mirror of
https://github.com/cirosantilli/linux-kernel-module-cheat.git
synced 2026-01-23 18:25:57 +01:00
107 lines
2.7 KiB
C
107 lines
2.7 KiB
C
/*
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Adapted from: http://free-electrons.com/pub/mirror/devmem2.c
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Forked because of the unpredictable access widths:
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https://bugs.busybox.net/show_bug.cgi?id=10171
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*/
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#include <ctype.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <sys/types.h>
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#include <termios.h>
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#include <unistd.h>
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#define FATAL do { fprintf(stderr, "Error at line %d, file %s (%d) [%s]\n", \
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__LINE__, __FILE__, errno, strerror(errno)); exit(1); } while(0)
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int main(int argc, char **argv) {
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int access_type = 'w';
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unsigned long map_size, map_mask;
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off_t target;
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uintmax_t read_result, writeval;
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int fd;
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void *map_base, *virt_addr;
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map_size = sysconf(_SC_PAGE_SIZE);
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map_mask = map_size - 1;
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if(argc < 2) {
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fprintf(stderr, "\nUsage:\t%s { address } [ type [ data ] ]\n"
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"\taddress : memory address to act upon\n"
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"\ttype : access operation type : [b]yte, [h]alfword, [w]ord\n"
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"\tdata : data to be written\n\n",
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argv[0]);
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exit(1);
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}
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target = strtoul(argv[1], 0, 0);
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if(argc > 2)
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access_type = tolower(argv[2][0]);
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if((fd = open("/dev/mem", O_RDWR | O_SYNC)) == -1) FATAL;
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printf("/dev/mem opened.\n");
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fflush(stdout);
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/* Map one page */
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map_base = mmap(0, map_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, target & ~map_mask);
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if(map_base == (void *) -1) FATAL;
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printf("Memory mapped at address %p.\n", map_base);
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fflush(stdout);
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virt_addr = map_base + (target & map_mask);
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switch(access_type) {
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case 'b':
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read_result = *((uint8_t *) virt_addr);
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break;
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case 'h':
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read_result = *((uint16_t *) virt_addr);
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break;
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case 'w':
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read_result = *((uint32_t *) virt_addr);
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break;
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case 'q':
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read_result = *((uint64_t *) virt_addr);
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break;
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default:
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fprintf(stderr, "Illegal data type '%c'.\n", access_type);
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exit(2);
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}
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printf("Value at address 0x%jX (%p): 0x%jX\n", (uintmax_t)target, virt_addr, (uintmax_t)read_result);
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fflush(stdout);
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if(argc > 3) {
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writeval = strtoul(argv[3], 0, 0);
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switch(access_type) {
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case 'b':
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*((uint8_t *) virt_addr) = writeval;
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read_result = *((uint8_t *) virt_addr);
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break;
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case 'h':
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*((uint16_t *) virt_addr) = writeval;
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read_result = *((uint16_t *) virt_addr);
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break;
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case 'w':
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*((uint32_t *) virt_addr) = writeval;
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read_result = *((uint32_t *) virt_addr);
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break;
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case 'q':
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*((uint64_t *) virt_addr) = writeval;
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read_result = *((uint64_t *) virt_addr);
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break;
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}
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printf("Written 0x%jX; readback 0x%jX\n", (uintmax_t)writeval, (uintmax_t)read_result);
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fflush(stdout);
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}
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if(munmap(map_base, map_size) == -1) FATAL;
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close(fd);
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return 0;
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}
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