qemu-ppc segfaults(SIGSEGV) on pthread_create

[William Barsse]

qemu-ppc running on x86-64 hardware leads to a segfault when running the
attached program (test.c). It simply creates a pthread, joins it and exits.

It was compiled as follows on a Debian testing system:
> powerpc-linux-gnuspe-gcc-6 -static -Wall -g -o test -pthread test.c

Sample execution (expected output is "Hello - World!"):
> qemu-ppc -cpu e500 ./test
[...output...]
Hello - qemu-ppc: /build/qemu-_M2UL5/qemu-2.8+dfsg/translate-all.c:175: tb_lock: Assertion `!have_tb_lock' failed.
qemu-ppc: /build/qemu-_M2UL5/qemu-2.8+dfsg/translate-all.c:175: tb_lock: Assertion `!have_tb_lock' failed.
[1] 25747 segmentation fault qemu-ppc -cpu e500 test
[...end output...]

The same behavior is observed when running on a PPC 604:

> powerpc-linux-gnu-gcc -Wall -g -o test -pthread test.c
> qemu-ppc ./test
[... as above ...]

Version information:
powerpc-linux-gnu-gcc -v => gcc version 6.3.0 20170124 (Debian 6.3.0-5)
qemu-ppc -version => qemu-ppc version 2.8.0(Debian 1:2.8+dfsg-2)

The same experiment was conducted again using qemu from the git repository (commit: 796b288f7be875045670f963ce99991b3c8e96ac):
~/tools/qemu/build/ppc-linux-user/qemu-ppc -version => qemu-ppc version 2.8.50 (v2.8.0-1417-g796b288f7b-dirty)
[...output...]
Hello - qemu-ppc: [...redacted...]/tools/qemu/translate-all.c:175: tb_lock: Assertion `!have_tb_lock' failed.
qemu-ppc: [...redacted...]/tools/qemu/translate-all.c:175: tb_lock: Assertion `!have_tb_lock' failed.
[1] 25996 segmentation fault ~/tools/qemu/build/ppc-linux-user/qemu-ppc -cpu e500 test
[...end output...]

Executing with -strace option yields a surprising entry (see second clone() syscall below):
[...]
26007 clone(CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID,child_stack=0xf67fde60,parent_tidptr=0xf67fe368,tls=0xf68057d0,child_tidptr=0xf67fe368) = 26009
26007 clone(0,child_stack=0xf67fde60,parent_tidptr=0xf67fe368,tls=0xf68057d0,child_tidptr=0xf67fe368) = -1 errno=22 (Invalid argument)

test.c works just fine if the pthread_create & pthread_join calls are removed
(i.e. when compiled with -DNO_PTHREAD_CREATE).

At first glance, the issue seems specific to PPC because compiling and running
for x86_64 using qemu-x86_64 works fine.

Additional info:
> lddtree =qemu-ppc
qemu-ppc => /usr/bin/qemu-ppc (interpreter => /lib64/ld-linux-x86-64.so.2)
    libgmodule-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgmodule-2.0.so.0
        libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2
            ld-linux-x86-64.so.2 => /lib64/ld-linux-x86-64.so.2
    libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0
        libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3
    librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6

> /lib/x86_64-linux-gnu/libc.so.6
GNU C Library (Debian GLIBC 2.24-9) stable release version 2.24, by Roland McGrath et al.

> uname -a
Linux [...redacted...] 4.9.0-1-amd64 #1 SMP Debian 4.9.6-3 (2017-01-28) x86_64 GNU/Linux

[William Barsse (wbarsse)]

Fixed by commit 2635531f2006bfb0f943ad25b41e176709b79b37 (available in 2.9.0rc0)