[Bug 907180] [NEW] od(1) doesn't compensate for Endianness of CPU

[Ron Widell]

Public bug reported:

Try the following experiment: pick a small binary file on your system
where the data and locations are unequivocally known. I recommend
something like /sys/firmware/acpi/tables/BOOT. Since only root can read
these files, you'll need to prefix each od(1) command with sudo or do
"sudo sh" to get a root command prompt.

Execute the following commands:

1)  od -t xz /sys/firmware/acpi/tables/BOOT

2)  od -t x2z /sys/firmware/acpi/tables/BOOT

3)  od -t x1z /sys/firmware/acpi/tables/BOOT

If you're running on a Little Endian (x86) machine you'll note that what
gets output in the left field is actually what gets loaded into the
CPU's registers & not the order of data in the file. In example 1, a
32-bit integer is loaded while a 16-bit integer is loaded in example 2
and a single byte is loaded into the register in example 3.

Note also that the right hand (ASCII strings) field remains constant in
all 3 examples.

I've never seen this issue on a Big Endian machine, but I'm surprised
that it still occurs this late in time on Little Endian machines.


xxx at yyyyyy:~$ lsb_release -rd
Description:	Ubuntu 10.04.3 LTS
Release:	10.04

xxx at yyyyyy:~$ apt-cache policy coreutils
coreutils:
  Installed: 7.4-2ubuntu3
  Candidate: 7.4-2ubuntu3
  Version table:
 *** 7.4-2ubuntu3 0
        500 http://us.archive.ubuntu.com/ubuntu/ lucid-updates/main Packages
        100 /var/lib/dpkg/status
     7.4-2ubuntu2 0
        500 http://us.archive.ubuntu.com/ubuntu/ lucid/main Packages

** Affects: coreutils (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/907180

Title:
  od(1) doesn't compensate for Endianness of CPU

Status in “coreutils” package in Ubuntu:
  New

Bug description:
  Try the following experiment: pick a small binary file on your system
  where the data and locations are unequivocally known. I recommend
  something like /sys/firmware/acpi/tables/BOOT. Since only root can
  read these files, you'll need to prefix each od(1) command with sudo
  or do "sudo sh" to get a root command prompt.

  Execute the following commands:

  1)  od -t xz /sys/firmware/acpi/tables/BOOT

  2)  od -t x2z /sys/firmware/acpi/tables/BOOT

  3)  od -t x1z /sys/firmware/acpi/tables/BOOT

  If you're running on a Little Endian (x86) machine you'll note that
  what gets output in the left field is actually what gets loaded into
  the CPU's registers & not the order of data in the file. In example 1,
  a 32-bit integer is loaded while a 16-bit integer is loaded in example
  2 and a single byte is loaded into the register in example 3.

  Note also that the right hand (ASCII strings) field remains constant
  in all 3 examples.

  I've never seen this issue on a Big Endian machine, but I'm surprised
  that it still occurs this late in time on Little Endian machines.

  
  xxx at yyyyyy:~$ lsb_release -rd
  Description:	Ubuntu 10.04.3 LTS
  Release:	10.04

  xxx at yyyyyy:~$ apt-cache policy coreutils
  coreutils:
    Installed: 7.4-2ubuntu3
    Candidate: 7.4-2ubuntu3
    Version table:
   *** 7.4-2ubuntu3 0
          500 http://us.archive.ubuntu.com/ubuntu/ lucid-updates/main Packages
          100 /var/lib/dpkg/status
       7.4-2ubuntu2 0
          500 http://us.archive.ubuntu.com/ubuntu/ lucid/main Packages

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