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 <aqi...@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.
--
2.47.3
