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| author | Wilco Dijkstra <wilco.dijkstra@arm.com> | 2024-03-21 16:48:33 +0000 |
|---|---|---|
| committer | Wilco Dijkstra <wilco.dijkstra@arm.com> | 2024-04-08 17:08:03 +0100 |
| commit | 24de733967029fd902c34073d2ab25b900887352 (patch) | |
| tree | b8c93346bef5294924553a48ecbcb86896d4f534 /sysdeps/aarch64 | |
| parent | b77e357bf9bf9972fc33bfbde4269d911eb9b682 (diff) | |
| download | glibc-24de733967029fd902c34073d2ab25b900887352.tar.gz glibc-24de733967029fd902c34073d2ab25b900887352.tar.xz glibc-24de733967029fd902c34073d2ab25b900887352.zip | |
AArch64: Check kernel version for SVE ifuncs
Old Linux kernels disable SVE after every system call. Calling the SVE-optimized memcpy afterwards will then cause a trap to reenable SVE. As a result, applications with a high use of syscalls may run slower with the SVE memcpy. This is true for kernels between 4.15.0 and before 6.2.0, except for 5.14.0 which was patched. Avoid this by checking the kernel version and selecting the SVE ifunc on modern kernels. Parse the kernel version reported by uname() into a 24-bit kernel.major.minor value without calling any library functions. If uname() is not supported or if the version format is not recognized, assume the kernel is modern. Tested-by: Florian Weimer <fweimer@redhat.com> Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com> (cherry picked from commit 2e94e2f5d2bf2de124c8ad7da85463355e54ccb2)
Diffstat (limited to 'sysdeps/aarch64')
| -rw-r--r-- | sysdeps/aarch64/multiarch/init-arch.h | 2 | ||||
| -rw-r--r-- | sysdeps/aarch64/multiarch/memcpy.c | 2 | ||||
| -rw-r--r-- | sysdeps/aarch64/multiarch/memmove.c | 2 |
3 files changed, 4 insertions, 2 deletions
diff --git a/sysdeps/aarch64/multiarch/init-arch.h b/sysdeps/aarch64/multiarch/init-arch.h index 5da1656954..5b2cf5cb12 100644 --- a/sysdeps/aarch64/multiarch/init-arch.h +++ b/sysdeps/aarch64/multiarch/init-arch.h @@ -36,5 +36,7 @@ MTE_ENABLED (); \ bool __attribute__((unused)) sve = \ GLRO(dl_aarch64_cpu_features).sve; \ + bool __attribute__((unused)) prefer_sve_ifuncs = \ + GLRO(dl_aarch64_cpu_features).prefer_sve_ifuncs; \ bool __attribute__((unused)) mops = \ GLRO(dl_aarch64_cpu_features).mops; diff --git a/sysdeps/aarch64/multiarch/memcpy.c b/sysdeps/aarch64/multiarch/memcpy.c index d1cf5bec16..3de66c14d4 100644 --- a/sysdeps/aarch64/multiarch/memcpy.c +++ b/sysdeps/aarch64/multiarch/memcpy.c @@ -47,7 +47,7 @@ select_memcpy_ifunc (void) { if (IS_A64FX (midr)) return __memcpy_a64fx; - return __memcpy_sve; + return prefer_sve_ifuncs ? __memcpy_sve : __memcpy_generic; } if (IS_THUNDERX (midr)) diff --git a/sysdeps/aarch64/multiarch/memmove.c b/sysdeps/aarch64/multiarch/memmove.c index 90729e0275..fdcf418820 100644 --- a/sysdeps/aarch64/multiarch/memmove.c +++ b/sysdeps/aarch64/multiarch/memmove.c @@ -47,7 +47,7 @@ select_memmove_ifunc (void) { if (IS_A64FX (midr)) return __memmove_a64fx; - return __memmove_sve; + return prefer_sve_ifuncs ? __memmove_sve : __memmove_generic; } if (IS_THUNDERX (midr)) |