summaryrefslogtreecommitdiffstats
path: root/arch/x86/entry/calling.h
blob: 9a9e5884066c6581878b56cde27e75f542b21249 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
#include <linux/jump_label.h>

/*

 x86 function call convention, 64-bit:
 -------------------------------------
  arguments           |  callee-saved      | extra caller-saved | return
 [callee-clobbered]   |                    | [callee-clobbered] |
 ---------------------------------------------------------------------------
 rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11             | rax, rdx [**]

 ( rsp is obviously invariant across normal function calls. (gcc can 'merge'
   functions when it sees tail-call optimization possibilities) rflags is
   clobbered. Leftover arguments are passed over the stack frame.)

 [*]  In the frame-pointers case rbp is fixed to the stack frame.

 [**] for struct return values wider than 64 bits the return convention is a
      bit more complex: up to 128 bits width we return small structures
      straight in rax, rdx. For structures larger than that (3 words or
      larger) the caller puts a pointer to an on-stack return struct
      [allocated in the caller's stack frame] into the first argument - i.e.
      into rdi. All other arguments shift up by one in this case.
      Fortunately this case is rare in the kernel.

For 32-bit we have the following conventions - kernel is built with
-mregparm=3 and -freg-struct-return:

 x86 function calling convention, 32-bit:
 ----------------------------------------
  arguments         | callee-saved        | extra caller-saved | return
 [callee-clobbered] |                     | [callee-clobbered] |
 -------------------------------------------------------------------------
 eax edx ecx        | ebx edi esi ebp [*] | <none>             | eax, edx [**]

 ( here too esp is obviously invariant across normal function calls. eflags
   is clobbered. Leftover arguments are passed over the stack frame. )

 [*]  In the frame-pointers case ebp is fixed to the stack frame.

 [**] We build with -freg-struct-return, which on 32-bit means similar
      semantics as on 64-bit: edx can be used for a second return value
      (i.e. covering integer and structure sizes up to 64 bits) - after that
      it gets more complex and more expensive: 3-word or larger struct returns
      get done in the caller's frame and the pointer to the return struct goes
      into regparm0, i.e. eax - the other arguments shift up and the
      function's register parameters degenerate to regparm=2 in essence.

*/

#ifdef CONFIG_X86_64

/*
 * 64-bit system call stack frame layout defines and helpers,
 * for assembly code:
 */

/* The layout forms the "struct pt_regs" on the stack: */
/*
 * C ABI says these regs are callee-preserved. They aren't saved on kernel entry
 * unless syscall needs a complete, fully filled "struct pt_regs".
 */
#define R15		0*8
#define R14		1*8
#define R13		2*8
#define R12		3*8
#define RBP		4*8
#define RBX		5*8
/* These regs are callee-clobbered. Always saved on kernel entry. */
#define R11		6*8
#define R10		7*8
#define R9		8*8
#define R8		9*8
#define RAX		10*8
#define RCX		11*8
#define RDX		12*8
#define RSI		13*8
#define RDI		14*8
/*
 * On syscall entry, this is syscall#. On CPU exception, this is error code.
 * On hw interrupt, it's IRQ number:
 */
#define ORIG_RAX	15*8
/* Return frame for iretq */
#define RIP		16*8
#define CS		17*8
#define EFLAGS		18*8
#define RSP		19*8
#define SS		20*8

#define SIZEOF_PTREGS	21*8

	.macro ALLOC_PT_GPREGS_ON_STACK addskip=0
	addq	$-(15*8+\addskip), %rsp
	.endm

	.macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1
	.if \r11
	movq %r11, 6*8+\offset(%rsp)
	.endif
	.if \r8910
	movq %r10, 7*8+\offset(%rsp)
	movq %r9,  8*8+\offset(%rsp)
	movq %r8,  9*8+\offset(%rsp)
	.endif
	.if \rax
	movq %rax, 10*8+\offset(%rsp)
	.endif
	.if \rcx
	movq %rcx, 11*8+\offset(%rsp)
	.endif
	movq %rdx, 12*8+\offset(%rsp)
	movq %rsi, 13*8+\offset(%rsp)
	movq %rdi, 14*8+\offset(%rsp)
	.endm
	.macro SAVE_C_REGS offset=0
	SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1
	.endm
	.macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0
	SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1
	.endm
	.macro SAVE_C_REGS_EXCEPT_R891011
	SAVE_C_REGS_HELPER 0, 1, 1, 0, 0
	.endm
	.macro SAVE_C_REGS_EXCEPT_RCX_R891011
	SAVE_C_REGS_HELPER 0, 1, 0, 0, 0
	.endm
	.macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11
	SAVE_C_REGS_HELPER 0, 0, 0, 1, 0
	.endm

	.macro SAVE_EXTRA_REGS offset=0
	movq %r15, 0*8+\offset(%rsp)
	movq %r14, 1*8+\offset(%rsp)
	movq %r13, 2*8+\offset(%rsp)
	movq %r12, 3*8+\offset(%rsp)
	movq %rbp, 4*8+\offset(%rsp)
	movq %rbx, 5*8+\offset(%rsp)
	.endm

	.macro RESTORE_EXTRA_REGS offset=0
	movq 0*8+\offset(%rsp), %r15
	movq 1*8+\offset(%rsp), %r14
	movq 2*8+\offset(%rsp), %r13
	movq 3*8+\offset(%rsp), %r12
	movq 4*8+\offset(%rsp), %rbp
	movq 5*8+\offset(%rsp), %rbx
	.endm

	.macro ZERO_EXTRA_REGS
	xorl	%r15d, %r15d
	xorl	%r14d, %r14d
	xorl	%r13d, %r13d
	xorl	%r12d, %r12d
	xorl	%ebp, %ebp
	xorl	%ebx, %ebx
	.endm

	.macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1
	.if \rstor_r11
	movq 6*8(%rsp), %r11
	.endif
	.if \rstor_r8910
	movq 7*8(%rsp), %r10
	movq 8*8(%rsp), %r9
	movq 9*8(%rsp), %r8
	.endif
	.if \rstor_rax
	movq 10*8(%rsp), %rax
	.endif
	.if \rstor_rcx
	movq 11*8(%rsp), %rcx
	.endif
	.if \rstor_rdx
	movq 12*8(%rsp), %rdx
	.endif
	movq 13*8(%rsp), %rsi
	movq 14*8(%rsp), %rdi
	.endm
	.macro RESTORE_C_REGS
	RESTORE_C_REGS_HELPER 1,1,1,1,1
	.endm
	.macro RESTORE_C_REGS_EXCEPT_RAX
	RESTORE_C_REGS_HELPER 0,1,1,1,1
	.endm
	.macro RESTORE_C_REGS_EXCEPT_RCX
	RESTORE_C_REGS_HELPER 1,0,1,1,1
	.endm
	.macro RESTORE_C_REGS_EXCEPT_R11
	RESTORE_C_REGS_HELPER 1,1,0,1,1
	.endm
	.macro RESTORE_C_REGS_EXCEPT_RCX_R11
	RESTORE_C_REGS_HELPER 1,0,0,1,1
	.endm

	.macro REMOVE_PT_GPREGS_FROM_STACK addskip=0
	subq $-(15*8+\addskip), %rsp
	.endm

	.macro icebp
	.byte 0xf1
	.endm

#endif /* CONFIG_X86_64 */

/*
 * This does 'call enter_from_user_mode' unless we can avoid it based on
 * kernel config or using the static jump infrastructure.
 */
.macro CALL_enter_from_user_mode
#ifdef CONFIG_CONTEXT_TRACKING
#ifdef HAVE_JUMP_LABEL
	STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
#endif
	call enter_from_user_mode
.Lafter_call_\@:
#endif
.endm