linux-toradex.git/include/linux/hw_breakpoint.h, branch v2.6.34

percpu: Add __percpu sparse annotations to hw_breakpoint

2010-02-27T15:23:39+00:00

Add __percpu sparse annotations to hw_breakpoint.

These annotations are to make sparse consider percpu variables to be
in a different address space and warn if accessed without going
through percpu accessors.  This patch doesn't affect normal builds.

In kernel/hw_breakpoint.c, per_cpu(nr_task_bp_pinned, cpu)'s will
trigger spurious noderef related warnings from sparse.  Changing it to
&per_cpu(nr_task_bp_pinned[0], cpu) will work around the problem but
deemed to ugly by the maintainer.  Leave it alone until better
solution can be found.

Signed-off-by: Tejun Heo 
Cc: Stephen Rothwell 
Cc: K.Prasad 
LKML-Reference: <4B7B4B7A.9050902@kernel.org>
Signed-off-by: Frederic Weisbecker

perf: Make bp_len type to u64 generic across the arch

2010-02-04T00:07:12+00:00

Change 'bp_len' type to __u64 to make it work across archs as
the s390 architecture watch point length can be upto 2^64.

reference:
	http://lkml.org/lkml/2010/1/25/212

This is an ABI change that is not backward compatible with
the previous hardware breakpoint info layout integrated in this
development cycle, a rebuilt of perf tools is necessary for
versions based on 2.6.33-rc1 - 2.6.33-rc6 to work with a
kernel based on this patch.

Signed-off-by: Mahesh Salgaonkar 
Acked-by: Peter Zijlstra 
Cc: Ananth N Mavinakayanahalli 
Cc: "K. Prasad" 
Cc: Maneesh Soni 
Cc: Heiko Carstens 
Cc: Martin 
LKML-Reference: <20100130045518.GA20776@in.ibm.com>
Signed-off-by: Frederic Weisbecker

perf, hw_breakpoint, kgdb: Do not take mutex for kernel debugger

2010-01-30T07:42:21+00:00

This patch fixes the regression in functionality where the
kernel debugger and the perf API do not nicely share hw
breakpoint reservations.

The kernel debugger cannot use any mutex_lock() calls because it
can start the kernel running from an invalid context.

A mutex free version of the reservation API needed to get
created for the kernel debugger to safely update hw breakpoint
reservations.

The possibility for a breakpoint reservation to be concurrently
processed at the time that kgdb interrupts the system is
improbable. Should this corner case occur the end user is
warned, and the kernel debugger will prohibit updating the
hardware breakpoint reservations.

Any time the kernel debugger reserves a hardware breakpoint it
will be a system wide reservation.

Signed-off-by: Jason Wessel 
Acked-by: Frederic Weisbecker 
Cc: kgdb-bugreport@lists.sourceforge.net
Cc: K.Prasad 
Cc: Peter Zijlstra 
Cc: Alan Stern 
Cc: torvalds@linux-foundation.org
LKML-Reference: <1264719883-7285-3-git-send-email-jason.wessel@windriver.com>
Signed-off-by: Ingo Molnar

hw-breakpoints: Handle bad modify_user_hw_breakpoint off-case return value

2009-12-11T11:03:53+00:00

While converting modify_user_hw_breakpoint() return value, we
forgot to handle the off-case. It's not returning a pointer
anymore.

This solves the build warning reported by Stephen Rothwell against
linux-next.

Reported-by: Stephen Rothwell 
Signed-off-by: Frederic Weisbecker 
Cc: Prasad 
LKML-Reference: <1260529122-6260-1-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar 
Cc: Prasad

hw-breakpoints: Modify breakpoints without unregistering them

2009-12-09T08:48:20+00:00

Currently, when ptrace needs to modify a breakpoint, like disabling
it, changing its address, type or len, it calls
modify_user_hw_breakpoint(). This latter will perform the heavy and
racy task of unregistering the old breakpoint and registering a new
one.

This is racy as someone else might steal the reserved breakpoint
slot under us, which is undesired as the breakpoint is only
supposed to be modified, sometimes in the middle of a debugging
workflow. We don't want our slot to be stolen in the middle.

So instead of unregistering/registering the breakpoint, just
disable it while we modify its breakpoint fields and re-enable it
after if necessary.

Signed-off-by: Frederic Weisbecker 
Cc: Peter Zijlstra 
Cc: Prasad 
LKML-Reference: <1260347148-5519-1-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar

hw-breakpoints: Zeroe the breakpoint attrs on initialization

2009-12-07T06:04:33+00:00

The perf attrs used to set up breakpoint parameters are often allocated
in the stack and not zeroed out before calling hw_breakpoint_init().
Handle it from this helper to avoid random attributes set by the stack.

Signed-off-by: Frederic Weisbecker 
Cc: Prasad

hw-breakpoints: Use overflow handler instead of the event callback

2009-12-06T07:27:18+00:00

struct perf_event::event callback was called when a breakpoint
triggers. But this is a rather opaque callback, pretty
tied-only to the breakpoint API and not really integrated into perf
as it triggers even when we don't overflow.

We prefer to use overflow_handler() as it fits into the perf events
rules, being called only when we overflow.

Reported-by: Peter Zijlstra 
Signed-off-by: Frederic Weisbecker 
Cc: Paul Mackerras 
Cc: Arnaldo Carvalho de Melo 
Cc: "K. Prasad"

hw-breakpoints: Drop callback and task parameters from modify helper

2009-12-06T07:27:17+00:00

Drop the callback and task parameters from modify_user_hw_breakpoint().
For now we have no user that need to modify a breakpoint to the point
of changing its handler or its task context.

Signed-off-by: Frederic Weisbecker 
Cc: "K. Prasad"

hw-breakpoints: Use struct perf_event_attr to define kernel breakpoints

2009-11-27T05:22:59+00:00

Kernel breakpoints are created using functions in which we pass
breakpoint parameters as individual variables: address, length
and type.

Although it fits well for x86, this just does not scale across
architectures that may support this api later as these may have
more or different needs. Pass in a perf_event_attr structure
instead because it is meant to evolve as much as possible into
a generic hardware breakpoint parameter structure.

Reported-by: K.Prasad 
Signed-off-by: Frederic Weisbecker 
LKML-Reference: <1259294154-5197-2-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar

hw-breakpoints: Use struct perf_event_attr to define user breakpoints

2009-11-27T05:22:58+00:00

In-kernel user breakpoints are created using functions in which
we pass breakpoint parameters as individual variables: address,
length and type.

Although it fits well for x86, this just does not scale across
archictectures that may support this api later as these may have
more or different needs. Pass in a perf_event_attr structure
instead because it is meant to evolve as much as possible into
a generic hardware breakpoint parameter structure.

Reported-by: K.Prasad 
Signed-off-by: Frederic Weisbecker 
LKML-Reference: <1259294154-5197-1-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar