x86, setup: preemptively save/restore edi and ebp around INT 15 E820
Impact: BIOS bugproofing
Since there are BIOSes known to clobber %ebx and %esi for INT 15 E820,
assume there is something out there clobbering %edi and/or %ebp too,
and don't wait for it to fail.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/x86/boot/memory.c b/arch/x86/boot/memory.c
index a99dbbe..fcdb10ad 100644
--- a/arch/x86/boot/memory.c
+++ b/arch/x86/boot/memory.c
@@ -20,7 +20,7 @@
{
int count = 0;
u32 next = 0;
- u32 size, id;
+ u32 size, id, edi;
u8 err;
struct e820entry *desc = boot_params.e820_map;
@@ -29,10 +29,11 @@
/* 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"
+ or explicitly marked clobbered. Given that, assume there
+ is something out there clobbering %ebp and %edi, too. */
+ asm("pushl %%ebp; int $0x15; popl %%ebp; setc %0"
: "=d" (err), "+b" (next), "=a" (id), "+c" (size),
- "=m" (*desc)
+ "=D" (edi), "=m" (*desc)
: "D" (desc), "d" (SMAP), "a" (0xe820)
: "esi");