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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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27
gdb/infrun.c
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@ -8684,25 +8684,6 @@ signals_info (char *signum_exp, int from_tty)
"to change these tables.\n"));
}
/* Check if it makes sense to read $_siginfo from the current thread
at this point. If not, throw an error. */
static void
validate_siginfo_access (void)
{
/* No current inferior, no siginfo. */
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. */
if (is_running (inferior_ptid))
error (_("Selected thread is running."));
}
/* The $_siginfo convenience variable is a bit special. We don't know
for sure the type of the value until we actually have a chance to
fetch the data. The type can change depending on gdbarch, so it is
@ -8721,7 +8702,9 @@ siginfo_value_read (struct value *v)
{
LONGEST transferred;
validate_siginfo_access ();
/* If we can access registers, so can we access $_siginfo. Likewise
vice versa. */
validate_registers_access ();
transferred =
target_read (&current_target, TARGET_OBJECT_SIGNAL_INFO,
@ -8742,7 +8725,9 @@ siginfo_value_write (struct value *v, struct value *fromval)
{
LONGEST transferred;
validate_siginfo_access ();
/* If we can access registers, so can we access $_siginfo. Likewise
vice versa. */
validate_registers_access ();
transferred = target_write (&current_target,
TARGET_OBJECT_SIGNAL_INFO,