[prev in list] [next in list] [prev in thread] [next in thread] 

List:       gdb
Subject:    Custom core file
From:       Nikolay Martyanov <nmartyanov () ptsecurity ! com>
Date:       2016-09-28 13:31:12
Message-ID: fb396495-657e-1429-d773-f302171ae3b7 () ptsecurity ! com
[Download RAW message or body]

Hello guys!

I have a self-written bare-metal hypervisor for x86 arch and I'd like to 
perform postmortem debugging of it's core (not VM, hypervisor itself!).
So the idea is to save physical memory state and later use GDB to 
interpret it.

As I understand, GDB can interpret only `core files`. But I didn't found 
a lot of info about this file format.
Some sources say it should be a specific ELF file with several mandatory 
".note" sections.
Others say `core file` can be in any format and adaptation should be 
done on BFD-level of GDB.

I looked through the code in corelow.c. Now my undestanding is somthing 
like:

1. Save data section of my hypervisor
2. Save current stack state of my hypervisor
3. Save current registers state (MSR?)
4. Define "sys/user.h"-like header with layout description of above 
mentioned structures
5. Using this header, implement function analog to 
`trad_unix_core_file_p()` in file analog to `trad-core.c` (It translates 
my `struct user` to `struct trad_core_struct`)
6. Implement functions like `supply_*regset()` in file like 
`i386-myhyper-nat.c`
7. ??? (magic I didn't realized yet)
8. Profit!

Note, steps 1-3 say nothing about ELF-format. It embarrasses me...

So my question is: am I looking in a right direction? Can you point me 
in to the issues in the plan (or even my understanding)?
Or may be there are any other ways to feed a raw physical memory to GDB?

Thanks,
Nikolay

[prev in list] [next in list] [prev in thread] [next in thread]