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Commit 32ec7fd0 authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

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: default avatarH. Peter Anvin <hpa@zytor.com>
parent 01522df3

arch/x86/boot/memory.c

+5 −4
Original line number Diff line number Diff line
@@ -20,7 +20,7 @@ static int detect_memory_e820(void) 
{

	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 @@ static int detect_memory_e820(void) 


		/* 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");