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| author | Sören Tempel <soeren@soeren-tempel.net> | 2022-01-21 19:22:46 +0000 |
|---|---|---|
| committer | Richard Sandiford <richard.sandiford@arm.com> | 2022-01-21 19:22:46 +0000 |
| commit | c163647ffbc9a20c8feb6e079dbecccfe016c82e (patch) | |
| tree | c690fbf0f1c2c425ab0d533eb7db6df6d954ba1d /gcc/common | |
| parent | afe91e2566f47a6041f45095a48fc255625cb468 (diff) | |
| download | gcc-c163647ffbc9a20c8feb6e079dbecccfe016c82e.zip gcc-c163647ffbc9a20c8feb6e079dbecccfe016c82e.tar.gz gcc-c163647ffbc9a20c8feb6e079dbecccfe016c82e.tar.bz2 | |
Disable -fsplit-stack support on non-glibc targets
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 <soeren@soeren-tempel.net>
gcc/ChangeLog:
* common/config/s390/s390-common.cc (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.
Diffstat (limited to 'gcc/common')
| -rw-r--r-- | gcc/common/config/s390/s390-common.cc | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/gcc/common/config/s390/s390-common.cc b/gcc/common/config/s390/s390-common.cc index 6ed2f89..547b082 100644 --- a/gcc/common/config/s390/s390-common.cc +++ b/gcc/common/config/s390/s390-common.cc @@ -116,13 +116,19 @@ 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) +s390_supports_split_stack (bool report, + struct gcc_options *opts) { - return true; + if (opts->x_linux_libc == LIBC_GLIBC) + return true; + + if (report) + error ("%<-fsplit-stack%> currently only supported on GNU/Linux"); + return false; } #undef TARGET_DEFAULT_TARGET_FLAGS |