[Crash-utility] Re: crash enhancements proposal

[David Wilder]

Dave Anderson wrote:

>Maneesh Soni wrote:
>
>  
>
>>Hi Dave,
>>
>>Following is a list of a few proposed improvements to crash utility though
>>for most of the items there are no names associated.
>>
>>Please let us know if these look useful or not. And if found appropriate
>>would it be possible for you to merge these with the crash todo list.
>>
>>Thanks to Badari Pulavarty, Richard Moore and Vara Prasad for the inputs.
>>
>>    
>>
>
>  
>
>>
>>DESCRIPTION:
>>    Code restructuring:
>>    - move as much code for advanced commands to libraries so that
>>      crash is at least able to open the dump image and perform minimal
>>      set of commands like bt, dump dmesg log, disassemble etc. irrespective
>>      of kernel version.
>>    - code is hard to read & understand - need to re-write some of the
>>      basic subsystems like memory mapping, pagetable management etc
>>
>>RESOLUTION STATUS:
>>        Work-in-progress by Dave Wilder <dwilder at us.ibm.com> and
>>        Maneesh Soni <maneesh at in.ibm.com>
>>
>>    
>>
>
>I don't quite understand how moving code to libraries is going to
>achieve the goal here.  Things in some of the various *_init() functions
>could certainly be streamlined (or skipped) in order to make it more
>likely to make it to the first prompt.  For example, the task table initialization
>could be made to simply fill in the context data for just the panic task.
>(But it almost sounds like you just want to use gdb alone for the minimal
>set of commands you've listed?)
>
>As far as "re-writes" are concerned, please keep in mind the
>necessity of backwards-compatibility.  I'd much rather keep the current
>code -- that's known to work -- in place, and if you come up with
>something new, or re-shuffled, make it only callable when the kernel
>is of a known kernel version or later.
>
>The point is, let's not just re-invent the wheel just for purpose of
>re-inventing the wheel.
>
>
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A big advantage to this approach is the ability to have multiple 
libraries, one per per kernel  version, at minimum a crash library for 
each major kernel version 2.4, 2.6, 2.7..    This would preserve 
backward compatibility as we can leave all the 2.4 stuff  alone when 
adding code for the 2.7 kernel for example.   If a distro has special 
needs for crash they can provide a crash library specific to their kernel. 

If crash is designed so that some minimal analysis can be performed with 
out  a dependency on the crash library (look at the running  cpus back 
traces, read the log..)  then a service person can get started on a 
crash dump and determine if a library will be needed or if changes to 
the library are needed for the specific kernel.  Often you just need a 
little information from a dump to identify known problems in the kernel.

-- 
David Wilder
IBM Linux Technology Center
Beaverton, Oregon, USA 
dwilder at us.ibm.com
(503)578-3789