Re: [PATCH] stack-protector: Check stack canary for noreturn function

[Jeff Law <jeffreyalaw@gmail.com>]

On 7/14/2022 3:55 PM, H.J. Lu via Gcc-patches wrote:
> Check stack canary for noreturn function to catch stack corruption
> before calling noreturn function.  For C++, check stack canary when
> throwing exception or resuming stack unwind to avoid corrupted stack.
>
> gcc/
>
> 	PR middle-end/58245
> 	* calls.cc (expand_call): Check stack canary for noreturn
> 	function.
>
> gcc/testsuite/
>
> 	PR middle-end/58245
> 	* c-c++-common/pr58245-1.c: New test.
> 	* g++.dg/pr58245-1.C: Likewise.
> 	* g++.dg/fstack-protector-strong.C: Adjusted.
But is this really something we want?   I'd actually lean towards 
eliminating the useless load -- I don't necessarily think we should be 
treating non-returning paths specially here.

The whole point of the stack protector is to prevent the *return* path 
from going to an attacker controlled location.  I'm not sure checking 
the protector at this point actually does anything particularly useful.

jeff