cmpconflash

cmpconflash

This tools allows you to identify how many flash pages/blocks match across different versions of a firmware image. This corresponds to the minimum number of flash pages/blocks that would need to be modified during a update between these firmware versions, assuming an ideal updater.

The idea is that this tool helps you model the expected speedup if your firmware updater was optimized to check for changes in each flash page before rewriting it. Often many pages in a firmware image don't change between versions.

The name comes from comparing and contrasting flash pages.

Obligatory Install Line

go install github.com/linux4life798/cmpconflash@latest

Usage

$ cmpconflash --help
Compare multiple files in sequence at different block sizes.

Usage:
  cmpconflash <file1> <file2> [files...] [flags]

Flags:
      --all           When specified, all pairing of files will be compared
      --bsizes ints   List of block sizes to compare against (default [8192,4096,2048,1024,512,256,1])
  -h, --help          help for cmpconflash
      --offset int    Offset to start comparing in byte indices.
      --size int      Size of region to compare in bytes. A size of -1 means unbounded. (default -1)

Examples

1. When provided random input, ony some random byte positions might match.

   dd if=/dev/urandom bs=2M count=1 of=file1
   dd if=/dev/urandom bs=2M count=1 of=file2
   
   cmpconflash file1 file2
   

   Output

   # Compare file1 vs. file2
   Block Size    Blocks-Mismatched    Blocks-Matched    Blocks-Total    Percent Matched
   1             2088965              8187              2097152         0.390387%
   256           8192                 0                 8192            0.000000%
   512           4096                 0                 4096            0.000000%
   1024          2048                 0                 2048            0.000000%
   2048          1024                 0                 1024            0.000000%
   4096          512                  0                 512             0.000000%
   8192          256                  0                 256             0.000000%
   

2. If we look for smaller block sizes, like 2 consecutive bytes, we can find a few more matches.

   cmpconflash --bsizes "1,2,3,4" file1 file2
   

   Output

   # Compare file1 vs. file2
   Block Size    Blocks-Mismatched    Blocks-Matched    Blocks-Total    Percent Matched
   1             2088965              8187              2097152         0.390387%
   2             1048561              15                1048576         0.001431%
   3             699051               0                 699051          0.000000%
   4             524288               0                 524288          0.000000%
   

3. When we deliberately copy the last 1MB of the file1 to file2, we have 1024 1k blocks that match, where we had none before.

   dd if=file1 of=file2 bs=1M skip=1 seek=1
   
   cmpconflash file1 file2
   

   Output

   # Compare file1 vs. file2
   Block Size    Blocks-Mismatched    Blocks-Matched    Blocks-Total    Percent Matched
   1             1044530              1052622           2097152         50.192928%
   256           4096                 4096              8192            50.000000%
   512           2048                 2048              4096            50.000000%
   1024          1024                 1024              2048            50.000000%
   2048          512                  512               1024            50.000000%
   4096          256                  256               512             50.000000%
   8192          128                  128               256             50.000000%