linux-kernel - [tip:timers/vdso] arm64: vdso: Build vDSO with -ffixed-x18

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Message-ID: <tip-98cd3c3f83fbba27a6bacd75ad12e8388a61a32a@git.kernel.org>
Date:   Sun, 23 Jun 2019 16:48:12 -0700
From:   tip-bot for Peter Collingbourne <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     huw@...eweavers.com, mingo@...nel.org, salyzyn@...roid.com,
        vincenzo.frascino@....com, will.deacon@....com, pcc@...gle.com,
        linux-kernel@...r.kernel.org, sthotton@...vell.com,
        linux@...linux.org.uk, ralf@...ux-mips.org, 0x7f454c46@...il.com,
        shuah@...nel.org, catalin.marinas@....com, tglx@...utronix.de,
        arnd@...db.de, andre.przywara@....com, hpa@...or.com,
        paul.burton@...s.com, salyzyn@...gle.com, linux@...musvillemoes.dk,
        daniel.lezcano@...aro.org
Subject: [tip:timers/vdso] arm64: vdso: Build vDSO with -ffixed-x18

Commit-ID:  98cd3c3f83fbba27a6bacd75ad12e8388a61a32a
Gitweb:     https://git.kernel.org/tip/98cd3c3f83fbba27a6bacd75ad12e8388a61a32a
Author:     Peter Collingbourne <pcc@...gle.com>
AuthorDate: Fri, 21 Jun 2019 10:52:32 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Sat, 22 Jun 2019 21:21:06 +0200

arm64: vdso: Build vDSO with -ffixed-x18

The vDSO needs to be built with x18 reserved in order to accommodate
userspace platform ABIs built on top of Linux that use the register
to carry inter-procedural state, as provided for by the AAPCS.
An example of such a platform ABI is the one that will be used by an
upcoming version of Android.

Although this change is currently a no-op due to the fact that the vDSO
is currently implemented in pure assembly on arm64, it is necessary
in order to prepare for using the generic C implementation of the vDSO.

[ tglx: Massaged changelog ]

Signed-off-by: Peter Collingbourne <pcc@...gle.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Shijith Thotton <sthotton@...vell.com>
Tested-by: Andre Przywara <andre.przywara@....com>
Cc: linux-arch@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-mips@...r.kernel.org
Cc: linux-kselftest@...r.kernel.org
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Russell King <linux@...linux.org.uk>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: Paul Burton <paul.burton@...s.com>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Mark Salyzyn <salyzyn@...roid.com>
Cc: Shuah Khan <shuah@...nel.org>
Cc: Dmitry Safonov <0x7f454c46@...il.com>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Huw Davies <huw@...eweavers.com>
Cc: Mark Salyzyn <salyzyn@...gle.com>
Link: https://lkml.kernel.org/r/20190621095252.32307-6-vincenzo.frascino@arm.com

---
 arch/arm64/kernel/vdso/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index 3acfc813e966..ec81d28aeb5d 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -20,7 +20,7 @@ obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
 ldflags-y := -shared -nostdlib -soname=linux-vdso.so.1 --hash-style=sysv \
 		--build-id -n -T
 
-ccflags-y := -fno-common -fno-builtin -fno-stack-protector
+ccflags-y := -fno-common -fno-builtin -fno-stack-protector -ffixed-x18
 ccflags-y += -DDISABLE_BRANCH_PROFILING
 
 VDSO_LDFLAGS := -Bsymbolic