[gcc r12-6811] x86: Properly disable -fsplit-stack support on non-glibc targets

[H.J. Lu]

https://gcc.gnu.org/g:60953a23d57b13a672f751bec0c6eefc059eb1ab

commit r12-6811-g60953a23d57b13a672f751bec0c6eefc059eb1ab
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Fri Jan 21 13:24:00 2022 -0800

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

Diff:
---
 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