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Subject[PATCH] x86, setup (2.6.30-stable) fix 80x34 and 80x60 console modes
As coded, most INT10 calls in video-vga.c allow the compiler to assume EAX 
remains unchanged across them, which is not always the case. This
triggers an optimisation issue that causes vga_set_vertical_end() to be
called with an incorrect number of scanlines. Fix this by beefing up the
asm constraints on these calls.

Reported-by: Marc Aurele La France <tsi@xfree86.org>
Signed-off-by: Marc Aurele La France <tsi@xfree86.org>
Acked-by: H. Peter Anvin <hpa@zytor.com>

diff -adNpru linux-2.6.30/arch/x86/boot/video-vga.c devel-2.6.30/arch/x86/boot/video-vga.c
--- linux-2.6.30/arch/x86/boot/video-vga.c 2009-06-10 12:33:53.000000000 -0600
+++ devel-2.6.30/arch/x86/boot/video-vga.c 2009-06-25 13:35:16.000000000 -0600
@@ -45,8 +45,10 @@ static u8 vga_set_basic_mode(void)

#ifdef CONFIG_VIDEO_400_HACK
if (adapter >= ADAPTER_VGA) {
+ ax = 0x1202;
asm volatile(INT10
- : : "a" (0x1202), "b" (0x0030)
+ : "+a" (ax)
+ : "b" (0x0030)
: "ecx", "edx", "esi", "edi");
}
#endif
@@ -81,44 +83,59 @@ static u8 vga_set_basic_mode(void)

static void vga_set_8font(void)
{
+ u16 ax;
+
/* Set 8x8 font - 80x43 on EGA, 80x50 on VGA */

/* Set 8x8 font */
- asm volatile(INT10 : : "a" (0x1112), "b" (0));
+ ax = 0x1112;
+ asm volatile(INT10 : "+a" (ax) : "b" (0));

/* Use alternate print screen */
- asm volatile(INT10 : : "a" (0x1200), "b" (0x20));
+ ax = 0x1200;
+ asm volatile(INT10 : "+a" (ax) : "b" (0x20));

/* Turn off cursor emulation */
- asm volatile(INT10 : : "a" (0x1201), "b" (0x34));
+ ax = 0x1201;
+ asm volatile(INT10 : "+a" (ax) : "b" (0x34));

/* Cursor is scan lines 6-7 */
- asm volatile(INT10 : : "a" (0x0100), "c" (0x0607));
+ ax = 0x0100;
+ asm volatile(INT10 : "+a" (ax) : "c" (0x0607));
}

static void vga_set_14font(void)
{
+ u16 ax;
+
/* Set 9x14 font - 80x28 on VGA */

/* Set 9x14 font */
- asm volatile(INT10 : : "a" (0x1111), "b" (0));
+ ax = 0x1111;
+ asm volatile(INT10 : "+a" (ax) : "b" (0));

/* Turn off cursor emulation */
- asm volatile(INT10 : : "a" (0x1201), "b" (0x34));
+ ax = 0x1201;
+ asm volatile(INT10 : "+a" (ax) : "b" (0x34));

/* Cursor is scan lines 11-12 */
- asm volatile(INT10 : : "a" (0x0100), "c" (0x0b0c));
+ ax = 0x0100;
+ asm volatile(INT10 : "+a" (ax) : "c" (0x0b0c));
}

static void vga_set_80x43(void)
{
+ u16 ax;
+
/* Set 80x43 mode on VGA (not EGA) */

/* Set 350 scans */
- asm volatile(INT10 : : "a" (0x1201), "b" (0x30));
+ ax = 0x1201;
+ asm volatile(INT10 : "+a" (ax) : "b" (0x30));

/* Reset video mode */
- asm volatile(INT10 : : "a" (0x0003));
+ ax = 0x0003;
+ asm volatile(INT10 : "+a" (ax));

vga_set_8font();
}
@@ -225,7 +242,7 @@ static int vga_set_mode(struct mode_info
*/
static int vga_probe(void)
{
- u16 ega_bx;
+ u16 ax, ega_bx;

static const char *card_name[] = {
"CGA/MDA/HGC", "EGA", "VGA"
@@ -242,9 +259,10 @@ static int vga_probe(void)
};
u8 vga_flag;

+ ax = 0x1200;
asm(INT10
- : "=b" (ega_bx)
- : "a" (0x1200), "b" (0x10) /* Check EGA/VGA */
+ : "+a" (ax), "=b" (ega_bx)
+ : "b" (0x10) /* Check EGA/VGA */
: "ecx", "edx", "esi", "edi");

#ifndef _WAKEUP
Marc.

+----------------------------------+----------------------------------+
| Marc Aurele La France | work: 1-780-492-9310 |
| Academic Information and | fax: 1-780-492-1729 |
| Communications Technologies | email: tsi@ualberta.ca |
| 352 General Services Building +----------------------------------+
| University of Alberta | |
| Edmonton, Alberta | Standard disclaimers apply |
| T6G 2H1 | |
| CANADA | |
+----------------------------------+----------------------------------+
XFree86 developer and VP. ATI driver and X server internals.

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