FROMLIST: [PATCH v5 10/12] arm64: vdso: replace gettimeofday.S with global vgettimeof...
authorMark Salyzyn <salyzyn@google.com>
Fri, 4 Aug 2017 16:58:40 +0000 (09:58 -0700)
committerMichael Benedict <michaelbt@live.com>
Sun, 22 Sep 2019 15:50:51 +0000 (01:50 +1000)
commit053814a3e9c4d6c5365179140aba810da3036c68
tree746638ab67cc305412392d4124d25eccf89608e9
parent0c8f7b59352c57ea8a61e7c276ce0bdbd185be33
FROMLIST: [PATCH v5 10/12] arm64: vdso: replace gettimeofday.S with global vgettimeofday.C

(cherry picked from url https://patchwork.kernel.org/patch/10044501/)

Take an effort from the previous 9 patches to recode the arm64 vdso
code from assembler to C previously submitted by
Andrew Pinski <apinski@cavium.com>, rework it for use in both arm and
arm64, overlapping any optimizations for each architecture. But
instead of landing it in arm64, land the result into lib/vdso and
unify both implementations to simplify future maintenance.

apinski@cavium.com makes the following claims in the original patch:

This allows the compiler to optimize the divide by 1000 and remove
the other divides.

On ThunderX, gettimeofday improves by 32%.  On ThunderX 2,
gettimeofday improves by 18%.

Note I noticed a bug in the old (arm64) implementation of
__kernel_clock_getres; it was checking only the lower 32bits of the
pointer; this would work for most cases but could fail in a few.

<end of claim>

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: James Morse <james.morse@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Andy Gross <andy.gross@linaro.org>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Andrew Pinski <apinski@cavium.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Bug: 63737556
Bug: 20045882
Change-Id: I71ff27ff5bfa323354fda6867b01ec908d8d6cbd
arch/arm64/include/asm/vdso_datapage.h
arch/arm64/kernel/asm-offsets.c
arch/arm64/kernel/vdso.c
arch/arm64/kernel/vdso/Makefile
arch/arm64/kernel/vdso/datapage.h [new file with mode: 0644]
arch/arm64/kernel/vdso/gettimeofday.S [deleted file]
arch/arm64/kernel/vdso/vgettimeofday.c [new file with mode: 0644]