| 1 | //
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| 2 | // Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
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| 3 | //
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| 4 | // The contents of this file are covered under the licence agreement in the
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| 5 | // file "LICENCE" distributed with Cforall.
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| 6 | //
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| 7 | // CtxSwitch-i386.S --
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| 8 | //
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| 9 | // Author : Thierry Delisle
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| 10 | // Created On : Tue Dec 6 12:27:26 2016
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| 11 | // Last Modified By : Peter A. Buhr
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| 12 | // Last Modified On : Sun Aug 16 08:46:22 2020
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| 13 | // Update Count : 4
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| 14 | //
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| 15 |
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| 16 | // The context switch routine requires the initial the stack of a thread to
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| 17 | // look like the thread has saved its context in the normal manner.
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| 18 |
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| 19 | // Offsets must synchronized with the __stack_context_t in invoke.h.
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| 20 |
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| 21 | #define PTR_BYTE 4
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| 22 | #define SP_OFFSET ( 0 * PTR_BYTE )
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| 23 | #define FP_OFFSET ( 1 * PTR_BYTE )
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| 24 |
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| 25 | // Context switch between coroutines/tasks.
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| 26 | // void __cfactx_switch( struct __stack_context_t * from, struct __stack_context_t * to ) ;
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| 27 | // Arguments "from" in register 4(%esp), "to" in register 20(%esp)
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| 28 |
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| 29 | .file "CtxSwitch-i386.S"
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| 30 | .text
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| 31 | .align 2
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| 32 | .global __cfactx_switch
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| 33 | .type __cfactx_switch, @function
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| 34 | __cfactx_switch:
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| 35 |
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| 36 | // Copy the "from" context argument from the stack to register eax
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| 37 | // Return address is at 0(%esp), with parameters following
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| 38 |
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| 39 | movl 4(%esp),%eax
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| 40 |
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| 41 | // Save volatile registers on the stack.
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| 42 |
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| 43 | pushl %ebx
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| 44 | pushl %edi
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| 45 | pushl %esi
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| 46 |
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| 47 | // Save old context in the "from" area.
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| 48 |
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| 49 | movl %esp,SP_OFFSET(%eax)
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| 50 | movl %ebp,FP_OFFSET(%eax)
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| 51 |
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| 52 | // Copy the "to" context argument from the stack to register eax
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| 53 | // Having pushed three words (= 12 bytes) on the stack, the
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| 54 | // argument is now at 8 + 12 = 20(%esp)
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| 55 |
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| 56 | movl 20(%esp),%eax
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| 57 |
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| 58 | // Load new context from the "to" area.
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| 59 |
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| 60 | movl SP_OFFSET(%eax),%esp
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| 61 | movl FP_OFFSET(%eax),%ebp
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| 62 |
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| 63 | // Load volatile registers from the stack.
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| 64 |
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| 65 | popl %esi
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| 66 | popl %edi
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| 67 | popl %ebx
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| 68 |
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| 69 | // Return to thread.
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| 70 |
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| 71 | ret
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| 72 | .size __cfactx_switch, .-__cfactx_switch
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| 73 |
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| 74 | // Local Variables: //
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| 75 | // mode: c //
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| 76 | // tab-width: 4 //
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| 77 | // End: //
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