diff mbox series

x86: Properly disable -fsplit-stack support on non-glibc targets

Message ID YesmNERXN3olQRPU@gmail.com
State New
Headers show
Series x86: Properly disable -fsplit-stack support on non-glibc targets | expand

Commit Message

H.J. Lu Jan. 21, 2022, 9:31 p.m. UTC 
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 <soeren@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(-)

Comments

Jakub Jelinek Jan. 21, 2022, 9:42 p.m. UTC | #1 
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 <soeren@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
diff mbox series

Patch

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)
diff --git a/gcc/config/i386/gnu-user-common.h b/gcc/config/i386/gnu-user-common.h
index 7525f788a9c..23b54c5be52 100644
--- a/gcc/config/i386/gnu-user-common.h
+++ b/gcc/config/i386/gnu-user-common.h
@@ -66,8 +66,7 @@  along with GCC; see the file COPYING3.  If not see
 #define STACK_CHECK_STATIC_BUILTIN 1
 
 /* We only build the -fsplit-stack support in libgcc if the
-   assembler has full support for the CFI directives and
-   targets glibc.  */
-#if HAVE_GAS_CFI_PERSONALITY_DIRECTIVE && OPTION_GLIBC
+   assembler has full support for the CFI directives.  */
+#if HAVE_GAS_CFI_PERSONALITY_DIRECTIVE
 #define TARGET_CAN_SPLIT_STACK
 #endif
diff --git a/gcc/config/i386/gnu.h b/gcc/config/i386/gnu.h
index daa505a5d45..401e60c9a02 100644
--- a/gcc/config/i386/gnu.h
+++ b/gcc/config/i386/gnu.h
@@ -35,10 +35,7 @@  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
 
-/* -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
+#ifdef TARGET_LIBC_PROVIDES_SSP
 
 /* i386 glibc provides __stack_chk_guard in %gs:0x14.  */
 #define TARGET_THREAD_SSP_OFFSET        0x14