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        off_t target;
  33        unsigned page_size, mapped_size, offset_in_page;
  34        int fd;
  35        unsigned width = 8 * sizeof(int);
  36
  37        /* devmem ADDRESS [WIDTH [VALUE]] */
  38// TODO: options?
  39// -r: read and output only the value in hex, with 0x prefix
  40// -w: write only, no reads before or after, and no output
  41// or make this behavior default?
  42// Let's try this and see how users react.
  43
  44        /* ADDRESS */
  45        if (!argv[1])
  46                bb_show_usage();
  47        errno = 0;
  48        target = bb_strtoull(argv[1], NULL, 0); /* allows hex, oct etc */
  49
  50        /* WIDTH */
  51        if (argv[2]) {
  52                if (isdigit(argv[2][0]) || argv[2][1])
  53                        width = xatou(argv[2]);
  54                else {
  55                        static const char bhwl[] ALIGN1 = "bhwl";
  56                        static const uint8_t sizes[] ALIGN1 = {
  57                                8 * sizeof(char),
  58                                8 * sizeof(short),
  59                                8 * sizeof(int),
  60                                8 * sizeof(long),
  61                                0 /* bad */
  62                        };
  63                        width = strchrnul(bhwl, (argv[2][0] | 0x20)) - bhwl;
  64                        width = sizes[width];
  65                }
  66        } else { /* argv[2] == NULL */
  67                /* make argv[3] to be a valid thing to fetch */
  68                argv--;
  69        }
  70        if (errno)
  71                bb_show_usage(); /* one of bb_strtouXX failed */
  72
  73        fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));
  74        mapped_size = page_size = bb_getpagesize();
  75        offset_in_page = (unsigned)target & (page_size - 1);
  76        if (offset_in_page + width > page_size) {
  77                /* This access spans pages.
  78                 * Must map two pages to make it possible: */
  79                mapped_size *= 2;
  80        }
  81        map_base = mmap(NULL,
  82                        mapped_size,
  83                        argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
  84                        MAP_SHARED,
  85                        fd,
  86                        target & ~(off_t)(page_size - 1));
  87        if (map_base == MAP_FAILED)
  88                bb_simple_perror_msg_and_die("mmap");
  89
  90//      printf("Memory mapped at address %p.\n", map_base);
  91
  92        virt_addr = (char*)map_base + offset_in_page;
  93
  94        if (!argv[3]) {
  95#ifdef __SIZEOF_INT128__
  96                if (width == 128) {
  97                        unsigned __int128 rd =
  98                                *(volatile unsigned __int128 *)virt_addr;
  99                        printf("0x%016llX%016llX\n",
 100                                (unsigned long long)(uint64_t)(rd >> 64),
 101                                (unsigned long long)(uint64_t)rd
 102                        );
 103                } else
 104#endif
 105                {
 106                        switch (width) {
 107                        case 8:
 108                                read_result = *(volatile uint8_t*)virt_addr;
 109                                break;
 110                        case 16:
 111                                read_result = *(volatile uint16_t*)virt_addr;
 112                                break;
 113                        case 32:
 114                                read_result = *(volatile uint32_t*)virt_addr;
 115                                break;
 116                        case 64:
 117                                read_result = *(volatile uint64_t*)virt_addr;
 118                                break;
 119                        default:
 120                                bb_simple_error_msg_and_die("bad width");
 121                        }
 122//                      printf("Value at address 0x%"OFF_FMT"X (%p): 0x%llX\n",
 123//                              target, virt_addr,
 124//                              (unsigned long long)read_result);
 125                        /* Zero-padded output shows the width of access just done */
 126                        printf("0x%0*llX\n", (width >> 2), (unsigned long long)read_result);
 127                }
 128        } else {
 129                /* parse VALUE */
 130#ifdef __SIZEOF_INT128__
 131                unsigned __int128 writeval = strtoumax(argv[3], NULL, 0);
 132#else
 133                uint64_t writeval = bb_strtoull(argv[3], NULL, 0);
 134#endif
 135                switch (width) {
 136                case 8:
 137                        *(volatile uint8_t*)virt_addr = writeval;
 138//                      read_result = *(volatile uint8_t*)virt_addr;
 139                        break;
 140                case 16:
 141                        *(volatile uint16_t*)virt_addr = writeval;
 142//                      read_result = *(volatile uint16_t*)virt_addr;
 143                        break;
 144                case 32:
 145                        *(volatile uint32_t*)virt_addr = writeval;
 146//                      read_result = *(volatile uint32_t*)virt_addr;
 147                        break;
 148                case 64:
 149                        *(volatile uint64_t*)virt_addr = writeval;
 150//                      read_result = *(volatile uint64_t*)virt_addr;
 151                        break;
 152#ifdef __SIZEOF_INT128__
 153                case 128:
 154                        *(volatile unsigned __int128 *)virt_addr = writeval;
 155//                      read_result = *(volatile uint64_t*)virt_addr;
 156                        break;
 157#endif
 158                default:
 159                        bb_simple_error_msg_and_die("bad width");
 160                }
 161//              printf("Written 0x%llX; readback 0x%llX\n",
 162//                              (unsigned long long)writeval,
 163//                              (unsigned long long)read_result);
 164        }
 165
 166        if (ENABLE_FEATURE_CLEAN_UP) {
 167                if (munmap(map_base, mapped_size) == -1)
 168                        bb_simple_perror_msg_and_die("munmap");
 169                close(fd);
 170        }
 171
 172        return EXIT_SUCCESS;
 173}
 174