Difference between revisions of "LeapFrog Pollux Platform: File Format CBF"

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== Description ==
 
== Description ==
The LeapFrog [[Leapster Explorer]] and [[LeapPad Explorer]] both use the CBF file format for the kernel firmware and Surgeon. This is a rather basic format, that contains some summary information about the kernel, size, load address, etc. This information is all rather easy to obtain out of the file, with a hex editor. You can also extract the zImage or Image of the kernel if desired. You can create your own cbf file a couple of ways.
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The LeapFrog [[Leapster Explorer]] and [[LeapPad Explorer]] both use the CBF file format for the kernel firmware and Surgeon. This is a rather basic format, that contains some summary information about the kernel, size, load address, etc. This information is all rather easy to obtain out of the file, with a hex editor. You can also extract the zImage or Image of the kernel if desired or use the python script in the [[LeapFrog_Pollux_Platform:_Source_Code | LeapFrog Sources]].
  
[[LeapFrog_Pollux_Platform:_OpenLFConnect | OpenLFConnect]] can't create a cbf file, unwrap its contents, or give a summary of the cbf information.
 
  
LeapFrog includes the Python script to turn a kernel image into a cbf file <Sources>/scripts/make_cbf.py.
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== Programs ==
 +
A list of programs/scripts that deal with CBF
 +
 
 +
<Sources>/scripts/make_cbf.py.
 +
 
 +
[[LeapFrog_Pollux_Platform:_OpenLFConnect | OpenLFConnect]]
 +
 
 +
 
 +
== Files ==
 +
''' LeapPad '''
 +
 
 +
Surgeon.cbf
 +
* zImage (Compressed kernel)
 +
* initramfs
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* kernel_load 0x8000
 +
* kernel_jup 0x8000
 +
 
 +
Kernel.cbf
 +
* Image (Uncompressed kernel)
 +
* kernel_load 0x10000
 +
* kernel_jup 0x0000
 +
 
 +
''' Explorer '''
 +
 
 +
Surgeon.cbf
 +
* zImage (Compressed kernel)
 +
* initramfs
 +
* kernel_load 0x8000
 +
* kernel_jup 0x8000
 +
 
 +
Kernel.cbf
 +
* Image (Compressed kernel)
 +
* kernel_load 0x8000
 +
* kernel_jup 0x8000
  
== make_cbf.py ==
 
There are two versions of the make_cbf.py script, starting with source release [[LeapFrog_Pollux_Platform:_Source_Code#LeapPad_Explorer | 20110602]] for the LeapPad, the cbf is built with an uncompressed kernel Image, instead of a gunzip compressed zImage. There is no indicator of this, other than a change to the Python script. There is a reference to a different version in this release's Surgeon script, referring to a make_compressed_cbf.py script. Which would seem to indicate Surgeon is built with the older version. This is also confirmed by the kernel_jump and kernel_load addresses, the lastest make_cbf.py script has the values 0x8000 while the older version has 0x10000, which is the value actually used in Surgeon Lpad and Explorer still.
 
  
 
== File Structure ==
 
== File Structure ==
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|}
 
|}
  
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== make_cbf.py ==
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''' Version 1 '''
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 +
This version uses a compressed kernel (zImage) and it's kernel_boot and kernel_load addresses are 0x8000. This script, referenced in the latest make_surgeon.cbf as make_compressed_cbf.py (assuming, as its not in the sources) is used on the Explorer Surgeon and Kernel as well as the LeapPad Surgeon.
 +
 +
''' Version 2 '''
 +
 +
This version uses an uncompressed kernel (Image) and it's kernel_boot and kernel_load addresses are 0x10000. The only CBF file this seems to be used on is the LeapPad kernel.
 +
 +
''' Usage '''
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The script graps the zImage or Image file, depending on version from <kernel>/arch/arm/boot/[Image|zImage] and wraps in with the CBF information, they use their own CRC routine in calculating the checksum. There is three options, of which only two look valid. -c deletes a previous kernel.cbf file, and -o specifies the output files name (default, kernel.cbf).
  
 
[[Category:LeapFrog Pollux Platform]]
 
[[Category:LeapFrog Pollux Platform]]

Revision as of 22:27, 3 February 2012

Description

The LeapFrog Leapster Explorer and LeapPad Explorer both use the CBF file format for the kernel firmware and Surgeon. This is a rather basic format, that contains some summary information about the kernel, size, load address, etc. This information is all rather easy to obtain out of the file, with a hex editor. You can also extract the zImage or Image of the kernel if desired or use the python script in the LeapFrog Sources.


Programs

A list of programs/scripts that deal with CBF

<Sources>/scripts/make_cbf.py.

OpenLFConnect


Files

LeapPad

Surgeon.cbf

  • zImage (Compressed kernel)
  • initramfs
  • kernel_load 0x8000
  • kernel_jup 0x8000

Kernel.cbf

  • Image (Uncompressed kernel)
  • kernel_load 0x10000
  • kernel_jup 0x0000

Explorer

Surgeon.cbf

  • zImage (Compressed kernel)
  • initramfs
  • kernel_load 0x8000
  • kernel_jup 0x8000

Kernel.cbf

  • Image (Compressed kernel)
  • kernel_load 0x8000
  • kernel_jup 0x8000


File Structure

There are three basic components of the CBF file, the summary, the kernel image, and padding. The Summary occupies the first 20 bytes of the file, which is followed by the summary CRC checksum. Directly after this starts the kernel image, which can vary in size depending on the options compiled in. It is then followed by the kernel image CRC checksum. This concludes the data portion, the file is then filled with 0xFF bytes until it is aligned to 16384 byte blocks of data.

Summary Summary CRC Kernel Kernel CRC Padding
[0:3] [4:7] [8:11] [12:15] [16:19] [20:23] [24:K end] [K end+1:+4] [..EOF]
Magic Number CBF Version Kernel Load Kernel Jump Kernel Size CRC32 Checksum Kernel Image CRC32 Checksum 0xFF


make_cbf.py

Version 1

This version uses a compressed kernel (zImage) and it's kernel_boot and kernel_load addresses are 0x8000. This script, referenced in the latest make_surgeon.cbf as make_compressed_cbf.py (assuming, as its not in the sources) is used on the Explorer Surgeon and Kernel as well as the LeapPad Surgeon.

Version 2

This version uses an uncompressed kernel (Image) and it's kernel_boot and kernel_load addresses are 0x10000. The only CBF file this seems to be used on is the LeapPad kernel.

Usage The script graps the zImage or Image file, depending on version from <kernel>/arch/arm/boot/[Image|zImage] and wraps in with the CBF information, they use their own CRC routine in calculating the checksum. There is three options, of which only two look valid. -c deletes a previous kernel.cbf file, and -o specifies the output files name (default, kernel.cbf).