dump vdso

dump_vdso.c

#include <stdio.h>
#include <string.h>
 
int
main()
{
	FILE *maps;
	void *vdso_begin, *vdso_end;
 
	maps = fopen("/proc/self/maps", "r");
	char buf[1024];
	while (fgets(buf, 1024, maps)) {
		if (strstr(buf, "[vdso]")) break;
	}
	fclose(maps);
 
	sscanf(buf, "%p-%p", &vdso_begin, &vdso_end);
	write(1, vdso_begin, vdso_end - vdso_begin);
 
	return 0;
}
 
/*#include 
#include 
#include 
#include 
 
static void *getsys(char **envp) 
{
   Elf64_auxv_t *auxv;
   
   /* walk past all env pointers */
   while (*envp++ != NULL);
 
   /* and find ELF auxiliary vectors (if this was an ELF binary) */
   auxv = (Elf64_auxv_t *) envp;
   
   for ( ; auxv->a_type != AT_NULL; auxv++)
     if (auxv->a_type == AT_SYSINFO_EHDR)
       return (void *)auxv->a_un.a_val;
   
   fprintf(stderr, "no AT_SYSINFO_EHDR auxv entry found\n");
   exit(1);
}
 
int main(int argc, char *argv[], char **envp)
{
   unsigned char buffer[4096];
   void *p;
   
   p=getsys(envp);
   fprintf(stderr, "AT_SYSINFO_EHDR at %p\n",p);
   memcpy(buffer, p, 4096);
   write(1, buffer, 4096);*/

dump_vdso.py

#!/usr/bin/env python
from ctypes import *
 
for ln in open('/proc/self/maps'):
    if '[vdso]' in ln:
        start, end = [int(x,16) for x in ln.split()[0].split('-')]
        CDLL('libc.so.6').write(1, c_void_p(start), end-start)
        break