本文共 2597 字,大约阅读时间需要 8 分钟。
之前的一篇文章: 。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#include #include #include 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.outmalloc mem: 0xbab010 - 0xbad410align page: 0xbac000 - 0xbad000root@ubuntu:~# ps -ef|grep a.outroot 1429 32072 0 00:24 pts/11 00:00:00 ./a.outroot 1718 1153 0 00:25 pts/17 00:00:00 grep --color=auto a.outroot@ubuntu:~# grep bac00 /proc/1429/maps -C 300400000-00401000 r-xp 00000000 00:18 53150451 /media/psf/Home/iLearn/learn_c/mprotect/a.out00600000-00601000 r--p 00000000 00:18 53150451 /media/psf/Home/iLearn/learn_c/mprotect/a.out00601000-00602000 rw-p 00001000 00:18 53150451 /media/psf/Home/iLearn/learn_c/mprotect/a.out00bab000-00bac000 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.so7f657e86f000-7f657ea6e000 ---p 001bc000 08:01 397412 /lib/x86_64-linux-gnu/libc-2.19.so
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