Unable to debug PIE binaries with QEMU gdb stub.

[Maxim Ostapenko]

The issue occurs on current trunk:

max@max:~/build/qemu$ cat test.c
#include <stdio.h>

int main() {
  printf("Hello, world!\n");
  return 0;
}

max@max:~/build/qemu$ gcc test.c -fPIC -pie -o bad.x
max@max:~/build/qemu$ ./x86_64-linux-user/qemu-x86_64 -g 1234 bad.x
.............................

max@max:~/build/qemu$ gdb
GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2) 7.7.1
........................................................................................
(gdb) file bad.x
Reading symbols from bad.x...(no debugging symbols found)...done.
(gdb) b main
Breakpoint 1 at 0x779
(gdb) target remote localhost:1234
Remote debugging using localhost:1234
Reading symbols from /lib64/ld-linux-x86-64.so.2...warning: the debug information found in "/lib64/ld-2.19.so" does not match "/lib64/ld-linux-x86-64.so.2" (CRC mismatch).

Reading symbols from /usr/lib/debug//lib/x86_64-linux-gnu/ld-2.19.so...done.
done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
Error in re-setting breakpoint 1: Cannot access memory at address 0x775
Error in re-setting breakpoint 1: Cannot access memory at address 0x775
0x0000004000a042d0 in _start () from /lib64/ld-linux-x86-64.so.2
(gdb) c
Continuing.
[Inferior 1 (Remote target) exited normally]
(gdb)

max@max:~/build/qemu$ cat config.log
# Configured with: '/home/max/src/qemu/configure' '--prefix=/home/max/install/qemu' '--target-list=arm-linux-user,aarch64-linux-user,x86_64-linux-user' '--static'

W/O QEMU or -pie flag breakpoint on main works fine.

[Maxim Ostapenko (m-ostapenko)]

GDB server itself actually supports PIE binaries.

[Lukas Durfina (lukasdurfina)]

This patch https://<email address hidden>/ fixes the issue.

[Thomas Huth (th-huth)]

Patch has been included in QEMU v4.2:
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=dc12567a53c88d7a91b9