[PATCH] mark %esi as clobbered in E820 BIOS call
From: Michael K. Johnson
Date: Fri Mar 27 2009 - 13:42:35 EST
Justin and Peter, please review this for stable .y trees. Peter,
please review this for trunk unless you decide to do a more
extensive workaround for BIOS register clobbering.
Thanks!
$ cat e820-esi-clobber-workaround.patch
Jordan Hargrave diagnosed a BIOS clobbering %esi in the E820 call.
That particular BIOS has been fixed, but there is a possibility that
this is responsible for other occasional reports of early boot
failure, and it does not hurt to add %esi to the clobbers.
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Justin Forbes <jmforbes@xxxxxxxxxxx>
Signed-off-by: Michael K Johnson <johnsonm@xxxxxxxxx>
diff --git a/arch/x86/boot/memory.c b/arch/x86/boot/memory.c
index 8c3c25f..fa85af7 100644
--- a/arch/x86/boot/memory.c
+++ b/arch/x86/boot/memory.c
@@ -27,13 +27,14 @@ static int detect_memory_e820(void)
do {
size = sizeof(struct e820entry);
- /* Important: %edx is clobbered by some BIOSes,
- so it must be either used for the error output
+ /* Important: %edx and %esi are clobbered by some BIOSes,
+ so they must be either used for the error output
or explicitly marked clobbered. */
asm("int $0x15; setc %0"
: "=d" (err), "+b" (next), "=a" (id), "+c" (size),
"=m" (*desc)
- : "D" (desc), "d" (SMAP), "a" (0xe820));
+ : "D" (desc), "d" (SMAP), "a" (0xe820)
+ : "%esi");
/* BIOSes which terminate the chain with CF = 1 as opposed
to %ebx = 0 don't always report the SMAP signature on
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