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Fix PR19388: Can't access $_siginfo in breakpoint (catch signal) condition

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This commit merges both the registers and $_siginfo "thread
running/executing" checks into a single function.

Accessing $_siginfo from a "catch signal" breakpoint condition doesn't
work.  The condition always fails with "Selected thread is running":

 (gdb) catch signal
 Catchpoint 3 (standard signals)
 (gdb)
 condition $bpnum $_siginfo.si_signo == 5
 (gdb) continue
 Continuing.
 Error in testing breakpoint condition:
 Selected thread is running.

 Catchpoint 3 (signal SIGUSR1), 0x0000003615e35877 in __GI_raise (sig=10) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
 56        return INLINE_SYSCALL (tgkill, 3, pid, selftid, sig);
 (gdb)

When accessing the $_siginfo object, we check whether the thread is
marked running (external/public) state and refuse the access if so.
This is so "print $_siginfo" at the prompt fails nicelly when the
current thread is running.  While evaluating breakpoint conditionals,
we haven't decided yet whether the thread is going to stop, so
is_running still returns true, and we thus always error out.

Evaluating an expression that requires registers access is really
conceptually the same -- we could think of $_siginfo as a pseudo
register.  However, in that case we check whether the thread is marked
executing (internal/private state), not running (external/public
state).  Changing the $_siginfo validation to check is_executing as
well fixes the bug in question.

Note that checking is_executing is not fully correct, not even for
registers.  See PR 19389.  However, I think this is the lesser of two
evils and ends up as an improvement.  We at least now have a single
place to fix.

Tested on x86_64 GNU/Linux.

gdb/ChangeLog:
2016-01-13  Pedro Alves  <palves@redhat.com>

	PR breakpoints/19388
	* frame.c (get_current_frame): Use validate_registers_access.
	* gdbthread.h (validate_registers_access): Declare.
	* infrun.c (validate_siginfo_access): Delete.
	(siginfo_value_read, siginfo_value_write): Use
	validate_registers_access.
	* thread.c (validate_registers_access): New function.

gdb/testsuite/ChangeLog:
2016-01-13  Pedro Alves  <palves@redhat.com>

	PR breakpoints/19388
	* gdb.base/catch-signal-siginfo-cond.c: New file.
	* gdb.base/catch-signal-siginfo-cond.exp: New file.
This commit is contained in:
Pedro Alves 2016-01-13 10:40:33 +00:00
parent 8405419985
commit a911d87ad7
8 changed files with 144 additions and 29 deletions
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22
gdb/thread.c
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@ -1098,6 +1098,28 @@ finish_thread_state_cleanup (void *arg)
finish_thread_state (*ptid_p);
}
/* See gdbthread.h. */
void
validate_registers_access (void)
{
/* No selected thread, no registers. */
if (ptid_equal (inferior_ptid, null_ptid))
error (_("No thread selected."));
/* Don't try to read from a dead thread. */
if (is_exited (inferior_ptid))
error (_("The current thread has terminated"));
/* ... or from a spinning thread. FIXME: This isn't actually fully
correct. It'll allow an user-requested access (e.g., "print $pc"
at the prompt) when a thread is not executing for some internal
reason, but is marked running from the user's perspective. E.g.,
the thread is waiting for its turn in the step-over queue. */
if (is_executing (inferior_ptid))
error (_("Selected thread is running."));
}
int
pc_in_thread_step_range (CORE_ADDR pc, struct thread_info *thread)
{