graphic: 0.614
instruction: 0.603
network: 0.588
semantic: 0.561
device: 0.546
other: 0.517
boot: 0.494
mistranslation: 0.485
vnc: 0.460
socket: 0.441
assembly: 0.384
KVM: 0.332

/proc/self/maps content returned to 32-bits guest under 64-bits qemu

Reading /proc/self/maps a user doesn't get a stack record. Not all programs relies on the maps file but some do.

The bug found by running 32-bits binaries with address sanitizer (Asan) instrumentations under 64-bit qemu.

$ echo "int main() { return 0; }" > /tmp/test.c
$ gcc -m32 -fsanitize=address -fno-common -Wall -g -fPIC -o /tmp/test /tmp/test.c
$ qemu-i386-static /tmp/test
==4092==AddressSanitizer CHECK failed: /home/michail/Downloads/gcc-4.9.0/libsanitizer/sanitizer_common/sanitizer_linux_libcdep.cc:63 "(((uptr)&rl >= start && (uptr)&rl < end)) != (0)" (0x0, 0x0)
    #0 0xf632ff01 (/home/michail/build/lib32/libasan.so.1+0x53f01)
    #1 0xf6333f49 (/home/michail/build/lib32/libasan.so.1+0x57f49)
    #2 0xf6338785 (/home/michail/build/lib32/libasan.so.1+0x5c785)
    #3 0xf6338bd1 (/home/michail/build/lib32/libasan.so.1+0x5cbd1)
    #4 0xf6331baf (/home/michail/build/lib32/libasan.so.1+0x55baf)
    #5 0xf6331dca (/home/michail/build/lib32/libasan.so.1+0x55dca)
    #6 0xf6331f5a (/home/michail/build/lib32/libasan.so.1+0x55f5a)
    #7 0xf6330bd4 (/home/michail/build/lib32/libasan.so.1+0x54bd4)
    #8 0xf67ebeec (/lib/ld-linux.so.2+0xeeec)
    #9 0xf67de10e (/lib/ld-linux.so.2+0x110e)

This happened because during initialization Asan can't find stack boundaries.

For some reasons Qemu wants to report stack boundaries just for several arch targets skipping other ones. This is from linux-user/syscall.c open_self_maps()

#if defined(TARGET_ARM) || defined(TARGET_M68K) || defined(TARGET_UNICORE32)
    dprintf(fd, "%08llx-%08llx rw-p %08llx 00:00 0          [stack]\n",
                (unsigned long long)ts->info->stack_limit,
                (unsigned long long)(ts->info->start_stack +
                                     (TARGET_PAGE_SIZE - 1)) & TARGET_PAGE_MASK,
                (unsigned long long)0);
#endif

Not very clear why the case covers just specific targets.

This bug continues the previously reported issue with not hiden system map http://lists.nongnu.org/archive/html/qemu-devel/2014-07/msg02793.html.

I think the ifdefs are just accident of history and we can safely remove them.

We removed the ifdefs at some point; the test case in this bug report now runs successfully.