/*
* thunks_32.S - assembly helpers for mixed-bitness code
* Copyright (c) 2015 Denys Vlasenko
*
* This program is free software; you can redistribute it and/or modify
* it under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope 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.
*
* These are little helpers that make it easier to switch bitness on
* the fly.
*/
.text
.code32
.global call64_from_32
.type call32_from_64, @function
// 4(%esp): function to call
call64_from_32:
// Fetch function address
mov 4(%esp), %eax
// Save registers which are callee-clobbered by 64-bit ABI
push %ecx
push %edx
push %esi
push %edi
// Switch to long mode
jmp $0x33,$1f
1: .code64
// Call the function
call *%rax
// Switch to compatibility mode
push $0x23 /* USER32_CS */
.code32; push $1f; .code64 /* hack: can't have X86_64_32S relocation in 32-bit ELF */
lretq
1: .code32
pop %edi
pop %esi
pop %edx
pop %ecx
ret
.size call64_from_32, .-call64_from_32
back