1 | /*
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2 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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3 | * Copyright (C) 2000, Jan-Derk Bakker (J.D.Bakker@its.tudelft.nl)
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4 | * Copyright (C) 2008, BusyBox Team. -solar 4/26/08
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5 | */
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6 |
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7 | #include "libbb.h"
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8 |
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9 | int devmem_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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10 | int devmem_main(int argc UNUSED_PARAM, char **argv)
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11 | {
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12 | void *map_base, *virt_addr;
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13 | uint64_t read_result;
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14 | uint64_t writeval = writeval; /* for compiler */
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15 | off_t target;
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16 | unsigned page_size, mapped_size, offset_in_page;
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17 | int fd;
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18 | unsigned width = 8 * sizeof(int);
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19 |
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20 | /* devmem ADDRESS [WIDTH [VALUE]] */
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21 | // TODO: options?
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22 | // -r: read and output only the value in hex, with 0x prefix
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23 | // -w: write only, no reads before or after, and no output
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24 | // or make this behavior default?
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25 | // Let's try this and see how users react.
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26 |
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27 | /* ADDRESS */
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28 | if (!argv[1])
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29 | bb_show_usage();
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30 | errno = 0;
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31 | target = bb_strtoull(argv[1], NULL, 0); /* allows hex, oct etc */
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32 |
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33 | /* WIDTH */
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34 | if (argv[2]) {
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35 | if (isdigit(argv[2][0]) || argv[2][1])
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36 | width = xatou(argv[2]);
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37 | else {
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38 | static const char bhwl[] ALIGN1 = "bhwl";
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39 | static const uint8_t sizes[] ALIGN1 = {
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40 | 8 * sizeof(char),
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41 | 8 * sizeof(short),
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42 | 8 * sizeof(int),
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43 | 8 * sizeof(long),
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44 | 0 /* bad */
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45 | };
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46 | width = strchrnul(bhwl, (argv[2][0] | 0x20)) - bhwl;
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47 | width = sizes[width];
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48 | }
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49 | /* VALUE */
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50 | if (argv[3])
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51 | writeval = bb_strtoull(argv[3], NULL, 0);
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52 | } else { /* argv[2] == NULL */
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53 | /* make argv[3] to be a valid thing to fetch */
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54 | argv--;
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55 | }
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56 | if (errno)
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57 | bb_show_usage(); /* one of bb_strtouXX failed */
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58 |
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59 | fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));
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60 | mapped_size = page_size = getpagesize();
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61 | offset_in_page = (unsigned)target & (page_size - 1);
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62 | if (offset_in_page + width > page_size) {
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63 | /* This access spans pages.
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64 | * Must map two pages to make it possible: */
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65 | mapped_size *= 2;
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66 | }
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67 | map_base = mmap(NULL,
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68 | mapped_size,
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69 | argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
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70 | MAP_SHARED,
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71 | fd,
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72 | target & ~(off_t)(page_size - 1));
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73 | if (map_base == MAP_FAILED)
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74 | bb_perror_msg_and_die("mmap");
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75 |
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76 | // printf("Memory mapped at address %p.\n", map_base);
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77 |
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78 | virt_addr = (char*)map_base + offset_in_page;
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79 |
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80 | if (!argv[3]) {
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81 | switch (width) {
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82 | case 8:
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83 | read_result = *(volatile uint8_t*)virt_addr;
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84 | break;
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85 | case 16:
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86 | read_result = *(volatile uint16_t*)virt_addr;
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87 | break;
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88 | case 32:
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89 | read_result = *(volatile uint32_t*)virt_addr;
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90 | break;
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91 | case 64:
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92 | read_result = *(volatile uint64_t*)virt_addr;
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93 | break;
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94 | default:
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95 | bb_error_msg_and_die("bad width");
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96 | }
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97 | // printf("Value at address 0x%"OFF_FMT"X (%p): 0x%llX\n",
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98 | // target, virt_addr,
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99 | // (unsigned long long)read_result);
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100 | /* Zero-padded output shows the width of access just done */
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101 | printf("0x%0*llX\n", (width >> 2), (unsigned long long)read_result);
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102 | } else {
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103 | switch (width) {
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104 | case 8:
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105 | *(volatile uint8_t*)virt_addr = writeval;
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106 | // read_result = *(volatile uint8_t*)virt_addr;
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107 | break;
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108 | case 16:
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109 | *(volatile uint16_t*)virt_addr = writeval;
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110 | // read_result = *(volatile uint16_t*)virt_addr;
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111 | break;
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112 | case 32:
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113 | *(volatile uint32_t*)virt_addr = writeval;
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114 | // read_result = *(volatile uint32_t*)virt_addr;
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115 | break;
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116 | case 64:
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117 | *(volatile uint64_t*)virt_addr = writeval;
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118 | // read_result = *(volatile uint64_t*)virt_addr;
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119 | break;
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120 | default:
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121 | bb_error_msg_and_die("bad width");
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122 | }
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123 | // printf("Written 0x%llX; readback 0x%llX\n",
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124 | // (unsigned long long)writeval,
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125 | // (unsigned long long)read_result);
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126 | }
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127 |
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128 | if (ENABLE_FEATURE_CLEAN_UP) {
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129 | if (munmap(map_base, mapped_size) == -1)
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130 | bb_perror_msg_and_die("munmap");
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131 | close(fd);
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132 | }
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133 |
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134 | return EXIT_SUCCESS;
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135 | }
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