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Commit 4ee5b10a authored by H. Peter Anvin's avatar H. Peter Anvin
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[x86 setup] Correct the SMAP check for INT 0x15, AX=0xe820 



The e820 probe code was checking %edx, not %eax, for the SMAP
signature on return.  This worked on *almost* all systems, since %edx
still contained SMAP from the call on entry, but on a handful of
systems it failed -- plus, we would have missed real mismatches.

The error output is "=d" to make sure gcc knows %edx is clobbered
here.

Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent ff0ce684

arch/i386/boot/memory.c

+6 −3
Original line number Diff line number Diff line
@@ -28,11 +28,14 @@ static int detect_memory_e820(void) 


	do {

		size = sizeof(struct e820entry);

		id = SMAP;



		/* Important: %edx is clobbered by some BIOSes,

		   so it must be either used for the error output

		   or explicitly marked clobbered. */

		asm("int $0x15; setc %0"

		    : "=am" (err), "+b" (next), "+d" (id), "+c" (size),

		    : "=d" (err), "+b" (next), "=a" (id), "+c" (size),

		      "=m" (*desc)

		    : "D" (desc), "a" (0xe820));

		    : "D" (desc), "d" (SMAP), "a" (0xe820));



		/* Some BIOSes stop returning SMAP in the middle of

		   the search loop.  We don't know exactly how the BIOS