elf_loader fails when trying to execute MAMBO with qemu about mambo HOT 3 CLOSED

A little update just to let you know that a fix for the reported bug was already committed to master:

• https://git.qemu.org/?p=qemu.git;a=commit;h=38138fab93584ad3560ddfcd70efbd5bb6b4a6f0
• https://git.qemu.org/?p=qemu.git;a=commit;h=28cbb997d66e4d1904a231bef1ce15c2cbb6bf73
• https://wiki.qemu.org/ChangeLog/3.0#User-mode_emulation

from mambo.

Last time I've tried to run MAMBO using qemu user mode emulation, I've ran into numerous qemu bugs. Use native hardware or system mode emulation. The assertion at elf_loader/elf_loader.c:127 should never fail when running natively. I'm curious to see what's causing it to fail in qemu, but I don't have a debug build available at the moment.

$ ./test/mmap_munmap 
mmap_munmap: mmap_munmap.c:33: main: Assertion `alloc == MAP_FAILED' failed.
qemu: uncaught target signal 6 (Aborted) - core dumped
Aborted (core dumped)

That's a qemu bug. Please report it to them. According to the mmap manual:

If len is zero, mmap() shall fail and no mapping shall be established.

from mambo.

Indeed, I stripped down mmap_munmap to:

#include <stdlib.h>
#include <assert.h>
#include <sys/mman.h>
#include <errno.h>
#include <stdio.h>

int main() {
  // Failing allocation
  void *alloc = mmap(NULL, 0, PROT_EXEC | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  
  printf("alloc: %d\n", alloc);
  printf("MAP_FAILED: %d\n", MAP_FAILED);
  printf("errno: %d\n", errno);
  
  assert(alloc == MAP_FAILED);

  return 0;
}

I cross compiled in x86_64:

aarch64-linux-gnu-gcc -static -std=gnu99 -lpthread test/mmap_qemu.c -o mmap_qemu

This is the output in x86_64:

$ ./mmap_qemu 
alloc: 0
MAP_FAILED: -1
errno: 0
mmap_qemu: test/mmap_qemu.c:15: main: Assertion `alloc == MAP_FAILED' failed.
qemu: uncaught target signal 6 (Aborted) - core dumped
Aborted (core dumped)

This is the output in a Jetson TX1:

$ ./mmap_qemu 
alloc: -1
MAP_FAILED: -1
errno: 22

So, as you said, qemu is not handling mmap properly. It is returning a success (0) when it should be returning a failure (-1, MAP_FAILED). I reported it to them: https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1783362

I'm closing this for now. Thanks!

from mambo.