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Fix pmbr issues > 2TB

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These issues have low impact because they require precise circumstances
to trigger one of them. The disk must be > 2 TiB in size and either:
- The primary GPT header is dammaged.
- The freebsd-boot partiton is located farther than the first 2 TiB of
  the disc and one of its sectors takes place at a lba value that makes
  the higher 32 bits of this very value change.
Errors and corrections folow:
- decl and incl don't affect CF, so replace with subl/addl $1
- repe uses %cx, so move size to it with movw
- moving a 64-bit value with %cx of 2 (should be 4) so addresses
  > 2TB will work.

PR:			233180
Reviewed by:		imp@ (applied patch using description in bug)
Differential Revision:	https://reviews.freebsd.org/D31100
This commit is contained in:
Emrion 2021-07-13 14:37:59 -06:00 committed by Warner Losh
parent a065ccb280
commit 0ca9f1d4a3
1 changed files with 6 additions and 5 deletions
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11
stand/i386/pmbr/pmbr.S
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@ -114,8 +114,9 @@ main.2b: cmpb $1,%dh # Reading primary?
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
main.3a: subl $1, (%si) # 0x0(%si) = last sec (0-31)
sbbl $0, 4(%si)
movw $4,%cx
rep
movsw # $lastsec--, copy it to $lba
jmp main.2a # Read the next sector
@ -128,7 +129,7 @@ load_part: movw $GPT_ADDR+GPT_PART_LBA,%si
call read
scan: movw %bx,%si # Compare partition UUID
movw $boot_uuid,%di # with FreeBSD boot UUID
movb $0x10,%cl
movw $0x10,%cx
repe cmpsb
jnz next_part # Didn't match, next partition
#
@ -150,7 +151,7 @@ load_boot: push %si # Save %si
jnz next_boot
mov %bx,%es # Reset %es to zero
jmp LOAD # Jump to boot code
next_boot: incl (%si) # Next LBA
next_boot: addl $1,(%si) # Next LBA
adcl $0,4(%si)
mov %es,%ax # Adjust segment for next
addw $SECSIZE/16,%ax # sector
@ -171,7 +172,7 @@ next_part: decl GPT_ADDR+GPT_NPART # Was this the last partition?
addw %ax,%bx # Next partition
cmpw $PART_ADDR+0x200,%bx # Still in sector?
jb scan
incl GPT_ADDR+GPT_PART_LBA # Next sector
addl $1, GPT_ADDR+GPT_PART_LBA # Next sector
adcl $0,GPT_ADDR+GPT_PART_LBA+4
jmp load_part
#