/*
   * 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)