source: MondoRescue/branches/2.2.9/mindi-busybox/miscutils/devmem.c@ 2725

/*
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 *  Copyright (C) 2000, Jan-Derk Bakker (J.D.Bakker@its.tudelft.nl)
 *  Copyright (C) 2008, BusyBox Team. -solar 4/26/08
 */

#include "libbb.h"

int devmem_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int devmem_main(int argc UNUSED_PARAM, char **argv)
{
    void *map_base, *virt_addr;
    uint64_t read_result;
    uint64_t writeval = writeval; /* for compiler */
    off_t target;
    unsigned page_size, mapped_size, offset_in_page;
    int fd;
    unsigned width = 8 * sizeof(int);

    /* devmem ADDRESS [WIDTH [VALUE]] */
// TODO: options?
// -r: read and output only the value in hex, with 0x prefix
// -w: write only, no reads before or after, and no output
// or make this behavior default?
// Let's try this and see how users react.

    /* ADDRESS */
    if (!argv[1])
        bb_show_usage();
    errno = 0;
    target = bb_strtoull(argv[1], NULL, 0); /* allows hex, oct etc */

    /* WIDTH */
    if (argv[2]) {
        if (isdigit(argv[2][0]) || argv[2][1])
            width = xatou(argv[2]);
        else {
            static const char bhwl[] ALIGN1 = "bhwl";
            static const uint8_t sizes[] ALIGN1 = {
                8 * sizeof(char),
                8 * sizeof(short),
                8 * sizeof(int),
                8 * sizeof(long),
                0 /* bad */
            };
            width = strchrnul(bhwl, (argv[2][0] | 0x20)) - bhwl;
            width = sizes[width];
        }
        /* VALUE */
        if (argv[3])
            writeval = bb_strtoull(argv[3], NULL, 0);
    } else { /* argv[2] == NULL */
        /* make argv[3] to be a valid thing to fetch */
        argv--;
    }
    if (errno)
        bb_show_usage(); /* one of bb_strtouXX failed */

    fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));
    mapped_size = page_size = getpagesize();
    offset_in_page = (unsigned)target & (page_size - 1);
    if (offset_in_page + width > page_size) {
        /* This access spans pages.
         * Must map two pages to make it possible: */
        mapped_size *= 2;
    }
    map_base = mmap(NULL,
            mapped_size,
            argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
            MAP_SHARED,
            fd,
            target & ~(off_t)(page_size - 1));
    if (map_base == MAP_FAILED)
        bb_perror_msg_and_die("mmap");

//  printf("Memory mapped at address %p.\n", map_base);

    virt_addr = (char*)map_base + offset_in_page;

    if (!argv[3]) {
        switch (width) {
        case 8:
            read_result = *(volatile uint8_t*)virt_addr;
            break;
        case 16:
            read_result = *(volatile uint16_t*)virt_addr;
            break;
        case 32:
            read_result = *(volatile uint32_t*)virt_addr;
            break;
        case 64:
            read_result = *(volatile uint64_t*)virt_addr;
            break;
        default:
            bb_error_msg_and_die("bad width");
        }
//      printf("Value at address 0x%"OFF_FMT"X (%p): 0x%llX\n",
//          target, virt_addr,
//          (unsigned long long)read_result);
        /* Zero-padded output shows the width of access just done */
        printf("0x%0*llX\n", (width >> 2), (unsigned long long)read_result);
    } else {
        switch (width) {
        case 8:
            *(volatile uint8_t*)virt_addr = writeval;
//          read_result = *(volatile uint8_t*)virt_addr;
            break;
        case 16:
            *(volatile uint16_t*)virt_addr = writeval;
//          read_result = *(volatile uint16_t*)virt_addr;
            break;
        case 32:
            *(volatile uint32_t*)virt_addr = writeval;
//          read_result = *(volatile uint32_t*)virt_addr;
            break;
        case 64:
            *(volatile uint64_t*)virt_addr = writeval;
//          read_result = *(volatile uint64_t*)virt_addr;
            break;
        default:
            bb_error_msg_and_die("bad width");
        }
//      printf("Written 0x%llX; readback 0x%llX\n",
//              (unsigned long long)writeval,
//              (unsigned long long)read_result);
    }

    if (ENABLE_FEATURE_CLEAN_UP) {
        if (munmap(map_base, mapped_size) == -1)
            bb_perror_msg_and_die("munmap");
        close(fd);
    }

    return EXIT_SUCCESS;
}