 154