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Test results for commit 5c5019c27c5a4a73ec53281b4b69044f82b179f0 on branch master
- From: sergiodj at redhat dot com
- To: gdb-testers at sourceware dot org
- Date: Fri, 20 Feb 2015 16:19:03 -0500
- Subject: Test results for commit 5c5019c27c5a4a73ec53281b4b69044f82b179f0 on branch master
- Authentication-results: sourceware.org; auth=none
*** TEST RESULTS FOR COMMIT 5c5019c27c5a4a73ec53281b4b69044f82b179f0 ***
Author: Pedro Alves <palves@redhat.com>
Branch: master
Commit: 5c5019c27c5a4a73ec53281b4b69044f82b179f0
PR18006: internal error if threaded program calls clone(CLONE_VM)
On GNU/Linux, if a pthreaded program has a thread call clone(CLONE_VM)
directly, and then that clone LWP hits a debug event (breakpoint,
etc.) GDB internal errors. Threaded programs shouldn't really be
calling clone directly, but GDB shouldn't crash either.
The crash looks like this:
(gdb) break clone_fn
Breakpoint 2 at 0x4007d8: file clone-thread_db.c, line 35.
(gdb) r
...
[Thread debugging using libthread_db enabled]
...
src/gdb/linux-nat.c:1030: internal-error: lin_lwp_attach_lwp: Assertion `lwpid > 0' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
The problem is that 'clone' ends up clearing the parent thread's tid
field in glibc's thread data structure. For x86_64, the glibc code in
question is here:
sysdeps/unix/sysv/linux/x86_64/clone.S:
...
testq $CLONE_THREAD, %rdi
jne 1f
testq $CLONE_VM, %rdi
movl $-1, %eax <----
jne 2f
movl $SYS_ify(getpid), %eax
syscall
2: movl %eax, %fs:PID
movl %eax, %fs:TID <----
1:
When GDB refreshes the thread list out of libthread_db, it finds a
thread with LWP with pid -1 (the clone's parent), which naturally
isn't yet on the thread list. GDB then tries to attach to that bogus
LWP id, which is caught by that assertion.
The fix is to detect the bad PID early.
Tested on x86-64 Fedora 20. GDBserver doesn't need any fix.
gdb/ChangeLog:
2015-02-20 Pedro Alves <palves@redhat.com>
PR threads/18006
* linux-thread-db.c (thread_get_info_callback): Return early if
the thread's lwp id is -1.
gdb/testsuite/ChangeLog:
2015-02-20 Pedro Alves <palves@redhat.com>
PR threads/18006
* gdb.threads/clone-thread_db.c: New file.
* gdb.threads/clone-thread_db.exp: New file.
- Follow-Ups:
- Failures on Fedora-ppc64be-m64, branch master
- Failures on Fedora-ppc64be-native-gdbserver-m64, branch master
- Failures on Debian-x86_64-native-extended-gdbserver-m64, branch master
- Failures on Fedora-ppc64be-native-extended-gdbserver-m64, branch master
- Failures on Debian-i686, branch master
- Failures on Debian-x86_64-m64, branch master
- Failures on Fedora-i686, branch master
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- Failures on Debian-x86_64-native-gdbserver-m64, branch master
- Failures on Fedora-ppc64le-m64, branch master
- Failures on Fedora-x86_64-cc-with-index, branch master
- Failures on Fedora-ppc64le-native-gdbserver-m64, branch master
- Failures on Fedora-x86_64-m64, branch master
- Failures on Fedora-x86_64-native-gdbserver-m32, branch master