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

These are test programs for the SDL library:

	testver		Check the version and dynamic loading and endianness
	testtypes	Check to see if the data types are the correct size
	testhread	Hacked up test of multi-threading
	testlock	Hacked up test of multi-threading and locking
	testerror	Tests multi-threaded error handling
	testsem		Tests SDL's semaphore implementation
	testtimer	Test the timer facilities
	loopwave	Audio test -- loop playing a WAV file
	testcdrom	Sample audio CD control program
	testkeys	List the available keyboard keys
	testvidinfo	Show the pixel format of the display and perfom the benchmark
	checkkeys	Watch the key events to check the keyboard
	testwin		Display a BMP image at various depths
	graywin		Display a gray gradient and center mouse on spacebar
	testsprite	Example of fast sprite movement on the screen
	testbitmap	Test displaying 1-bit bitmaps
	testalpha	Display an alpha faded icon -- paint with mouse
	testwm		Test window manager -- title, icon, events
	threadwin	Test multi-threaded event handling
	testgl		A very simple example of using OpenGL with SDL
	testjoystick	List joysticks and watch joystick events
	testoverlay	Tests the software/hardware overlay functionality.
	testoverlay2	Tests the overlay flickering/scaling during playback.
	testblitspeed	Tests performance of SDL's blitters and converters.