Linux kernel mirror (for testing)
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linux
1/*
2
3 x86 function call convention, 64-bit:
4 -------------------------------------
5 arguments | callee-saved | extra caller-saved | return
6 [callee-clobbered] | | [callee-clobbered] |
7 ---------------------------------------------------------------------------
8 rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**]
9
10 ( rsp is obviously invariant across normal function calls. (gcc can 'merge'
11 functions when it sees tail-call optimization possibilities) rflags is
12 clobbered. Leftover arguments are passed over the stack frame.)
13
14 [*] In the frame-pointers case rbp is fixed to the stack frame.
15
16 [**] for struct return values wider than 64 bits the return convention is a
17 bit more complex: up to 128 bits width we return small structures
18 straight in rax, rdx. For structures larger than that (3 words or
19 larger) the caller puts a pointer to an on-stack return struct
20 [allocated in the caller's stack frame] into the first argument - i.e.
21 into rdi. All other arguments shift up by one in this case.
22 Fortunately this case is rare in the kernel.
23
24For 32-bit we have the following conventions - kernel is built with
25-mregparm=3 and -freg-struct-return:
26
27 x86 function calling convention, 32-bit:
28 ----------------------------------------
29 arguments | callee-saved | extra caller-saved | return
30 [callee-clobbered] | | [callee-clobbered] |
31 -------------------------------------------------------------------------
32 eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**]
33
34 ( here too esp is obviously invariant across normal function calls. eflags
35 is clobbered. Leftover arguments are passed over the stack frame. )
36
37 [*] In the frame-pointers case ebp is fixed to the stack frame.
38
39 [**] We build with -freg-struct-return, which on 32-bit means similar
40 semantics as on 64-bit: edx can be used for a second return value
41 (i.e. covering integer and structure sizes up to 64 bits) - after that
42 it gets more complex and more expensive: 3-word or larger struct returns
43 get done in the caller's frame and the pointer to the return struct goes
44 into regparm0, i.e. eax - the other arguments shift up and the
45 function's register parameters degenerate to regparm=2 in essence.
46
47*/
48
49
50/*
51 * 64-bit system call stack frame layout defines and helpers, for
52 * assembly code (note that the seemingly unnecessary parentheses
53 * are to prevent cpp from inserting spaces in expressions that get
54 * passed to macros):
55 */
56
57#define R15 (0)
58#define R14 (8)
59#define R13 (16)
60#define R12 (24)
61#define RBP (32)
62#define RBX (40)
63
64/* arguments: interrupts/non tracing syscalls only save up to here: */
65#define R11 (48)
66#define R10 (56)
67#define R9 (64)
68#define R8 (72)
69#define RAX (80)
70#define RCX (88)
71#define RDX (96)
72#define RSI (104)
73#define RDI (112)
74#define ORIG_RAX (120) /* + error_code */
75/* end of arguments */
76
77/* cpu exception frame or undefined in case of fast syscall: */
78#define RIP (128)
79#define CS (136)
80#define EFLAGS (144)
81#define RSP (152)
82#define SS (160)
83
84#define ARGOFFSET R11
85#define SWFRAME ORIG_RAX
86
87 .macro SAVE_ARGS addskip=0, norcx=0, nor891011=0
88 subq $9*8+\addskip, %rsp
89 CFI_ADJUST_CFA_OFFSET 9*8+\addskip
90 movq %rdi, 8*8(%rsp)
91 CFI_REL_OFFSET rdi, 8*8
92 movq %rsi, 7*8(%rsp)
93 CFI_REL_OFFSET rsi, 7*8
94 movq %rdx, 6*8(%rsp)
95 CFI_REL_OFFSET rdx, 6*8
96 .if \norcx
97 .else
98 movq %rcx, 5*8(%rsp)
99 CFI_REL_OFFSET rcx, 5*8
100 .endif
101 movq %rax, 4*8(%rsp)
102 CFI_REL_OFFSET rax, 4*8
103 .if \nor891011
104 .else
105 movq %r8, 3*8(%rsp)
106 CFI_REL_OFFSET r8, 3*8
107 movq %r9, 2*8(%rsp)
108 CFI_REL_OFFSET r9, 2*8
109 movq %r10, 1*8(%rsp)
110 CFI_REL_OFFSET r10, 1*8
111 movq %r11, (%rsp)
112 CFI_REL_OFFSET r11, 0*8
113 .endif
114 .endm
115
116#define ARG_SKIP (9*8)
117
118 .macro RESTORE_ARGS skiprax=0, addskip=0, skiprcx=0, skipr11=0, \
119 skipr8910=0, skiprdx=0
120 .if \skipr11
121 .else
122 movq (%rsp), %r11
123 CFI_RESTORE r11
124 .endif
125 .if \skipr8910
126 .else
127 movq 1*8(%rsp), %r10
128 CFI_RESTORE r10
129 movq 2*8(%rsp), %r9
130 CFI_RESTORE r9
131 movq 3*8(%rsp), %r8
132 CFI_RESTORE r8
133 .endif
134 .if \skiprax
135 .else
136 movq 4*8(%rsp), %rax
137 CFI_RESTORE rax
138 .endif
139 .if \skiprcx
140 .else
141 movq 5*8(%rsp), %rcx
142 CFI_RESTORE rcx
143 .endif
144 .if \skiprdx
145 .else
146 movq 6*8(%rsp), %rdx
147 CFI_RESTORE rdx
148 .endif
149 movq 7*8(%rsp), %rsi
150 CFI_RESTORE rsi
151 movq 8*8(%rsp), %rdi
152 CFI_RESTORE rdi
153 .if ARG_SKIP+\addskip > 0
154 addq $ARG_SKIP+\addskip, %rsp
155 CFI_ADJUST_CFA_OFFSET -(ARG_SKIP+\addskip)
156 .endif
157 .endm
158
159 .macro LOAD_ARGS offset, skiprax=0
160 movq \offset(%rsp), %r11
161 movq \offset+8(%rsp), %r10
162 movq \offset+16(%rsp), %r9
163 movq \offset+24(%rsp), %r8
164 movq \offset+40(%rsp), %rcx
165 movq \offset+48(%rsp), %rdx
166 movq \offset+56(%rsp), %rsi
167 movq \offset+64(%rsp), %rdi
168 .if \skiprax
169 .else
170 movq \offset+72(%rsp), %rax
171 .endif
172 .endm
173
174#define REST_SKIP (6*8)
175
176 .macro SAVE_REST
177 subq $REST_SKIP, %rsp
178 CFI_ADJUST_CFA_OFFSET REST_SKIP
179 movq %rbx, 5*8(%rsp)
180 CFI_REL_OFFSET rbx, 5*8
181 movq %rbp, 4*8(%rsp)
182 CFI_REL_OFFSET rbp, 4*8
183 movq %r12, 3*8(%rsp)
184 CFI_REL_OFFSET r12, 3*8
185 movq %r13, 2*8(%rsp)
186 CFI_REL_OFFSET r13, 2*8
187 movq %r14, 1*8(%rsp)
188 CFI_REL_OFFSET r14, 1*8
189 movq %r15, (%rsp)
190 CFI_REL_OFFSET r15, 0*8
191 .endm
192
193 .macro RESTORE_REST
194 movq (%rsp), %r15
195 CFI_RESTORE r15
196 movq 1*8(%rsp), %r14
197 CFI_RESTORE r14
198 movq 2*8(%rsp), %r13
199 CFI_RESTORE r13
200 movq 3*8(%rsp), %r12
201 CFI_RESTORE r12
202 movq 4*8(%rsp), %rbp
203 CFI_RESTORE rbp
204 movq 5*8(%rsp), %rbx
205 CFI_RESTORE rbx
206 addq $REST_SKIP, %rsp
207 CFI_ADJUST_CFA_OFFSET -(REST_SKIP)
208 .endm
209
210 .macro SAVE_ALL
211 SAVE_ARGS
212 SAVE_REST
213 .endm
214
215 .macro RESTORE_ALL addskip=0
216 RESTORE_REST
217 RESTORE_ARGS 0, \addskip
218 .endm
219
220 .macro icebp
221 .byte 0xf1
222 .endm