0703599a49
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.
54 lines
1.3 KiB
C
54 lines
1.3 KiB
C
/* This testcase is part of GDB, the GNU debugger.
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Copyright 2015 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include <unistd.h>
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#include <pthread.h>
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#include <assert.h>
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/* NOP instruction: must have the same size as the breakpoint
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instruction for the test to be effective. */
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#if defined (__s390__) || defined (__s390x__)
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# define NOP asm ("nopr 0")
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#else
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# define NOP asm ("nop")
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#endif
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void *
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thread_function (void *arg)
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{
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NOP; /* set breakpoint here */
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while (1);
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}
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int
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main (void)
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{
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int res;
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pthread_t thread;
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alarm (300);
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res = pthread_create (&thread,
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NULL,
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thread_function,
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NULL);
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assert (res == 0);
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pthread_join (thread, NULL);
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return 0;
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}
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