x86 setup: fix ghost entries under /sys/firmware/edd take 3 (6cdcdb99) · Commits · 戴 / test

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>

arch/x86/boot/edd.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -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)

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