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/* i386.s -- assembly support. */
/*
// QuickThreads -- Threads-building toolkit.
// Copyright (c) 1993 by David Keppel
//
// Permission to use, copy, modify and distribute this software and
// its documentation for any purpose and without fee is hereby
// granted, provided that the above copyright notice and this notice
// appear in all copies. This software is provided as a
// proof-of-concept and for demonstration purposes; there is no
// representation about the suitability of this software for any
// purpose. */
/* NOTE: double-labeled `_name' and `name' for System V compatability. */
/* NOTE: Mixed C/C++-style comments used. Sorry! */
/* Callee-save: %esi, %edi, %ebx, %ebp
// Caller-save: %eax, %ecx
// Can't tell: %edx (seems to work w/o saving it.)
//
// Assignment:
//
// See ``i386.h'' for the somewhat unconventional stack layout. */
.text
.align 2
.globl _qt_abort
.globl qt_abort
.globl _qt_block
.globl qt_block
.globl _qt_blocki
.globl qt_blocki
.globl _qt_align
.globl qt_align
/* These all have the type signature
//
// void *blocking (helper, arg0, arg1, new)
//
// On procedure entry, the helper is at 4(sp), args at 8(sp) and
// 12(sp) and the new thread's sp at 16(sp). It *appears* that the
// calling convention for the 8X86 requires the caller to save all
// floating-point registers, this makes our life easy. */
/* Halt the currently-running thread. Save it's callee-save regs on
// to the stack, 32 bytes. Switch to the new stack (next == 16+32(sp))
// and call the user function (f == 4+32(sp) with arguments: old sp
// arg1 (8+32(sp)) and arg2 (12+32(sp)). When the user function is
// done, restore the new thread's state and return.
//
// `qt_abort' is (currently) an alias for `qt_block' because most of
// the work is shared. We could save the insns up to `qt_common' by
// replicating, but w/o replicating we need an inital subtract (to
// offset the stack as if it had been a qt_block) and then a jump
// to qt_common. For the cost of a jump, we might as well just do
// all the work.
//
// The helper function (4(sp)) can return a void* that is returned
// by the call to `qt_blockk{,i}'. Since we don't touch %eax in
// between, we get that ``for free''. */
_qt_abort:
qt_abort:
_qt_block:
qt_block:
_qt_blocki:
qt_blocki:
pushl %ebp /* Save callee-save, sp-=4. */
pushl %esi /* Save callee-save, sp-=4. */
pushl %edi /* Save callee-save, sp-=4. */
pushl %ebx /* Save callee-save, sp-=4. */
movl %esp, %eax /* Remember old stack pointer. */
qt_common:
movl 32(%esp), %esp /* Move to new thread. */
pushl 28(%eax) /* Push arg 2. */
pushl 24(%eax) /* Push arg 1. */
pushl %eax /* Push arg 0. */
movl 20(%eax), %ebx /* Get function to call. */
call *%ebx /* Call f. */
addl $12, %esp /* Pop args. */
popl %ebx /* Restore callee-save, sp+=4. */
popl %edi /* Restore callee-save, sp+=4. */
popl %esi /* Restore callee-save, sp+=4. */
popl %ebp /* Restore callee-save, sp+=4. */
_qt_align:
qt_align:
ret /* Resume the stopped function. */
.globl _qt_tramp
.globl qt_tramp
_qt_tramp:
qt_tramp:
movl 12(%esp), %eax /* Load 'qt_error' address */
sub $4, %esp /* Align stack pointer to 16-byte boundary */
jmp *%eax /* call 'qt_error' */
hlt /* 'qt_error' never returns */
/* Start a varargs thread. */
.globl _qt_vstart
.globl qt_vstart
_qt_vstart:
qt_vstart:
pushl %edi /* Push `pt' arg to `startup'. */
call *%ebp /* Call `startup'. */
popl %eax /* Clean up the stack. */
call *%ebx /* Call the user's function. */
pushl %eax /* Push return from user's. */
pushl %edi /* Push `pt' arg to `cleanup'. */
call *%esi /* Call `cleanup'. */
hlt /* `cleanup' never returns. */
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