https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87220
Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
CC| |ebotcazou at gcc dot gnu.org
Resolution|--- |WORKSFORME
--- Comment #3 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> -fstack-check produces the code (x86_64; similar for 32-bit):
>
> foo:
> subq $4152, %rsp
> orq $0, (%rsp)
> addq $4128, %rsp
> leaq 6(%rsp), %rdi
> call bar
> addq $24, %rsp
> ret
>
> This test:
> 1. Unnecessarily touches an extra page of stack that's not used, wasting
> memory.
It's as designed (the extra page is necessary to unwind the stack).
> 2. Skips over a whole page, potentially clobbering (data race) data on the
> other side of a guard page.
Likewise, because of 1.
> 3. Is completely unnecessary; since less than a page of stack is needed,
> only a probe of the final desired stack pointer (after the third
> instruction) is needed, and it's performed implicitly by the call.
Likewise, because of 1.
> The excessive stack usage, unsafety (jumping the guard page), and size and
> potential performance hit from unnecessary checks seem to make -fstack-check
> unsuitable for its intended purpose at this time.
-fstack-check was designed to implement stack checking in Ada, it has nothing
to do with stack protection, you want to use -fstack-clash-protection instead.
