summaryrefslogtreecommitdiff
path: root/arch/x86/include/asm/calling.h
blob: cb4c73bfeb48169056001d1c8426492a3ad4af79 (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
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
/*

 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.

*/

#include <asm/dwarf2.h>

#ifdef CONFIG_X86_64

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

#define R15		  0
#define R14		  8
#define R13		 16
#define R12		 24
#define RBP		 32
#define RBX		 40

/* arguments: interrupts/non tracing syscalls only save up to here: */
#define R11		 48
#define R10		 56
#define R9		 64
#define R8		 72
#define RAX		 80
#define RCX		 88
#define RDX		 96
#define RSI		104
#define RDI		112
#define ORIG_RAX	120       /* + error_code */
/* end of arguments */

/* cpu exception frame or undefined in case of fast syscall: */
#define RIP		128
#define CS		136
#define EFLAGS		144
#define RSP		152
#define SS		160

#define ARGOFFSET	R11
#define SWFRAME		ORIG_RAX

	.macro SAVE_ARGS addskip=0, save_rcx=1, save_r891011=1
	subq  $9*8+\addskip, %rsp
	CFI_ADJUST_CFA_OFFSET	9*8+\addskip
	movq_cfi rdi, 8*8
	movq_cfi rsi, 7*8
	movq_cfi rdx, 6*8

	.if \save_rcx
	movq_cfi rcx, 5*8
	.endif

	movq_cfi rax, 4*8

	.if \save_r891011
	movq_cfi r8,  3*8
	movq_cfi r9,  2*8
	movq_cfi r10, 1*8
	movq_cfi r11, 0*8
	.endif

	.endm

#define ARG_SKIP	(9*8)

	.macro RESTORE_ARGS rstor_rax=1, addskip=0, rstor_rcx=1, rstor_r11=1, \
			    rstor_r8910=1, rstor_rdx=1
	.if \rstor_r11
	movq_cfi_restore 0*8, r11
	.endif

	.if \rstor_r8910
	movq_cfi_restore 1*8, r10
	movq_cfi_restore 2*8, r9
	movq_cfi_restore 3*8, r8
	.endif

	.if \rstor_rax
	movq_cfi_restore 4*8, rax
	.endif

	.if \rstor_rcx
	movq_cfi_restore 5*8, rcx
	.endif

	.if \rstor_rdx
	movq_cfi_restore 6*8, rdx
	.endif

	movq_cfi_restore 7*8, rsi
	movq_cfi_restore 8*8, rdi

	.if ARG_SKIP+\addskip > 0
	addq $ARG_SKIP+\addskip, %rsp
	CFI_ADJUST_CFA_OFFSET	-(ARG_SKIP+\addskip)
	.endif
	.endm

	.macro LOAD_ARGS offset, skiprax=0
	movq \offset(%rsp),    %r11
	movq \offset+8(%rsp),  %r10
	movq \offset+16(%rsp), %r9
	movq \offset+24(%rsp), %r8
	movq \offset+40(%rsp), %rcx
	movq \offset+48(%rsp), %rdx
	movq \offset+56(%rsp), %rsi
	movq \offset+64(%rsp), %rdi
	.if \skiprax
	.else
	movq \offset+72(%rsp), %rax
	.endif
	.endm

#define REST_SKIP	(6*8)

	.macro SAVE_REST
	subq $REST_SKIP, %rsp
	CFI_ADJUST_CFA_OFFSET	REST_SKIP
	movq_cfi rbx, 5*8
	movq_cfi rbp, 4*8
	movq_cfi r12, 3*8
	movq_cfi r13, 2*8
	movq_cfi r14, 1*8
	movq_cfi r15, 0*8
	.endm

	.macro RESTORE_REST
	movq_cfi_restore 0*8, r15
	movq_cfi_restore 1*8, r14
	movq_cfi_restore 2*8, r13
	movq_cfi_restore 3*8, r12
	movq_cfi_restore 4*8, rbp
	movq_cfi_restore 5*8, rbx
	addq $REST_SKIP, %rsp
	CFI_ADJUST_CFA_OFFSET	-(REST_SKIP)
	.endm

	.macro SAVE_ALL
	SAVE_ARGS
	SAVE_REST
	.endm

	.macro RESTORE_ALL addskip=0
	RESTORE_REST
	RESTORE_ARGS 1, \addskip
	.endm

	.macro icebp
	.byte 0xf1
	.endm

#else /* CONFIG_X86_64 */

/*
 * For 32bit only simplified versions of SAVE_ALL/RESTORE_ALL. These
 * are different from the entry_32.S versions in not changing the segment
 * registers. So only suitable for in kernel use, not when transitioning
 * from or to user space. The resulting stack frame is not a standard
 * pt_regs frame. The main use case is calling C code from assembler
 * when all the registers need to be preserved.
 */

	.macro SAVE_ALL
	pushl_cfi %eax
	CFI_REL_OFFSET eax, 0
	pushl_cfi %ebp
	CFI_REL_OFFSET ebp, 0
	pushl_cfi %edi
	CFI_REL_OFFSET edi, 0
	pushl_cfi %esi
	CFI_REL_OFFSET esi, 0
	pushl_cfi %edx
	CFI_REL_OFFSET edx, 0
	pushl_cfi %ecx
	CFI_REL_OFFSET ecx, 0
	pushl_cfi %ebx
	CFI_REL_OFFSET ebx, 0
	.endm

	.macro RESTORE_ALL
	popl_cfi %ebx
	CFI_RESTORE ebx
	popl_cfi %ecx
	CFI_RESTORE ecx
	popl_cfi %edx
	CFI_RESTORE edx
	popl_cfi %esi
	CFI_RESTORE esi
	popl_cfi %edi
	CFI_RESTORE edi
	popl_cfi %ebp
	CFI_RESTORE ebp
	popl_cfi %eax
	CFI_RESTORE eax
	.endm

#endif /* CONFIG_X86_64 */