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* [Bug threads/18006] New: internal error if threaded program calls clone(CLONE_VM)
@ 2015-02-20 18:20 palves at redhat dot com
2015-02-20 19:03 ` [Bug threads/18006] " palves at redhat dot com
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: palves at redhat dot com @ 2015-02-20 18:20 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=18006
Bug ID: 18006
Summary: internal error if threaded program calls
clone(CLONE_VM)
Product: gdb
Version: HEAD
Status: NEW
Severity: normal
Priority: P2
Component: threads
Assignee: unassigned at sourceware dot org
Reporter: palves at redhat dot com
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.
On GDB 7.9, the crash looks like:
(gdb) break clone_fn
Breakpoint 2 at 0x4007d8: file clone-thread_db.c, line 35.
(gdb) r
...
[Thread debugging using libthread_db enabled]
...
/home/pedro/gdb/mygit/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.
On earlier releases, it looked like this:
(gdb) b clone_fn
Breakpoint 1 at 0x4007d8: file clone-thread_db.c, line 35.
(gdb) r
...
[Thread debugging using libthread_db enabled]
...
[New Thread 0x7ffff7fc2700 (LWP 3886)]
../../gdb/linux-thread-db.c:437: internal-error: thread_get_info_callback:
Assertion `inout->thread_info != NULL' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
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* [Bug threads/18006] internal error if threaded program calls clone(CLONE_VM)
2015-02-20 18:20 [Bug threads/18006] New: internal error if threaded program calls clone(CLONE_VM) palves at redhat dot com
@ 2015-02-20 19:03 ` palves at redhat dot com
2015-02-20 21:47 ` cvs-commit at gcc dot gnu.org
2015-02-20 23:32 ` palves at redhat dot com
2 siblings, 0 replies; 4+ messages in thread
From: palves at redhat dot com @ 2015-02-20 19:03 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=18006
Pedro Alves <palves at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at sourceware dot org |palves at redhat dot com
--- Comment #1 from Pedro Alves <palves at redhat dot com> ---
Mine.
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* [Bug threads/18006] internal error if threaded program calls clone(CLONE_VM)
2015-02-20 18:20 [Bug threads/18006] New: internal error if threaded program calls clone(CLONE_VM) palves at redhat dot com
2015-02-20 19:03 ` [Bug threads/18006] " palves at redhat dot com
@ 2015-02-20 21:47 ` cvs-commit at gcc dot gnu.org
2015-02-20 23:32 ` palves at redhat dot com
2 siblings, 0 replies; 4+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2015-02-20 21:47 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=18006
--- Comment #2 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Pedro Alves <palves@sourceware.org>:
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=5c5019c27c5a4a73ec53281b4b69044f82b179f0
commit 5c5019c27c5a4a73ec53281b4b69044f82b179f0
Author: Pedro Alves <palves@redhat.com>
Date: Fri Feb 20 19:00:21 2015 +0000
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.
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* [Bug threads/18006] internal error if threaded program calls clone(CLONE_VM)
2015-02-20 18:20 [Bug threads/18006] New: internal error if threaded program calls clone(CLONE_VM) palves at redhat dot com
2015-02-20 19:03 ` [Bug threads/18006] " palves at redhat dot com
2015-02-20 21:47 ` cvs-commit at gcc dot gnu.org
@ 2015-02-20 23:32 ` palves at redhat dot com
2 siblings, 0 replies; 4+ messages in thread
From: palves at redhat dot com @ 2015-02-20 23:32 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=18006
Pedro Alves <palves at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #3 from Pedro Alves <palves at redhat dot com> ---
Fixed.
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end of thread, other threads:[~2015-02-20 21:47 UTC | newest]
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2015-02-20 18:20 [Bug threads/18006] New: internal error if threaded program calls clone(CLONE_VM) palves at redhat dot com
2015-02-20 19:03 ` [Bug threads/18006] " palves at redhat dot com
2015-02-20 21:47 ` cvs-commit at gcc dot gnu.org
2015-02-20 23:32 ` palves at redhat dot com
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