view src/SDL_fatal.c @ 1176:dd2a8deeb26d

Date: Mon, 17 Oct 2005 20:09:03 -0400 From: Mark Schreiber <mark7@alumni.cmu.edu> To: ryan@clutteredmind.org Subject: [PATCH]SDL mprotect() crash fix (I'm going to throw this patch your way at the suggestion of #SDL -- for some reason, I had some difficulty sending it to the main list last time, and I go bonkers subscribing to send each email or patch...) Currently, when I run SDL applications as non-root using SDL_VIDEODRIVER=dga, the fbdev fallback mprotect()s read/write the proper size of mmapped /dev/fb0 (7.5MB), but on framebuffer release mprotect()s read-only the range by the entire size of my video memory (128MB), which causes a segfault: #0 0x002a9a27 in ?? () from /lib/libc.so.6 #1 0x04a63eb6 in SDL_XDGAUnmapFramebuffer (screen=3D0) at XF86DGA2.c:978 #2 0x04a63efc in SDL_XDGACloseFramebuffer (dpy=3D0x9d3f008, screen=3D0) at XF86DGA2.c:268 #3 0x04a68b57 in DGA_Available () at SDL_dgavideo.c:98 #4 0x04a53677 in SDL_VideoInit (driver_name=3D0xbfb0bfc7 "dga", flags=3D0) at SDL_video.c:180 #5 0x04a2613f in SDL_InitSubSystem (flags=3D32) at SDL.c:74 #6 0x04a2617c in SDL_Init (flags=3D32) at SDL.c:166 #7 0x08049722 in main (argc=3D1, argv=3D0x0) at testwin.c:32 This is SDL 1.2.8 on Fedora Core 4, radeon driver for a Radeon 9250, xorg-x11-6.8.2-37. I've attached a one-line patch against SDL CVS that updates the size of the framebuffer at framebuffer map time so that the mprotect() on unmap will be the same size. I'm not sure if this is the best approach (i.e. one might want to retain the original value), but it does make my SDL applications work without segfaulting. -- Best of luck, Mark Schreiber
author Ryan C. Gordon <icculus@icculus.org>
date Sat, 19 Nov 2005 18:57:00 +0000
parents 51a8702d8ecd
children c9b51268668f
line wrap: on
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/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2004 Sam Lantinga

    This 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.

    This 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 this library; if not, write to the Free
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    Sam Lantinga
    slouken@libsdl.org
*/

#ifdef SAVE_RCSID
static char rcsid =
 "@(#) $Id$";
#endif

#ifdef _WIN32_WCE
#define NO_SIGNAL_H
#endif
 
/* General fatal signal handling code for SDL */

#ifdef NO_SIGNAL_H

/* No signals on this platform, nothing to do.. */

void SDL_InstallParachute(void)
{
	return;
}

void SDL_UninstallParachute(void)
{
	return;
}

#else

#include <stdlib.h>
#include <stdio.h>
#include <signal.h>
#include <string.h>

#include "SDL.h"
#include "SDL_fatal.h"

#ifdef __CYGWIN__
#define DISABLE_STDIO
#endif

/* This installs some signal handlers for the more common fatal signals,
   so that if the programmer is lazy, the app doesn't die so horribly if
   the program crashes.
*/

static void print_msg(const char *text)
{
#ifndef DISABLE_STDIO
	fprintf(stderr, "%s", text);
#endif
}

static void SDL_Parachute(int sig)
{
	signal(sig, SIG_DFL);
	print_msg("Fatal signal: ");
	switch (sig) {
		case SIGSEGV:
			print_msg("Segmentation Fault");
			break;
#ifdef SIGBUS
#if SIGBUS != SIGSEGV
		case SIGBUS:
			print_msg("Bus Error");
			break;
#endif
#endif /* SIGBUS */
#ifdef SIGFPE
		case SIGFPE:
			print_msg("Floating Point Exception");
			break;
#endif /* SIGFPE */
#ifdef SIGQUIT
		case SIGQUIT:
			print_msg("Keyboard Quit");
			break;
#endif /* SIGQUIT */
#ifdef SIGPIPE
		case SIGPIPE:
			print_msg("Broken Pipe");
			break;
#endif /* SIGPIPE */
		default:
#ifndef DISABLE_STDIO
			fprintf(stderr, "# %d", sig);
#endif
			break;
	}
	print_msg(" (SDL Parachute Deployed)\n");
	SDL_Quit();
	exit(-sig);
}

static int SDL_fatal_signals[] = {
	SIGSEGV,
#ifdef SIGBUS
	SIGBUS,
#endif
#ifdef SIGFPE
	SIGFPE,
#endif
#ifdef SIGQUIT
	SIGQUIT,
#endif
	0
};

void SDL_InstallParachute(void)
{
	/* Set a handler for any fatal signal not already handled */
	int i;
#ifdef HAVE_SIGACTION
	struct sigaction action;

	for ( i=0; SDL_fatal_signals[i]; ++i ) {
		sigaction(SDL_fatal_signals[i], NULL, &action);
		if ( action.sa_handler == SIG_DFL ) {
			action.sa_handler = SDL_Parachute;
			sigaction(SDL_fatal_signals[i], &action, NULL);
		}
	}
#ifdef SIGALRM
	/* Set SIGALRM to be ignored -- necessary on Solaris */
	sigaction(SIGALRM, NULL, &action);
	if ( action.sa_handler == SIG_DFL ) {
		action.sa_handler = SIG_IGN;
		sigaction(SIGALRM, &action, NULL);
	}
#endif
#else
	void (*ohandler)(int);

	for ( i=0; SDL_fatal_signals[i]; ++i ) {
		ohandler = signal(SDL_fatal_signals[i], SDL_Parachute);
		if ( ohandler != SIG_DFL ) {
			signal(SDL_fatal_signals[i], ohandler);
		}
	}
#endif /* HAVE_SIGACTION */
	return;
}

void SDL_UninstallParachute(void)
{
	/* Remove a handler for any fatal signal handled */
	int i;
#ifdef HAVE_SIGACTION
	struct sigaction action;

	for ( i=0; SDL_fatal_signals[i]; ++i ) {
		sigaction(SDL_fatal_signals[i], NULL, &action);
		if ( action.sa_handler == SDL_Parachute ) {
			action.sa_handler = SIG_DFL;
			sigaction(SDL_fatal_signals[i], &action, NULL);
		}
	}
#else
	void (*ohandler)(int);

	for ( i=0; SDL_fatal_signals[i]; ++i ) {
		ohandler = signal(SDL_fatal_signals[i], SIG_DFL);
		if ( ohandler != SDL_Parachute ) {
			signal(SDL_fatal_signals[i], ohandler);
		}
	}
#endif /* HAVE_SIGACTION */
}

#endif /* NO_SIGNAL_H */