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x86/EDD: check MBR for BIOS magic before considering signature valid
Signed-off-by: Jan Beulich <JBeulich@suse.com> Acked-by: Keir Fraser <keir@xen.org>
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Jan Beulich committed
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commit
9f78a9e4d9
1 file changed
+5
-1
@@ -53,12 +53,16 @@ edd_mbr_sig_read:
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jc edd_mbr_sig_done # on failure, we're done.
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cmpb $0, %ah # some BIOSes do not set CF
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jne edd_mbr_sig_done # on failure, we're done.
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cmpw $0xaa55, bootsym(boot_edd_info)+0x1fe
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jne .Ledd_mbr_sig_next
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movl bootsym(boot_edd_info)+EDD_MBR_SIG_OFFSET,%eax
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movb %dl, (%bx) # store BIOS drive number
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movl %eax, 4(%bx) # store signature from MBR
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incb bootsym(boot_mbr_signature_nr) # note that we stored something
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incb %dl # increment to next device
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addw $8, %bx # increment sig buffer ptr
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.Ledd_mbr_sig_next:
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incb %dl # increment to next device
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jz edd_mbr_sig_done
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cmpb $EDD_MBR_SIG_MAX,bootsym(boot_mbr_signature_nr)
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jb edd_mbr_sig_read
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edd_mbr_sig_done:
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