rwsem.S
3.56 KB
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/*
* 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)