New patch to review for coreboot: ef6dfc1 Fix register corruption during Intel Microcode update

[Stefan Reinauer]

Stefan Reinauer ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/996

-gerrit

commit ef6dfc1d0656f34331519fb97e5ec87784c4686d
Author: Stefan Reinauer 
Date:   Wed May 2 16:41:55 2012 -0700

Fix register corruption during Intel Microcode update

Another bug in the Intel microcode update code that existed since we switched
    to LinuxBIOSv2 in 2004:

The inline assembly code that reads the CPU revision from an MSR after running
    cpuid(1) trashes registers EBX and ECX. Only ECX was mentioned in the clobber
    list. C code running after this function could silently access completely wrong
    data, which resulted in the wrong date being printed on microcode updates (and
    potentially other issues happening until the C code writes to EBX again)

Change-Id: Ida733fa1747565ec9824d3a37d08b1a73cd8355f
    Signed-off-by: Stefan Reinauer 
---
 src/cpu/intel/microcode/microcode.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/cpu/intel/microcode/microcode.c b/src/cpu/intel/microcode/microcode.c
index ae1c26a..ec42fb9 100644
--- a/src/cpu/intel/microcode/microcode.c
+++ b/src/cpu/intel/microcode/microcode.c
@@ -63,7 +63,7 @@ static inline u32 read_microcode_rev(void)
    	"=a" (msr.lo), "=d" (msr.hi)
    	: /* inputs */
    	: /* trashed */
-		 "ecx"
+		 "ebx", "ecx"
    );
    return msr.hi;
 }