view src/thread/linux/clone.S @ 968:4675910b0b7b

Date: Mon, 11 Oct 2004 15:17:27 +0300 (EEST) From: Hannu Savolainen Subject: Re: SDL uses obsolete OSS features I did some work on getting OSS to work better with SDL. There have been some problems with select which should be fixed now. I'm having some problems in understanding what is the purpose of the DSP_WaitAudio() routine. I added a return to the very beginning of this routine and commendted out the define for USE_BLOCKING_WRITES. At least lbreakout2 seems to work as well as earlier. The latencies are the same. An ordinary blocking write does exactly the same thing than DSP_WaitAudio does. So I would recommend using the USE_BLOCKING_WRITES approach and removing everything from the DSP_WaitAudio routine. Also enabling USE_BLOCKING_WRITES makes it possible to simplify DSP_PlayAudio() because you don't need to handle the partial writes (the do-while loop). Attached is a patch against SDL-1.2.7. After these changes SDL will use OSS as it's designed to be used (make it as simple as possible). This code should work with all OSS implementations because it uses only the very fundamental features that have been there since the jurassic times.
author Sam Lantinga <slouken@libsdl.org>
date Fri, 12 Nov 2004 21:39:04 +0000
parents 74212992fb08
children 974ba6ae0fa3
line wrap: on
line source


/* Taken with thanks from LinuxThreads 0.6 */

/* This is no longer necessary with glibc-2.1, which has it's own clone() */
#ifdef linux
/* Look to see if glibc is available, and if so, what version */
#include <features.h>

#if (__GLIBC__ > 2) || ((__GLIBC__ == 2) && (__GLIBC_MINOR__ >= 1))
#define HAVE_CLONE
#endif /* glibc 2.1 or newer */
#endif /* linux */

#if defined(linux) && !defined(SDL_USE_PTHREADS) && !defined(HAVE_CLONE)

#if defined(__i386__)
/************************************************************************/
/* Copyright (C) 1996, 1997 Free Software Foundation, Inc.
   Contributed by Richard Henderson (rth@tamu.edu)

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,

#ifdef SAVE_RCSID
static char rcsid =
 "@(#) $Id$";
#endif
Cambridge, MA 02139, USA.  */

/* clone() is even more special than fork() as it mucks with stacks
   and invokes a function in the right context after its all over.  */

#include <asm/errno.h>
#include <asm/unistd.h>

/* int clone(int (*fn)(void *arg), void *child_stack, int flags, void *arg); */

        .text
	.align	4
	.globl	__clone
        .type   __clone,@function
	.weak	clone
	clone   = __clone
__clone:
	/* Sanity check arguments.  */
	movl	$-EINVAL,%eax
	movl	4(%esp),%ecx		/* no NULL function pointers */
	testl	%ecx,%ecx
	jz	syscall_error
	movl	8(%esp),%ecx		/* no NULL stack pointers */
	testl	%ecx,%ecx
	jz	syscall_error

	/* Insert the argument onto the new stack.  */
	subl	$8,%ecx
	movl	16(%esp),%eax
	movl	%eax,4(%ecx)

	/* Save the function pointer as the zeroth argument. */
	/* It will be popped off in the child in the ebx frobbing below.  */
	movl	4(%esp),%eax
	movl	%eax,0(%ecx)

	/* Do the system call */
	pushl	%ebx
	movl	16(%esp),%ebx
	movl	$__NR_clone,%eax
	int	$0x80
	popl	%ebx

	test	%eax,%eax
	jl	syscall_error
	jz	thread_start

	ret

syscall_error:
	negl    %eax
        pushl   %eax
#ifdef __PIC__
        call    __errno_location@PLT
#else
        call    __errno_location
#endif
        popl    0(%eax)
	movl	$-1, %eax
	ret

thread_start:
	subl	%ebp,%ebp	/* terminate the stack frame */
	call	*%ebx
        pushl   %eax
#ifdef __PIC__
	call	_exit@PLT
#else
	call	_exit
#endif
/************************************************************************/
#elif defined(sparc)
/************************************************************************/
/* Copyright (C) 1996, 1997 Free Software Foundation, Inc.
   Contributed by Miguel de Icaza (miguel@nuclecu.unam.mx)
   Based on code written for the Intel by Richard 
   Henderson (rth@tamu.edu)
	
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

/* clone() is even more special than fork() as it mucks with stacks
   and invokes a function in the right context after its all over.  */
	
#include <asm/errno.h>
#include <asm/unistd.h>

/* int clone(int (*fn)(void *arg), void *child_stack, int flags, void *arg); */

	.text
	.align	4
	.globl	__clone
	.type	__clone,@function
	.weak	clone
	clone   = __clone
__clone:	
	save	%sp,-96,%sp
	/* sanity check arguments */
	tst	%i0
	be	__clone_syscall_error
	tst	%i1
	be	__clone_syscall_error
        nop

	/* Do the system call */
	mov	%i1,%o1
	mov	%i2,%o0
	set	__NR_clone,%g1
	ta	0x10
	bcs	__clone_syscall_error
	tst	%o1
	bne	__thread_start
	nop
	mov	%o0,%i0
	ret
	restore
	
__clone_syscall_error:
	call	__errno_location
	set	EINVAL,%i0
	st	%i0,[%o0]
	mov	-1,%i0
	ret
	restore

__thread_start:
	call	%i0
	mov	%i3,%o0
	call	_exit,0
	nop
/************************************************************************/
#else 
#error "Unknown Linux architecture"
#endif

#endif /* Linux && ! SDL_USE_PTHREADS */