[Qemu-devel] [Bug 1704638] [NEW] weak symbol access makes qemu in user m

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[Qemu-devel] [Bug 1704638] [NEW] weak symbol access makes qemu in user m

From:	Bruno Haible
Subject:	[Qemu-devel] [Bug 1704638] [NEW] weak symbol access makes qemu in user mode hang for mips, mips64
Date:	Sun, 16 Jul 2017 11:10:14 -0000

Public bug reported:

A program that is statically linked and invokes a weak pointer should
crash (because the weak pointer evaluates to NULL).

With qemu in user mode, for mips and mips64, it hangs. The process needs
to be killed with "kill -9".

How to reproduce for mips:
- Compile the program: mips-linux-gnu-gcc-5 -O -Wall -static -o 
testpthsigmask-mips testpthsigmask.c -pthread
- Set environment variables for running qemu-mips.
- ~/inst-qemu/2.9.0/bin/qemu-mips testpthsigmask-mips

How to reproduce for mips64:
- Compile the program: mips64-linux-gnuabi64-gcc-5 -O -Wall -static -o 
testpthsigmask-mips64 testpthsigmask.c -lpthread
- Set environment variables for running qemu-mips64.
- ~/inst-qemu/2.9.0/bin/qemu-mips64 testpthsigmask-mips64

When I attach gdb to the process, I see that it is hanging inside
'gen_intermediate_code':

$ gdb /home/bruno/inst-qemu/2.9.0/bin/qemu-mips 9726
...
Reading symbols from /home/bruno/inst-qemu/2.9.0/bin/qemu-mips...done.
Attaching to program: /home/bruno/inst-qemu/2.9.0/bin/qemu-mips, process 9726
...
(gdb) info threads
  Id   Target Id         Frame 
* 1    Thread 0x7f1e7e535740 (LWP 9726) "qemu-mips" __lll_lock_wait () at 
../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135
  2    Thread 0x7f1e7d0ad700 (LWP 9727) "qemu-mips" syscall () at 
../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
(gdb) where
#0  __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135
#1  0x00007f1e7d6f1dbd in __GI___pthread_mutex_lock (address@hidden 
<tcg_ctx+272>) at ../nptl/pthread_mutex_lock.c:80
#2  0x000055de1c527199 in qemu_mutex_lock (address@hidden <tcg_ctx+272>)
    at /media/develdata/devel/build/qemu-2.9.0/util/qemu-thread-posix.c:60
#3  0x000055de1c435083 in tb_lock () at 
/media/develdata/devel/build/qemu-2.9.0/translate-all.c:167
#4  cpu_restore_state (address@hidden, address@hidden) at 
/media/develdata/devel/build/qemu-2.9.0/translate-all.c:350
#5  0x000055de1c4658d0 in handle_cpu_signal (old_set=0x7ffe5ffd8ea8, 
is_write=0, address=0, pc=94412445741767)
    at /media/develdata/devel/build/qemu-2.9.0/user-exec.c:124
#6  cpu_mips_signal_handler (address@hidden, address@hidden, address@hidden)
    at /media/develdata/devel/build/qemu-2.9.0/user-exec.c:229
#7  0x000055de1c4803be in host_signal_handler (host_signum=11, 
info=0x7ffe5ffd8eb0, puc=0x7ffe5ffd8d80)
    at /media/develdata/devel/build/qemu-2.9.0/linux-user/signal.c:646
#8  <signal handler called>
#9  __bswap_32 (__bsx=<optimized out>) at 
/usr/include/x86_64-linux-gnu/bits/byteswap.h:47
#10 bswap32 (x=<optimized out>) at 
/media/develdata/devel/build/qemu-2.9.0/include/qemu/bswap.h:21
#11 ldl_be_p (ptr=<optimized out>) at 
/media/develdata/devel/build/qemu-2.9.0/include/qemu/bswap.h:434
#12 cpu_ldl_code (env=0x55de1e91df48, ptr=0) at 
/media/develdata/devel/build/qemu-2.9.0/include/exec/cpu_ldst_useronly_template.h:68
#13 gen_intermediate_code (address@hidden, address@hidden)
    at /media/develdata/devel/build/qemu-2.9.0/target/mips/translate.c:19962
#14 0x000055de1c4352e6 in tb_gen_code (address@hidden, address@hidden, 
address@hidden, address@hidden, cflags=<optimized out>, 
    address@hidden) at 
/media/develdata/devel/build/qemu-2.9.0/translate-all.c:1295
#15 0x000055de1c436a7a in tb_find (tb_exit=0, last_tb=0x0, cpu=<optimized out>) 
at /media/develdata/devel/build/qemu-2.9.0/cpu-exec.c:365
#16 cpu_exec (cpu=<optimized out>) at 
/media/develdata/devel/build/qemu-2.9.0/cpu-exec.c:673
#17 0x000055de1c466278 in cpu_loop (env=0x55de1e91df48) at 
/media/develdata/devel/build/qemu-2.9.0/linux-user/main.c:2236
#18 0x000055de1c433103 in main (argc=<optimized out>, argv=0x7ffe5ffd9de8, 
envp=<optimized out>)
    at /media/develdata/devel/build/qemu-2.9.0/linux-user/main.c:4860
(gdb) thread 2
[Switching to thread 2 (Thread 0x7f1e7d0ad700 (LWP 9727))]
#0  syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
38      ../sysdeps/unix/sysv/linux/x86_64/syscall.S: Datei oder Verzeichnis 
nicht gefunden.
(gdb) where
#0  syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
#1  0x000055de1c527605 in qemu_futex_wait (val=<optimized out>, f=<optimized 
out>) at /media/develdata/devel/build/qemu-2.9.0/include/qemu/futex.h:26
#2  qemu_event_wait (address@hidden <rcu_call_ready_event>) at 
/media/develdata/devel/build/qemu-2.9.0/util/qemu-thread-posix.c:399
#3  0x000055de1c52d41e in call_rcu_thread (opaque=<optimized out>) at 
/media/develdata/devel/build/qemu-2.9.0/util/rcu.c:249
#4  0x00007f1e7d6ef6ba in start_thread (arg=0x7f1e7d0ad700) at 
pthread_create.c:333
#5  0x00007f1e7d4253dd in clone () at 
../sysdeps/unix/sysv/linux/x86_64/clone.S:109

** Affects: qemu
     Importance: Undecided
         Status: New

** Attachment added: "Test program"
   
https://bugs.launchpad.net/bugs/1704638/+attachment/4915583/+files/testpthsigmask.c

-- 
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https://bugs.launchpad.net/bugs/1704638

Title:
  weak symbol access makes qemu in user mode hang for mips, mips64

Status in QEMU:
  New

Bug description:
  A program that is statically linked and invokes a weak pointer should
  crash (because the weak pointer evaluates to NULL).

  With qemu in user mode, for mips and mips64, it hangs. The process
  needs to be killed with "kill -9".

  How to reproduce for mips:
  - Compile the program: mips-linux-gnu-gcc-5 -O -Wall -static -o 
testpthsigmask-mips testpthsigmask.c -pthread
  - Set environment variables for running qemu-mips.
  - ~/inst-qemu/2.9.0/bin/qemu-mips testpthsigmask-mips

  How to reproduce for mips64:
  - Compile the program: mips64-linux-gnuabi64-gcc-5 -O -Wall -static -o 
testpthsigmask-mips64 testpthsigmask.c -lpthread
  - Set environment variables for running qemu-mips64.
  - ~/inst-qemu/2.9.0/bin/qemu-mips64 testpthsigmask-mips64

  When I attach gdb to the process, I see that it is hanging inside
  'gen_intermediate_code':

  $ gdb /home/bruno/inst-qemu/2.9.0/bin/qemu-mips 9726
  ...
  Reading symbols from /home/bruno/inst-qemu/2.9.0/bin/qemu-mips...done.
  Attaching to program: /home/bruno/inst-qemu/2.9.0/bin/qemu-mips, process 9726
  ...
  (gdb) info threads
    Id   Target Id         Frame 
  * 1    Thread 0x7f1e7e535740 (LWP 9726) "qemu-mips" __lll_lock_wait () at 
../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135
    2    Thread 0x7f1e7d0ad700 (LWP 9727) "qemu-mips" syscall () at 
../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
  (gdb) where
  #0  __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135
  #1  0x00007f1e7d6f1dbd in __GI___pthread_mutex_lock (address@hidden 
<tcg_ctx+272>) at ../nptl/pthread_mutex_lock.c:80
  #2  0x000055de1c527199 in qemu_mutex_lock (address@hidden <tcg_ctx+272>)
      at /media/develdata/devel/build/qemu-2.9.0/util/qemu-thread-posix.c:60
  #3  0x000055de1c435083 in tb_lock () at 
/media/develdata/devel/build/qemu-2.9.0/translate-all.c:167
  #4  cpu_restore_state (address@hidden, address@hidden) at 
/media/develdata/devel/build/qemu-2.9.0/translate-all.c:350
  #5  0x000055de1c4658d0 in handle_cpu_signal (old_set=0x7ffe5ffd8ea8, 
is_write=0, address=0, pc=94412445741767)
      at /media/develdata/devel/build/qemu-2.9.0/user-exec.c:124
  #6  cpu_mips_signal_handler (address@hidden, address@hidden, address@hidden)
      at /media/develdata/devel/build/qemu-2.9.0/user-exec.c:229
  #7  0x000055de1c4803be in host_signal_handler (host_signum=11, 
info=0x7ffe5ffd8eb0, puc=0x7ffe5ffd8d80)
      at /media/develdata/devel/build/qemu-2.9.0/linux-user/signal.c:646
  #8  <signal handler called>
  #9  __bswap_32 (__bsx=<optimized out>) at 
/usr/include/x86_64-linux-gnu/bits/byteswap.h:47
  #10 bswap32 (x=<optimized out>) at 
/media/develdata/devel/build/qemu-2.9.0/include/qemu/bswap.h:21
  #11 ldl_be_p (ptr=<optimized out>) at 
/media/develdata/devel/build/qemu-2.9.0/include/qemu/bswap.h:434
  #12 cpu_ldl_code (env=0x55de1e91df48, ptr=0) at 
/media/develdata/devel/build/qemu-2.9.0/include/exec/cpu_ldst_useronly_template.h:68
  #13 gen_intermediate_code (address@hidden, address@hidden)
      at /media/develdata/devel/build/qemu-2.9.0/target/mips/translate.c:19962
  #14 0x000055de1c4352e6 in tb_gen_code (address@hidden, address@hidden, 
address@hidden, address@hidden, cflags=<optimized out>, 
      address@hidden) at 
/media/develdata/devel/build/qemu-2.9.0/translate-all.c:1295
  #15 0x000055de1c436a7a in tb_find (tb_exit=0, last_tb=0x0, cpu=<optimized 
out>) at /media/develdata/devel/build/qemu-2.9.0/cpu-exec.c:365
  #16 cpu_exec (cpu=<optimized out>) at 
/media/develdata/devel/build/qemu-2.9.0/cpu-exec.c:673
  #17 0x000055de1c466278 in cpu_loop (env=0x55de1e91df48) at 
/media/develdata/devel/build/qemu-2.9.0/linux-user/main.c:2236
  #18 0x000055de1c433103 in main (argc=<optimized out>, argv=0x7ffe5ffd9de8, 
envp=<optimized out>)
      at /media/develdata/devel/build/qemu-2.9.0/linux-user/main.c:4860
  (gdb) thread 2
  [Switching to thread 2 (Thread 0x7f1e7d0ad700 (LWP 9727))]
  #0  syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
  38      ../sysdeps/unix/sysv/linux/x86_64/syscall.S: Datei oder Verzeichnis 
nicht gefunden.
  (gdb) where
  #0  syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
  #1  0x000055de1c527605 in qemu_futex_wait (val=<optimized out>, f=<optimized 
out>) at /media/develdata/devel/build/qemu-2.9.0/include/qemu/futex.h:26
  #2  qemu_event_wait (address@hidden <rcu_call_ready_event>) at 
/media/develdata/devel/build/qemu-2.9.0/util/qemu-thread-posix.c:399
  #3  0x000055de1c52d41e in call_rcu_thread (opaque=<optimized out>) at 
/media/develdata/devel/build/qemu-2.9.0/util/rcu.c:249
  #4  0x00007f1e7d6ef6ba in start_thread (arg=0x7f1e7d0ad700) at 
pthread_create.c:333
  #5  0x00007f1e7d4253dd in clone () at 
../sysdeps/unix/sysv/linux/x86_64/clone.S:109

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