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authorPedro Alves <palves@redhat.com>2015-02-11 09:45:41 +0000
committerPedro Alves <palves@redhat.com>2015-02-11 09:45:41 +0000
commit0703599a49d082a957ee233fe018fb6ea7864920 (patch)
tree53db4e74b8c7f9342cf59412ecd5c4c7fd422204 /gdb/infrun.c
parent07f107f306e422497915e62f6c3d3d6d7b20e8e1 (diff)
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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.c2
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))