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arm64: avoid instrumenting atomic_ll_sc.o

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Our out-of-line atomics are built with a special calling convention,
preventing pointless stack spilling, and allowing us to patch call sites
with ARMv8.1 atomic instructions.

Instrumentation inserted by the compiler may result in calls to
functions not following this special calling convention, resulting in
registers being unexpectedly clobbered, and various problems resulting
from this.

For example, if a kernel is built with KCOV and ARM64_LSE_ATOMICS, the
compiler inserts calls to __sanitizer_cov_trace_pc in the prologues of
the atomic functions. This has been observed to result in spurious
cmpxchg failures, leading to a hang early on in the boot process.

This patch avoids such issues by preventing instrumentation of our
out-of-line atomics.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Mark Rutland 2018-04-27 11:50:36 +01:00 committed by Will Deacon
parent 5e1ca5e23b
commit 3789c122d0
1 changed files with 4 additions and 0 deletions
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4
arch/arm64/lib/Makefile
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@ -19,5 +19,9 @@ CFLAGS_atomic_ll_sc.o := -fcall-used-x0 -ffixed-x1 -ffixed-x2 \
-fcall-saved-x13 -fcall-saved-x14 -fcall-saved-x15 \
-fcall-saved-x18 -fomit-frame-pointer
CFLAGS_REMOVE_atomic_ll_sc.o := -pg
GCOV_PROFILE_atomic_ll_sc.o := n
KASAN_SANITIZE_atomic_ll_sc.o := n
KCOV_INSTRUMENT_atomic_ll_sc.o := n
UBSAN_SANITIZE_atomic_ll_sc.o := n
lib-$(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) += uaccess_flushcache.o