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authorAndrey Borzenkov <arvidjaar@newmail.ru>2008-10-03 13:08:49 -0400
committerH. Peter Anvin <hpa@zytor.com>2008-10-03 13:15:29 -0400
commit6cdcdb99cf7c2e1835fc5b471864d21161c3e679 (patch)
treee3dab8fad3748c93fc0870964cbfa8ec8f2e84b6
parent464f04c9e9b3b1c4f5ffb89c51d8ba2a2034c846 (diff)
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>
-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)
43 char *mbrbuf_ptr, *mbrbuf_end; 43 char *mbrbuf_ptr, *mbrbuf_end;
44 u32 buf_base, mbr_base; 44 u32 buf_base, mbr_base;
45 extern char _end[]; 45 extern char _end[];
46 u16 mbr_magic;
46 47
47 sector_size = ei->params.bytes_per_sector; 48 sector_size = ei->params.bytes_per_sector;
48 if (!sector_size) 49 if (!sector_size)
@@ -60,11 +61,15 @@ static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig)
60 if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr) 61 if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr)
61 return -1; 62 return -1;
62 63
64 memset(mbrbuf_ptr, 0, sector_size);
63 if (read_mbr(devno, mbrbuf_ptr)) 65 if (read_mbr(devno, mbrbuf_ptr))
64 return -1; 66 return -1;
65 67
66 *mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET]; 68 *mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];
67 return 0; 69 mbr_magic = *(u16 *)&mbrbuf_ptr[510];
70
71 /* check for valid MBR magic */
72 return mbr_magic == 0xAA55 ? 0 : -1;
68} 73}
69 74
70static int get_edd_info(u8 devno, struct edd_info *ei) 75static int get_edd_info(u8 devno, struct edd_info *ei)