/*
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* thunks_32.S - assembly helpers for mixed-bitness code
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* Copyright (c) 2015 Denys Vlasenko
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* These are little helpers that make it easier to switch bitness on
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* the fly.
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*/
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.text
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.code32
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.global call64_from_32
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.type call32_from_64, @function
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// 4(%esp): function to call
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call64_from_32:
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// Fetch function address
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mov 4(%esp), %eax
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// Save registers which are callee-clobbered by 64-bit ABI
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push %ecx
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push %edx
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push %esi
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push %edi
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// Switch to long mode
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jmp $0x33,$1f
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1: .code64
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// Call the function
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call *%rax
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// Switch to compatibility mode
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push $0x23 /* USER32_CS */
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.code32; push $1f; .code64 /* hack: can't have X86_64_32S relocation in 32-bit ELF */
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lretq
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1: .code32
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pop %edi
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pop %esi
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pop %edx
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pop %ecx
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ret
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.size call64_from_32, .-call64_from_32
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