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- /*
- * 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
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