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| author | Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | 2022-01-24 20:12:45 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-02-02 15:11:35 +0300 |
| commit | 233e667e1ae3e348686bd9dd0172e62a09d852e1 (patch) | |
| tree | 5aab42ce471316adc344bc450e47808ec7fd9264 /tools/testing/selftests/rseq/rseq.h | |
| parent | 886ddfba933f5ce9d76c278165d834d114ba4ffc (diff) | |
| download | linux-233e667e1ae3e348686bd9dd0172e62a09d852e1.tar.xz | |
selftests/rseq: Uplift rseq selftests for compatibility with glibc-2.35
glibc-2.35 (upcoming release date 2022-02-01) exposes the rseq per-thread
data in the TCB, accessible at an offset from the thread pointer, rather
than through an actual Thread-Local Storage (TLS) variable, as the
Linux kernel selftests initially expected.
The __rseq_abi TLS and glibc-2.35's ABI for per-thread data cannot
actively coexist in a process, because the kernel supports only a single
rseq registration per thread.
Here is the scheme introduced to ensure selftests can work both with an
older glibc and with glibc-2.35+:
- librseq exposes its own "rseq_offset, rseq_size, rseq_flags" ABI.
- librseq queries for glibc rseq ABI (__rseq_offset, __rseq_size,
__rseq_flags) using dlsym() in a librseq library constructor. If those
are found, copy their values into rseq_offset, rseq_size, and
rseq_flags.
- Else, if those glibc symbols are not found, handle rseq registration
from librseq and use its own IE-model TLS to implement the rseq ABI
per-thread storage.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220124171253.22072-8-mathieu.desnoyers@efficios.com
Diffstat (limited to 'tools/testing/selftests/rseq/rseq.h')
| -rw-r--r-- | tools/testing/selftests/rseq/rseq.h | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h index ca668a2af172..17531ccd3090 100644 --- a/tools/testing/selftests/rseq/rseq.h +++ b/tools/testing/selftests/rseq/rseq.h @@ -43,12 +43,19 @@ #define RSEQ_INJECT_FAILED #endif -extern __thread struct rseq_abi __rseq_abi; -extern int __rseq_handled; +#include "rseq-thread-pointer.h" + +/* Offset from the thread pointer to the rseq area. */ +extern int rseq_offset; +/* Size of the registered rseq area. 0 if the registration was + unsuccessful. */ +extern unsigned int rseq_size; +/* Flags used during rseq registration. */ +extern unsigned int rseq_flags; static inline struct rseq_abi *rseq_get_abi(void) { - return &__rseq_abi; + return (struct rseq_abi *) ((uintptr_t) rseq_thread_pointer() + rseq_offset); } #define rseq_likely(x) __builtin_expect(!!(x), 1) |