3 files changed, 83 insertions, 1 deletions

diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index 08e442bc3ab9..9d38a13b4ceb 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -319,7 +319,7 @@ config X86_L1_CACHE_SHIFT
 
 config X86_XADD
         def_bool y
-        depends on X86_32 && !M386
+        depends on X86_64 || !M386
 
 config X86_PPRO_FENCE
         bool "PentiumPro memory ordering errata workaround"
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index cffd754f3039..c80245131fdc 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -39,4 +39,5 @@ else
         lib-y += thunk_64.o clear_page_64.o copy_page_64.o
         lib-y += memmove_64.o memset_64.o
         lib-y += copy_user_64.o rwlock_64.o copy_user_nocache_64.o
+        lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem_64.o
 endif
diff --git a/arch/x86/lib/rwsem_64.S b/arch/x86/lib/rwsem_64.S
new file mode 100644
index 000000000000..15acecf0d7aa
--- /dev/null
+++ b/arch/x86/lib/rwsem_64.S
@@ -0,0 +1,81 @@
+/*
+ * x86-64 rwsem wrappers
+ *
+ * This interfaces the inline asm code to the slow-path
+ * C routines. We need to save the call-clobbered regs
+ * that the asm does not mark as clobbered, and move the
+ * argument from %rax to %rdi.
+ *
+ * NOTE! We don't need to save %rax, because the functions
+ * will always return the semaphore pointer in %rax (which
+ * is also the input argument to these helpers)
+ *
+ * The following can clobber %rdx because the asm clobbers it:
+ *   call_rwsem_down_write_failed
+ *   call_rwsem_wake
+ * but %rdi, %rsi, %rcx, %r8-r11 always need saving.
+ */
+
+#include <linux/linkage.h>
+#include <asm/rwlock.h>
+#include <asm/alternative-asm.h>
+#include <asm/frame.h>
+#include <asm/dwarf2.h>
+
+#define save_common_regs \
+        pushq %rdi; \
+        pushq %rsi; \
+        pushq %rcx; \
+        pushq %r8; \
+        pushq %r9; \
+        pushq %r10; \
+        pushq %r11
+
+#define restore_common_regs \
+        popq %r11; \
+        popq %r10; \
+        popq %r9; \
+        popq %r8; \
+        popq %rcx; \
+        popq %rsi; \
+        popq %rdi
+
+/* Fix up special calling conventions */
+ENTRY(call_rwsem_down_read_failed)
+        save_common_regs
+        pushq %rdx
+        movq %rax,%rdi
+        call rwsem_down_read_failed
+        popq %rdx
+        restore_common_regs
+        ret
+        ENDPROC(call_rwsem_down_read_failed)
+
+ENTRY(call_rwsem_down_write_failed)
+        save_common_regs
+        movq %rax,%rdi
+        call rwsem_down_write_failed
+        restore_common_regs
+        ret
+        ENDPROC(call_rwsem_down_write_failed)
+
+ENTRY(call_rwsem_wake)
+        decw %dx    /* do nothing if still outstanding active readers */
+        jnz 1f
+        save_common_regs
+        movq %rax,%rdi
+        call rwsem_wake
+        restore_common_regs
+1:      ret
+        ENDPROC(call_rwsem_wake)
+
+/* Fix up special calling conventions */
+ENTRY(call_rwsem_downgrade_wake)
+        save_common_regs
+        pushq %rdx
+        movq %rax,%rdi
+        call rwsem_downgrade_wake
+        popq %rdx
+        restore_common_regs
+        ret
+        ENDPROC(call_rwsem_downgrade_wake)