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vga_init(3)		      Svgalib User Manual		   vga_init(3)

NAME
       vga_init	- initialize svgalib library

SYNOPSIS
       #include	<vga.h>

       int vga_init(void);

DESCRIPTION
       It detects the chipset and gives	up supervisor rights. This is the rec-
       ommended	  first	  line	 of   any   program   that    uses    svgalib.
       vga_setchipset(3) can be	called before it to avoid detection.

       Svgalib	catches	 a  bunch of signals that usually kill your program to
       restore textmode. If you	catch signal's before calling  vga_init()  sv-
       galib will restore textmode and prepare for shutdown and	then call your
       handler routine.	If you don't want this,	catch the signal after calling
       vga_init	and do not daisychain to svgalib's original handler.

       WARNING!	 svgalib needs two signals for it's own	purposes (that is man-
       aging console switches).	To avoid problems it uses the otherwise	unused
       signals	SIGUSR1	 and SIGUSR2.  However,	this means that	you cannot use
       them in your program by any means. They are setup by vga_init() as  ev-
       erything	else is.

       Since  version  1.2.11 vga_init() includes code to hunt for a free vir-
       tual console on its own in case you are not starting the	 program  from
       one (but	instead	over a network or modem	login, from within 'screen' or
       an 'xterm'). Provided there is a	free console, this succeeds if you are
       root or if the svgalib calling user own the current console. This is to
       avoid people not	using the console being	able to	fiddle	with  it.   On
       graceful	 exit  the  program  returns  to the console from which	it was
       started.	 Otherwise it remains in text mode at the VC which svgalib al-
       located	to  allow  you to see any error	messages. In any case, any I/O
       the svgalib makes in text mode (after calling vga_init) will also  take
       place at	this new console.

       Alas, some games	misuse their suid root priviledge and run as full root
       process.	svgalib	cannot detect this and allows Joe Blow User to open  a
       new  VC	on  the	 console. If this annoys you ROOT_VC_SHORTCUT in Make-
       file.cfg	allows you to disable allocating a new	VC  for	 root  (except
       when  he	 owns the current console) when	compiling svgalib. This	is the
       default (disabling the allocation for root).

       vga_init() returns a non-zero value in case of errors. As of this writ-
       ing  it will return -1 if it is unable to allocate a graphical console.
       Otherwise, 0 is returned.

BUGS
       Svgalib versions	prior to 1.2.11	had a security hole where it would  be
       possible	 to regain root	priviledges even after a vga_init() call. This
       is not necessarily a problem, but if your program is vulnerable to buf-
       fer overflows and other attacks,	an attacker may	exploit	this.

       However,	prior to your call, your program will need to run setuid root,
       so you should be	very careful. The ioperm library by Olaf Titz will al-
       low svgalib programs to run not setuid root. However, it	gives all pro-
       grams unlimited access to the hardware. Again, a	malicious  person  can
       exploit this (albeit a bit more difficult) too.	Thus, in general, make
       your svgalib programs as	secure as any setuid root program.

       Some programs may (accidently) rely on the  old	behaviour  (which  was
       probably	 due  to  the author not knowing about saved uids (which might
       actually	even not have existed in Linux at that time)). A line:

       security	compat

       in the configuration file /etc/vga/libvga.conf will reinstate  the  old
       behaviour whereas

       security	revoke-all-privs

       enables the (currently default) action.

SEE ALSO
       svgalib(7),   vga_setmode(3),  mouse_init(3),  vga_claimvideomemory(3),
       vga_ext_set(3),	vga_fillblt(3),	 vga_getcurrentchipset(3),  vga_getde-
       faultmode(3),  vga_getgraphmem(3),  vga_runinbackground(3),  vga_runin-
       background_version(3),	   vga_safety_fork(3),	    vga_setchipset(3),
       vga_setchipsetandfeatures(3), vgagl(7), libvga.config(5),

AUTHOR
       This  manual page was edited by Michael Weller <eowmob@exp-math.uni-es-
       sen.de>.	The exact source of the	referenced function as well as of  the
       original	documentation is unknown.

       It is very likely that both are at least	to some	extent are due to Harm
       Hanemaayer <H.Hanemaayer@inter.nl.net>.

       Occasionally this might be wrong. I hereby asked	to be excused  by  the
       original	author and will	happily	accept any additions or	corrections to
       this first version of the svgalib manual.

Svgalib	(>= 1.2.11)		 27 July 1997			   vga_init(3)

NAME | SYNOPSIS | DESCRIPTION | BUGS | SEE ALSO | AUTHOR

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