mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-11-01 17:08:10 +00:00
4544ba8c6b
Document explicitly that %edx can get clobbered on the slow path, on 32-bit kernels. Something I learned the hard way. :-\ Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: linux-next@vger.kernel.org Link: http://lkml.kernel.org/r/20160516093428.GA26108@pd.tnic Signed-off-by: Ingo Molnar <mingo@kernel.org>
144 lines
3.4 KiB
ArmAsm
144 lines
3.4 KiB
ArmAsm
/*
|
|
* 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/frame.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 which is either a return
|
|
* value or just gets clobbered. Same is true for %edx so make sure GCC
|
|
* reloads it after the slow path, by making it hold a temporary, for
|
|
* example see ____down_write().
|
|
*/
|
|
|
|
#define save_common_regs \
|
|
pushl %ecx
|
|
|
|
#define restore_common_regs \
|
|
popl %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 %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
|
|
|
|
#endif
|
|
|
|
/* Fix up special calling conventions */
|
|
ENTRY(call_rwsem_down_read_failed)
|
|
FRAME_BEGIN
|
|
save_common_regs
|
|
__ASM_SIZE(push,) %__ASM_REG(dx)
|
|
movq %rax,%rdi
|
|
call rwsem_down_read_failed
|
|
__ASM_SIZE(pop,) %__ASM_REG(dx)
|
|
restore_common_regs
|
|
FRAME_END
|
|
ret
|
|
ENDPROC(call_rwsem_down_read_failed)
|
|
|
|
ENTRY(call_rwsem_down_write_failed)
|
|
FRAME_BEGIN
|
|
save_common_regs
|
|
movq %rax,%rdi
|
|
call rwsem_down_write_failed
|
|
restore_common_regs
|
|
FRAME_END
|
|
ret
|
|
ENDPROC(call_rwsem_down_write_failed)
|
|
|
|
ENTRY(call_rwsem_down_write_failed_killable)
|
|
FRAME_BEGIN
|
|
save_common_regs
|
|
movq %rax,%rdi
|
|
call rwsem_down_write_failed_killable
|
|
restore_common_regs
|
|
FRAME_END
|
|
ret
|
|
ENDPROC(call_rwsem_down_write_failed_killable)
|
|
|
|
ENTRY(call_rwsem_wake)
|
|
FRAME_BEGIN
|
|
/* 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: FRAME_END
|
|
ret
|
|
ENDPROC(call_rwsem_wake)
|
|
|
|
ENTRY(call_rwsem_downgrade_wake)
|
|
FRAME_BEGIN
|
|
save_common_regs
|
|
__ASM_SIZE(push,) %__ASM_REG(dx)
|
|
movq %rax,%rdi
|
|
call rwsem_downgrade_wake
|
|
__ASM_SIZE(pop,) %__ASM_REG(dx)
|
|
restore_common_regs
|
|
FRAME_END
|
|
ret
|
|
ENDPROC(call_rwsem_downgrade_wake)
|