Re: Using the stack from inline assembly

[Florian Weimer <fweimer at redhat dot com>]

On 12/13/2016 10:48 AM, Andrew Haley wrote:
> On 13/12/16 07:13, Florian Weimer wrote:
> > Is it possible to use the stack from inline assembly?  I'm particularly
> > interested in i386 and x86_64, and push/pop instructions and function calls.
> >
> > Will GCC automatically disable use of the red zone on x86_64 if inline
> > assembly is used, or at least assume it's clobbered by inline assembly?
> > If not, how is this supposed to work if it does at all?
>
> It's up to the writer of inline asembly code to DTRT.  You're
> expected to know the ABI or not mess with the stack.

The ABI does not talk about inline assembly. :-/

I was just wondering if GCC does something here to simplify matters. 
Although it would pessimize code for probably 99% of the users of inline 
assembly.

If GCC doesn't disable the red zone on x86_64, calls and push/pop are 
quite unsafe, and we have a couple of time bombs in glibc.

Thanks,
Florian