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 #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
 161         subq $REST_SKIP, %rsp
 162         CFI_ADJUST_CFA_OFFSET   REST_SKIP
 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
 179         CFI_ADJUST_CFA_OFFSET   -(REST_SKIP)
 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