old-cross-binutils/gdb/testsuite/gdb.base/bp-permanent.c

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fix skipping permanent breakpoints The gdb.arch/i386-bp_permanent.exp test is currently failing an assertion recently added: (gdb) stepi ../../src/gdb/infrun.c:2237: internal-error: resume: Assertion `sig != GDB_SIGNAL_0' failed. A problem internal to GDB has been detected, further debugging may prove unreliable. Quit this debugging session? (y or n) FAIL: gdb.arch/i386-bp_permanent.exp: Single stepping past permanent breakpoint. (GDB internal error) The assertion expects that the only reason we currently need to step a breakpoint instruction is when we have a signal to deliver. But when stepping a permanent breakpoint (with or without a signal) we also reach this code. The assertion is correct and the permanent breakpoints skipping code is wrong. Consider the case of the user doing "step/stepi" when stopped at a permanent breakpoint. GDB's `resume' calls the gdbarch_skip_permanent_breakpoint hook and then happily continues stepping: /* Normally, by the time we reach `resume', the breakpoints are either removed or inserted, as appropriate. The exception is if we're sitting at a permanent breakpoint; we need to step over it, but permanent breakpoints can't be removed. So we have to test for it here. */ if (breakpoint_here_p (aspace, pc) == permanent_breakpoint_here) { gdbarch_skip_permanent_breakpoint (gdbarch, regcache); } But since gdbarch_skip_permanent_breakpoint already advanced the PC manually, this ends up executing the instruction that is _after_ the breakpoint instruction. The user-visible result is that a single-step steps two instructions. The gdb.arch/i386-bp_permanent.exp test is actually ensuring that that's indeed how things work. It runs to an int3 instruction, does "stepi", and checks that "leave" was executed with that "stepi". Like this: (gdb) b *0x0804848c Breakpoint 2 at 0x804848c (gdb) c Continuing. Breakpoint 2, 0x0804848c in standard () (gdb) disassemble Dump of assembler code for function standard: 0x08048488 <+0>: push %ebp 0x08048489 <+1>: mov %esp,%ebp 0x0804848b <+3>: push %edi => 0x0804848c <+4>: int3 0x0804848d <+5>: leave 0x0804848e <+6>: ret 0x0804848f <+7>: nop (gdb) si 0x0804848e in standard () (gdb) disassemble Dump of assembler code for function standard: 0x08048488 <+0>: push %ebp 0x08048489 <+1>: mov %esp,%ebp 0x0804848b <+3>: push %edi 0x0804848c <+4>: int3 0x0804848d <+5>: leave => 0x0804848e <+6>: ret 0x0804848f <+7>: nop End of assembler dump. (gdb) One would instead expect that a stepi at 0x0804848c stops at 0x0804848d, _before_ the "leave" is executed. This commit changes GDB this way. Care is taken to make stepping into a signal handler when the step starts at a permanent breakpoint instruction work correctly. The patch adjusts gdb.arch/i386-bp_permanent.exp in this direction, and also makes it work on x86_64 (currently it only works on i*86). The patch also adds a new gdb.base/bp-permanent.exp test that exercises many different code paths related to stepping permanent breakpoints, including the stepping with signals cases. The test uses "hack/trick" to make it work on all (or most) platforms -- it doesn't really hard code a breakpoint instruction. Tested on x86_64 Fedora 20, native and gdbserver. gdb/ 2014-11-12 Pedro Alves <palves@redhat.com> * infrun.c (resume): Clear the thread's 'stepped_breakpoint' flag. Rewrite stepping over a permanent breakpoint. (thread_still_needs_step_over, proceed): Don't set stepping_over_breakpoint for permanent breakpoints. (handle_signal_stop): Don't clear stepped_breakpoint. Also pull single-step breakpoints out of the target on hardware step targets. (process_event_stop_test): If stepping a permanent breakpoint doesn't hit the step-resume breakpoint, delete the step-resume breakpoint. (switch_back_to_stepped_thread): Also check if the stepped thread has advanced already on hardware step targets. (currently_stepping): Return true if the thread stepped a breakpoint. gdb/testsuite/ 2014-11-12 Pedro Alves <palves@redhat.com> * gdb.arch/i386-bp_permanent.c: New file. * gdb.arch/i386-bp_permanent.exp: Don't skip on x86_64. (srcfile): Set to i386-bp_permanent.c. (top level): Adjust to work in both 32-bit and 64-bit modes. Test that stepi does not execute the 'leave' instruction, instead of testing it does execute. * gdb.base/bp-permanent.c: New file. * gdb.base/bp-permanent.exp: New file.
2014-11-12 10:10:49 +00:00
/* Copyright (C) 2014 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <string.h>
#ifdef SIGNALS
#include <signal.h>
#endif
#define NOP asm("nop")
/* Buffer holding the breakpoint instruction. */
unsigned char buffer[16];
volatile unsigned char *addr_bp;
volatile unsigned char *addr_after_bp;
int counter = 0;
void
test (void)
{
NOP;
NOP;
NOP;
NOP; /* write permanent bp here */
NOP; /* after permanent bp */
NOP;
NOP;
NOP;
NOP;
NOP;
counter++;
}
void
setup (void)
{
memcpy (buffer, (void *) addr_bp, addr_after_bp - addr_bp);
}
void
test_basics (void)
{
test (); /* for SIGTRAP */
test (); /* for breakpoint once */
test (); /* for breakpoint twice */
test (); /* for disabled bp SIGTRAP */
test (); /* for breakpoint thrice */
}
void
test_next (void)
{
test (); /* for next */
counter = 0; /* after next */
}
#ifdef SIGNALS
static void
test_signal_handler (int sig)
{
}
void
test_signal_with_handler (void)
{
signal (SIGUSR1, test_signal_handler);
test ();
}
void
test_signal_no_handler (void)
{
signal (SIGUSR1, SIG_IGN);
test ();
}
static void
test_signal_nested_handler ()
{
test ();
}
void
test_signal_nested_done (void)
{
}
void
test_signal_nested (void)
{
counter = 0;
signal (SIGALRM, test_signal_nested_handler);
alarm (1);
test ();
test_signal_nested_done ();
}
#endif
int
main (void)
{
setup ();
test_basics ();
test_next ();
#ifdef SIGNALS
test_signal_nested ();
test_signal_with_handler ();
test_signal_no_handler ();
#endif
return 0;
}