Boot Engineering Extension Record B.E.E.R.

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Boot Engineering Extension Record(B.E.E.R.)
By Curtis E. Stevens
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Agenda

• Introduction to Booting
• Why BEER?
• BEER and Booting
• BEER and Runtime Services
• BEER and SETUP
• Summary

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Introduction to Booting
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System Initialization

• Enable ISA and PCI devices
• Detect ATAPI/ATAPI devices
• Phoenix proprietary
• Uses Floating Bus Test, Device Diagnostics, and
  sometimes reads/writes cylinder registers when
  device remains busy too long
• Wait up to 31 seconds for BSY
• Save ATAPI signature...
• Wait up to 31 seconds for RDY

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System Initialization

• Issue ID Device or ATAPI ID Device as necessary
  (uses much shorter timeout)
• Continue the boot process
• Configure the devices and interfaces for their
  operational modes
• Includes PIO, DMA, UDMA, etc.
• Continue the boot process
• Execute INT 19 initial boot load

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BIOS Booting

• Real Mode
• INT 13 based
• Load sector at CHS0,0,1 or LBA 0 to system
  memory 7C0h0
• Clear registers to 0
• Set DL boot drive (00h or 80h)
• Jump to 7C0h0

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MBR Booting

• Code in MBR is written by various OS
  manufacturers
• Can be by any OS installed on the system
• Good virus target because there is actually no
  owner
• Scans the partition table looking for an active
  partition
• Loads the first sector of the partition into
  memory and jumps to it
• Generally at 7C0h0 as well.

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Process Drawbacks

• No MBR Owner
• Lots of different programs manipulating the same
  data structure
• Partition types are out of control and
  conflicting
• System information is assumed
• Code is INT 13 based
• If INT 13 changes data structures become invalid
• No good way to detect error conditions

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Enter SETMAX

• Custom uses for this space are already happening
• Now there are multiple applications looking to
  use this area
• New area of expansion has no defined owner
• New area of expansion needs organization!!
• Big Big mess 1-2 years from now...

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Why BEER?
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BEER

• Provides BIOS readable information regarding
  drive formatting
• Resides in protected area
• Some degree of protection from viruses
• Provides centralized organization as systems move
  towards supporting multiple operating
  environments
• Allows for the authentication of data before it
  is placed in protected areas

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BIOS readable information

• INT 13 parameters and ID Device parameters used
  to make calculations
• BIOS useable vs reported sectors/drive
• Last INT 13 device number assigned to drive
• Device name
• Can be manufacturer ID
• Can also be other things

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More BIOS Readable Information

• Self describing service areas
• Eliminates the need for interpretive code
• Allows the user to pick and choose from something
  that makes sense
• Allows several uses for the SETMAX area
  including
• Diagnostics/Recovery
• Suspend to Disk
• Other protected BIOS level data storage

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BEER Formatted Disk
Normal User Space
Managed SETMAX Space
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SETMAX Space
Managed Space
Diagnostics
BIOS Utilities
Suspend Information
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BEER and Booting
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Booting Assumptions

• No effect on non-BEER drives
• Normal booting process continues to function
• BEER booting enabled when a BEER sector is
  present
• BEER capabilities are enabled by user
  intervention
• Keypress during post
• Integration with boot menu feature

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BIOS Booting Changes

• If BEER is available and there are no user boot
  requests
• Load parameters from the Service Area with the
  last boot flag set
• Issue SETMAX to the end of the Service Area
• Load the first sector of the Service Area to
  7C0h0
• Jump to 7C0h0

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More Booting Changes

• If BEER is available and there ARE user boot
  requests
• Load parameters from the Service Area selected by
  the user or BIOS
• Issue SETMAX to the end of the Service Area
• Load the first sector of the Service Area to
  7C0h0
• Jump to 7C0h0

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Boot Selection

• Can be OEM platform specific
• For instance, systems can have a watchdog
  function, if windows fails to boot the system
  automatically boots to diagnostics the next time.
• Can be general at the same time
• POST or SETUP option for selecting the next
  service to boot

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BEER and Runtime Services
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Runtime Services

• Only INT 13 changes
• Fn 8/48
• Parameters are generated from the Directory of
  Services (DOS)
• Only the current service area is reported
• All media access functions
• Add the Service Area Start to the media address
• SETMAX limits the high end of the media access

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Advantages of this method

• No ATA protocol changes required
• Works with drives shipping today
• BIOS changes are minimal
• Supports all DOS based applications as written
• Limits exposure to viruses

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Disadvantages Of This Method

• Applications that provide proprietary disk
  interfaces will fail
• Possible drive corruption
• Code overhead to the BIOS
• New technology
• Need to protect SETMAX Command

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BEER and SETUP
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Whats Necessary

• A method for selecting the alternate boot
  capability. An entry like Boot to Diagnostics
  would probably suffice
• Could easily be made to perform the function for
  one boot only
• If the system is not field updateable, the drive
  can be preconfigured and no other SETUP changes
  are necessary

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Field UpdatesScenario 1

• Need a drive maintenance mode
• Prepares new drives by creating the BEER sector
• Updates existing drives by adding entries to the
  directory of services
• Can transfer data from other devices into the
  directory of services
• May authenticate the data

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Field UpdatesScenario 2

• Need a drive maintenance mode
• Prepares new drives be creating the BEER sector
• Updates existing drives by adding entries to the
  directory of services
• Enables a service area
• Boot from floppy or other device and the BIOS
  presents the service area as an empty device
• Use normal DOS utilities to format the space

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In Summary

• BEER is a management data structure controlled by
  the BIOS for allowing several Operating Systems
  to co-exist on a disk drive, but only 1 OS to
  execute
• There is a lot of room for product
  differentiation
• There is a lot of room to expand this capability

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• If system manufacturers are interested in the
  concept presented here
• Interaction of INT 13 and INT 19 with BEER can be
  added to the specification
• Other capabilities can be added to BEER