Re: [PATCH 4/6] trace: Make UPROBES depend on PERF_EVENTS

[Andi Kleen]

On Fri, Oct 04, 2013 at 08:52:53PM -0400, Steven Rostedt wrote:
> On Fri,  4 Oct 2013 14:39:46 -0700
> Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
> 
> > From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> > 
> > UPROBES need the perf events code, so add a dependency
> > from PERF_EVENTS to UPROBES.
> 
> Can you please be a bit more specific on what uprobes requires of perf?
> That is, what part of the perf events code is needed, and why?

Without this dependency, when UPROBE_EVENT is enabled and PERF_EVENTS disabled 
I first get

warning: (UPROBE_EVENT) selects UPROBES which has unmet direct dependencies (UPROBE_EVENT && PERF_EVENTS)
warning: (UPROBE_EVENT) selects UPROBES which has unmet direct dependencies (UPROBE_EVENT && PERF_EVENTS)

and then later lots of errors like 

arch/x86/built-in.o: In function `do_notify_resume':
/home/ak/lsrc/git/linux-2.6/arch/x86/kernel/signal.c:743: undefined reference to `uprobe_notify_resume'
arch/x86/built-in.o: In function `arch_uprobe_exception_notify':
/home/ak/lsrc/git/linux-2.6/arch/x86/kernel/uprobes.c:637: undefined reference to `uprobe_pre_sstep_notifier'
/home/ak/lsrc/git/linux-2.6/arch/x86/kernel/uprobes.c:643: undefined reference to `uprobe_post_sstep_notifier'
kernel/built-in.o: In function `mmput':
/home/ak/lsrc/git/linux-2.6/kernel/fork.c:608: undefined reference to `uprobe_clear_state'

I'm not fully sure why UPROBES has the && PERF_EVENTS; I didn't add that.

-Andi
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