[Bug backtrace/31294] New: cant unwind __libc_do_syscall from gcore in arm 32 bits

[Bug backtrace/31294] New: cant unwind __libc_do_syscall from gcore in arm 32 bits

[blarsen at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31294

            Bug ID: 31294
           Summary: cant unwind __libc_do_syscall from gcore in arm 32
                    bits
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: backtrace
          Assignee: unassigned at sourceware dot org
          Reporter: blarsen at redhat dot com
  Target Milestone: ---

The newly introduced test gdb.threads/threadcrash.exp has revealed a
pre-existing issue in 32 bit arm.

using "info threads" on a regular corefile gives the following thread list:

info threads
  Id   Target Id                      Frame 
* 1    Thread 0xf7dbe7e0 (LWP 476389) 0x00830cea in crash_function () at
/home/tcwg-buildslave/workspace/tcwg_gnu_4/abe/snapshots/gdb.git~master/gdb/testsuite/gdb.threads/threadcrash.c:381
  2    Thread 0xf7c6f3a0 (LWP 476390) do_spin_task (location=NORMAL) at
/home/tcwg-buildslave/workspace/tcwg_gnu_4/abe/snapshots/gdb.git~master/gdb/testsuite/gdb.threads/threadcrash.c:139
  3    Thread 0xf746e3a0 (LWP 476391) do_spin_task (location=SIGNAL_HANDLER) at
/home/tcwg-buildslave/workspace/tcwg_gnu_4/abe/snapshots/gdb.git~master/gdb/testsuite/gdb.threads/threadcrash.c:139
  4    Thread 0xf6c6d3a0 (LWP 476392) do_spin_task (location=SIGNAL_ALT_STACK)
at
/home/tcwg-buildslave/workspace/tcwg_gnu_4/abe/snapshots/gdb.git~master/gdb/testsuite/gdb.threads/threadcrash.c:139
  5    Thread 0xf52fe3a0 (LWP 476395) __libc_do_syscall () at
../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:46
  6    Thread 0xf646c3a0 (LWP 476393) __libc_do_syscall () at
../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:46
  7    Thread 0xf5aff3a0 (LWP 476394) __libc_do_syscall () at
../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:46

Whereas the same command when loading a gcore yields:

info threads
  Id   Target Id         Frame 
* 1    LWP 476440        0x00400cea in crash_function () at
/home/tcwg-buildslave/workspace/tcwg_gnu_4/abe/snapshots/gdb.git~master/gdb/testsuite/gdb.threads/threadcrash.c:381
  2    LWP 476442        do_spin_task (location=NORMAL) at
/home/tcwg-buildslave/workspace/tcwg_gnu_4/abe/snapshots/gdb.git~master/gdb/testsuite/gdb.threads/threadcrash.c:139
  3    LWP 476443        do_spin_task (location=SIGNAL_HANDLER) at
/home/tcwg-buildslave/workspace/tcwg_gnu_4/abe/snapshots/gdb.git~master/gdb/testsuite/gdb.threads/threadcrash.c:139
  4    LWP 476444        do_spin_task (location=SIGNAL_ALT_STACK) at
/home/tcwg-buildslave/workspace/tcwg_gnu_4/abe/snapshots/gdb.git~master/gdb/testsuite/gdb.threads/threadcrash.c:139
  5    LWP 476445        0xf7eadb04 in ?? ()
  6    LWP 476446        0xf7eadb04 in ?? ()
  7    LWP 476447        0xf7eadb04 in ?? ()

Notice how the threads are in the same order, and threads 5, 6 and 7 all fail
the unwinding. This can be shown in the Linaro CI bug GNU-1120[1], even though
the main focus of the bug is unrelated to this.

I'm opening this mostly as a papertrail to add a KFAIL to the test, but it
should probably be fixed at some point.

[1] https://linaro.atlassian.net/browse/GNU-1120

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[Bug corefiles/31294] gcores do not work in 32-bit arm targets

[blarsen at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31294

Guinevere Larsen <blarsen at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|backtrace                   |corefiles
            Summary|cant unwind                 |gcores do not work in
                   |__libc_do_syscall from      |32-bit arm targets
                   |gcore in arm 32 bits        |

--- Comment #1 from Guinevere Larsen <blarsen at redhat dot com> ---
The rest of gdb.threads/threadcrash.exp gcore section has even worse results.
The log for "thread apply all backtrace" is as follows:

thread apply all backtrace^M
^M
Thread 7 (LWP 776476):^M
#0  0xf7eadb04 in ?? ()^M
#1  0xf7f13a7e in ?? ()^M
Backtrace stopped: previous frame identical to this frame (corrupt stack?)^M
^M
Thread 6 (LWP 776475):^M
#0  0xf7eadb04 in ?? ()^M
#1  0xf7f13a7e in ?? ()^M
Backtrace stopped: previous frame identical to this frame (corrupt stack?)^M
^M
Thread 5 (LWP 776474):^M
#0  0xf7eadb04 in ?? ()^M
#1  0xf7f13a7e in ?? ()^M
Backtrace stopped: previous frame identical to this frame (corrupt stack?)^M
^M
Thread 4 (LWP 776473):^M
#0  do_spin_task (location=SIGNAL_ALT_STACK) at
/home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/snapshots/gdb.git~master/gdb/testsuite/gdb.threads/threadcrash.c:139^M
#1  0x00400a5e in signal_handler (signo=10) at
/home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/snapshots/gdb.git~master/gdb/testsuite/gdb.threads/threadcrash.c:241^M
#2  <signal handler called>^M
#3  0xf7eadb06 in ?? ()^M
#4  0xf7eed292 in ?? ()^M
Backtrace stopped: previous frame identical to this frame (corrupt stack?)^M
^M
Thread 3 (LWP 776472):^M
#0  do_spin_task (location=SIGNAL_HANDLER) at
/home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/snapshots/gdb.git~master/gdb/testsuite/gdb.threads/threadcrash.c:139^M
#1  0x00400a5e in signal_handler (signo=10) at
/home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/snapshots/gdb.git~master/gdb/testsuite/gdb.threads/threadcrash.c:241^M
#2  <signal handler called>^M
#3  0xf7eadb06 in ?? ()^M
#4  0xf7eed292 in ?? ()^M
Backtrace stopped: previous frame identical to this frame (corrupt stack?)^M

Seems that either the writing or reading of gcores is thoroughly broken.

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[Bug corefiles/31294] gcores do not work in 32-bit arm targets

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31294

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sam at gentoo dot org

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[Bug corefiles/31294] gcores do not work in 32-bit arm targets

[thiago.bauermann at linaro dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31294

Thiago Jung Bauermann <thiago.bauermann at linaro dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |thiago.bauermann at linaro dot org

--- Comment #2 from Thiago Jung Bauermann <thiago.bauermann at linaro dot org> ---
I'm currently looking into bug #31254 which has similar symptoms.

I narrowed the problem in that bug down to the "arm exidx" unwinder, which uses
C++ exception tables to unwind frames. I think there's a memory corruption
issue with one of its data structures. I'm hoping to have more information
tomorrow.

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[Bug corefiles/31294] gcores do not work in 32-bit arm targets

[thiago.bauermann at linaro dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31294

--- Comment #3 from Thiago Jung Bauermann <thiago.bauermann at linaro dot org> ---
(In reply to Thiago Jung Bauermann from comment #2)
> I'm currently looking into bug #31254 which has similar symptoms.

Tom de Vries posted a fix to that bug, but even with it applied, I can still
reproduce this problem so they are different issues.

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[Bug corefiles/31294] gcores do not work in 32-bit arm targets

[thiago.bauermann at linaro dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31294

--- Comment #4 from Thiago Jung Bauermann <thiago.bauermann at linaro dot org> ---
I can't reproduce this problem anymore, so I did git bisect, which found that
commit 9c0aa4c53104 ("Fix disabling of year 2038 support on 32-bit hosts by
default") fixed the bug.

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[Bug corefiles/31294] gcores do not work in 32-bit arm targets

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31294

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
                 CC|                            |vries at gcc dot gnu.org
   Target Milestone|---                         |15.1
             Status|NEW                         |RESOLVED

--- Comment #5 from Tom de Vries <vries at gcc dot gnu.org> ---
Fixed.

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