1vga_init(3) Svgalib User Manual vga_init(3)
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6 vga_init - initialize svgalib library
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9 #include <vga.h>
10 int vga_init(void);
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15 It detects the chipset and gives up supervisor rights. This is the rec‐
16 ommended first line of any program that uses svgalib.
17 vga_setchipset(3) can be called before it to avoid detection.
18 Svgalib catches a bunch of signals that usually kill your program to
20 restore textmode. If you catch signal's before calling vga_init()
21 svgalib will restore textmode and prepare for shutdown and then call
22 your handler routine. If you don't want this, catch the signal after
23 calling vga_init and do not daisychain to svgalib's original handler.
24 WARNING! svgalib needs two signals for it's own purposes (that is man‐
26 aging console switches). To avoid problems it uses the otherwise unused
27 signals SIGUSR1 and SIGUSR2. However, this means that you cannot use
28 them in your program by any means. They are setup by vga_init() as
29 everything else is.
30 Since version 1.2.11 vga_init() includes code to hunt for a free vir‐
32 tual console on its own in case you are not starting the program from
33 one (but instead over a network or modem login, from within 'screen' or
34 an 'xterm'). Provided there is a free console, this succeeds if you are
35 root or if the svgalib calling user own the current console. This is to
36 avoid people not using the console being able to fiddle with it. On
37 graceful exit the program returns to the console from which it was
38 started. Otherwise it remains in text mode at the VC which svgalib
39 allocated to allow you to see any error messages. In any case, any I/O
40 the svgalib makes in text mode (after calling vga_init) will also take
41 place at this new console.
42 Alas, some games misuse their suid root privilege and run as full root
44 process. svgalib cannot detect this and allows Joe Blow User to open a
45 new VC on the console. If this annoys you ROOT_VC_SHORTCUT in Make‐
46 file.cfg allows you to disable allocating a new VC for root (except
47 when he owns the current console) when compiling svgalib. This is the
48 default (disabling the allocation for root).
49 vga_init() returns a non-zero value in case of errors. As of this writ‐
51 ing it will return -1 if it is unable to allocate a graphical console.
52 Otherwise, 0 is returned.
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56 Svgalib versions prior to 1.2.11 had a security hole where it would be
57 possible to regain root privileges even after a vga_init() call. This
58 is not necessarily a problem, but if your program is vulnerable to buf‐
59 fer overflows and other attacks, an attacker may exploit this.
60 However, prior to your call, your program will need to run setuid root,
62 so you should be very careful. The ioperm library by Olaf Titz will
63 allow svgalib programs to run not setuid root. However, it gives all
64 programs unlimited access to the hardware. Again, a malicious person
65 can exploit this (albeit a bit more difficult) too. Thus, in general,
66 make your svgalib programs as secure as any setuid root program.
67 Some programs may (accidently) rely on the old behaviour (which was
69 probably due to the author not knowing about saved uids (which might
70 actually even not have existed in Linux at that time)). A line:
71 security compat
73 in the configuration file /etc/vga/libvga.conf will reinstate the old
75 behaviour whereas
76 security revoke-all-privs
78 enables the (currently default) action.
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83 svgalib(7), vga_setmode(3), mouse_init(3), vga_claimvideomemory(3),
84 vga_ext_set(3), vga_fillblt(3), vga_getcurrentchipset(3), vga_getde‐
85 faultmode(3), vga_getgraphmem(3), vga_runinbackground(3), vga_runin‐
86 background_version(3), vga_safety_fork(3), vga_setchipset(3),
87 vga_setchipsetandfeatures(3), vgagl(7), libvga.config(5),
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91 This manual page was edited by Michael Weller <eowmob@exp-math.uni-
92 essen.de>. The exact source of the referenced function as well as of
93 the original documentation is unknown.
94 It is very likely that both are at least to some extent are due to Harm
96 Hanemaayer <H.Hanemaayer@inter.nl.net>.
97 Occasionally this might be wrong. I hereby asked to be excused by the
99 original author and will happily accept any additions or corrections to
100 this first version of the svgalib manual.
101Svgalib (>= 1.2.11) 27 July 1997 vga_init(3)