x86: Unify rwsem assembly implementation

Rather than having two functionally identical implementations
for 32- and 64-bit configurations, use the previously extended
assembly abstractions to fold the rwsem two implementations into
a shared one.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4E258DF3020000780004E3ED@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 136 insertions, 0 deletions

diff --git a/arch/x86/lib/rwsem.S b/arch/x86/lib/rwsem.S
new file mode 100644
index 000000000000..5dff5f042468
--- /dev/null
+++ b/arch/x86/lib/rwsem.S
@@ -0,0 +1,136 @@
+/*
+ * x86 semaphore implementation.
+ *
+ * (C) Copyright 1999 Linus Torvalds
+ *
+ * Portions Copyright 1999 Red Hat, Inc.
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ *
+ * rw semaphores implemented November 1999 by Benjamin LaHaise <bcrl@kvack.org>
+ */
+
+#include <linux/linkage.h>
+#include <asm/alternative-asm.h>
+#include <asm/dwarf2.h>
+
+#define __ASM_HALF_REG(reg)	__ASM_SEL(reg, e##reg)
+#define __ASM_HALF_SIZE(inst)	__ASM_SEL(inst##w, inst##l)
+
+#ifdef CONFIG_X86_32
+
+/*
+ * The semaphore operations have a special calling sequence that
+ * allow us to do a simpler in-line version of them. These routines
+ * need to convert that sequence back into the C sequence when
+ * there is contention on the semaphore.
+ *
+ * %eax contains the semaphore pointer on entry. Save the C-clobbered
+ * registers (%eax, %edx and %ecx) except %eax whish is either a return
+ * value or just clobbered..
+ */
+
+#define save_common_regs \
+	pushl_cfi %ecx; CFI_REL_OFFSET ecx, 0
+
+#define restore_common_regs \
+	popl_cfi %ecx; CFI_RESTORE ecx
+
+	/* Avoid uglifying the argument copying x86-64 needs to do. */
+	.macro movq src, dst
+	.endm
+
+#else
+
+/*
+ * 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.
+ */
+
+#define save_common_regs \
+	pushq_cfi %rdi; CFI_REL_OFFSET rdi, 0; \
+	pushq_cfi %rsi; CFI_REL_OFFSET rsi, 0; \
+	pushq_cfi %rcx; CFI_REL_OFFSET rcx, 0; \
+	pushq_cfi %r8;  CFI_REL_OFFSET r8,  0; \
+	pushq_cfi %r9;  CFI_REL_OFFSET r9,  0; \
+	pushq_cfi %r10; CFI_REL_OFFSET r10, 0; \
+	pushq_cfi %r11; CFI_REL_OFFSET r11, 0
+
+#define restore_common_regs \
+	popq_cfi %r11; CFI_RESTORE r11; \
+	popq_cfi %r10; CFI_RESTORE r10; \
+	popq_cfi %r9;  CFI_RESTORE r9; \
+	popq_cfi %r8;  CFI_RESTORE r8; \
+	popq_cfi %rcx; CFI_RESTORE rcx; \
+	popq_cfi %rsi; CFI_RESTORE rsi; \
+	popq_cfi %rdi; CFI_RESTORE rdi
+
+#endif
+
+/* Fix up special calling conventions */
+ENTRY(call_rwsem_down_read_failed)
+	CFI_STARTPROC
+	save_common_regs
+	__ASM_SIZE(push,_cfi) %__ASM_REG(dx)
+	CFI_REL_OFFSET __ASM_REG(dx), 0
+	movq %rax,%rdi
+	call rwsem_down_read_failed
+	__ASM_SIZE(pop,_cfi) %__ASM_REG(dx)
+	CFI_RESTORE __ASM_REG(dx)
+	restore_common_regs
+	ret
+	CFI_ENDPROC
+ENDPROC(call_rwsem_down_read_failed)
+
+ENTRY(call_rwsem_down_write_failed)
+	CFI_STARTPROC
+	save_common_regs
+	movq %rax,%rdi
+	call rwsem_down_write_failed
+	restore_common_regs
+	ret
+	CFI_ENDPROC
+ENDPROC(call_rwsem_down_write_failed)
+
+ENTRY(call_rwsem_wake)
+	CFI_STARTPROC
+	/* do nothing if still outstanding active readers */
+	__ASM_HALF_SIZE(dec) %__ASM_HALF_REG(dx)
+	jnz 1f
+	save_common_regs
+	movq %rax,%rdi
+	call rwsem_wake
+	restore_common_regs
+1:	ret
+	CFI_ENDPROC
+ENDPROC(call_rwsem_wake)
+
+ENTRY(call_rwsem_downgrade_wake)
+	CFI_STARTPROC
+	save_common_regs
+	__ASM_SIZE(push,_cfi) %__ASM_REG(dx)
+	CFI_REL_OFFSET __ASM_REG(dx), 0
+	movq %rax,%rdi
+	call rwsem_downgrade_wake
+	__ASM_SIZE(pop,_cfi) %__ASM_REG(dx)
+	CFI_RESTORE __ASM_REG(dx)
+	restore_common_regs
+	ret
+	CFI_ENDPROC
+ENDPROC(call_rwsem_downgrade_wake)