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Re: Obscure crashes due to gcc 4.9 -O2 => -fisolate-erroneous-paths-dereference


On 28/02/2015 9:12 am, Manuel López-Ibáñez wrote:
On 02/19/15 14:56, Chris Johns wrote:

My main concern is not knowing the trap has been added to the code. If I
could build an application and audit it somehow then I can manage it. We
have a similar issue with the possible use of FP registers being used in
general code (ISR save/restore trade off).

Can the ELF be annotated in some GCC specific way that makes it to the
final executable to flag this is happening ? We can then create tools to
audit the executables.

Simply ignore me if I'm misunderstanding the issue: Couldn't GCC
generate, instead of a trap, a call to a noinline noreturn cold weak
function __gcc_is_a_trap that by default calls the trap? Then, audit
tools can inspect the code and see if such a function call appears and
even override it with something else.

Yes it could and this is a nice idea.


Chris, wouldn't that be enough for your purposes?


I think it does because we can scan an executable for the call locations and audit them.

Chris


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