arch/x86/include/asm/calling.h

   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
  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