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| author | Will Deacon <will.deacon@arm.com> | 2015-02-03 13:39:03 +0100 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2015-07-27 16:28:50 +0200 |
| commit | c0385b24af15020a1e505f2c984db0d7c0d017e1 (patch) | |
| tree | 50cf977ef4ba5de29e1c9a931588bc340c9e103c /arch/arm64/lib | |
| parent | arm64: alternatives: add cpu feature for lse atomics (diff) | |
| download | linux-c0385b24af15020a1e505f2c984db0d7c0d017e1.tar.xz linux-c0385b24af15020a1e505f2c984db0d7c0d017e1.zip | |
arm64: introduce CONFIG_ARM64_LSE_ATOMICS as fallback to ll/sc atomics
In order to patch in the new atomic instructions at runtime, we need to
generate wrappers around the out-of-line exclusive load/store atomics.
This patch adds a new Kconfig option, CONFIG_ARM64_LSE_ATOMICS. which
causes our atomic functions to branch to the out-of-line ll/sc
implementations. To avoid the register spill overhead of the PCS, the
out-of-line functions are compiled with specific compiler flags to
force out-of-line save/restore of any registers that are usually
caller-saved.
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/lib')
| -rw-r--r-- | arch/arm64/lib/Makefile | 13 | ||||
| -rw-r--r-- | arch/arm64/lib/atomic_ll_sc.c | 3 |
2 files changed, 16 insertions, 0 deletions
diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile index d98d3e39879e..1a811ecf71da 100644 --- a/arch/arm64/lib/Makefile +++ b/arch/arm64/lib/Makefile @@ -3,3 +3,16 @@ lib-y := bitops.o clear_user.o delay.o copy_from_user.o \ clear_page.o memchr.o memcpy.o memmove.o memset.o \ memcmp.o strcmp.o strncmp.o strlen.o strnlen.o \ strchr.o strrchr.o + +# Tell the compiler to treat all general purpose registers as +# callee-saved, which allows for efficient runtime patching of the bl +# instruction in the caller with an atomic instruction when supported by +# the CPU. Result and argument registers are handled correctly, based on +# the function prototype. +lib-$(CONFIG_ARM64_LSE_ATOMICS) += atomic_ll_sc.o +CFLAGS_atomic_ll_sc.o := -fcall-used-x0 -ffixed-x1 -ffixed-x2 \ + -ffixed-x3 -ffixed-x4 -ffixed-x5 -ffixed-x6 \ + -ffixed-x7 -fcall-saved-x8 -fcall-saved-x9 \ + -fcall-saved-x10 -fcall-saved-x11 -fcall-saved-x12 \ + -fcall-saved-x13 -fcall-saved-x14 -fcall-saved-x15 \ + -fcall-saved-x16 -fcall-saved-x17 -fcall-saved-x18 diff --git a/arch/arm64/lib/atomic_ll_sc.c b/arch/arm64/lib/atomic_ll_sc.c new file mode 100644 index 000000000000..b0c538b0da28 --- /dev/null +++ b/arch/arm64/lib/atomic_ll_sc.c @@ -0,0 +1,3 @@ +#include <asm/atomic.h> +#define __ARM64_IN_ATOMIC_IMPL +#include <asm/atomic_ll_sc.h> |