Linux C 动态打桩实现

#include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <memory.h> #include <errno.h> #include <limits.h> #include <sys/mman.h> #include "stub.h" static long pagesize = -1; static inline void *pageof(const void* p) { return (void *)((unsigned long)p & ~(pagesize - 1)); } void stub_set(struct func_stub *pstub, void *fn, void *fn_stub) { pstub->fn = fn; memcpy(pstub->code_buf, fn, CODESIZE); if (-1 == mprotect(pageof(fn), pagesize * 2, PROT_READ | PROT_WRITE | PROT_EXEC)) { perror("mprotect to w+r+x faild"); exit(errno); } *(unsigned char *)fn = (unsigned char)0xE9; *(unsigned int *)((unsigned char *)fn + 1) = (unsigned char *)fn_stub - (unsigned char *)fn - CODESIZE; if (-1 == mprotect(pageof(fn), pagesize * 2, PROT_READ | PROT_EXEC)) { perror("mprotect to r+x failed"); exit(errno); } return; } void stub_reset(struct func_stub *pstub) { if (NULL == pstub->fn) { return; } if (-1 == mprotect(pageof(pstub->fn), pagesize * 2, PROT_READ | PROT_WRITE | PROT_EXEC)) { perror("mprotect to w+r+x faild"); exit(errno); } memcpy(pstub->fn, pstub->code_buf, CODESIZE); if (-1 == mprotect(pageof(pstub->fn), pagesize * 2, PROT_READ | PROT_EXEC)) { perror("mprotect to r+x failed"); exit(errno); } memset(pstub, 0, sizeof(struct func_stub)); return; } int stub_init(void) { int ret; pagesize = sysconf(_SC_PAGE_SIZE); ret = 0; if (pagesize < 0) { perror("get system _SC_PAGE_SIZE configure failed"); ret = -1; } return ret; }