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authorAndrey Borzenkov <arvidjaar@newmail.ru>2008-10-03 19:08:49 +0200
committerH. Peter Anvin <hpa@zytor.com>2008-10-03 19:15:29 +0200
commit6cdcdb99cf7c2e1835fc5b471864d21161c3e679 (patch)
treee3dab8fad3748c93fc0870964cbfa8ec8f2e84b6 /arch
parentx86: fix ghost EDD devices in /sys again (diff)
downloadlinux-6cdcdb99cf7c2e1835fc5b471864d21161c3e679.tar.xz
linux-6cdcdb99cf7c2e1835fc5b471864d21161c3e679.zip
x86 setup: fix ghost entries under /sys/firmware/edd take 3
Some BIOSes do not indicate error when trying to read from non- existing device. Zero buffer before reading and check that we possibly have valid MBR by looking for MBR magic. This was fixed in different way for edd.S in http://marc.info/?l=linux-kernel&m=114087765422490&w=2, but lost again when edd.S was rewritten in C. Signed-off-by: Andrey Borzenkov < arvidjaar@mail.ru> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/boot/edd.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/x86/boot/edd.c b/arch/x86/boot/edd.c
index bf4ae6ff518e..067e28cd3c5f 100644
--- a/arch/x86/boot/edd.c
+++ b/arch/x86/boot/edd.c
@@ -43,6 +43,7 @@ static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig)
char *mbrbuf_ptr, *mbrbuf_end;
u32 buf_base, mbr_base;
extern char _end[];
+ u16 mbr_magic;
sector_size = ei->params.bytes_per_sector;
if (!sector_size)
@@ -60,11 +61,15 @@ static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig)
if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr)
return -1;
+ memset(mbrbuf_ptr, 0, sector_size);
if (read_mbr(devno, mbrbuf_ptr))
return -1;
*mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];
- return 0;
+ mbr_magic = *(u16 *)&mbrbuf_ptr[510];
+
+ /* check for valid MBR magic */
+ return mbr_magic == 0xAA55 ? 0 : -1;
}
static int get_edd_info(u8 devno, struct edd_info *ei)