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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* thunks_32.S - assembly helpers for mixed-bitness code
* Copyright (c) 2015 Denys Vlasenko
*
* 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
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