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/* $OpenBSD: eficall.S,v 1.1 2015/09/02 01:52:25 yasuoka Exp $ */
/*
* Copyright (c) 2015 YASUOKA Masahiko <yasuoka@yasuoka.net>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <machine/asm.h>
/*
* Rearrange the arguments to call the given function by EFI ABI.
*
* efi_call(nargs, func, arg[0], arg[1], arg[2], arg[3], arg[4], ...)
* ----------------------------------------------------------------------
* BSD: RDI RSI RDX RCX R8 R9 stack
* EFI: - - RCX RDX R8 R9 stack (w/shadow)
*/
ENTRY(efi_call)
push %rbp
mov %rsp, %rbp
xchg %rcx, %rdx
mov %rcx, %rax
mov %rdi, %rcx
/*
* set "nargs - 2 + 4 + 1" (= %rdi + 3) for next call stack size.
* (nargs - 2) is for arguments in stack, +4 for shadow registers
* and +1 for alignment
*/
add $3, %rdi
shl $3, %rdi /* 64-bit word */
sub %rdi, %rsp /* get the stack */
and $(-0x10), %rsp /* align 16 bytes */
/* copy args */
sub $3, %rcx
cmp $1, %rcx
jle 2f
1: /* loop arg[n-1] .. arg[4] */
mov 0x8(%rbp, %rcx, 8), %rdi
mov %rdi, 0x18(%rsp, %rcx, 8)
loopnz 1b
2:
mov %rax, %rcx
call *%rsi
mov %rbp, %rsp
pop %rbp
retq
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