x86, setup: mark %esi as clobbered in E820 BIOS call

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.

-stable candidate patch.

Cc: Justin Forbes <jmforbes@linuxtx.org>
Signed-off-by: Michael K Johnson <johnsonm@rpath.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: stable@kernel.org

1 files changed, 4 insertions, 3 deletions

diff --git a/arch/x86/boot/memory.c b/arch/x86/boot/memory.c
index 8c3c25f35578..a99dbbe77a0c 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