aslr.patch

来自「MINIX操作系统的内核修改补丁」· PATCH 代码 · 共 33 行

diff -c -r src.clean/servers/pm/exec.c src/servers/pm/exec.c
*** src.clean/servers/pm/exec.c	Thu Nov 13 17:54:55 2008
--- src/servers/pm/exec.c	Thu Nov 13 21:21:59 2008
***************
*** 64,69 ****
--- 64,72 ----
    vir_clicks sc;
    struct stat s_buf[2], *s_p;
    vir_bytes pc;
+   int rand;
+   int gap;
+   clock_t time;
  
    /* Do some validity checks. */
    rmp = mp;
***************
*** 126,131 ****
--- 129,142 ----
    vsp = (vir_bytes) rmp->mp_seg[S].mem_vir << CLICK_SHIFT;
    vsp += (vir_bytes) rmp->mp_seg[S].mem_len << CLICK_SHIFT;
    vsp -= stk_bytes;
+   gap =rmp->mp_seg[S].mem_vir - rmp->mp_seg[D].mem_vir - rmp->mp_seg[D].mem_len;
+   getuptime(&time);
+   if (gap > 6){
+      rand = (int)( (time*5269+619853) % ( 512 * (gap-3)));
+   }else{
+      rand = (int)((time*5269+619853)%1024);
+   }
+   vsp -= rand;
    patch_ptr(mbuf, vsp);
    src = (vir_bytes) mbuf;
    r = sys_datacopy(PM_PROC_NR, (vir_bytes) src,