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When GPT signature is invalid in the primary GPT header, then try to

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read backup GPT header.

Submitted by:	hrs (previous version)
This commit is contained in:
Andrey V. Elsukov 2012-08-05 12:57:38 +00:00
parent db58456d4c
commit 95caf34849
1 changed files with 36 additions and 7 deletions
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43
sys/boot/i386/pmbr/pmbr.s
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@ -42,8 +42,8 @@
.set STACK,EXEC+SECSIZE*4 # Stack address
.set GPT_ADDR,STACK # GPT header address
.set GPT_SIG,0
.set GPT_SIG_0,0x20494645
.set GPT_SIG_1,0x54524150
.set GPT_SIG_0,0x20494645 # "EFI "
.set GPT_SIG_1,0x54524150 # "PART"
.set GPT_MYLBA,24
.set GPT_PART_LBA,72
.set GPT_NPART,80
@ -52,6 +52,8 @@
.set PART_TYPE,0
.set PART_START_LBA,32
.set PART_END_LBA,40
.set DPBUF,PART_ADDR+SECSIZE
.set DPBUF_SEC,0x10 # Number of sectors
.set NHRDRV,0x475 # Number of hard drives
@ -91,15 +93,32 @@ main: cmpb $0x80,%dl # Drive valid?
jb main.2 # Yes
main.1: movb $0x80,%dl # Assume drive 0x80
#
# Load the primary GPT header from LBA 1 and verify signature.
# Load the GPT header and verify signature. Try LBA 1 for the primary one and
# the last LBA for the backup if it is broken.
#
main.2: movw $GPT_ADDR,%bx
main.2: call getdrvparams # Read drive parameters
movb $1,%dh # %dh := 1 (reading primary)
main.2a: movw $GPT_ADDR,%bx
movw $lba,%si
call read
call read # Read header and check GPT sig
cmpl $GPT_SIG_0,GPT_ADDR+GPT_SIG
jnz err_pt
jnz main.2b
cmpl $GPT_SIG_1,GPT_ADDR+GPT_SIG+4
jnz err_pt
jnz main.2b
jmp load_part
main.2b: cmpb $1,%dh # Reading primary?
jne err_pt # If no - invalid table found
#
# Try alternative LBAs from the last sector for the GPT header.
#
main.3: movb $0,%dh # %dh := 0 (reading backup)
movw $DPBUF+DPBUF_SEC,%si # %si = last sector + 1
movw $lba,%di # %di = $lba
main.3a: decl (%si) # 0x0(%si) = last sec (0-31)
movw $2,%cx
rep
movsw # $lastsec--, copy it to $lba
jmp main.2a # Read the next sector
#
# Load a partition table sector from disk and look for a FreeBSD boot
# partition.
@ -172,6 +191,16 @@ read: pushl 0x4(%si) # Set the LBA
jc err_rd # If error
ret
#
# Check the number of LBAs on the drive index %dx. Trashes %ax and %si.
#
getdrvparams:
movw $DPBUF,%si # Set the address of result buf
movw $0x001e,(%si) # len
movw $0x4800,%ax # BIOS: Read Drive Parameters
int $0x13 # Call the BIOS
jc err_rd # "I/O error" if error
ret
#
# Various error message entry points.
#
err_big: movw $msg_big,%si # "Boot loader too