From: Andreas Schwab <schwab@suse.de>
Date: Tue, 27 Jan 2009 20:45:57 +0000 (+0100)
Subject: x86 setup: fix asm constraints in vesa_store_edid
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=042cbaf88ab48e11afb725541e3c2cbf5b483680;p=linux-beck.git

x86 setup: fix asm constraints in vesa_store_edid

Impact: fix potential miscompile (currently believed non-manifest)

As the comment explains, the VBE DDC call can clobber any register.
Tell the compiler about that fact.

Signed-off-by: Andreas Schwab <schwab@suse.de>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---

diff --git a/arch/x86/boot/video-vesa.c b/arch/x86/boot/video-vesa.c
index 75115849af33..4a58c8ce3f69 100644
--- a/arch/x86/boot/video-vesa.c
+++ b/arch/x86/boot/video-vesa.c
@@ -269,9 +269,8 @@ void vesa_store_edid(void)
 	   we genuinely have to assume all registers are destroyed here. */
 
 	asm("pushw %%es; movw %2,%%es; "INT10"; popw %%es"
-	    : "+a" (ax), "+b" (bx)
-	    :  "c" (cx), "D" (di)
-	    : "esi");
+	    : "+a" (ax), "+b" (bx), "+c" (cx), "+D" (di)
+	    : : "esi", "edx");
 
 	if (ax != 0x004f)
 		return;		/* No EDID */
@@ -285,9 +284,9 @@ void vesa_store_edid(void)
 	dx = 0;			/* EDID block number */
 	di =(size_t) &boot_params.edid_info; /* (ES:)Pointer to block */
 	asm(INT10
-	    : "+a" (ax), "+b" (bx), "+d" (dx), "=m" (boot_params.edid_info)
-	    : "c" (cx), "D" (di)
-	    : "esi");
+	    : "+a" (ax), "+b" (bx), "+d" (dx), "=m" (boot_params.edid_info),
+	      "+c" (cx), "+D" (di)
+	    : : "esi");
 #endif /* CONFIG_FIRMWARE_EDID */
 }