On Fri, Jan 21, 2022 at 10:42:03PM +0100, Jakub Jelinek wrote:
> 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
> ...
>
Here is the v2 patch.
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 | 17 +++++++++++------
gcc/config/i386/gnu-user-common.h | 5 ++---
gcc/config/i386/gnu.h | 5 +----
3 files changed, 14 insertions(+), 13 deletions(-)
diff --git a/gcc/common/config/i386/i386-common.cc
b/gcc/common/config/i386/i386-common.cc
index cae0b880d79..7496d179892 100644
--- a/gcc/common/config/i386/i386-common.cc
+++ b/gcc/common/config/i386/i386-common.cc
@@ -1714,16 +1714,21 @@ ix86_option_init_struct (struct gcc_options *opts)
field in the TCB, so they cannot be used together. */
static bool
-ix86_supports_split_stack (bool report ATTRIBUTE_UNUSED,
+ix86_supports_split_stack (bool report,
struct gcc_options *opts ATTRIBUTE_UNUSED)
{
+#ifdef TARGET_THREAD_SPLIT_STACK_OFFSET
+ if (opts->x_linux_libc != LIBC_GLIBC)
+#endif
+ {
+ if (report)
+ error ("%<-fsplit-stack%> currently only supported on GNU/Linux");
+ return false;
+ }
+
bool ret = true;
-#ifndef TARGET_THREAD_SPLIT_STACK_OFFSET
- if (report)
- error ("%<-fsplit-stack%> currently only supported on GNU/Linux");
- ret = false;
-#else
+#ifdef TARGET_THREAD_SPLIT_STACK_OFFSET
if (!HAVE_GAS_CFI_PERSONALITY_DIRECTIVE)
{
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
--
2.34.1
