转自：https://blog.csdn.net/thisinnocence/article/details/80414008
之前的一篇文章: Linux C/C++内存越界定位: 利用mprotect使程序在crash在第一现场。里面没有用malloc来申请按页对齐的内存，其实也可以适配malloc，多申请2页，取中间按照页对齐的内存使用。使用malloc，可以使得进程的地址空间布局不会相对原来发生太大变化。代码如下：
#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> struct mem_align { void *origin_start; // for free void *start; // data addr start, align page size void *end; // data addr end, align page size void *origin_end; }; int malloc_align_page(size_t memsize, struct mem_align *mem) { if (memsize == 0 || mem == NULL) return -1; memset(mem, 0, sizeof(*mem)); long pagesize = sysconf(_SC_PAGE_SIZE); if (pagesize == -1) { perror("sysconf err"); return -1; } size_t datasize = memsize + pagesize * 2; mem->origin_start = malloc(datasize); if(mem->origin_start == NULL) return -1; mem->origin_end = mem->origin_start + datasize; long mask = pagesize - 1; mem->start = (void *)((long)(mem->origin_start + pagesize) & ~mask); long pagenum = memsize / pagesize + 1; mem->end = mem->start + pagesize * pagenum; return 0; } int main() { int ret; struct mem_align mem; ret = malloc_align_page(1024, &mem); if (ret != 0) { return ret; } ret = mprotect(mem.start, (size_t)(mem.end - mem.start), PROT_READ); if (ret == -1) { perror("mportect"); return ret; } sleep(600); // 让进程先挂起不退出，看/proc/[pid]/maps里的地址空间对应页的权限 // free(mem.origin_start); return 0; }
一组运行结果如下：
root@ubuntu:/media/psf/Home/iLearn/learn_c/mprotect# ./a.out malloc mem: 0xbab010 - 0xbad410 align page: 0xbac000 - 0xbad000 root@ubuntu:~# ps -ef|grep a.out root 1429 32072 0 00:24 pts/11 00:00:00 ./a.out root 1718 1153 0 00:25 pts/17 00:00:00 grep --color=auto a.out root@ubuntu:~# grep bac00 /proc/1429/maps -C 3 00400000-00401000 r-xp 00000000 00:18 53150451 /media/psf/Home/iLearn/learn_c/mprotect/a.out 00600000-00601000 r--p 00000000 00:18 53150451 /media/psf/Home/iLearn/learn_c/mprotect/a.out 00601000-00602000 rw-p 00001000 00:18 53150451 /media/psf/Home/iLearn/learn_c/mprotect/a.out 00bab000-00bac000 rw-p 00000000 00:00 0 [heap] 00bac000-00bad000 r--p 00000000 00:00 0 [heap] # 这块对内存页已经被改成了只读权限 00bad000-00bce000 rw-p 00000000 00:00 0 [heap] 7f657e6b3000-7f657e86f000 r-xp 00000000 08:01 397412 /lib/x86_64-linux-gnu/libc-2.19.so 7f657e86f000-7f657ea6e000 ---p 001bc000 08:01 397412 /lib/x86_64-linux-gnu/libc-2.19.so