| 1 | // -*- Mode: Asm -*-
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| 2 | //
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| 3 | // Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
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| 4 | //
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| 5 | // The contents of this file are covered under the licence agreement in the
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| 6 | // file "LICENCE" distributed with Cforall.
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| 7 | //
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| 8 | // CtxSwitch-i386.S --
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| 9 | //
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| 10 | // Author : Thierry Delisle
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| 11 | // Created On : Tue Dec 6 12:27:26 2016
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| 12 | // Last Modified By : Thierry Delisle
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| 13 | // Last Modified On : Tue Dec 6 12:27:26 2016
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| 14 | // Update Count : 0
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| 15 | //
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| 16 | // This library is free software; you can redistribute it and/or modify it
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| 17 | // under the terms of the GNU Lesser General Public License as published by the
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| 18 | // Free Software Foundation; either version 2.1 of the License, or (at your
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| 19 | // option) any later version.
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| 20 | //
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| 21 | // This library is distributed in the hope that it will be useful, but WITHOUT
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| 22 | // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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| 23 | // FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
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| 24 | // for more details.
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| 25 | //
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| 26 | // You should have received a copy of the GNU Lesser General Public License
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| 27 | // along with this library.
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| 28 | //
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| 29 |
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| 30 | // This context switch routine depends on the fact that the stack of a new
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| 31 | // thread has been set up to look like the thread has saved its context in
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| 32 | // the normal manner.
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| 33 | //
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| 34 | // void CtxSwitch( machine_context *from, machine_context *to );
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| 35 |
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| 36 | // Offsets in the context structure. This needs to be synchronized with the
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| 37 | // high level code a little better.
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| 38 |
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| 39 | #define PTR_BYTE 4
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| 40 | #define SP_OFFSET ( 0 * PTR_BYTE )
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| 41 | #define FP_OFFSET ( 1 * PTR_BYTE )
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| 42 | #define PC_OFFSET ( 2 * PTR_BYTE )
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| 43 |
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| 44 | .text
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| 45 | .align 2
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| 46 | .globl CtxSwitch
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| 47 | CtxSwitch:
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| 48 |
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| 49 | // Copy the "from" context argument from the stack to register eax
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| 50 | // Return address is at 0(%esp), with parameters following
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| 51 |
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| 52 | movl 4(%esp),%eax
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| 53 |
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| 54 | // Save volatile registers on the stack.
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| 55 |
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| 56 | pushl %ebx
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| 57 | pushl %edi
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| 58 | pushl %esi
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| 59 |
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| 60 | // Save old context in the "from" area.
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| 61 |
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| 62 | movl %esp,SP_OFFSET(%eax)
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| 63 | movl %ebp,FP_OFFSET(%eax)
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| 64 | // movl 4(%ebp),%ebx // save previous eip for debugger
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| 65 | // movl %ebx,PC_OFFSET(%eax)
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| 66 |
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| 67 | // Copy the "to" context argument from the stack to register eax
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| 68 | // Having pushed three words (= 12 bytes) on the stack, the
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| 69 | // argument is now at 8 + 12 = 20(%esp)
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| 70 |
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| 71 | movl 20(%esp),%eax
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| 72 |
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| 73 | // Load new context from the "to" area.
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| 74 |
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| 75 | movl SP_OFFSET(%eax),%esp
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| 76 | movl FP_OFFSET(%eax),%ebp
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| 77 |
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| 78 | // Load volatile registers from the stack.
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| 79 |
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| 80 | popl %esi
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| 81 | popl %edi
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| 82 | popl %ebx
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| 83 |
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| 84 | // Return to thread.
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| 85 |
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| 86 | ret
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| 87 |
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| 88 | // Local Variables: //
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| 89 | // compile-command: "make install" //
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| 90 | // End: //
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