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authorWill Deacon <will.deacon@arm.com>2015-02-03 15:39:03 +0300
committerWill Deacon <will.deacon@arm.com>2015-07-27 17:28:50 +0300
commitc0385b24af15020a1e505f2c984db0d7c0d017e1 (patch)
tree50cf977ef4ba5de29e1c9a931588bc340c9e103c /arch/arm64/lib
parentd964b7229e7f94428a1e8d26999adffbe8a69db2 (diff)
downloadlinux-c0385b24af15020a1e505f2c984db0d7c0d017e1.tar.xz
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/Makefile13
-rw-r--r--arch/arm64/lib/atomic_ll_sc.c3
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>