1/*
2 * x86 semaphore implementation.
3 *
4 * (C) Copyright 1999 Linus Torvalds
5 *
6 * Portions Copyright 1999 Red Hat, Inc.
7 *
8 *	This program is free software; you can redistribute it and/or
9 *	modify it under the terms of the GNU General Public License
10 *	as published by the Free Software Foundation; either version
11 *	2 of the License, or (at your option) any later version.
12 *
13 * rw semaphores implemented November 1999 by Benjamin LaHaise <bcrl@kvack.org>
14 */
15
16#include <linux/linkage.h>
17#include <asm/alternative-asm.h>
18#include <asm/dwarf2.h>
19
20#define __ASM_HALF_REG(reg)	__ASM_SEL(reg, e##reg)
21#define __ASM_HALF_SIZE(inst)	__ASM_SEL(inst##w, inst##l)
22
23#ifdef CONFIG_X86_32
24
25/*
26 * The semaphore operations have a special calling sequence that
27 * allow us to do a simpler in-line version of them. These routines
28 * need to convert that sequence back into the C sequence when
29 * there is contention on the semaphore.
30 *
31 * %eax contains the semaphore pointer on entry. Save the C-clobbered
32 * registers (%eax, %edx and %ecx) except %eax whish is either a return
33 * value or just clobbered..
34 */
35
36#define save_common_regs \
37	pushl_cfi_reg ecx
38
39#define restore_common_regs \
40	popl_cfi_reg ecx
41
42	/* Avoid uglifying the argument copying x86-64 needs to do. */
43	.macro movq src, dst
44	.endm
45
46#else
47
48/*
49 * x86-64 rwsem wrappers
50 *
51 * This interfaces the inline asm code to the slow-path
52 * C routines. We need to save the call-clobbered regs
53 * that the asm does not mark as clobbered, and move the
54 * argument from %rax to %rdi.
55 *
56 * NOTE! We don't need to save %rax, because the functions
57 * will always return the semaphore pointer in %rax (which
58 * is also the input argument to these helpers)
59 *
60 * The following can clobber %rdx because the asm clobbers it:
61 *   call_rwsem_down_write_failed
62 *   call_rwsem_wake
63 * but %rdi, %rsi, %rcx, %r8-r11 always need saving.
64 */
65
66#define save_common_regs \
67	pushq_cfi_reg rdi; \
68	pushq_cfi_reg rsi; \
69	pushq_cfi_reg rcx; \
70	pushq_cfi_reg r8;  \
71	pushq_cfi_reg r9;  \
72	pushq_cfi_reg r10; \
73	pushq_cfi_reg r11
74
75#define restore_common_regs \
76	popq_cfi_reg r11; \
77	popq_cfi_reg r10; \
78	popq_cfi_reg r9; \
79	popq_cfi_reg r8; \
80	popq_cfi_reg rcx; \
81	popq_cfi_reg rsi; \
82	popq_cfi_reg rdi
83
84#endif
85
86/* Fix up special calling conventions */
87ENTRY(call_rwsem_down_read_failed)
88	CFI_STARTPROC
89	save_common_regs
90	__ASM_SIZE(push,_cfi_reg) __ASM_REG(dx)
91	movq %rax,%rdi
92	call rwsem_down_read_failed
93	__ASM_SIZE(pop,_cfi_reg) __ASM_REG(dx)
94	restore_common_regs
95	ret
96	CFI_ENDPROC
97ENDPROC(call_rwsem_down_read_failed)
98
99ENTRY(call_rwsem_down_write_failed)
100	CFI_STARTPROC
101	save_common_regs
102	movq %rax,%rdi
103	call rwsem_down_write_failed
104	restore_common_regs
105	ret
106	CFI_ENDPROC
107ENDPROC(call_rwsem_down_write_failed)
108
109ENTRY(call_rwsem_wake)
110	CFI_STARTPROC
111	/* do nothing if still outstanding active readers */
112	__ASM_HALF_SIZE(dec) %__ASM_HALF_REG(dx)
113	jnz 1f
114	save_common_regs
115	movq %rax,%rdi
116	call rwsem_wake
117	restore_common_regs
1181:	ret
119	CFI_ENDPROC
120ENDPROC(call_rwsem_wake)
121
122ENTRY(call_rwsem_downgrade_wake)
123	CFI_STARTPROC
124	save_common_regs
125	__ASM_SIZE(push,_cfi_reg) __ASM_REG(dx)
126	movq %rax,%rdi
127	call rwsem_downgrade_wake
128	__ASM_SIZE(pop,_cfi_reg) __ASM_REG(dx)
129	restore_common_regs
130	ret
131	CFI_ENDPROC
132ENDPROC(call_rwsem_downgrade_wake)
133