From: Segher Boessenkool <segher@kernel.crashing.org>
To: Jeff Law <law@redhat.com>
Cc: Martin Sebor <msebor@redhat.com>,
Gcc Patch List <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] warn for unsafe calls to __builtin_return_address
Date: Sat, 25 Jul 2015 15:59:00 -0000 [thread overview]
Message-ID: <20150725142035.GB7309@gate.crashing.org> (raw)
In-Reply-To: <55B1C845.1030000@redhat.com>
On Thu, Jul 23, 2015 at 11:08:21PM -0600, Jeff Law wrote:
> >There's the following comment in expand_builtin_frame_address:
> >
> > /* Some ports cannot access arbitrary stack frames. */
> >
> >just before a block of code where the function can lead to
> >an "invalid argument" warning which would cause the newly
> >added tests to fail (since the newly added warning wouldn't
> >be issued).
> >
> >I tried to determine what ports these might be so I could add
> >conditionals to the tests to prevent false positives there but
> >couldn't find any.
A quick grep shows aarch64. Also many other ports, for
__builtin_return_address. For __builtin_frame_address there is no
non-hacky way for ports to say "I cannot access other frames"; see
mmix_dynamic_chain_address for more complaints about this.
> You have to start thinking creatively. For example, consider ports
> without dwarf2 unwinders :-) Consider ports where the linker inserts
> stubs between caller & callee for various reasons Consider cases where
> the next outermost frame is compiled by something other than GCC, or
> perhaps was written in pure assembly. Or consider the case when we're
> currently in a signal handling frame...
Or simply the case where the caller does not have a frame pointer, and
the ABI does not provide another way to get at (the size of) stack frames.
> So, my suggestion would be to warn for any call with a nonzero value.
The current documentation says that you should only use nonzero values
for debug purposes. A warning would help yes, how many people read the
manual after all :-)
Segher
next prev parent reply other threads:[~2015-07-25 14:20 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-21 19:37 [PATCH] clarify doc for __builtin_return_address Martin Sebor
2015-05-21 20:50 ` Sandra Loosemore
2015-05-21 21:22 ` Martin Sebor
2015-05-21 22:00 ` Pedro Alves
2015-06-11 23:22 ` [PATCH] warn for unsafe calls to __builtin_return_address Martin Sebor
2015-06-18 17:32 ` [PING] " Martin Sebor
2015-06-27 0:48 ` [PING 2] " Martin Sebor
2015-07-07 3:41 ` [PING 3] " Martin Sebor
2015-07-07 10:14 ` Pedro Alves
2015-07-24 5:30 ` Jeff Law
2015-07-25 15:59 ` Segher Boessenkool [this message]
2015-07-28 3:44 ` Martin Sebor
2015-07-28 15:19 ` Segher Boessenkool
2015-07-28 16:03 ` Martin Sebor
2015-07-31 16:46 ` Jeff Law
2015-08-02 23:15 ` Martin Sebor
2015-08-03 11:55 ` [BUILDROBOT] Go runtime: calling ‘__builtin_frame_address’ with a nonzero argument is unsafe (was: warn for unsafe calls to __builtin_return_address) Jan-Benedict Glaw
2015-08-03 14:48 ` [BUILDROBOT] Go runtime: calling ‘__builtin_frame_address’ with a nonzero argument is unsafe Martin Sebor
2015-08-03 15:29 ` Jeff Law
2015-08-05 7:28 ` [PATCH] warn for unsafe calls to __builtin_return_address Andreas Schwab
2015-08-05 16:03 ` Jiong Wang
2015-08-05 17:56 ` Martin Sebor
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