The rseq selftests rely on features provided by glibc that may not be available in non-glibc C libraries:

1. The __GNU_PREREQ macro and glibc's thread pointer implementation are not available in non-glibc libraries 2. The __NR_rseq syscall number may not be defined in non-glibc headers

Add a fallback thread pointer implementation for non-glibc systems using the pre-existing inline assembly to access thread-local storage directly via %fs/%gs registers. Also provide a fallback definition for __NR_rseq when not already defined by the C library headers: 527 for alpha and 293 for other architectures.

Signed-off-by: Aqib Faruqui aqibaf@amazon.com --- .../selftests/rseq/rseq-x86-thread-pointer.h | 14 ++++++++++++++ tools/testing/selftests/rseq/rseq.c | 8 ++++++++ 2 files changed, 22 insertions(+)

diff --git a/tools/testing/selftests/rseq/rseq-x86-thread-pointer.h b/tools/testing/selftests/rseq/rseq-x86-thread-pointer.h index d3133587d..a7c402926 100644 --- a/tools/testing/selftests/rseq/rseq-x86-thread-pointer.h +++ b/tools/testing/selftests/rseq/rseq-x86-thread-pointer.h @@ -14,6 +14,7 @@ extern "C" { #endif

+#ifdef __GLIBC__ #if __GNUC_PREREQ (11, 1) static inline void *rseq_thread_pointer(void) { @@ -32,6 +33,19 @@ static inline void *rseq_thread_pointer(void) return __result; } #endif /* !GCC 11 */ +#else +static inline void *rseq_thread_pointer(void) +{ + void *__result; + +# ifdef __x86_64__ + __asm__ ("mov %%fs:0, %0" : "=r" (__result)); +# else + __asm__ ("mov %%gs:0, %0" : "=r" (__result)); +# endif + return __result; +} +#endif /* !__GLIBC__ */

#ifdef __cplusplus } diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c index 663a9cef1..1a6f73c98 100644 --- a/tools/testing/selftests/rseq/rseq.c +++ b/tools/testing/selftests/rseq/rseq.c @@ -36,6 +36,14 @@ #include "../kselftest.h" #include "rseq.h"

+#ifndef __NR_rseq +#ifdef __alpha__ +#define __NR_rseq 527 +#else +#define __NR_rseq 293 +#endif +#endif + /* * Define weak versions to play nice with binaries that are statically linked * against a libc that doesn't support registering its own rseq.