Re: [RFC] Unify KVM kernel-space and user-space code into a single project

Avi Kivity
2010-03-24T18:20:40Z

On 03/24/2010 07:47 PM, Arnaldo Carvalho de Melo wrote:
> Em Wed, Mar 24, 2010 at 06:09:30PM +0200, Avi Kivity escreveu:
>
>> Doesn't perf already has a dependency on naming conventions for finding
>> debug information?
>>
> It looks at several places, from most symbol rich (/usr/lib/debug/, aka
> -debuginfo packages, where we have full symtabs) to poorest (the
> packaged binary, where we may just have a .dynsym).
>
> In an ideal world, it would just get the build-id (a SHA1 cookie that is
> in an ELF session inserted in every binary (aka DSOs), kernel module,
> kallsyms or vmlinux file) and use that to look first in a local cache
> (implemented in perf for a long time already) or in some symbol server.
>
> For instance, for a random perf.data file I collected here in my machine
> I have:
>
> [acme@doppio linux-2.6-tip]$ perf buildid-list | grep libpthread
> 5c68f7afeb33309c78037e374b0deee84dd441f6 /lib64/libpthread-2.10.2.so
> [acme@doppio linux-2.6-tip]$
>
> So I don't have to access /lib64/libpthread-2.10.2.so directly, nor some
> convention to get a debuginfo in a local file like:
>
> /usr/lib/debug/lib64/libpthread-2.10.2.so.debug
>
> Instead the tools look at:
>
> [acme@doppio linux-2.6-tip]$ l ~/.debug/.build-id/5c/68f7afeb33309c78037e374b0deee84dd441f6
> lrwxrwxrwx 1 acme acme 73 2010-01-06 18:53 /home/acme/.debug/.build-id/5c/68f7afeb33309c78037e374b0deee84dd441f6 -> ../../lib64/libpthread-2.10.2.so/5c68f7afeb33309c78037e374b0deee84dd441f6*
>
> To find the file for that specific build-id, not the one installed in my
> machine (or on the different machine, of a different architecture) that
> may be completely unrelated, a new one, or one for a different arch.
>

Thanks. I believe qemu could easily act as a symbol server for this use
case.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.