dump-vvar.c

#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>

int main()
{
	FILE *maps;
	void *vvar_begin, *vvar_end;
	int found_vvar = 0;

	maps = fopen("/proc/self/maps", "r");
	char buf[1024];
	while (fgets(buf, 1024, maps)) {
		if (strstr(buf, "[vvar]")) {
			found_vvar = 1;
			break;
		}
	}
	fclose(maps);

	if (!found_vvar) {
		fprintf(stderr, "Could not find vvar mapping\n");
		return 1;
	}

	sscanf(buf, "%p-%p", &vvar_begin, &vvar_end);

	fprintf(stderr, "vvar mapping is at 0x%lx to 0x%lx\n",
		(unsigned long)vvar_begin, (unsigned long)vvar_end);

	maps = fopen("/proc/self/maps", "r");
	mremap(vvar_begin, vvar_end-vvar_begin, vvar_end-vvar_begin, MREMAP_FIXED | MREMAP_MAYMOVE, 0x0badc0de0000);

	mremap(vvar_begin - 4096, 4096, 4096, MREMAP_FIXED | MREMAP_MAYMOVE, 0x0badc0de0000 - 4096);

	while (fgets(buf, 1024, maps)) {
		fprintf(stderr, "%s", buf);
	}

	vvar_end = (void*)0x0badc0de0000 + (vvar_end - vvar_begin);
	vvar_begin = (void*)0x0badc0de0000;

	write(1, vvar_begin, vvar_end - vvar_begin);

	mprotect(vvar_begin, vvar_end - vvar_begin, PROT_READ | PROT_WRITE);

	return 0;
}