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| author | Florian Weimer <fweimer@redhat.com> | 2024-07-08 21:14:00 +0200 |
|---|---|---|
| committer | Florian Weimer <fweimer@redhat.com> | 2024-07-09 19:33:37 +0200 |
| commit | 2e456ccf0c34a056e3ccafac4a0c7effef14d918 (patch) | |
| tree | f8850016fc638b37f5edb32a729bb023d8084fa6 /sysdeps/unix/sysv/linux | |
| parent | 7e7f35278cf5980f6eb1ddd384217a04a5293bc8 (diff) | |
| download | glibc-2e456ccf0c34a056e3ccafac4a0c7effef14d918.zip glibc-2e456ccf0c34a056e3ccafac4a0c7effef14d918.tar.gz glibc-2e456ccf0c34a056e3ccafac4a0c7effef14d918.tar.bz2 | |
Linux: Make __rseq_size useful for feature detection (bug 31965)
The __rseq_size value is now the active area of struct rseq
(so 20 initially), not the full struct size including padding
at the end (32 initially).
Update misc/tst-rseq to print some additional diagnostics.
Reviewed-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Diffstat (limited to 'sysdeps/unix/sysv/linux')
| -rw-r--r-- | sysdeps/unix/sysv/linux/rseq-internal.h | 23 | ||||
| -rw-r--r-- | sysdeps/unix/sysv/linux/tst-rseq.c | 10 |
2 files changed, 30 insertions, 3 deletions
diff --git a/sysdeps/unix/sysv/linux/rseq-internal.h b/sysdeps/unix/sysv/linux/rseq-internal.h index 48eebc1..7ea935b 100644 --- a/sysdeps/unix/sysv/linux/rseq-internal.h +++ b/sysdeps/unix/sysv/linux/rseq-internal.h @@ -25,15 +25,34 @@ #include <stdio.h> #include <sys/rseq.h> +/* 32 is the initially required value for the area size. The + actually used rseq size may be less (20 bytes initially). */ +#define RSEQ_AREA_SIZE_INITIAL 32 +#define RSEQ_AREA_SIZE_INITIAL_USED 20 + +/* The variables are in .data.relro but are not yet write-protected. */ +extern unsigned int _rseq_size attribute_hidden; +extern ptrdiff_t _rseq_offset attribute_hidden; + #ifdef RSEQ_SIG static inline bool rseq_register_current_thread (struct pthread *self, bool do_rseq) { if (do_rseq) { + unsigned int size; +#if IS_IN (rtld) + /* Use the hidden symbol in ld.so. */ + size = _rseq_size; +#else + size = __rseq_size; +#endif + if (size < RSEQ_AREA_SIZE_INITIAL) + /* The initial implementation used only 20 bytes out of 32, + but still expected size 32. */ + size = RSEQ_AREA_SIZE_INITIAL; int ret = INTERNAL_SYSCALL_CALL (rseq, &self->rseq_area, - sizeof (self->rseq_area), - 0, RSEQ_SIG); + size, 0, RSEQ_SIG); if (!INTERNAL_SYSCALL_ERROR_P (ret)) return true; } diff --git a/sysdeps/unix/sysv/linux/tst-rseq.c b/sysdeps/unix/sysv/linux/tst-rseq.c index 2c90409..08a9533 100644 --- a/sysdeps/unix/sysv/linux/tst-rseq.c +++ b/sysdeps/unix/sysv/linux/tst-rseq.c @@ -29,6 +29,7 @@ # include <stdlib.h> # include <string.h> # include <syscall.h> +# include <sys/auxv.h> # include <thread_pointer.h> # include <tls.h> # include "tst-rseq.h" @@ -42,7 +43,8 @@ do_rseq_main_test (void) TEST_COMPARE (__rseq_flags, 0); TEST_VERIFY ((char *) __thread_pointer () + __rseq_offset == (char *) &pd->rseq_area); - TEST_COMPARE (__rseq_size, sizeof (pd->rseq_area)); + /* The current implementation only supports the initial size. */ + TEST_COMPARE (__rseq_size, 20); } static void @@ -52,6 +54,12 @@ do_rseq_test (void) { FAIL_UNSUPPORTED ("kernel does not support rseq, skipping test"); } + printf ("info: __rseq_size: %u\n", __rseq_size); + printf ("info: __rseq_offset: %td\n", __rseq_offset); + printf ("info: __rseq_flags: %u\n", __rseq_flags); + printf ("info: getauxval (AT_RSEQ_FEATURE_SIZE): %ld\n", + getauxval (AT_RSEQ_FEATURE_SIZE)); + printf ("info: getauxval (AT_RSEQ_ALIGN): %ld\n", getauxval (AT_RSEQ_ALIGN)); do_rseq_main_test (); } #else /* RSEQ_SIG */ |