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linux-sg2042
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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>
This commit is contained in:
H. Peter Anvin 2009-03-28 13:53:26 -07:00
parent 01522df346
commit 32ec7fd08b
1 changed files with 5 additions and 4 deletions
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9
arch/x86/boot/memory.c
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@ -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");