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| author | Pedro Alves <palves@redhat.com> | 2015-02-11 09:45:41 +0000 |
|---|---|---|
| committer | Pedro Alves <palves@redhat.com> | 2015-02-11 09:45:41 +0000 |
| commit | 0703599a49d082a957ee233fe018fb6ea7864920 (patch) | |
| tree | 53db4e74b8c7f9342cf59412ecd5c4c7fd422204 /gdb/infrun.c | |
| parent | 07f107f306e422497915e62f6c3d3d6d7b20e8e1 (diff) | |
| download | gdb-0703599a49d082a957ee233fe018fb6ea7864920.zip gdb-0703599a49d082a957ee233fe018fb6ea7864920.tar.gz gdb-0703599a49d082a957ee233fe018fb6ea7864920.tar.bz2 | |
Fix adjust_pc_after_break, remove still current thread check
On decr_pc_after_break targets, GDB adjusts the PC incorrectly if a
background single-step stops somewhere where PC-$decr_pc has a
breakpoint, and the thread that finishes the step is not the current
thread, like:
ADDR1 nop <-- breakpoint here
ADDR2 jmp PC
IOW, say thread A is stepping ADDR2's line in the background (an
infinite loop), and the user switches focus to thread B. GDB's
adjust_pc_after_break logic confuses the single-step stop of thread A
for a hit of the breakpoint at ADDR1, and thus adjusts thread A's PC
to point at ADDR1 when it should not, and reports a breakpoint hit,
when thread A did not execute the instruction at ADDR1 at all.
The test added by this patch exercises exactly that.
I can't find any reason we'd need the "thread to be examined is still
the current thread" condition in adjust_pc_after_break, at least
nowadays; it might have made sense in the past. Best just remove it,
and rely on currently_stepping().
Here's the test's log of a run with an unpatched GDB:
35 while (1);
(gdb) PASS: gdb.threads/step-bg-decr-pc-switch-thread.exp: next over nop
next&
(gdb) PASS: gdb.threads/step-bg-decr-pc-switch-thread.exp: next& over inf loop
thread 1
[Switching to thread 1 (Thread 0x7ffff7fc2740 (LWP 29027))](running)
(gdb)
PASS: gdb.threads/step-bg-decr-pc-switch-thread.exp: switch to main thread
Breakpoint 2, thread_function (arg=0x0) at ...src/gdb/testsuite/gdb.threads/step-bg-decr-pc-switch-thread.c:34
34 NOP; /* set breakpoint here */
FAIL: gdb.threads/step-bg-decr-pc-switch-thread.exp: no output while stepping
gdb/ChangeLog:
2015-02-11 Pedro Alves <pedro@codesourcery.com>
* infrun.c (adjust_pc_after_break): Don't adjust the PC just
because the event thread is not the current thread.
gdb/testsuite/ChangeLog:
2015-02-11 Pedro Alves <pedro@codesourcery.com>
* gdb.threads/step-bg-decr-pc-switch-thread.c: New file.
* gdb.threads/step-bg-decr-pc-switch-thread.exp: New file.
Diffstat (limited to 'gdb/infrun.c')
| -rw-r--r-- | gdb/infrun.c | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/gdb/infrun.c b/gdb/infrun.c index 5770d77..15589b6 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -3487,7 +3487,6 @@ adjust_pc_after_break (struct execution_control_state *ecs) The SIGTRAP can be due to a completed hardware single-step only if - we didn't insert software single-step breakpoints - - the thread to be examined is still the current thread - this thread is currently being stepped If any of these events did not occur, we must have stopped due @@ -3499,7 +3498,6 @@ adjust_pc_after_break (struct execution_control_state *ecs) we also need to back up to the breakpoint address. */ if (thread_has_single_step_breakpoints_set (ecs->event_thread) - || !ptid_equal (ecs->ptid, inferior_ptid) || !currently_stepping (ecs->event_thread) || (ecs->event_thread->stepped_breakpoint && ecs->event_thread->prev_pc == breakpoint_pc)) |