Re: [PATCH 2/2] x86,vdso: Fix vdso_install

Andy Lutomirski
2014-06-11T17:43:14Z

On Wed, Jun 11, 2014 at 10:33 AM, Josh Boyer <jwboyer@fedoraproject.org> wrote:
> On Wed, Jun 11, 2014 at 1:27 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>> On 06/11/2014 10:23 AM, Josh Boyer wrote:
>>>
>>> So this does fix the invocation of 'make vdso_install' and the
>>> resulting files look to be accurate to me, with the glaring exception
>>> that now we get e.g. vdso64.so on x86_64 as the installed file instead
>>> of vdso.so. How much that actually matters, I have no idea.
>>> Plausibly fixed with a symlink if we really need to perhaps.
>>>
>>
>> You have that problem anyway, no? After all, there are three different
>> vdso images for 32 bits, and you can run 32-bit apps on 64-bit systems, too.
>
> Yeah, true.
>
>> Is there realistically any way for the debugger to pick up the correct one?
>
> Probably not.

Sure there is: build ids. See /usr/lib/debug/.build-id.

It would be great if we could teach the various debugging tools
(libdw? gdb? I don't know what's responsible for the search path) to
search both /usr/lib/debug/.build-id and /lib/modules/`uname
-r`/build-id or something like that.

>
> I'm planning on pushing out our first 3.16 build with
> these two patches with no symlink. I very much doubt anyone is going
> to complain. It was just something I noticed.

Does the Fedora RPM magic debuginfo script notice these files and
symlink them into the .build-id directory?

Of course, we don't seem to be generating build ids right now. I
thought we were. I'll see if I can fix it.

--Andy

>
> josh

--
Andy Lutomirski
AMA Capital Management, LLC