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112 lines
3.2 KiB
NASM
112 lines
3.2 KiB
NASM
;; i386.asm -- assembly support.
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;;
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;; QuickThreads -- Threads-building toolkit.
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;; Copyright (c) 2001, 2006 Free Software Foundation, Inc.
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;;
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;; Permission to use, copy, modify and distribute this software and
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;; its documentation for any purpose and without fee is hereby
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;; granted, provided that the above copyright notice and this notice
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;; appear in all copies. This software is provided as a
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;; proof-of-concept and for demonstration purposes; there is no
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;; representation about the suitability of this software for any
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;; purpose.
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;; NOTE: double-labeled `_name' and `name' for System V compatability.
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;; NOTE: Comment lines start like this one, or with '//' ONLY. Sorry!
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;; Callee-save: %esi, %edi, %ebx, %ebp
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;; Caller-save: %eax, %ecx
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;; Can't tell: %edx (seems to work w/o saving it.)
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;;
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;; Assignment:
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;;
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;; See ``i386.h'' for the somewhat unconventional stack layout.
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.386p
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.model flat
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.code
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public _qt_abort
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public qt_abort
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public _qt_block
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public qt_block
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public _qt_blocki
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public qt_blocki
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;; These all have the type signature
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;;
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;; void *blocking (helper, arg0, arg1, new)
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;;
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;; On procedure entry, the helper is at 4(sp), args at 8(sp) and
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;; 12(sp) and the new thread's sp at 16(sp). It *appears* that the
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;; calling convention for the 8X86 requires the caller to save all
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;; floating-point registers, this makes our life easy.
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;; Halt the currently-running thread. Save it's callee-save regs on
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;; to the stack, 32 bytes. Switch to the new stack (next == 16+32(sp))
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;; and call the user function (f == 4+32(sp) with arguments: old sp
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;; arg1 (8+32(sp)) and arg2 (12+32(sp)). When the user function is
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;; done, restore the new thread's state and return.
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;;
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;; `qt_abort' is (currently) an alias for `qt_block' because most of
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;; the work is shared. We could save the insns up to `qt_common' by
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;; replicating, but w/o replicating we need an inital subtract (to
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;; offset the stack as if it had been a qt_block) and then a jump
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;; to qt_common. For the cost of a jump, we might as well just do
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;; all the work.
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;;
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;; The helper function (4(sp)) can return a void* that is returned
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;; by the call to `qt_blockk{,i}'. Since we don't touch %eax in
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;; between, we get that ``for free''.
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_qt_abort:
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qt_abort:
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_qt_block:
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qt_block:
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_qt_blocki:
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qt_blocki:
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push ebp ; Save callee-save, sp-=4.
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push esi ; Save callee-save, sp-=4.
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push edi ; Save callee-save, sp-=4.
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push ebx ; Save callee-save, sp-=4.
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mov eax, esp ; Remember old stack pointer.
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qt_common:
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mov esp, [esp+32] ; Move to new thread.
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push [eax+28] ; Push arg 2.
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push [eax+24] ; Push arg 1.
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push eax ; Push arg 0.
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mov ebx, [eax+20] ; Get function to call.
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call ebx ; Call f.
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add esp, 12 ; Pop args.
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pop ebx ; Restore callee-save, sp+=4.
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pop edi ; Restore callee-save, sp+=4.
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pop esi ; Restore callee-save, sp+=4.
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pop ebp ; Restore callee-save, sp+=4.
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ret ; Resume the stopped function.
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hlt
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;; Start a varargs thread.
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public _qt_vstart
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public qt_vstart
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_qt_vstart:
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qt_vstart:
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push edi ; Push `pt' arg to `startup'.
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call ebp ; Call `startup'.
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pop eax ; Clean up the stack.
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call ebx ; Call the user's function.
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push eax ; Push return from user's.
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push edi ; Push `pt' arg to `cleanup'.
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call esi ; Call `cleanup'.
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hlt ; `cleanup' never returns.
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end
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