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Commit 042cbaf8 authored by Andreas Schwab's avatar Andreas Schwab Committed by H. Peter Anvin
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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: default avatarAndreas Schwab <schwab@suse.de>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 7cb36b6c

arch/x86/boot/video-vesa.c

+5 −6
Original line number Diff line number Diff line
@@ -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 */

}