Linux Kernel  3.7.1
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calling.h
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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 
24 For 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 #include <asm/dwarf2.h>
50 
51 /*
52  * 64-bit system call stack frame layout defines and helpers,
53  * for assembly code:
54  */
55 
56 #define R15 0
57 #define R14 8
58 #define R13 16
59 #define R12 24
60 #define RBP 32
61 #define RBX 40
62 
63 /* arguments: interrupts/non tracing syscalls only save up to here: */
64 #define R11 48
65 #define R10 56
66 #define R9 64
67 #define R8 72
68 #define RAX 80
69 #define RCX 88
70 #define RDX 96
71 #define RSI 104
72 #define RDI 112
73 #define ORIG_RAX 120 /* + error_code */
74 /* end of arguments */
75 
76 /* cpu exception frame or undefined in case of fast syscall: */
77 #define RIP 128
78 #define CS 136
79 #define EFLAGS 144
80 #define RSP 152
81 #define SS 160
82 
83 #define ARGOFFSET R11
84 #define SWFRAME ORIG_RAX
85 
86  .macro SAVE_ARGS addskip=0, save_rcx=1, save_r891011=1
87  subq $9*8+\addskip, %rsp
88  CFI_ADJUST_CFA_OFFSET 9*8+\addskip
89  movq_cfi rdi, 8*8
90  movq_cfi rsi, 7*8
91  movq_cfi rdx, 6*8
92 
93  .if \save_rcx
94  movq_cfi rcx, 5*8
95  .endif
96 
97  movq_cfi rax, 4*8
98 
99  .if \save_r891011
100  movq_cfi r8, 3*8
101  movq_cfi r9, 2*8
102  movq_cfi r10, 1*8
103  movq_cfi r11, 0*8
104  .endif
105 
106  .endm
107 
108 #define ARG_SKIP (9*8)
109 
110  .macro RESTORE_ARGS rstor_rax=1, addskip=0, rstor_rcx=1, rstor_r11=1, \
111  rstor_r8910=1, rstor_rdx=1
112  .if \rstor_r11
113  movq_cfi_restore 0*8, r11
114  .endif
115 
116  .if \rstor_r8910
117  movq_cfi_restore 1*8, r10
118  movq_cfi_restore 2*8, r9
119  movq_cfi_restore 3*8, r8
120  .endif
121 
122  .if \rstor_rax
123  movq_cfi_restore 4*8, rax
124  .endif
125 
126  .if \rstor_rcx
127  movq_cfi_restore 5*8, rcx
128  .endif
129 
130  .if \rstor_rdx
131  movq_cfi_restore 6*8, rdx
132  .endif
133 
134  movq_cfi_restore 7*8, rsi
135  movq_cfi_restore 8*8, rdi
136 
137  .if ARG_SKIP+\addskip > 0
138  addq $ARG_SKIP+\addskip, %rsp
139  CFI_ADJUST_CFA_OFFSET -(ARG_SKIP+\addskip)
140  .endif
141  .endm
142 
143  .macro LOAD_ARGS offset, skiprax=0
144  movq \offset(%rsp), %r11
145  movq \offset+8(%rsp), %r10
146  movq \offset+16(%rsp), %r9
147  movq \offset+24(%rsp), %r8
148  movq \offset+40(%rsp), %rcx
149  movq \offset+48(%rsp), %rdx
150  movq \offset+56(%rsp), %rsi
151  movq \offset+64(%rsp), %rdi
152  .if \skiprax
153  .else
154  movq \offset+72(%rsp), %rax
155  .endif
156  .endm
157 
158 #define REST_SKIP (6*8)
159 
160  .macro SAVE_REST
163  movq_cfi rbx, 5*8
164  movq_cfi rbp, 4*8
165  movq_cfi r12, 3*8
166  movq_cfi r13, 2*8
167  movq_cfi r14, 1*8
168  movq_cfi r15, 0*8
169  .endm
170 
171  .macro RESTORE_REST
172  movq_cfi_restore 0*8, r15
173  movq_cfi_restore 1*8, r14
174  movq_cfi_restore 2*8, r13
175  movq_cfi_restore 3*8, r12
176  movq_cfi_restore 4*8, rbp
177  movq_cfi_restore 5*8, rbx
178  addq $REST_SKIP, %rsp
180  .endm
181 
182  .macro SAVE_ALL
183  SAVE_ARGS
184  SAVE_REST
185  .endm
186 
187  .macro RESTORE_ALL addskip=0
188  RESTORE_REST
189  RESTORE_ARGS 1, \addskip
190  .endm
191 
192  .macro icebp
193  .byte 0xf1
194  .endm