From: H. Peter Anvin Date: Fri, 28 Sep 2007 00:17:12 +0000 (-0700) Subject: [x86 setup] Correct the SMAP check for INT 0x15, AX=0xe820 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=4ee5b10abeb2b5581be10d3022694cd19084e9b0;p=linux-beck.git [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 --- diff --git a/arch/i386/boot/memory.c b/arch/i386/boot/memory.c index bccaa1cf6645..378353956b5d 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