/*

 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>

/*
 * 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

.macro UNWIND_END_OF_STACK
        417:
        .pushsection __unwind_end_of_stack, "a"
                .quad 417b
        .popsection
.endm

.macro UNWIND_UNSAFE_STACK
        417:
        .pushsection __unwind_unsafe_stack, "a"
                .quad 417b
        .popsection
.endm