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/*
* Copyright (C) 2005 Karl Vogel, Giridhar Pemmasani
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*/
#include <linux/linkage.h>
#ifdef CONFIG_X86_64
/*
# Windows <---> Linux register usage conversion when calling functions
# V = Volatile
# NV = Non Volatile (needs to be saved)
#
# Win Lin
# ---------------------------------------
# Rax Return V Return V
# Rbx NV NV
# Rcx Arg1 V Arg4 V
# Rdx Arg2 V Arg3 V
# Rsi NV Arg2 V
# Rdi NV Arg1 V
# Rsp NV NV
# Rbp NV NV
# R8 Arg3 V Arg5 V
# R9 Arg4 V Arg6 V
# R10 V V
# R11 V V
# R12 NV NV
# R13 NV NV
# R14 NV NV
# R15 NV NV
#
# In addition, Linux uses %rax to indicate number of SSE registers used
# when variadic functions are called. Since there is no way to obtain this
# from Windows, for now, we just assume this is 0 (hence %rax is cleared).
#
# Windows pushes arguments 5 and higher onto stack in case of integer
# variables and 4 and higher in case of floating point variabes (passed
# in SSE registers).
In a windows function, the stackframe/registers look like this:
# 0x0048 ....
# 0x0040 arg8
# 0x0038 arg7
# 0x0030 arg6
# 0x0028 arg5
# 0x0020 register spill space
# 0x0018 register spill space
# 0x0010 register spill space
# 0x0008 register spill space
# 0x0000 ret
# register spill space is same irrespective of number of arguments - even
# if Windows function takes less than 4 arguments, 32 bytes above return
# address is reserved for the function
In Linux it should look like:
# 0x0018 ....
# 0x0010 arg8
# 0x0008 arg7
# 0x0000 ret
*/
#
# setup for Windows to Linux function call
#
.text
.macro win2lin_prolog
push %rsi
push %rdi
.endm
.macro win2lin_epilog
pop %rdi
pop %rsi
.endm
# when Windows function calls Linux function, the function address is in %r10
.macro call_lin_func
xor %rax, %rax # rax indicates number of SSE regs
call *%r10
.endm
# before prolog, 0(%rsp) is return address, 8(%rsp) would be arg1
# (but it is in register) and so on, so n'th arg would be at n*8(%rsp)
# for n > 4. But in prolog, we push 2 registers that are non-volaile in
# Windows, but volatile in Linux. So after prolog, args are at (n+2)*8(%rsp)
#define win2lin_win_arg(n) (n+2)*8(%rsp)
#define win2lin_arg1 mov %rcx, %rdi
#define win2lin_arg2 mov %rdx, %rsi
#define win2lin_arg3 mov %r8, %rdx
#define win2lin_arg4 mov %r9, %rcx
#define win2lin_arg5 mov win2lin_win_arg(5), %r8
#define win2lin_arg6 mov win2lin_win_arg(6), %r9
win2lin0:
win2lin_prolog
call_lin_func
win2lin_epilog
ret
win2lin1:
win2lin_prolog
win2lin_arg1
call_lin_func
win2lin_epilog
ret
win2lin2:
win2lin_prolog
win2lin_arg1
win2lin_arg2
call_lin_func
win2lin_epilog
ret
win2lin3:
win2lin_prolog
win2lin_arg1
win2lin_arg2
win2lin_arg3
call_lin_func
win2lin_epilog
ret
win2lin4:
win2lin_prolog
win2lin_arg1
win2lin_arg2
win2lin_arg3
win2lin_arg4
call_lin_func
win2lin_epilog
ret
win2lin5:
win2lin_prolog
win2lin_arg1
win2lin_arg2
win2lin_arg3
win2lin_arg4
win2lin_arg5
call_lin_func
win2lin_epilog
ret
win2lin6:
win2lin_prolog
win2lin_arg1
win2lin_arg2
win2lin_arg3
win2lin_arg4
win2lin_arg5
win2lin_arg6
call_lin_func
win2lin_epilog
ret
# Allocate stack frame for Linux arguments before calling function.
# First 6 args are passed through registers, so we need space for 7 and above.
# The arguments should have been copied onto stack already.
.macro call_lin_func_args n
sub $(\n-6)*8, %rsp
call_lin_func
add $(\n-6)*8, %rsp
.endm
# m is index of Linux arg required, n is total number of args to function
# After stack frame is allocated, Linux arg 7 should be at 0(%rsp),
# arg 8 should be at 1*8(%rsp) and so on. So Linux arg m should be at (m-7)*8
# Stack frame starts at -(n-6)*8(%rsp), so before stack frame is allocated
# Linux arg m should be at (6-n+m-7)*8(%rsp)
#define win2lin_lin_arg(m,n) (m-1-n)*8(%rsp)
win2lin7:
win2lin_prolog
win2lin_arg1
win2lin_arg2
win2lin_arg3
win2lin_arg4
win2lin_arg5
win2lin_arg6
# copy windows argument 7 onto stack for Linux function
mov win2lin_win_arg(7), %r11
mov %r11, win2lin_lin_arg(7,7)
call_lin_func_args(7)
win2lin_epilog
ret
win2lin8:
win2lin_prolog
win2lin_arg1
win2lin_arg2
win2lin_arg3
win2lin_arg4
win2lin_arg5
win2lin_arg6
# copy windows arguments 7 and 8 onto stack for Linux function
mov win2lin_win_arg(7), %r11
mov %r11, win2lin_lin_arg(7,8)
mov win2lin_win_arg(8), %r11
mov %r11, win2lin_lin_arg(8,8)
call_lin_func_args(8)
win2lin_epilog
ret
win2lin9:
win2lin10:
win2lin11:
win2lin12:
win2lin_prolog
# since we destroy rsi and rdi here, first copy windows
# arguments 7 through 12 onto stack for Linux function
mov %rcx, %r11 # save rcx
lea win2lin_win_arg(7), %rsi # source (windows arg 7 and up)
lea win2lin_lin_arg(7,12), %rdi # = destination
mov $6, %rcx # 6 arguments
rep
movsq
mov %r11, %rcx # restore rcx
win2lin_arg1
win2lin_arg2
win2lin_arg3
win2lin_arg4
win2lin_arg5
win2lin_arg6
call_lin_func_args(12)
win2lin_epilog
ret
#define win2lin(name, argc) \
ENTRY(win2lin_ ## name ## _ ## argc) \
lea name(%rip), %r10 ; \
jmp win2lin ## argc
#include "win2lin_stubs.h"
#endif // CONFIG_X86_64
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