Re: [PATCH v2] Disable -fsplit-stack support on non-glibc targets
"H.J. Lu" wrote: > OPTION_GLIBC can't be used here since OPTION_GLIBC is > evaluated at run-time: > > https://gcc.gnu.org/pipermail/gcc-regression/2022-January/076271.html Oops, my bad, sorry! This accidentally broke in one of the two cleanup commits. Originally I justed use TARGET_GLIBC_MAJOR in PATCH v1. Would that be acceptable? Greetings, Sören
Re: [PATCH v2] Disable -fsplit-stack support on non-glibc targets
On Sat, Dec 18, 2021 at 4:20 AM soeren--- via Gcc-patches
wrote:
>
> From: Sören Tempel
>
> The -fsplit-stack option requires the pthread_t TCB definition in the
> libc to provide certain struct fields at specific hardcoded offsets. As
> far as I know, only glibc provides these fields at the required offsets.
> Most notably, musl libc does not have these fields. However, since gcc
> accesses the fields using a fixed offset, this does not cause a
> compile-time error, but instead results in a silent memory corruption at
> run-time with musl libc. For example, on s390x libgcc's
> __stack_split_initialize CTOR will overwrite the cancel field in the
> pthread_t TCB on musl.
>
> The -fsplit-stack option is used within the gcc code base itself by
> gcc-go (if available). On musl-based systems with split-stack support
> (i.e. s390x or x86) this causes Go programs compiled with gcc-go to
> misbehave at run-time.
>
> This patch fixes gcc-go on musl by disabling -fsplit-stack in gcc itself
> since it is not supported on non-glibc targets anyhow. This is achieved
> by checking if gcc targets a glibc-based system. This check has been
> added for x86 and s390x, the rs6000 config already checks for
> TARGET_GLIBC_MAJOR. Other architectures do not have split-stack
> support. With this patch applied, the gcc-go configure script will
> detect that -fsplit-stack support is not available and will not use it.
>
> See https://www.openwall.com/lists/musl/2012/10/16/12
>
> This patch was written under the assumption that glibc is the only libc
> implementation which supports the required fields at the required
> offsets in the pthread_t TCB. The patch has been tested on Alpine Linux
> Edge on the s390x and x86 architectures by bootstrapping Google's Go
> implementation with gcc-go.
>
> Signed-off-by: Sören Tempel
>
> 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.
> ---
> This version of the patch addresses feedback by Andrew Pinski and uses
> OPTION_GLIBC as well as opts->x_linux_libc == LIBC_GLIBC to detect glibc
> targets (instead of relying on TARGET_GLIBC_MAJOR).
>
> gcc/common/config/s390/s390-common.c | 11 +--
> gcc/config/i386/gnu-user-common.h| 5 +++--
> gcc/config/i386/gnu.h| 6 +-
> 3 files changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/gcc/common/config/s390/s390-common.c
> b/gcc/common/config/s390/s390-common.c
> index b6bc8501742..fc86e0bc5e7 100644
> --- a/gcc/common/config/s390/s390-common.c
> +++ b/gcc/common/config/s390/s390-common.c
> @@ -116,13 +116,20 @@ s390_handle_option (struct gcc_options *opts
> ATTRIBUTE_UNUSED,
>
> /* -fsplit-stack uses a field in the TCB, available with glibc-2.23.
> We don't verify it, since earlier versions just have padding at
> - its place, which works just as well. */
> + its place, which works just as well. For other libc implementations
> + we disable the feature entirely to avoid corrupting the TCB. */
>
> static bool
> s390_supports_split_stack (bool report ATTRIBUTE_UNUSED,
>struct gcc_options *opts ATTRIBUTE_UNUSED)
> {
> - return true;
> + if (opts->x_linux_libc == LIBC_GLIBC) {
> +return true;
> + } else {
> +if (report)
> + error("%<-fsplit-stack%> currently only supported on GNU/Linux");
> +return false;
> + }
> }
>
> #undef TARGET_DEFAULT_TARGET_FLAGS
> diff --git a/gcc/config/i386/gnu-user-common.h
> b/gcc/config/i386/gnu-user-common.h
> index 00226f5a455..6e13315b5a3 100644
> --- a/gcc/config/i386/gnu-user-common.h
> +++ b/gcc/config/i386/gnu-user-common.h
> @@ -66,7 +66,8 @@ 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. */
> -#if HAVE_GAS_CFI_PERSONALITY_DIRECTIVE
> + assembler has full support for the CFI directives and
> + targets glibc. */
> +#if HAVE_GAS_CFI_PERSONALITY_DIRECTIVE && OPTION_GLIBC
OPTION_GLIBC can't be used here since OPTION_GLIBC is
evaluated at run-time:
https://gcc.gnu.org/pipermail/gcc-regression/2022-January/076271.html
> #define TARGET_CAN_SPLIT_STACK
> #endif
> diff --git a/gcc/config/i386/gnu.h b/gcc/config/i386/gnu.h
> index 25fbc07f58c..adfe817201e 100644
> --- a/gcc/config/i386/gnu.h
> +++ b/gcc/config/i386/gnu.h
> @@ -35,7 +35,11 @@ along with GCC. If not, see
>
Re: [PATCH v2] Disable -fsplit-stack support on non-glibc targets
On Thu, Jan 20, 2022 at 11:52 PM Richard Sandiford
wrote:
>
> cc:ing the x86 and s390 maintainers
>
> soeren--- via Gcc-patches writes:
> > From: Sören Tempel
> >
> > The -fsplit-stack option requires the pthread_t TCB definition in the
> > libc to provide certain struct fields at specific hardcoded offsets. As
> > far as I know, only glibc provides these fields at the required offsets.
> > Most notably, musl libc does not have these fields. However, since gcc
> > accesses the fields using a fixed offset, this does not cause a
> > compile-time error, but instead results in a silent memory corruption at
> > run-time with musl libc. For example, on s390x libgcc's
> > __stack_split_initialize CTOR will overwrite the cancel field in the
> > pthread_t TCB on musl.
> >
> > The -fsplit-stack option is used within the gcc code base itself by
> > gcc-go (if available). On musl-based systems with split-stack support
> > (i.e. s390x or x86) this causes Go programs compiled with gcc-go to
> > misbehave at run-time.
> >
> > This patch fixes gcc-go on musl by disabling -fsplit-stack in gcc itself
> > since it is not supported on non-glibc targets anyhow. This is achieved
> > by checking if gcc targets a glibc-based system. This check has been
> > added for x86 and s390x, the rs6000 config already checks for
> > TARGET_GLIBC_MAJOR. Other architectures do not have split-stack
> > support. With this patch applied, the gcc-go configure script will
> > detect that -fsplit-stack support is not available and will not use it.
> >
> > See https://www.openwall.com/lists/musl/2012/10/16/12
> >
> > This patch was written under the assumption that glibc is the only libc
> > implementation which supports the required fields at the required
> > offsets in the pthread_t TCB. The patch has been tested on Alpine Linux
> > Edge on the s390x and x86 architectures by bootstrapping Google's Go
> > implementation with gcc-go.
> >
> > Signed-off-by: Sören Tempel
> >
> > 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.
LGTM for x86 parts.
Thanks,
Uros.
> > ---
> > This version of the patch addresses feedback by Andrew Pinski and uses
> > OPTION_GLIBC as well as opts->x_linux_libc == LIBC_GLIBC to detect glibc
> > targets (instead of relying on TARGET_GLIBC_MAJOR).
> >
> > gcc/common/config/s390/s390-common.c | 11 +--
> > gcc/config/i386/gnu-user-common.h| 5 +++--
> > gcc/config/i386/gnu.h| 6 +-
> > 3 files changed, 17 insertions(+), 5 deletions(-)
>
> Sorry for the slow review. The patch LGTM bar some minor formatting
> nits below, but target maintainers should have the final say.
>
> > diff --git a/gcc/common/config/s390/s390-common.c
> > b/gcc/common/config/s390/s390-common.c
> > index b6bc8501742..fc86e0bc5e7 100644
> > --- a/gcc/common/config/s390/s390-common.c
> > +++ b/gcc/common/config/s390/s390-common.c
> > @@ -116,13 +116,20 @@ s390_handle_option (struct gcc_options *opts
> > ATTRIBUTE_UNUSED,
> >
> > /* -fsplit-stack uses a field in the TCB, available with glibc-2.23.
> > We don't verify it, since earlier versions just have padding at
> > - its place, which works just as well. */
> > + its place, which works just as well. For other libc implementations
>
> GCC style is to use 2 spaces after a full stop. Same for the x86 part.
>
> > + we disable the feature entirely to avoid corrupting the TCB. */
> >
> > static bool
> > s390_supports_split_stack (bool report ATTRIBUTE_UNUSED,
> > struct gcc_options *opts ATTRIBUTE_UNUSED)
>
> These parameters are no longer unused after the patch, so it'd be good
> to remove the attributes.
>
> > {
> > - return true;
> > + if (opts->x_linux_libc == LIBC_GLIBC) {
> > +return true;
> > + } else {
> > +if (report)
> > + error("%<-fsplit-stack%> currently only supported on GNU/Linux");
> > +return false;
> > + }
>
> Normal GCC formatting would be something like:
>
> if (opts->x_linux_libc == LIBC_GLIBC)
> return true;
>
> if (report)
> error ("%<-fsplit-stack%> currently only supported on GNU/Linux");
> return false;
>
> Sorry for the fussy rules.
>
> Thanks,
> Richard
>
> > }
> >
> > #undef TARGET_DEFAULT_TARGET_FLAGS
> > diff --git a/gcc/config/i386/gnu-user-common.h
> > b/gcc/config/i386/gnu-user-common.h
> > index 00226f5a455..6e13315b5a3 100644
> > --- a/gcc/config/i386/gnu-user-common.h
> > +++ b/gcc/config/i386/gnu-user-common.h
> > @@ -66,7 +66,8 @@ 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. */
> > -#if HAVE_GAS_CFI_PERSONALITY_DIRECTIVE
> > + assembler has full support for
Re: [PATCH v2] Disable -fsplit-stack support on non-glibc targets
On 1/20/22 23:52, Richard Sandiford wrote:
> cc:ing the x86 and s390 maintainers
>
> soeren--- via Gcc-patches writes:
>> From: Sören Tempel
>>
>> The -fsplit-stack option requires the pthread_t TCB definition in the
>> libc to provide certain struct fields at specific hardcoded offsets. As
>> far as I know, only glibc provides these fields at the required offsets.
>> Most notably, musl libc does not have these fields. However, since gcc
>> accesses the fields using a fixed offset, this does not cause a
>> compile-time error, but instead results in a silent memory corruption at
>> run-time with musl libc. For example, on s390x libgcc's
>> __stack_split_initialize CTOR will overwrite the cancel field in the
>> pthread_t TCB on musl.
>>
>> The -fsplit-stack option is used within the gcc code base itself by
>> gcc-go (if available). On musl-based systems with split-stack support
>> (i.e. s390x or x86) this causes Go programs compiled with gcc-go to
>> misbehave at run-time.
>>
>> This patch fixes gcc-go on musl by disabling -fsplit-stack in gcc itself
>> since it is not supported on non-glibc targets anyhow. This is achieved
>> by checking if gcc targets a glibc-based system. This check has been
>> added for x86 and s390x, the rs6000 config already checks for
>> TARGET_GLIBC_MAJOR. Other architectures do not have split-stack
>> support. With this patch applied, the gcc-go configure script will
>> detect that -fsplit-stack support is not available and will not use it.
>>
>> See https://www.openwall.com/lists/musl/2012/10/16/12
>>
>> This patch was written under the assumption that glibc is the only libc
>> implementation which supports the required fields at the required
>> offsets in the pthread_t TCB. The patch has been tested on Alpine Linux
>> Edge on the s390x and x86 architectures by bootstrapping Google's Go
>> implementation with gcc-go.
>>
>> Signed-off-by: Sören Tempel
>>
>> 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.
s390 parts are ok.
Thanks!
Andreas
>> ---
>> This version of the patch addresses feedback by Andrew Pinski and uses
>> OPTION_GLIBC as well as opts->x_linux_libc == LIBC_GLIBC to detect glibc
>> targets (instead of relying on TARGET_GLIBC_MAJOR).
>>
>> gcc/common/config/s390/s390-common.c | 11 +--
>> gcc/config/i386/gnu-user-common.h| 5 +++--
>> gcc/config/i386/gnu.h| 6 +-
>> 3 files changed, 17 insertions(+), 5 deletions(-)
>
> Sorry for the slow review. The patch LGTM bar some minor formatting
> nits below, but target maintainers should have the final say.
>
>> diff --git a/gcc/common/config/s390/s390-common.c
>> b/gcc/common/config/s390/s390-common.c
>> index b6bc8501742..fc86e0bc5e7 100644
>> --- a/gcc/common/config/s390/s390-common.c
>> +++ b/gcc/common/config/s390/s390-common.c
>> @@ -116,13 +116,20 @@ s390_handle_option (struct gcc_options *opts
>> ATTRIBUTE_UNUSED,
>>
>> /* -fsplit-stack uses a field in the TCB, available with glibc-2.23.
>> We don't verify it, since earlier versions just have padding at
>> - its place, which works just as well. */
>> + its place, which works just as well. For other libc implementations
>
> GCC style is to use 2 spaces after a full stop. Same for the x86 part.
>
>> + we disable the feature entirely to avoid corrupting the TCB. */
>>
>> static bool
>> s390_supports_split_stack (bool report ATTRIBUTE_UNUSED,
>> struct gcc_options *opts ATTRIBUTE_UNUSED)
>
> These parameters are no longer unused after the patch, so it'd be good
> to remove the attributes.
>
>> {
>> - return true;
>> + if (opts->x_linux_libc == LIBC_GLIBC) {
>> +return true;
>> + } else {
>> +if (report)
>> + error("%<-fsplit-stack%> currently only supported on GNU/Linux");
>> +return false;
>> + }
>
> Normal GCC formatting would be something like:
>
> if (opts->x_linux_libc == LIBC_GLIBC)
> return true;
>
> if (report)
> error ("%<-fsplit-stack%> currently only supported on GNU/Linux");
> return false;
>
> Sorry for the fussy rules.
>
> Thanks,
> Richard
>
>> }
>>
>> #undef TARGET_DEFAULT_TARGET_FLAGS
>> diff --git a/gcc/config/i386/gnu-user-common.h
>> b/gcc/config/i386/gnu-user-common.h
>> index 00226f5a455..6e13315b5a3 100644
>> --- a/gcc/config/i386/gnu-user-common.h
>> +++ b/gcc/config/i386/gnu-user-common.h
>> @@ -66,7 +66,8 @@ 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. */
>> -#if HAVE_GAS_CFI_PERSONALITY_DIRECTIVE
>> + assembler has full support for the CFI directives and
>> + targets glibc. */
>> +#if HAVE_GAS_CFI_PERSONALITY_DIRECTIVE
Re: [PATCH v2] Disable -fsplit-stack support on non-glibc targets
cc:ing the x86 and s390 maintainers
soeren--- via Gcc-patches writes:
> From: Sören Tempel
>
> The -fsplit-stack option requires the pthread_t TCB definition in the
> libc to provide certain struct fields at specific hardcoded offsets. As
> far as I know, only glibc provides these fields at the required offsets.
> Most notably, musl libc does not have these fields. However, since gcc
> accesses the fields using a fixed offset, this does not cause a
> compile-time error, but instead results in a silent memory corruption at
> run-time with musl libc. For example, on s390x libgcc's
> __stack_split_initialize CTOR will overwrite the cancel field in the
> pthread_t TCB on musl.
>
> The -fsplit-stack option is used within the gcc code base itself by
> gcc-go (if available). On musl-based systems with split-stack support
> (i.e. s390x or x86) this causes Go programs compiled with gcc-go to
> misbehave at run-time.
>
> This patch fixes gcc-go on musl by disabling -fsplit-stack in gcc itself
> since it is not supported on non-glibc targets anyhow. This is achieved
> by checking if gcc targets a glibc-based system. This check has been
> added for x86 and s390x, the rs6000 config already checks for
> TARGET_GLIBC_MAJOR. Other architectures do not have split-stack
> support. With this patch applied, the gcc-go configure script will
> detect that -fsplit-stack support is not available and will not use it.
>
> See https://www.openwall.com/lists/musl/2012/10/16/12
>
> This patch was written under the assumption that glibc is the only libc
> implementation which supports the required fields at the required
> offsets in the pthread_t TCB. The patch has been tested on Alpine Linux
> Edge on the s390x and x86 architectures by bootstrapping Google's Go
> implementation with gcc-go.
>
> Signed-off-by: Sören Tempel
>
> 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.
> ---
> This version of the patch addresses feedback by Andrew Pinski and uses
> OPTION_GLIBC as well as opts->x_linux_libc == LIBC_GLIBC to detect glibc
> targets (instead of relying on TARGET_GLIBC_MAJOR).
>
> gcc/common/config/s390/s390-common.c | 11 +--
> gcc/config/i386/gnu-user-common.h| 5 +++--
> gcc/config/i386/gnu.h| 6 +-
> 3 files changed, 17 insertions(+), 5 deletions(-)
Sorry for the slow review. The patch LGTM bar some minor formatting
nits below, but target maintainers should have the final say.
> diff --git a/gcc/common/config/s390/s390-common.c
> b/gcc/common/config/s390/s390-common.c
> index b6bc8501742..fc86e0bc5e7 100644
> --- a/gcc/common/config/s390/s390-common.c
> +++ b/gcc/common/config/s390/s390-common.c
> @@ -116,13 +116,20 @@ s390_handle_option (struct gcc_options *opts
> ATTRIBUTE_UNUSED,
>
> /* -fsplit-stack uses a field in the TCB, available with glibc-2.23.
> We don't verify it, since earlier versions just have padding at
> - its place, which works just as well. */
> + its place, which works just as well. For other libc implementations
GCC style is to use 2 spaces after a full stop. Same for the x86 part.
> + we disable the feature entirely to avoid corrupting the TCB. */
>
> static bool
> s390_supports_split_stack (bool report ATTRIBUTE_UNUSED,
> struct gcc_options *opts ATTRIBUTE_UNUSED)
These parameters are no longer unused after the patch, so it'd be good
to remove the attributes.
> {
> - return true;
> + if (opts->x_linux_libc == LIBC_GLIBC) {
> +return true;
> + } else {
> +if (report)
> + error("%<-fsplit-stack%> currently only supported on GNU/Linux");
> +return false;
> + }
Normal GCC formatting would be something like:
if (opts->x_linux_libc == LIBC_GLIBC)
return true;
if (report)
error ("%<-fsplit-stack%> currently only supported on GNU/Linux");
return false;
Sorry for the fussy rules.
Thanks,
Richard
> }
>
> #undef TARGET_DEFAULT_TARGET_FLAGS
> diff --git a/gcc/config/i386/gnu-user-common.h
> b/gcc/config/i386/gnu-user-common.h
> index 00226f5a455..6e13315b5a3 100644
> --- a/gcc/config/i386/gnu-user-common.h
> +++ b/gcc/config/i386/gnu-user-common.h
> @@ -66,7 +66,8 @@ 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. */
> -#if HAVE_GAS_CFI_PERSONALITY_DIRECTIVE
> + assembler has full support for the CFI directives and
> + targets glibc. */
> +#if HAVE_GAS_CFI_PERSONALITY_DIRECTIVE && OPTION_GLIBC
> #define TARGET_CAN_SPLIT_STACK
> #endif
> diff --git a/gcc/config/i386/gnu.h b/gcc/config/i386/gnu.h
> index 25fbc07f58c..adfe817201e 100644
> --- a/gcc/config/i386/gnu.h
> +++ b/gcc/config/i386/gnu.h
> @@
Re: Re: [PATCH v2] Disable -fsplit-stack support on non-glibc targets
Ping.
Summary: Patch disable -fstack-split on non-glibc targets to prevent
corruptions of the TCB on libcs which do not support the required
fields in pthread_t. This is an important fix for having gccgo work on
musl by default.
See: https://gcc.gnu.org/pipermail/gcc-patches/2021-December/587142.html
If the patch needs to be revised further please let me know.
Greetings,
Sören
Sören Tempel wrote:
> The -fsplit-stack option requires the pthread_t TCB definition in the
> libc to provide certain struct fields at specific hardcoded offsets. As
> far as I know, only glibc provides these fields at the required offsets.
> Most notably, musl libc does not have these fields. However, since gcc
> accesses the fields using a fixed offset, this does not cause a
> compile-time error, but instead results in a silent memory corruption at
> run-time with musl libc. For example, on s390x libgcc's
> __stack_split_initialize CTOR will overwrite the cancel field in the
> pthread_t TCB on musl.
>
> The -fsplit-stack option is used within the gcc code base itself by
> gcc-go (if available). On musl-based systems with split-stack support
> (i.e. s390x or x86) this causes Go programs compiled with gcc-go to
> misbehave at run-time.
>
> This patch fixes gcc-go on musl by disabling -fsplit-stack in gcc itself
> since it is not supported on non-glibc targets anyhow. This is achieved
> by checking if gcc targets a glibc-based system. This check has been
> added for x86 and s390x, the rs6000 config already checks for
> TARGET_GLIBC_MAJOR. Other architectures do not have split-stack
> support. With this patch applied, the gcc-go configure script will
> detect that -fsplit-stack support is not available and will not use it.
>
> See https://www.openwall.com/lists/musl/2012/10/16/12
>
> This patch was written under the assumption that glibc is the only libc
> implementation which supports the required fields at the required
> offsets in the pthread_t TCB. The patch has been tested on Alpine Linux
> Edge on the s390x and x86 architectures by bootstrapping Google's Go
> implementation with gcc-go.
>
> Signed-off-by: Sören Tempel
>
> 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.
> ---
> This version of the patch addresses feedback by Andrew Pinski and uses
> OPTION_GLIBC as well as opts->x_linux_libc == LIBC_GLIBC to detect glibc
> targets (instead of relying on TARGET_GLIBC_MAJOR).
>
> gcc/common/config/s390/s390-common.c | 11 +--
> gcc/config/i386/gnu-user-common.h| 5 +++--
> gcc/config/i386/gnu.h| 6 +-
> 3 files changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/gcc/common/config/s390/s390-common.c
> b/gcc/common/config/s390/s390-common.c
> index b6bc8501742..fc86e0bc5e7 100644
> --- a/gcc/common/config/s390/s390-common.c
> +++ b/gcc/common/config/s390/s390-common.c
> @@ -116,13 +116,20 @@ s390_handle_option (struct gcc_options *opts
> ATTRIBUTE_UNUSED,
>
> /* -fsplit-stack uses a field in the TCB, available with glibc-2.23.
> We don't verify it, since earlier versions just have padding at
> - its place, which works just as well. */
> + its place, which works just as well. For other libc implementations
> + we disable the feature entirely to avoid corrupting the TCB. */
>
> static bool
> s390_supports_split_stack (bool report ATTRIBUTE_UNUSED,
> struct gcc_options *opts ATTRIBUTE_UNUSED)
> {
> - return true;
> + if (opts->x_linux_libc == LIBC_GLIBC) {
> +return true;
> + } else {
> +if (report)
> + error("%<-fsplit-stack%> currently only supported on GNU/Linux");
> +return false;
> + }
> }
>
> #undef TARGET_DEFAULT_TARGET_FLAGS
> diff --git a/gcc/config/i386/gnu-user-common.h
> b/gcc/config/i386/gnu-user-common.h
> index 00226f5a455..6e13315b5a3 100644
> --- a/gcc/config/i386/gnu-user-common.h
> +++ b/gcc/config/i386/gnu-user-common.h
> @@ -66,7 +66,8 @@ 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. */
> -#if HAVE_GAS_CFI_PERSONALITY_DIRECTIVE
> + assembler has full support for the CFI directives and
> + targets glibc. */
> +#if HAVE_GAS_CFI_PERSONALITY_DIRECTIVE && OPTION_GLIBC
> #define TARGET_CAN_SPLIT_STACK
> #endif
> diff --git a/gcc/config/i386/gnu.h b/gcc/config/i386/gnu.h
> index 25fbc07f58c..adfe817201e 100644
> --- a/gcc/config/i386/gnu.h
> +++ b/gcc/config/i386/gnu.h
> @@ -35,7 +35,11 @@ along with GCC. If not, see
>
