Currently we enable the breakpoint back only if the breakpoint
modification was successful. If it fails we can leave the breakpoint in
disabled state with attr->disabled == 0.

We can safely enable the breakpoint back for both the fail and success
paths by checking the bp->attr.disabled, which either holds the new
'requested' disabled state or the original breakpoint state.
Suggested-by: NOleg Nesterov <oleg@redhat.com>
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Acked-by: NFrederic Weisbecker <frederic@kernel.org>
Acked-by: NOleg Nesterov <oleg@redhat.com>
Tested-by: NArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Milind Chabbi <chabbi.milind@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180827091228.2878-5-jolsa@kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Once the breakpoint was succesfully modified, the attr->disabled value
is in bp->attr.disabled. So there's no reason to set it again, removing
that.
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Acked-by: NFrederic Weisbecker <frederic@kernel.org>
Acked-by: NOleg Nesterov <oleg@redhat.com>
Tested-by: NArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Milind Chabbi <chabbi.milind@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180827091228.2878-4-jolsa@kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

We need to change the breakpoint even if the attr with new fields has
disabled set to true.

Current code prevents following user code to change the breakpoint
address:

  ptrace(PTRACE_POKEUSER, child, offsetof(struct user, u_debugreg[0]), addr_1)
  ptrace(PTRACE_POKEUSER, child, offsetof(struct user, u_debugreg[0]), addr_2)
  ptrace(PTRACE_POKEUSER, child, offsetof(struct user, u_debugreg[7]), dr7)

The first PTRACE_POKEUSER creates the breakpoint with attr.disabled set
to true:

  ptrace_set_breakpoint_addr(nr = 0)
    struct perf_event *bp = t->ptrace_bps[nr];

    ptrace_register_breakpoint(..., disabled = true)
      ptrace_fill_bp_fields(..., disabled)
      register_user_hw_breakpoint

So the second PTRACE_POKEUSER will be omitted:

  ptrace_set_breakpoint_addr(nr = 0)
    struct perf_event *bp = t->ptrace_bps[nr];
    struct perf_event_attr attr = bp->attr;

    modify_user_hw_breakpoint(bp, &attr)
      if (!attr->disabled)
        modify_user_hw_breakpoint_check
Reported-by: NMilind Chabbi <chabbi.milind@gmail.com>
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Acked-by: NFrederic Weisbecker <frederic@kernel.org>
Acked-by: NOleg Nesterov <oleg@redhat.com>
Tested-by: NArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180827091228.2878-3-jolsa@kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Remove the dance around old and new attributes. Just don't modify the
previous breakpoint at all until we have verified everything.
Original-patch-by: NAndy Lutomirski <luto@kernel.org>
Reported-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NFrederic Weisbecker <frederic@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joel Fernandes <joel.opensrc@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/1529981939-8231-13-git-send-email-frederic@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

We soon won't be able to rely on bp->attr anymore to get the new
type of the modifying breakpoint because the new attributes are going
to be copied only once we successfully modified the breakpoint slot.

This will fix the current misdesigned layout where the new attr are
copied to the modifying breakpoint before we actually know if the
modification will be validated.

In order to prepare for that, allow modify_breakpoint_slot() to take
the new breakpoint type.
Signed-off-by: NFrederic Weisbecker <frederic@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joel Fernandes <joel.opensrc@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/1529981939-8231-12-git-send-email-frederic@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

All architectures have implemented it, we can now remove the poor weak
version.
Signed-off-by: NFrederic Weisbecker <frederic@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joel Fernandes <joel.opensrc@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/1529981939-8231-11-git-send-email-frederic@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

We can't pass the breakpoint directly on arch_check_bp_in_kernelspace()
anymore because its architecture internal datas (struct arch_hw_breakpoint)
are not yet filled by the time we call the function, and most
implementation need this backend to be up to date. So arrange the
function to take the probing struct instead.
Signed-off-by: NFrederic Weisbecker <frederic@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joel Fernandes <joel.opensrc@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/1529981939-8231-3-git-send-email-frederic@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

arch_validate_hwbkpt_settings() mixes up attribute check and commit into
a single code entity. Therefore the validation may return an error due to
incorrect atributes while still leaving halfway modified architecture
breakpoint data.

This is harmless when we deal with a new breakpoint but it becomes a
problem when we modify an existing breakpoint.

Split attribute parse and commit to fix that. The architecture is
passed a "struct arch_hw_breakpoint" to fill on top of the new attr
and the core takes care about copying the backend data once it's fully
validated. The architectures then need to implement the new API.
Original-patch-by: NAndy Lutomirski <luto@kernel.org>
Reported-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NFrederic Weisbecker <frederic@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joel Fernandes <joel.opensrc@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/1529981939-8231-2-git-send-email-frederic@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Annoyingly, modify_user_hw_breakpoint() unnecessarily complicates the
modification of a breakpoint - simplify it and remove the pointless
local variables.

Also update the stale Docbook while at it.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Problem and motivation: Once a breakpoint perf event (PERF_TYPE_BREAKPOINT)
is created, there is no flexibility to change the breakpoint type
(bp_type), breakpoint address (bp_addr), or breakpoint length (bp_len). The
only option is to close the perf event and configure a new breakpoint
event. This inflexibility has a significant performance overhead. For
example, sampling-based, lightweight performance profilers (and also
concurrency bug detection tools),  monitor different addresses for a short
duration using PERF_TYPE_BREAKPOINT and change the address (bp_addr) to
another address or change the kind of breakpoint (bp_type) from  "write" to
a "read" or vice-versa or change the length (bp_len) of the address being
monitored. The cost of these modifications is prohibitive since it involves
unmapping the circular buffer associated with the perf event, closing the
perf event, opening another perf event and mmaping another circular buffer.

Solution: The new ioctl flag for perf events,
PERF_EVENT_IOC_MODIFY_ATTRIBUTES, introduced in this patch takes a pointer
to a struct perf_event_attr as an argument to update an old breakpoint
event with new address, type, and size. This facility allows retaining a
previous mmaped perf events ring buffer and avoids having to close and
reopen another perf event.

This patch supports only changing PERF_TYPE_BREAKPOINT event type; future
implementations can extend this feature. The patch replicates some of its
functionality of modify_user_hw_breakpoint() in
kernel/events/hw_breakpoint.c. modify_user_hw_breakpoint cannot be called
directly since perf_event_ctx_lock() is already held in _perf_ioctl().

Evidence: Experiments show that the baseline (not able to modify an already
created breakpoint) costs an order of magnitude (~10x) more than the
suggested optimization (having the ability to dynamically modifying a
configured breakpoint via ioctl). When the breakpoints typically do not
trap, the speedup due to the suggested optimization is ~10x; even when the
breakpoints always trap, the speedup is ~4x due to the suggested
optimization.

Testing: tests posted at
https://github.com/linux-contrib/perf_event_modify_bp demonstrate the
performance significance of this patch. Tests also check the functional
correctness of the patch.
Signed-off-by: NMilind Chabbi <chabbi.milind@gmail.com>
[ Using modify_user_hw_breakpoint_check function. ]
[ Reformated PERF_EVENT_IOC_*, so the values are all in one column. ]
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oleg Nesterov <onestero@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20180312134548.31532-8-jolsa@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

And rename it to modify_user_hw_breakpoint_check().

We are about to use modify_user_hw_breakpoint_check() for user space
breakpoints modification, we must be very strict to check only the
fields we can change have changed. As Peter explained:

 "Suppose someone does:

        attr = malloc(sizeof(*attr)); // uninitialized memory
        attr->type = BP;
        attr->bp_addr = new_addr;
        attr->bp_type = bp_type;
        attr->bp_len = bp_len;
        ioctl(fd, PERF_IOC_MOD_ATTR, &attr);

  And feeds absolute shite for the rest of the fields.
  Then we later want to extend IOC_MOD_ATTR to allow changing
  attr::sample_type but we can't, because that would break the
  above application."

I'm making this check optional because we already export
modify_user_hw_breakpoint() and with this check we could
break existing users.
Suggested-by: NPeter Zijlstra <peterz@infradead.org>
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Milind Chabbi <chabbi.milind@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oleg Nesterov <onestero@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20180312134548.31532-6-jolsa@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Moving out all the functionality without the events
disabling/enabling calls, because we want to call another
disabling/enabling functions in following change.
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Milind Chabbi <chabbi.milind@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oleg Nesterov <onestero@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20180312134548.31532-5-jolsa@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Add the modify_bp_slot() function to keep slot numbers
correct when changing the breakpoint type.

Using existing __release_bp_slot()/__reserve_bp_slot()
call sequence to update the slot counts.
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Milind Chabbi <chabbi.milind@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oleg Nesterov <onestero@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20180312134548.31532-4-jolsa@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Passing bp_type argument to __reserve_bp_slot() and __release_bp_slot()
functions, so we can pass another bp_type than the one defined in
bp->attr.bp_type. This will be handy in following change that fixes
breakpoint slot counts during its modification.
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Milind Chabbi <chabbi.milind@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oleg Nesterov <onestero@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20180312134548.31532-3-jolsa@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Pass bp_type directly as a find_slot_idx() argument,
so we don't need to have whole event to get the
breakpoint slot type. It will be used in following
changes.
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Milind Chabbi <chabbi.milind@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oleg Nesterov <onestero@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20180312134548.31532-2-jolsa@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

There is one common bug left in all the event_function_call() users,
between loading ctx->task and getting to the remote_function(),
ctx->task can already have been changed.

Therefore we need to double check and retry if ctx->task != current.

Insert another trampoline specific to event_function_call() that
checks for this and further validates state. This also allows getting
rid of the active/inactive functions.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

The only reason CQM had to use a hard-coded pmu type was so it could use
cqm_target in hw_perf_event.

Do away with the {tp,bp,cqm}_target pointers and provide a non type
specific one.

This allows us to do away with that silly pmu type as well.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Vince Weaver <vince@deater.net>
Cc: acme@kernel.org
Cc: acme@redhat.com
Cc: hpa@zytor.com
Cc: jolsa@redhat.com
Cc: kanaka.d.juvva@intel.com
Cc: matt.fleming@intel.com
Cc: tglx@linutronix.de
Cc: torvalds@linux-foundation.org
Cc: vikas.shivappa@linux.intel.com
Link: http://lkml.kernel.org/r/20150305211019.GU21418@twins.programming.kicks-ass.netSigned-off-by: NIngo Molnar <mingo@kernel.org>

Andy reported that the current state of event_idx is rather confused.
So remove all but the x86_pmu implementation and change the default to
return 0 (the safe option).
Reported-by: NAndy Lutomirski <luto@amacapital.net>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Cody P Schafer <cody@linux.vnet.ibm.com>
Cc: Cody P Schafer <dev@codyps.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Cc: Himangi Saraogi <himangi774@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: sukadev@linux.vnet.ibm.com <sukadev@linux.vnet.ibm.com>
Cc: Thomas Huth <thuth@linux.vnet.ibm.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: linux390@de.ibm.com
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

This patch simply moves all per-cpu variables into the new
single per-cpu "struct bp_cpuinfo".

To me this looks more logical and clean, but this can also
simplify the further potential changes. In particular, I do not
think this memory should be per-cpu, it is never used "locally".
After this change it is trivial to turn it into, say,
bootmem[nr_cpu_ids].
Reported-by: NVince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20130620155020.GA6350@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

1. register_wide_hw_breakpoint() can use unregister_ if failure,
   no need to duplicate the code.

2. "struct perf_event **pevent" adds the unnecesary lever of
   indirection and complication, use per_cpu(*cpu_events, cpu).
Reported-by: NVince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20130620155018.GA6347@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Add the trivial helper which simply returns cpumask_of() or
cpu_possible_mask depending on bp->cpu.

Change fetch_bp_busy_slots() and toggle_bp_slot() to always do
for_each_cpu(cpumask_of_bp) to simplify the code and avoid the
code duplication.
Reported-by: NVince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20130620155015.GA6340@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Change toggle_bp_slot() to make "weight" negative if !enable.
This way we can always use "+ weight" without additional "if
(enable)" check and toggle_bp_task_slot() no longer needs this
arg.
Reported-by: NVince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20130620155013.GA6337@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

The enable/disable logic in toggle_bp_slot() is not symmetrical
and imho very confusing. "old_count" in toggle_bp_task_slot() is
actually new_count because this bp was already removed from the
list.

Change toggle_bp_slot() to always call list_add/list_del after
toggle_bp_task_slot(). This way old_idx is task_bp_pinned() and
this entry should be decremented, new_idx is +/-weight and we
need to increment this element. The code/logic looks obvious.
Reported-by: NVince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20130620155011.GA6330@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

fetch_bp_busy_slots() and toggle_bp_slot() use
for_each_online_cpu(), this is obviously wrong wrt cpu_up() or
cpu_down(), we can over/under account the per-cpu numbers.

For example:

	# echo 0 >> /sys/devices/system/cpu/cpu1/online
	# perf record -e mem:0x10 -p 1 &
	# echo 1 >> /sys/devices/system/cpu/cpu1/online
	# perf record -e mem:0x10,mem:0x10,mem:0x10,mem:0x10 -C1 -a &
	# taskset -p 0x2 1

triggers the same WARN_ONCE("Can't find any breakpoint slot") in
arch_install_hw_breakpoint().
Reported-by: NVince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20130620155009.GA6327@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

trinity fuzzer triggered WARN_ONCE("Can't find any breakpoint
slot") in arch_install_hw_breakpoint() but the problem is not
arch-specific.

The problem is, task_bp_pinned(cpu) checks "cpu == iter->cpu"
but this doesn't account the "all cpus" events with iter->cpu <
0.

This means that, say, register_user_hw_breakpoint(tsk) can
happily create the arbitrary number > HBP_NUM of breakpoints
which can not be activated. toggle_bp_task_slot() is equally
wrong by the same reason and nr_task_bp_pinned[] can have
negative entries.

Simple test:

	# perl -e 'sleep 1 while 1' &
	# perf record -e mem:0x10,mem:0x10,mem:0x10,mem:0x10,mem:0x10 -p `pidof perl`

Before this patch this triggers the same problem/WARN_ON(),
after the patch it correctly fails with -ENOSPC.
Reported-by: NVince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20130620155006.GA6324@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

The hw breakpoint pmu 'add' function is missing the
period_left update needed for SW events.

The perf HW breakpoint events use the SW events framework
to process the overflow, so it needs to be properly initialized
in the PMU 'add' method.
Signed-off-by: NJiri Olsa <jolsa@redhat.com>
Reviewed-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Stephane Eranian <eranian@google.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1367421944-19082-5-git-send-email-jolsa@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Obviously this is a typo and could result in memory leaks if kzalloc
fails on a given cpu.
Signed-off-by: NDaniel Baluta <dbaluta@ixiacom.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1360186160-7566-1-git-send-email-dbaluta@ixiacom.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

I've been trying to get hardware breakpoints with perf to work
on POWER7 but I'm getting the following:

  % perf record -e mem:0x10000000 true

    Error: sys_perf_event_open() syscall returned with 28 (No space left on device).  /bin/dmesg may provide additional information.

    Fatal: No CONFIG_PERF_EVENTS=y kernel support configured?

  true: Terminated

(FWIW adding -a and it works fine)

Debugging it seems that __reserve_bp_slot() is returning ENOSPC
because it thinks there are no free breakpoint slots on this
CPU.

I have a 2 CPUs, so perf userspace is doing two perf_event_open
syscalls to add a counter to each CPU [1].  The first syscall
succeeds but the second is failing.

On this second syscall, fetch_bp_busy_slots() sets slots.pinned
to be 1, despite there being no breakpoint on this CPU.  This is
because the call the task_bp_pinned, checks all CPUs, rather
than just the current CPU. POWER7 only has one hardware
breakpoint per CPU (ie. HBP_NUM=1), so we return ENOSPC.

The following patch fixes this by checking the associated CPU
for each breakpoint in task_bp_pinned.  I'm not familiar with
this code, so it's provided as a reference to the above issue.
Signed-off-by: NMichael Neuling <mikey@neuling.org>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Jovi Zhang <bookjovi@gmail.com>
Cc: K Prasad <prasad@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1351268936-2956-1-git-send-email-fweisbec@gmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

While debugging a warning message on PowerPC while using hardware
breakpoints, it was discovered that when perf_event_disable is invoked
through hw_breakpoint_handler function with interrupts disabled, a
subsequent IPI in the code path would trigger a WARN_ON_ONCE message in
smp_call_function_single function.

This patch calls __perf_event_disable() when interrupts are already
disabled, instead of perf_event_disable().
Reported-by: NEdjunior Barbosa Machado <emachado@linux.vnet.ibm.com>
Signed-off-by: NK.Prasad <Prasad.Krishnan@gmail.com>
[naveen.n.rao@linux.vnet.ibm.com: v3: Check to make sure we target current task]
Signed-off-by: NNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120802081635.5811.17737.stgit@localhost.localdomain
[ Fixed build error on MIPS. ]
Signed-off-by: NIngo Molnar <mingo@kernel.org>

PERF_SAMPLE_BRANCH_* is disabled for:

 - SW events (sw counters, tracepoints)
 - HW breakpoints
 - ALL but Intel x86 architecture
 - AMD64 processors
Signed-off-by: NStephane Eranian <eranian@google.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1328826068-11713-10-git-send-email-eranian@google.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

If kzalloc() for TYPE_DATA failed on a given cpu, previous chunk
of TYPE_INST will be leaked. Fix it.

Thanks to Peter Zijlstra for suggesting this better solution. It
should work as long as the initial value of the region is all
0's and that's the case of static (per-cpu) memory allocation.
Signed-off-by: NNamhyung Kim <namhyung.kim@lge.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Link: http://lkml.kernel.org/r/1330391978-28070-1-git-send-email-namhyung.kim@lge.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

Put the logic to compute the event index into a per pmu method. This
is required because the x86 rules are weird and wonderful and don't
match the capabilities of the current scheme.

AFAIK only powerpc actually has a usable userspace read of the PMCs
but I'm not at all sure anybody actually used that.

ARM is restored to the default since it currently does not support
userspace access at all. And all software events are provided with a
method that reports their index as 0 (disabled).
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Michael Cree <mcree@orcon.net.nz>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Arun Sharma <asharma@fb.com>
Link: http://lkml.kernel.org/n/tip-dfydxodki16lylkt3gl2j7cw@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@elte.hu>

The perf_event overflow handler does not receive any caller-derived
argument, so many callers need to resort to looking up the perf_event
in their local data structure.  This is ugly and doesn't scale if a
single callback services many perf_events.

Fix by adding a context parameter to perf_event_create_kernel_counter()
(and derived hardware breakpoints APIs) and storing it in the perf_event.
The field can be accessed from the callback as event->overflow_handler_context.
All callers are updated.
Signed-off-by: NAvi Kivity <avi@redhat.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1309362157-6596-2-git-send-email-avi@redhat.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

As part of the events sybsystem unification, relocate hw_breakpoint.c
into its new destination.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NBorislav Petkov <borislav.petkov@amd.com>

Extend the perf_pmu_register() interface to allow for named and
dynamic pmu types.

Because we need to support the existing static types we cannot use
dynamic types for everything, hence provide a type argument.

If we want to enumerate the PMUs they need a name, provide one.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101117222056.259707703@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

When using early debugging, the kernel does not initialize the
hw_breakpoint API early enough and causes the late initialization of
the kernel debugger to fail. The boot arguments are:

    earlyprintk=vga ekgdboc=kbd kgdbwait

Then simply type "go" at the kdb prompt and boot. The kernel will
later emit the message:

    kgdb: Could not allocate hwbreakpoints

And at that point the kernel debugger will cease to work correctly.

The solution is to initialize the hw_breakpoint at the same time that
all the other perf call backs are initialized instead of using a
core_initcall() initialization which happens well after the kernel
debugger can make use of hardware breakpoints.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
CC: Frederic Weisbecker <fweisbec@gmail.com>
CC: Ingo Molnar <mingo@elte.hu>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4CD3396D.1090308@windriver.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

hw_breakpoint creation needs to account stuff per-task to ensure there
is always sufficient hardware resources to back these things due to
ptrace.

With the perf per pmu context changes the event initialization no
longer has access to the event context, for the simple reason that we
need to first find the pmu (result of initialization) before we can
find the context.

This makes hw_breakpoints unhappy, because it can no longer do per
task accounting, cure this by frobbing a task pointer in the event::hw
bits for now...
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20101014203625.391543667@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Hardware breakpoints can't be registered within pid namespaces
because tsk->pid is passed rather than the pid in the current
namespace.

(See https://bugzilla.kernel.org/show_bug.cgi?id=17281 )

This is a quick fix demonstrating the problem but is not the
best method of solving the problem since passing pids internally
is not the best way to avoid pid namespace bugs. Subsequent patches
will show a better solution.

Much thanks to Frederic Weisbecker <fweisbec@gmail.com> for doing
the bulk of the work finding this bug.
Reported-by: NRobin Green <greenrd@greenrd.org>
Signed-off-by: NMatt Helsley <matthltc@us.ibm.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Cc: 2.6.33-2.6.35 <stable@kernel.org>
LKML-Reference: <f63454af09fb1915717251570423eb9ddd338340.1284407762.git.matthltc@us.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

The kernel perf event creation path shouldn't use find_task_by_vpid()
because a vpid exists in a specific namespace. find_task_by_vpid() uses
current's pid namespace which isn't always the correct namespace to use
for the vpid in all the places perf_event_create_kernel_counter() (and
thus find_get_context()) is called.

The goal is to clean up pid namespace handling and prevent bugs like:

	https://bugzilla.kernel.org/show_bug.cgi?id=17281

Instead of using pids switch find_get_context() to use task struct
pointers directly. The syscall is responsible for resolving the pid to
a task struct. This moves the pid namespace resolution into the syscall
much like every other syscall that takes pid parameters.
Signed-off-by: NMatt Helsley <matthltc@us.ibm.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Robin Green <greenrd@greenrd.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
LKML-Reference: <a134e5e392ab0204961fd1a62c84a222bf5874a9.1284407763.git.matthltc@us.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Hardware breakpoints can't be registered within pid namespaces
because tsk->pid is passed rather than the pid in the current
namespace.

(See https://bugzilla.kernel.org/show_bug.cgi?id=17281 )

This is a quick fix demonstrating the problem but is not the
best method of solving the problem since passing pids internally
is not the best way to avoid pid namespace bugs. Subsequent patches
will show a better solution.

Much thanks to Frederic Weisbecker <fweisbec@gmail.com> for doing the
bulk of the work finding this bug.
Signed-off-by: NMatt Helsley <matthltc@us.ibm.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Robin Green <greenrd@greenrd.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
LKML-Reference: <f63454af09fb1915717251570423eb9ddd338340.1284407762.git.matthltc@us.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>