| /* |
| * thunks.S - assembly helpers for mixed-bitness code |
| * Copyright (c) 2015 Andrew Lutomirski |
| * |
| * 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 |
| |
| .global call32_from_64 |
| .type call32_from_64, @function |
| call32_from_64: |
| // rdi: stack to use |
| // esi: function to call |
| |
| // Save registers |
| pushq %rbx |
| pushq %rbp |
| pushq %r12 |
| pushq %r13 |
| pushq %r14 |
| pushq %r15 |
| pushfq |
| |
| // Switch stacks |
| mov %rsp,(%rdi) |
| mov %rdi,%rsp |
| |
| // Switch to compatibility mode |
| pushq $0x23 /* USER32_CS */ |
| pushq $1f |
| lretq |
| |
| 1: |
| .code32 |
| // Call the function |
| call *%esi |
| // Switch back to long mode |
| jmp $0x33,$1f |
| .code64 |
| |
| 1: |
| // Restore the stack |
| mov (%rsp),%rsp |
| |
| // Restore registers |
| popfq |
| popq %r15 |
| popq %r14 |
| popq %r13 |
| popq %r12 |
| popq %rbp |
| popq %rbx |
| |
| ret |
| |
| .size call32_from_64, .-call32_from_64 |
