From 4ee5b10abeb2b5581be10d3022694cd19084e9b0 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Thu, 27 Sep 2007 17:17:12 -0700 Subject: [PATCH] [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: H. Peter Anvin --- arch/i386/boot/memory.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/i386/boot/memory.c b/arch/i386/boot/memory.c index bccaa1c..3783539 100644 --- a/arch/i386/boot/memory.c +++ b/arch/i386/boot/memory.c @@ -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 -- 2.7.4