| 1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
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| 2 | /* |
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| 3 | * thunks_32.S - assembly helpers for mixed-bitness code |
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| 4 | * Copyright (c) 2015 Denys Vlasenko |
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| 5 | * |
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| 6 | * These are little helpers that make it easier to switch bitness on |
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| 7 | * the fly. |
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| 8 | */ |
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| 9 | |
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| 10 | .text |
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| 11 | .code32 |
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| 12 | |
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| 13 | .global call64_from_32 |
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| 14 | .type call32_from_64, @function |
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| 15 | |
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| 16 | // 4(%esp): function to call |
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| 17 | call64_from_32: |
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| 18 | // Fetch function address |
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| 19 | mov 4(%esp), %eax |
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| 20 | |
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| 21 | // Save registers which are callee-clobbered by 64-bit ABI |
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| 22 | push %ecx |
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| 23 | push %edx |
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| 24 | push %esi |
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| 25 | push %edi |
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| 26 | |
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| 27 | // Switch to long mode |
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| 28 | jmp $0x33,$1f |
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| 29 | 1: .code64 |
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| 30 | |
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| 31 | // Call the function |
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| 32 | call *%rax |
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| 33 | |
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| 34 | // Switch to compatibility mode |
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| 35 | push $0x23 /* USER32_CS */ |
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| 36 | .code32; push $1f; .code64 /* hack: can't have X86_64_32S relocation in 32-bit ELF */ |
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| 37 | lretq |
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| 38 | 1: .code32 |
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| 39 | |
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| 40 | pop %edi |
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| 41 | pop %esi |
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| 42 | pop %edx |
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| 43 | pop %ecx |
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| 44 | |
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| 45 | ret |
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| 46 | |
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| 47 | .size call64_from_32, .-call64_from_32 |
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| 48 | |
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| 49 | .section .note.GNU-stack,"" ,%progbits |
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| 50 | |
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