[PATCH/SPARC-branch] Make call dummies on non-executable stack work
Michael Snyder
msnyder@redhat.com
Wed Oct 15 22:28:00 GMT 2003
Mark Kettenis wrote:
> The attached patch makes call dummies on a non-executable stack
> working. I checked this in on my SPARC branch. What do people think
> about checking this in on mainline? I don't think this will get much
> exposure on the branch.
>
> Mark
I guess the only way you would get a false positive here
would be if you took a SEGV while executing a breakpoint trap.
I *guess* that seems unlikely -- but I wonder if there's a
pathological case, or if one might see this happening while
porting gdb to a new target, an immature sim, or something?
Is there a gotcha, for instance, for VLIW machines?
Might execute the trap, and another instruction simultaneously?
Kevin?
>
> Index: ChangeLog
> from Mark Kettenis <kettenis@gnu.org>
>
> * infrun.c (handle_inferior_event): Allow for breakpoint
> instructions to generate a SIGSEGV in addition to SIGTRAP, SIGILL
> and SIGEMT. Update comments.
>
> Index: infrun.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/infrun.c,v
> retrieving revision 1.113
> diff -u -p -r1.113 infrun.c
> --- infrun.c 14 Sep 2003 16:32:13 -0000 1.113
> +++ infrun.c 15 Oct 2003 19:54:43 -0000
> @@ -1845,16 +1845,21 @@ handle_inferior_event (struct execution_
> will be made according to the signal handling tables. */
>
> /* First, distinguish signals caused by the debugger from signals
> - that have to do with the program's own actions.
> - Note that breakpoint insns may cause SIGTRAP or SIGILL
> - or SIGEMT, depending on the operating system version.
> - Here we detect when a SIGILL or SIGEMT is really a breakpoint
> - and change it to SIGTRAP. */
> + that have to do with the program's own actions. Note that
> + breakpoint insns may cause SIGTRAP or SIGILL or SIGEMT, depending
> + on the operating system version. Here we detect when a SIGILL or
> + SIGEMT is really a breakpoint and change it to SIGTRAP. We do
> + something similar for SIGSEGV, since a SIGSEGV will be generated
> + when we're trying to execute a breakpoint instruction on a
> + non-executable stack. This happens for call dummy breakpoints
> + for architectures like SPARC that place call dummies on the
> + stack. */
>
> if (stop_signal == TARGET_SIGNAL_TRAP
> || (breakpoints_inserted &&
> (stop_signal == TARGET_SIGNAL_ILL
> - || stop_signal == TARGET_SIGNAL_EMT))
> + || stop_signal == TARGET_SIGNAL_EMT
> + || stop_signal == TARGET_SIGNAL_SEGV))
> || stop_soon == STOP_QUIETLY
> || stop_soon == STOP_QUIETLY_NO_SIGSTOP)
> {
> @@ -1937,10 +1942,14 @@ handle_inferior_event (struct execution_
>
> If someone ever tries to get get call dummys on a
> non-executable stack to work (where the target would stop
> - with something like a SIGSEG), then those tests might need to
> - be re-instated. Given, however, that the tests were only
> + with something like a SIGSEGV), then those tests might need
> + to be re-instated. Given, however, that the tests were only
> enabled when momentary breakpoints were not being used, I
> - suspect that it won't be the case. */
> + suspect that it won't be the case.
> +
> + NOTE: kettenis/2003-10-15: Indeed such checks don't seem to
> + be necessary for call dummies on a non-executable stack on
> + SPARC. */
>
> if (stop_signal == TARGET_SIGNAL_TRAP)
> ecs->random_signal
>
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