From: H. Peter Anvin <hpa@zytor.com>
Date: Thu, 23 Aug 2007 16:28:42 +0000 (-0700)
Subject: [x86 setup] Make sure AH=00h when setting a video mode
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=71351b98b9be6a867aa00276d67716c0728cfff7;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git

[x86 setup] Make sure AH=00h when setting a video mode

Passing a u8 into a register doesn't mean gcc will zero-extend it.
Also, don't depend on thhe register not to change.

Per bug report from Saul Tamari.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---

diff --git a/arch/i386/boot/video-vga.c b/arch/i386/boot/video-vga.c
index d660e608cd58..aef02f9ec0c1 100644
--- a/arch/i386/boot/video-vga.c
+++ b/arch/i386/boot/video-vga.c
@@ -73,9 +73,10 @@ static u8 vga_set_basic_mode(void)
 		mode = 3;
 
 	/* Set the mode */
+	ax = mode;
 	asm volatile(INT10
-		     : : "a" (mode)
-		     : "ebx", "ecx", "edx", "esi", "edi");
+		     : "+a" (ax)
+		     : : "ebx", "ecx", "edx", "esi", "edi");
 	do_restore = 1;
 	return mode;
 }