Re: [Fastboot] [PATCH] Reserving backup region for kexec based crashdumps.

[Itsuro Oda]

Hi,

On 02 Feb 2005 08:24:03 -0700
ebiederm@xxxxxxxxxxxx (Eric W. Biederman) wrote:
> 
> So the kernel+initrd that captures a crash dump will live and execute
> in a reserved area of memory.  It needs to know which memory regions
> are valid, and it needs to know small things like the final register
> state of each cpu. 

Exactly.

Please let me clarify what you are going to.
1) standard kernel: reserve a small contigous area for a dump kernel
   (this is not changed as the current code)
2) standard kernel: export the information of valid physical memory
   regions. (/proc/iomem or /proc/cpumem etc.)
3) kexec (system call?): store the information of valid physical memory
   regions as ELF program header to the reserved area (mentioned 1)).
4) standard kernel: when a panic occur, append (ex.) the register
   information as ELF note after the memory information (if necessary).
   and jump new kernel
5) dump kernel: export all valid physical memory (and saved register
   information) to the user. (as /dev/oldmem /proc/vmcore ?)

Is this correct ?  one question: how the dump kernel know the saved
area of ELF headers ?

one more question: I don't understand what the 640K backup area is. 
Please let me know why it is necessary.

Thanks.
-- 
Itsuro ODA <oda@xxxxxxxxxxxxx>

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