devmem2实现代码

ゝ一纸荒年。 2022-06-01 11:57 205阅读 0赞

## 简介 ##

Jan-Derk Bakker 写的一个读写linux任意地址内存的工具, 是通过 mmap 映射`/dev/mem` 设备到用户空间来实现的内存操作

## 代码 ##

/* * devmem2.c: Simple program to read/write from/to any location in memory. * * Copyright (C) 2000, Jan-Derk Bakker (jdb@lartmaker.nl) * * * This software has been developed for the LART computing board * (http://www.lart.tudelft.nl/). The development has been sponsored by * the Mobile MultiMedia Communications (http://www.mmc.tudelft.nl/) * and Ubiquitous Communications (http://www.ubicom.tudelft.nl/) * projects. * * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * */
    
    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <string.h>
    #include <errno.h>
    #include <signal.h>
    #include <fcntl.h>
    #include <ctype.h>
    #include <termios.h>
    #include <sys/types.h>
    #include <sys/mman.h>
    
    #define FATAL do { fprintf(stderr, "Error at line %d, file %s (%d) [%s]\n", \
      __LINE__, __FILE__, errno, strerror(errno)); exit(1); } while(0)
    
    #define MAP_SIZE 4096UL
    #define MAP_MASK (MAP_SIZE - 1)
    
    int main(int argc, char **argv) {
        int fd;
        void *map_base, *virt_addr; 
        unsigned long read_result, writeval;
        off_t target;
        int access_type = 'w';
    
        if(argc < 2) {
            fprintf(stderr, "\nUsage:\t%s { address } [ type [ data ] ]\n"
                "\taddress : memory address to act upon\n"
                "\ttype : access operation type : [b]yte, [h]alfword, [w]ord\n"
                "\tdata : data to be written\n\n",
                argv[0]);
            exit(1);
        }
        target = strtoul(argv[1], 0, 0);
    
        if(argc > 2)
            access_type = tolower(argv[2][0]);
    
    
        if((fd = open("/dev/mem", O_RDWR | O_SYNC)) == -1) FATAL;
        printf("/dev/mem opened.\n"); 
        fflush(stdout);
    
        /* Map one page */
        map_base = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, target & ~MAP_MASK);
        if(map_base == (void *) -1) FATAL;
        printf("Memory mapped at address %p.\n", map_base); 
        fflush(stdout);
    
        virt_addr = map_base + (target & MAP_MASK);
        switch(access_type) {
            case 'b':
                read_result = *((unsigned char *) virt_addr);
                break;
            case 'h':
                read_result = *((unsigned short *) virt_addr);
                break;
            case 'w':
                read_result = *((unsigned long *) virt_addr);
                break;
            default:
                fprintf(stderr, "Illegal data type '%c'.\n", access_type);
                exit(2);
        }
        printf("Value at address 0x%X (%p): 0x%X\n", target, virt_addr, read_result); 
        fflush(stdout);
    
        if(argc > 3) {
            writeval = strtoul(argv[3], 0, 0);
            switch(access_type) {
                case 'b':
                    *((unsigned char *) virt_addr) = writeval;
                    read_result = *((unsigned char *) virt_addr);
                    break;
                case 'h':
                    *((unsigned short *) virt_addr) = writeval;
                    read_result = *((unsigned short *) virt_addr);
                    break;
                case 'w':
                    *((unsigned long *) virt_addr) = writeval;
                    read_result = *((unsigned long *) virt_addr);
                    break;
            }
            printf("Written 0x%X; readback 0x%X\n", writeval, read_result); 
            fflush(stdout);
        }
    
        if(munmap(map_base, MAP_SIZE) == -1) FATAL;
        close(fd);
        return 0;
    }

# 引用 #

> [http://www.lartmaker.nl/lartware/port/devmem2.c][http_www.lartmaker.nl_lartware_port_devmem2.c]  
> [http://blog.csdn.net/x356982611/article/details/79192204][http_blog.csdn.net_x356982611_article_details_79192204]

[http_www.lartmaker.nl_lartware_port_devmem2.c]: http://www.lartmaker.nl/lartware/port/devmem2.c
[http_blog.csdn.net_x356982611_article_details_79192204]: http://blog.csdn.net/x356982611/article/details/79192204