On Fri, Jan 21, 2022 at 01:31:32PM -0800, H.J. Lu wrote:
> On Fri, Jan 21, 2022 at 09:18:41PM +0100, Jakub Jelinek via Gcc-patches wrote:
> > On Fri, Jan 21, 2022 at 08:16:11PM +0100, soeren--- via Gcc-patches wrote:
> > > gcc/ChangeLog:
> > >
> > > * common/config/s390/s390-common.c (s390_supports_split_stack):
> > > Only support split-stack on glibc targets.
> > > * config/i386/gnu-user-common.h (STACK_CHECK_STATIC_BUILTIN): Ditto.
> > > * config/i386/gnu.h (defined): Ditto.
> >
> > Besides breaking bootstrap, this doesn't do what it talks about:
> >
> > > --- a/gcc/config/i386/gnu.h
> > > +++ b/gcc/config/i386/gnu.h
> > > @@ -35,7 +35,10 @@ along with GCC. If not, see
> > > <http://www.gnu.org/licenses/>.
> > > crti.o%s
> > > %{static:crtbeginT.o%s;shared|pie:crtbeginS.o%s;:crtbegin.o%s}"
> > > #endif
> > >
> > > -#ifdef TARGET_LIBC_PROVIDES_SSP
> > > +/* -fsplit-stack uses a field in the TCB at a fixed offset. This
> > > + field is only available for glibc. Disable -fsplit-stack for
> > > + other libc implementations to avoid silent TCB corruptions. */
> > > +#if defined (TARGET_LIBC_PROVIDES_SSP) && OPTION_GLIBC
> > >
> > > /* i386 glibc provides __stack_chk_guard in %gs:0x14. */
> > > #define TARGET_THREAD_SSP_OFFSET 0x14
> >
> > Because this doesn't disable just -fsplit-stack support, but also
> > -fstack-protector*.
> > Does that one work on musl?
> > I think common/config/i386/i386-common.c (ix86_supports_split_stack)
> > should have been changed instead of the config/i386/gnu*.h headers.
> >
>
> Like this?
>
>
> H.J.
> ---
> Revert x86 changes in
>
> commit c163647ffbc9a20c8feb6e079dbecccfe016c82e
> Author: Soren Tempel <soe...@soeren-tempel.net>
> Date: Fri Jan 21 19:22:46 2022 +0000
>
> Disable -fsplit-stack support on non-glibc targets
>
> and change ix86_supports_split_stack to return true only on glibc.
>
> PR bootstrap/104170
> * common/config/i386/i386-common.cc (ix86_supports_split_stack):
> Return true only on glibc.
> * config/i386/gnu-user-common.h (STACK_CHECK_STATIC_BUILTIN):
> Revert commit c163647ffbc.
> * config/i386/gnu.h (TARGET_LIBC_PROVIDES_SSP): Likewise.
> ---
> gcc/common/config/i386/i386-common.cc | 4 ++--
> gcc/config/i386/gnu-user-common.h | 5 ++---
> gcc/config/i386/gnu.h | 5 +----
> 3 files changed, 5 insertions(+), 9 deletions(-)
>
> diff --git a/gcc/common/config/i386/i386-common.cc
> b/gcc/common/config/i386/i386-common.cc
> index cae0b880d79..78e6ff730aa 100644
> --- a/gcc/common/config/i386/i386-common.cc
> +++ b/gcc/common/config/i386/i386-common.cc
> @@ -1715,9 +1715,9 @@ ix86_option_init_struct (struct gcc_options *opts)
>
> static bool
> ix86_supports_split_stack (bool report ATTRIBUTE_UNUSED,
> - struct gcc_options *opts ATTRIBUTE_UNUSED)
> + struct gcc_options *opts)
> {
> - bool ret = true;
> + bool ret = opts->x_linux_libc == LIBC_GLIBC;
>
> #ifndef TARGET_THREAD_SPLIT_STACK_OFFSET
> if (report)
Almost.
I'd think you should honor report and drop ATTRIBUTE_UNUSED from both args.
So instead:
bool ret = true;
if (opts->x_linux_libc != LIBC_GLIBC)
{
if (report)
error ("%<-fsplit-stack%> currently only supported on GNU/Linux");
return false;
}
#ifndef TARGET_THREAD_SPLIT_STACK_OFFSET
...
Jakub
