nerd/rufus
1
1
Fork 0
mirror of https://github.com/pbatard/rufus.git synced 2024-08-14 23:57:05 +00:00
Code Issues 1 Projects Releases Wiki Activity

[core] fix MBR protective message overwriting the primary GPT

Browse source 
* We distractedly chose to populate the message from our protective MBR
  for GPT/UEFI-only boot media into the 4KB that directly followed the
  MBR, which of course is space that is being used by the primary GPT.
* This resulted on systems having to fall back to using the secondary
  GPT, which not all appear to be designed to do.
* Alter the code to ensure the protective message is written at LBA 34,
  after the primary GPT.
* Closes #1507
This commit is contained in:
Pete Batard 2020-04-13 17:05:33 +01:00
parent 129aa64394
commit 2dd538b7cb
No known key found for this signature in database
GPG key ID: 38E0CF5E69EDD671
9 changed files with 60 additions and 57 deletions
Download patch file Download diff file Expand all files Collapse all files

8
res/mbr/msg.S
View file

@ -31,6 +31,7 @@
/********************************************************************************/
MBR_ADDR = 0x7c00
MBR_RESERVED = 0x1b8 # Start of the reserved section (partition table, etc.)
MSG_SECTOR = 0x22 # First sector of the message (must be after the GPT)
NB_SECTORS = 0x08 # Number of sectors to read
PT_MAX = 0x04 # Number of partition entries in the partition table
PT_ENTRY_SIZE = 0x10 # Size of a partition entry in the partition table
@ -109,10 +110,9 @@ read_sectors: # Copy the next sectors into RAM
ext: # http://en.wikipedia.org/wiki/INT_13H#INT_13h_AH.3D42h:_Extended_Read_Sectors_From_Drive
xor eax, eax
push eax # bits 32-63 of sector address
inc eax
push eax # bits 0-31 of sector address
push MSG_SECTOR # bits 0-31 of sector address
push es # destination segment
push 0x0000 # destination address
push eax # destination address (0)
push NB_SECTORS # number of sectors to be read
push 0x0010 # size of DAP struct
mov si, sp # DAP address (= stack)
@ -125,7 +125,7 @@ ext: # http://en.wikipedia.org/wiki/INT_13H#INT_13h_AH.3D42h:_Extended_Read_Sect
no_ext: # http://en.wikipedia.org/wiki/INT_13H#INT_13h_AH.3D02h:_Read_Sectors_From_Drive
mov ax, 0x0200 + NB_SECTORS
mov cx, 0x0002 # Sector address (starts at 1)
mov cx, (MSG_SECTOR + 1) # Sector address (starts at 1)
mov dx, 0x0080 # Drive ID
xor bx, bx # Destination address in ES
int 0x13