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Date:	Tue, 4 Mar 2014 18:31:34 +0100
From:	Oleg Nesterov <>
To:	Russell King - ARM Linux <>
Cc:	David Long <>,, Rabin Vincent <>,
	"Jon Medhurst (Tixy)" <>,
	Srikar Dronamraju <>,
	Ingo Molnar <>,
	Masami Hiramatsu <>,
	Ananth N Mavinakayanahalli <>,
	Anil S Keshavamurthy <>,, Peter Zijlstra <>,
	Paul Mackerras <>,
	Arnaldo Carvalho de Melo <>,
Subject: Re: [PATCH v6 00/14] uprobes: Add uprobes support for ARM

On 03/04, Russell King - ARM Linux wrote:
> On Mon, Mar 03, 2014 at 09:50:39PM +0100, Oleg Nesterov wrote:
> >
> > And why CONFIG_UPROBES should depend on PERF_EVENTS? uprobes can be
> > used by (say) systemtap without UPROBE_EVENT/PERF_EVENTS.
> >
> > But as Russell pointed out the events directory is only built if
> > CONFIG_PERF_EVENTS=y, so it should depend on it or select...
> >
> >
> > I dunno. Personally I vote for the patch from Srikar in
> >
> >
> >
> > This is what we currently have, currently CONFIG_UPROBES is not
> > user-selectable anyway.
> Yes, me too, but with the proviso that UPROBE_EVENT also sorts itself
> out with PERF_EVENTS in some way too (either by selecting it, which
> IMHO isn't nice, or by depending on it, or the build dependency itself
> gets sorted.)

OK... what do you think about the patch below for now?

> Maybe a simpler answer would be to change the build stuff (hand-crafted):
> kernel/Makefile
> -obj-$(CONFIG_PERF_EVENTS) += events/
> +obj-y += events/
> and kernel/events/Makefile:
> -obj-y := core.o ring_buffer.o callchain.o
> +perf-y := core.o ring_buffer.o callchain.o
> -obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
> +perf-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
> +
> +obj-${CONFIG_PERF_EVENTS) += $(perf-y)

I fully agree. Except I can't review this change ;) But hopefully I
can understand what it should do.

But personally I'd prefer to start with the simple/safe change which
allows us to merge this series. If nothing else, even if I think that
kernel/events/uprobes.c doesn't need CONFIG_PERF_EVENTS, this should
be verified and discussed with perf maintainers.

If you agree with the patch below, how should we route it? I won't
argue if you push it along with other patches from David.

BTW... why UPROBE_EVENT depends on MMU? I think that ARCH_SUPPORTS_UPROBES
should not be true if !CONFIG_MMU.


diff --git a/arch/Kconfig b/arch/Kconfig
index 80bbb8c..97ff872 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -86,9 +86,7 @@ config KPROBES_ON_FTRACE
 	 optimize on top of function tracing.
 config UPROBES
-	bool "Transparent user-space probes (EXPERIMENTAL)"
-	default n
+	def_bool n
 	  Uprobes is the user-space counterpart to kprobes: they
@@ -101,8 +99,6 @@ config UPROBES
 	    managed by the kernel and kept transparent to the probed
 	    application. )
-	  If in doubt, say "N".
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 015f85a..8639819 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -424,6 +424,7 @@ config UPROBE_EVENT
 	bool "Enable uprobes-based dynamic events"
 	depends on MMU
+	depends on PERF_EVENTS
 	select UPROBES
 	select TRACING

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