Re: [Xen-devel] [PATCH v5 00/17] xenctx: Many changes.

[Don Slutz <dslutz@xxxxxxxxxxx>]

On 03/21/14 11:14, Ian Campbell wrote:
> On Thu, 2014-03-20 at 15:06 -0400, Don Slutz wrote:
> > Add more functionality to xenctx.
> So, I've been through this and it mostly seems independently useful, but
> the overriding thought I've been having is: aren't you piecemeal
> reinventing the debugger (like gdbsx)?
Sort of.  If this were a new command, I would think that "reinventing
the debugger" would be more important.

There are several issues with using gdbsx to get a quick look at a domU:

1) you need to start gdbsx & gdb

2) gdb does not simply take a System.map file, nor is vmlinuz a big help.
    There is most likely a way to get gdb to use a System.map but I do not
    currently remember it.

3) Getting a call trace in gdb is hard without debugging symbols. And 
last I
    knew there was no native command to format it like xenctx:

      Call Trace:
         [<ffffffff8006bdd8>] default_idle+0x29 <--
         [<ffffffff8004958f>] cpu_idle+0x95
         [<ffffffff80471809>] start_kernel+0x220
         [<ffffffff8047122f>] x86_64_start_kernel+0x22f


4) You need to remember if this domU is in 32 or 64 bit mode (looks like
     saying 64, for a 32 may be ok).

5) Older gdb's do not display the registers that xenctx does.


The main new features would be -d and -m.  The rest are enhancements or
fixes.

 Hope this helps.
   -Don Slutz

> Ian.

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