e6e1ace990
We use signed values for limit checking since the values can go negative under certain circumstances. However, sizeof() is unsigned and forces the comparison to be unsigned, so move the comparison into the heap_free() macros so we can ensure it is a signed comparison. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
126 lines
2.8 KiB
C
126 lines
2.8 KiB
C
/* -*- linux-c -*- ------------------------------------------------------- *
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright 2007 rPath, Inc. - All Rights Reserved
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*
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* This file is part of the Linux kernel, and is made available under
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* the terms of the GNU General Public License version 2.
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*
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* ----------------------------------------------------------------------- */
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/*
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* arch/i386/boot/video-bios.c
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*
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* Standard video BIOS modes
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*
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* We have two options for this; silent and scanned.
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*/
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#include "boot.h"
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#include "video.h"
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__videocard video_bios;
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/* Set a conventional BIOS mode */
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static int set_bios_mode(u8 mode);
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static int bios_set_mode(struct mode_info *mi)
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{
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return set_bios_mode(mi->mode - VIDEO_FIRST_BIOS);
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}
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static int set_bios_mode(u8 mode)
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{
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u16 ax;
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u8 new_mode;
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ax = mode; /* AH=0x00 Set Video Mode */
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asm volatile(INT10
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: "+a" (ax)
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: : "ebx", "ecx", "edx", "esi", "edi");
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ax = 0x0f00; /* Get Current Video Mode */
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asm volatile(INT10
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: "+a" (ax)
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: : "ebx", "ecx", "edx", "esi", "edi");
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do_restore = 1; /* Assume video contents were lost */
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new_mode = ax & 0x7f; /* Not all BIOSes are clean with the top bit */
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if (new_mode == mode)
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return 0; /* Mode change OK */
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if (new_mode != boot_params.screen_info.orig_video_mode) {
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/* Mode setting failed, but we didn't end up where we
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started. That's bad. Try to revert to the original
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video mode. */
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ax = boot_params.screen_info.orig_video_mode;
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asm volatile(INT10
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: "+a" (ax)
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: : "ebx", "ecx", "edx", "esi", "edi");
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}
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return -1;
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}
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static int bios_probe(void)
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{
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u8 mode;
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u8 saved_mode = boot_params.screen_info.orig_video_mode;
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u16 crtc;
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struct mode_info *mi;
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int nmodes = 0;
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if (adapter != ADAPTER_EGA && adapter != ADAPTER_VGA)
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return 0;
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set_fs(0);
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crtc = vga_crtc();
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video_bios.modes = GET_HEAP(struct mode_info, 0);
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for (mode = 0x14; mode <= 0x7f; mode++) {
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if (!heap_free(sizeof(struct mode_info)))
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break;
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if (mode_defined(VIDEO_FIRST_BIOS+mode))
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continue;
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if (set_bios_mode(mode))
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continue;
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/* Try to verify that it's a text mode. */
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/* Attribute Controller: make graphics controller disabled */
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if (in_idx(0x3c0, 0x10) & 0x01)
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continue;
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/* Graphics Controller: verify Alpha addressing enabled */
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if (in_idx(0x3ce, 0x06) & 0x01)
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continue;
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/* CRTC cursor location low should be zero(?) */
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if (in_idx(crtc, 0x0f))
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continue;
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mi = GET_HEAP(struct mode_info, 1);
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mi->mode = VIDEO_FIRST_BIOS+mode;
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mi->x = rdfs16(0x44a);
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mi->y = rdfs8(0x484)+1;
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nmodes++;
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}
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set_bios_mode(saved_mode);
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return nmodes;
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}
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__videocard video_bios =
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{
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.card_name = "BIOS (scanned)",
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.probe = bios_probe,
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.set_mode = bios_set_mode,
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.unsafe = 1,
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.xmode_first = VIDEO_FIRST_BIOS,
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.xmode_n = 0x80,
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};
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