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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> | 2024-04-10 14:03:08 +0100 |
| commit | 92da7c2cfeeea36d651142f47e570dd5076bc166 (patch) | |
| tree | 0171c53dfe04109b214650da900ca354215e9be3 /sysdeps/aarch64/multiarch/memmove.c | |
| parent | 1bf17ce978da71431dbd1fc3660cfae3dff0672f (diff) | |
| download | glibc-92da7c2cfeeea36d651142f47e570dd5076bc166.tar.gz glibc-92da7c2cfeeea36d651142f47e570dd5076bc166.tar.xz glibc-92da7c2cfeeea36d651142f47e570dd5076bc166.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/multiarch/memmove.c')
| -rw-r--r-- | sysdeps/aarch64/multiarch/memmove.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/sysdeps/aarch64/multiarch/memmove.c b/sysdeps/aarch64/multiarch/memmove.c index 7602a5d57d..6b77166851 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)) |