1. 03 2月, 2016 1 次提交
    • H
      perf probe: Search both .eh_frame and .debug_frame sections for probe location · 270bde1e
      Hemant Kumar 提交于
      'perf probe' through debuginfo__find_probes() in util/probe-finder.c
      checks for the functions' frame descriptions in either .eh_frame section
      of an ELF or the .debug_frame.
      
      The check is based on whether either one of these sections is present.
      Depending on distro, toolchain defaults, architetcutre, build flags,
      etc., CFI might be found in either .eh_frame and/or .debug_frame.
      Sometimes, it may happen that, .eh_frame, even if present, may not be
      complete and may miss some descriptions.
      
      Therefore, to be sure, to find the CFI covering an address we will
      always have to investigate both if available.
      
      For e.g., in powerpc, this may happen:
        $ gcc -g bin.c -o bin
      
        $ objdump --dwarf ./bin
        <1><145>: Abbrev Number: 7 (DW_TAG_subprogram)
           <146> DW_AT_external   : 1
           <146> DW_AT_name       : (indirect string, offset: 0x9e): main
           <14a> DW_AT_decl_file  : 1
           <14b> DW_AT_decl_line  : 39
           <14c> DW_AT_prototyped : 1
           <14c> DW_AT_type       : <0x57>
           <150> DW_AT_low_pc     : 0x100007b8
      
      If the .eh_frame and .debug_frame are checked for the same binary, we
      will find that, .eh_frame (although present) doesn't contain a
      description for "main" function.
      
      But, .debug_frame has a description:
      
        000000d8 00000024 00000000 FDE cie=00000000 pc=100007b8..10000838
          DW_CFA_advance_loc: 16 to 100007c8
          DW_CFA_def_cfa_offset: 144
          DW_CFA_offset_extended_sf: r65 at cfa+16
        ...
      
      Due to this (since, perf checks whether .eh_frame is present and goes on
      searching for that address inside that frame), perf is unable to process
      the probes:
      
        # perf probe -x ./bin main
          Failed to get call frame on 0x100007b8
          Error: Failed to add events.
      
      To avoid this issue, we need to check both the sections (.eh_frame and
      .debug_frame), which is done in this patch.
      
      Note that, we can always force everything into both .eh_frame and
      .debug_frame by:
      
        $ gcc bin.c -fasynchronous-unwind-tables  -fno-dwarf2-cfi-asm -g -o bin
      Signed-off-by: NHemant Kumar <hemant@linux.vnet.ibm.com>
      Acked-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
      Cc: linuxppc-dev@lists.ozlabs.org
      Cc: Mark Wielaard <mjw@redhat.com>
      Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
      Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
      Link: http://lkml.kernel.org/r/1454426806-13974-1-git-send-email-hemant@linux.vnet.ibm.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
      270bde1e
  2. 02 2月, 2016 1 次提交
    • A
      perf tools: Fix thread lifetime related segfaut in intel_pt · 3a4acda1
      Adrian Hunter 提交于
      intel_pt_process_auxtrace_info() creates a pt->unknown_thread thread
      that eventually needs to be freed by the last thread__put() on it, when
      its refcount hits zero, which may happen in
      intel_pt_process_auxtrace_info() error handling path and triggers the
      following segfault, which would happen as well at intel_pt_free, when
      tools using this intel_pt codebase frees up resources:
      
        # perf record -I -e intel_pt/tsc=1,noretcomp=1/u /bin/ls
        0  a  anaconda-ks.cfg  bin   perf.data	perf.data.old  perf-f23-bringup.todo
        [ perf record: Woken up 1 times to write data ]
        [ perf record: Captured and wrote 0.217 MB perf.data ]
        #
        # perf script -F event,comm,pid,tid,time,addr,ip,sym,dso,iregs
        Samples for 'instructions:u' event do not have IREGS attribute set. Cannot print 'iregs' field.
        intel_pt_synth_events: failed to synthesize 'instructions' event type
        Segmentation fault (core dumped)
        #
      
      The problem is: there's a union in 'struct thread' combines a list_head
      and a rb_node. The standard life cycle of a thread is: init rb_node in
      the constructor, insert it into machine->threads rbtree using rb_node,
      move it to machine->dead_threads using list_head, clean in the last
      thread__put: list_del_init(&thread->node).
      
      In the above command, it clean a thread before adding it into list,
      causes the above segfault.
      
      Since pt->unknown_thread will never live in an rbtree, initialize its
      list node so that when list_del_init() is done on it we don't segfault.
      
      After this patch:
      
        # perf script -F event,comm,pid,tid,time,addr,ip,sym,dso,iregs
        Samples for 'instructions:u' event do not have IREGS attribute set. Cannot print 'iregs' field.
        intel_pt_synth_events: failed to synthesize 'instructions' event type
        0x248 [0x88]: failed to process type: 70
        #
      Reported-by: NTong Zhang <ztong@vt.edu>
      Reported-by: NWang Nan <wangnan0@huawei.com>
      Signed-off-by: NAdrian Hunter <adrian.hunter@intel.com>
      Tested-by: NArnaldo Carvalho de Melo <acme@redhat.com>
      Cc: Josh Poimboeuf <jpoimboe@redhat.com>
      Link: http://lkml.kernel.org/r/1454296865-19749-1-git-send-email-wangnan0@huawei.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
      3a4acda1
  3. 01 2月, 2016 1 次提交
    • A
      perf tools: tracepoint_error() can receive e=NULL, robustify it · ec183d22
      Adrian Hunter 提交于
      Fixes segmentation fault using, for instance:
      
        (gdb) run record -I -e intel_pt/tsc=1,noretcomp=1/u /bin/ls
        Starting program: /home/acme/bin/perf record -I -e intel_pt/tsc=1,noretcomp=1/u /bin/ls
        Missing separate debuginfos, use: dnf debuginfo-install glibc-2.22-7.fc23.x86_64
        [Thread debugging using libthread_db enabled]
        Using host libthread_db library "/lib64/libthread_db.so.1".
      
       Program received signal SIGSEGV, Segmentation fault.
        0 x00000000004b9ea5 in tracepoint_error (e=0x0, err=13, sys=0x19b1370 "sched", name=0x19a5d00 "sched_switch") at util/parse-events.c:410
        (gdb) bt
        #0  0x00000000004b9ea5 in tracepoint_error (e=0x0, err=13, sys=0x19b1370 "sched", name=0x19a5d00 "sched_switch") at util/parse-events.c:410
        #1  0x00000000004b9fc5 in add_tracepoint (list=0x19a5d20, idx=0x7fffffffb8c0, sys_name=0x19b1370 "sched", evt_name=0x19a5d00 "sched_switch", err=0x0, head_config=0x0)
            at util/parse-events.c:433
        #2  0x00000000004ba334 in add_tracepoint_event (list=0x19a5d20, idx=0x7fffffffb8c0, sys_name=0x19b1370 "sched", evt_name=0x19a5d00 "sched_switch", err=0x0, head_config=0x0)
            at util/parse-events.c:498
        #3  0x00000000004bb699 in parse_events_add_tracepoint (list=0x19a5d20, idx=0x7fffffffb8c0, sys=0x19b1370 "sched", event=0x19a5d00 "sched_switch", err=0x0, head_config=0x0)
            at util/parse-events.c:936
        #4  0x00000000004f6eda in parse_events_parse (_data=0x7fffffffb8b0, scanner=0x19a49d0) at util/parse-events.y:391
        #5  0x00000000004bc8e5 in parse_events__scanner (str=0x663ff2 "sched:sched_switch", data=0x7fffffffb8b0, start_token=258) at util/parse-events.c:1361
        #6  0x00000000004bca57 in parse_events (evlist=0x19a5220, str=0x663ff2 "sched:sched_switch", err=0x0) at util/parse-events.c:1401
        #7  0x0000000000518d5f in perf_evlist__can_select_event (evlist=0x19a3b90, str=0x663ff2 "sched:sched_switch") at util/record.c:253
        #8  0x0000000000553c42 in intel_pt_track_switches (evlist=0x19a3b90) at arch/x86/util/intel-pt.c:364
        #9  0x00000000005549d1 in intel_pt_recording_options (itr=0x19a2c40, evlist=0x19a3b90, opts=0x8edf68 <record+232>) at arch/x86/util/intel-pt.c:664
        #10 0x000000000051e076 in auxtrace_record__options (itr=0x19a2c40, evlist=0x19a3b90, opts=0x8edf68 <record+232>) at util/auxtrace.c:539
        #11 0x0000000000433368 in cmd_record (argc=1, argv=0x7fffffffde60, prefix=0x0) at builtin-record.c:1264
        #12 0x000000000049bec2 in run_builtin (p=0x8fa2a8 <commands+168>, argc=5, argv=0x7fffffffde60) at perf.c:390
        #13 0x000000000049c12a in handle_internal_command (argc=5, argv=0x7fffffffde60) at perf.c:451
        #14 0x000000000049c278 in run_argv (argcp=0x7fffffffdcbc, argv=0x7fffffffdcb0) at perf.c:495
        #15 0x000000000049c60a in main (argc=5, argv=0x7fffffffde60) at perf.c:618
      (gdb)
      
      Intel PT attempts to find the sched:sched_switch tracepoint but that seg
      faults if tracefs is not readable, because the error reporting structure
      is null, as errors are not reported when automatically adding
      tracepoints.  Fix by checking before using.
      
      Committer note:
      
      This doesn't take place in a kernel that supports
      perf_event_attr.context_switch, that is the default way that will be
      used for tracking context switches, only in older kernels, like 4.2, in
      a machine with Intel PT (e.g. Broadwell) for non-priviledged users.
      
      Further info from a similar patch by Wang:
      
      The error is in tracepoint_error: it assumes the 'e' parameter is valid.
      
      However, there are many situation a parse_event() can be called without
      parse_events_error. See result of
      
        $ grep 'parse_events(.*NULL)' ./tools/perf/ -r'
      Signed-off-by: NAdrian Hunter <adrian.hunter@intel.com>
      Tested-by: NArnaldo Carvalho de Melo <acme@redhat.com>
      Cc: Jiri Olsa <jolsa@redhat.com>
      Cc: Josh Poimboeuf <jpoimboe@redhat.com>
      Cc: Tong Zhang <ztong@vt.edu>
      Cc: Wang Nan <wangnan0@huawei.com>
      Cc: stable@vger.kernel.org # v4.4+
      Fixes: 19658171 ("perf tools: Enhance parsing events tracepoint error output")
      Link: http://lkml.kernel.org/r/1453809921-24596-2-git-send-email-adrian.hunter@intel.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
      ec183d22
  4. 30 1月, 2016 1 次提交
  5. 29 1月, 2016 15 次提交
    • P
      perf: Remove/simplify lockdep annotation · 5fa7c8ec
      Peter Zijlstra 提交于
      Now that the perf_event_ctx_lock_nested() call has moved from
      put_event() into perf_event_release_kernel() the first reason is no
      longer valid as that can no longer happen.
      
      The second reason seems to have been invalidated when Al Viro made fput()
      unconditionally async in the following commit:
      
        4a9d4b02 ("switch fput to task_work_add")
      
      such that munmap()->fput()->release()->perf_release() would no longer happen.
      
      Therefore, remove the annotation. This should increase the efficiency
      of lockdep coverage of perf locking.
      Suggested-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com>
      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>
      5fa7c8ec
    • P
      perf: Synchronously clean up child events · c6e5b732
      Peter Zijlstra 提交于
      The orphan cleanup workqueue doesn't always catch orphans, for example,
      if they never schedule after they are orphaned. IOW, the event leak is
      still very real. It also wouldn't work for kernel counters.
      
      Doing it synchonously is a little hairy due to lock inversion issues,
      but is made to work.
      
      Patch based on work by Alexander Shishkin.
      Suggested-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com>
      Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
      Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
      Cc: David Ahern <dsahern@gmail.com>
      Cc: Jiri Olsa <jolsa@kernel.org>
      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>
      Cc: vince@deater.net
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      c6e5b732
    • P
      perf: Untangle 'owner' confusion · 60beda84
      Peter Zijlstra 提交于
      There are two concepts of owner wrt an event and they are conflated:
      
       - event::owner / event::owner_list,
         used by prctl(.option = PR_TASK_PERF_EVENTS_{EN,DIS}ABLE).
      
       - the 'owner' of the event object, typically the file descriptor.
      
      Currently these two concepts are conflated, which gives trouble with
      scm_rights passing of file descriptors. Passing the event and then
      closing the creating task would render the event 'orphan' and would
      have it cleared out. Unlikely what is expectd.
      
      This patch untangles these two concepts by using PERF_EVENT_STATE_EXIT
      to denote the second type.
      Reported-by: NAlexei Starovoitov <alexei.starovoitov@gmail.com>
      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>
      60beda84
    • P
      perf: Add flags argument to perf_remove_from_context() · 45a0e07a
      Peter Zijlstra 提交于
      In preparation to adding more options, convert the boolean argument
      into a flags word.
      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>
      45a0e07a
    • P
      perf: Clean up sync_child_event() · 8ba289b8
      Peter Zijlstra 提交于
      sync_child_event() has outgrown its purpose, it does far too much.
      Bring it back to its named purpose.
      
      Rename __perf_event_exit_task() to perf_event_exit_event() to better
      reflect what it does and move the event->state assignment under the
      ctx->lock, like state changes ought to be.
      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>
      8ba289b8
    • P
      perf: Robustify event->owner usage and SMP ordering · f47c02c0
      Peter Zijlstra 提交于
      Use smp_store_release() to clear event->owner and
      lockless_dereference() to observe it. Further use READ_ONCE() for all
      lockless reads.
      
      This changes perf_remove_from_owner() to leave event->owner cleared.
      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>
      f47c02c0
    • P
      perf: Fix STATE_EXIT usage · 6e801e01
      Peter Zijlstra 提交于
      We should never attempt to enable a STATE_EXIT event.
      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>
      6e801e01
    • P
      perf: Update locking order · 07c4a776
      Peter Zijlstra 提交于
      Update the locking order to note that ctx::lock nests inside of
      child_mutex, as per:
      
        perf_ioctl():                ctx::mutex
        -> perf_event_for_each():    event::child_mutex
          -> _perf_event_enable():   ctx::lock
      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>
      07c4a776
    • P
      perf: Remove __free_event() · a0733e69
      Peter Zijlstra 提交于
      There is but a single caller, remove the function - we already have
      _free_event(), the extra indirection is nonsensical..
      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>
      a0733e69
    • A
      perf/bpf: Convert perf_event_array to use struct file · e03e7ee3
      Alexei Starovoitov 提交于
      Robustify refcounting.
      Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
      Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
      Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
      Cc: Daniel Borkmann <daniel@iogearbox.net>
      Cc: David Ahern <dsahern@gmail.com>
      Cc: Jiri Olsa <jolsa@kernel.org>
      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>
      Cc: Wang Nan <wangnan0@huawei.com>
      Cc: vince@deater.net
      Link: http://lkml.kernel.org/r/20160126045947.GA40151@ast-mbp.thefacebook.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      e03e7ee3
    • P
      perf: Fix NULL deref · 828b6f0e
      Peter Zijlstra 提交于
      Dan reported:
      
        1229                  if (ctx->task == TASK_TOMBSTONE ||
        1230                      !atomic_inc_not_zero(&ctx->refcount)) {
        1231                          raw_spin_unlock(&ctx->lock);
        1232                          ctx = NULL;
                                      ^^^^^^^^^^
      ctx is NULL.
      
        1233                  }
        1234
        1235                  WARN_ON_ONCE(ctx->task != task);
                                           ^^^^^^^^^^^^^^^^^
      The patch adds a NULL dereference.
      Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
      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>
      Fixes: 63b6da39 ("perf: Fix perf_event_exit_task() race")
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      828b6f0e
    • P
      perf/x86: De-obfuscate code · 8f04b853
      Peter Zijlstra 提交于
      Get rid of the 'onln' obfuscation.
      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>
      8f04b853
    • P
      perf/x86: Fix uninitialized value usage · e01d8718
      Peter Zijlstra 提交于
      When calling intel_alt_er() with .idx != EXTRA_REG_RSP_* we will not
      initialize alt_idx and then use this uninitialized value to index an
      array.
      
      When that is not fatal, it can result in an infinite loop in its
      caller __intel_shared_reg_get_constraints(), with IRQs disabled.
      
      Alternative error modes are random memory corruption due to the
      cpuc->shared_regs->regs[] array overrun, which manifest in either
      get_constraints or put_constraints doing weird stuff.
      
      Only took 6 hours of painful debugging to find this. Neither GCC nor
      Smatch warnings flagged this bug.
      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: Kan Liang <kan.liang@intel.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>
      Fixes: ae3f011f ("perf/x86/intel: Fix SLM MSR_OFFCORE_RSP1 valid_mask")
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      e01d8718
    • P
      perf: Fix race in perf_event_exit_task_context() · 6a3351b6
      Peter Zijlstra 提交于
      There is a race between perf_event_exit_task_context() and
      orphans_remove_work() which results in a use-after-free.
      
      We mark ctx->task with TASK_TOMBSTONE to indicate a context is
      'dead', under ctx->lock. After which point event_function_call()
      on any event of that context will NOP
      
      A concurrent orphans_remove_work() will only hold ctx->mutex for
      the list iteration and not serialize against this. Therefore its
      possible that orphans_remove_work()'s perf_remove_from_context()
      call will fail, but we'll continue to free the event, with the
      result of free'd memory still being on lists and everything.
      
      Once perf_event_exit_task_context() gets around to acquiring
      ctx->mutex it too will iterate the event list, encounter the
      already free'd event and proceed to free it _again_. This fails
      with the WARN in free_event().
      
      Plug the race by having perf_event_exit_task_context() hold
      ctx::mutex over the whole tear-down, thereby 'naturally'
      serializing against all other sites, including the orphan work.
      Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
      Cc: Jiri Olsa <jolsa@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.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>
      Cc: alexander.shishkin@linux.intel.com
      Cc: dsahern@gmail.com
      Cc: namhyung@kernel.org
      Link: http://lkml.kernel.org/r/20160125130954.GY6357@twins.programming.kicks-ass.netSigned-off-by: NIngo Molnar <mingo@kernel.org>
      6a3351b6
    • P
      perf: Fix orphan hole · 78cd2c74
      Peter Zijlstra 提交于
      We should set event->owner before we install the event,
      otherwise there is a hole where the target task can fork() and
      we'll not inherit the event because it thinks the event is
      orphaned.
      Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
      Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
      Cc: Jiri Olsa <jolsa@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: linux-kernel@vger.kernel.org
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      78cd2c74
  6. 26 1月, 2016 4 次提交
  7. 22 1月, 2016 16 次提交
    • A
      perf: Synchronously free aux pages in case of allocation failure · 45c815f0
      Alexander Shishkin 提交于
      We are currently using asynchronous deallocation in the error path in
      AUX mmap code, which is unnecessary and also presents a problem for users
      that wish to probe for the biggest possible buffer size they can get:
      they'll get -EINVAL on all subsequent attemts to allocate a smaller
      buffer before the asynchronous deallocation callback frees up the pages
      from the previous unsuccessful attempt.
      
      Currently, gdb does that for allocating AUX buffers for Intel PT traces.
      More specifically, overwrite mode of AUX pmus that don't support hardware
      sg (some implementations of Intel PT, for instance) is limited to only
      one contiguous high order allocation for its buffer and there is no way
      of knowing its size without trying.
      
      This patch changes error path freeing to be synchronous as there won't
      be any contenders for the AUX pages at that point.
      Reported-by: NMarkus Metzger <markus.t.metzger@intel.com>
      Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com>
      Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Arnaldo Carvalho de Melo <acme@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>
      Cc: vince@deater.net
      Link: http://lkml.kernel.org/r/1453216469-9509-1-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      45c815f0
    • S
      perf/x86: add Intel SkyLake uncore IMC PMU support · 0e1eb0a1
      Stephane Eranian 提交于
      This patch enables the uncore_imc PMU for Intel
      SkyLake Desktop processors (Core i7-6700, model 94).
      
      It is possible to compute memory read/write bandwidth
      using:
      
        $ perf stat -a -e uncore_imc/data_reads/,uncore_imc/data_writes/ ....
      Signed-off-by: NStephane Eranian <eranian@google.com>
      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: Thomas Gleixner <tglx@linutronix.de>
      Cc: Vince Weaver <vincent.weaver@maine.edu>
      Cc: kan.liang@intel.com
      Link: http://lkml.kernel.org/r/1452151546-8853-1-git-send-email-eranian@google.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      0e1eb0a1
    • P
      perf: Fix perf_event_exit_task() race · 63b6da39
      Peter Zijlstra 提交于
      There is a race against perf_event_exit_task() vs
      event_function_call(),find_get_context(),perf_install_in_context()
      (iow, everyone).
      
      Since there is no permanent marker on a context that its dead, it is
      quite possible that we access (and even modify) a context after its
      passed through perf_event_exit_task().
      
      For instance, find_get_context() might find the context still
      installed, but by the time we get to perf_install_in_context() it
      might already have passed through perf_event_exit_task() and be
      considered dead, we will however still add the event to it.
      
      Solve this by marking a ctx dead by setting its ctx->task value to -1,
      it must be !0 so we still know its a (former) task context.
      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>
      63b6da39
    • P
      perf: Add more assertions · c97f4736
      Peter Zijlstra 提交于
      Try to trigger warnings before races do damage.
      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>
      c97f4736
    • P
      perf: Collapse and fix event_function_call() users · fae3fde6
      Peter Zijlstra 提交于
      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>
      fae3fde6
    • P
      perf: Specialize perf_event_exit_task() · 32132a3d
      Peter Zijlstra 提交于
      The perf_remove_from_context() usage in __perf_event_exit_task() is
      different from the other usages in that this site has already
      detached and scheduled out the task context.
      
      This will stand in the way of stronger assertions checking the (task)
      context scheduling invariants.
      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>
      32132a3d
    • P
      perf: Fix task context scheduling · 39a43640
      Peter Zijlstra 提交于
      There is a very nasty problem wrt disabling the perf task scheduling
      hooks.
      
      Currently we {set,clear} ctx->is_active on every
      __perf_event_task_sched_{in,out}, _however_ this means that if we
      disable these calls we'll have task contexts with ->is_active set that
      are not active and 'active' task contexts without ->is_active set.
      
      This can result in event_function_call() looping on the ctx->is_active
      condition basically indefinitely.
      
      Resolve this by changing things such that contexts without events do
      not set ->is_active like we used to. From this invariant it trivially
      follows that if there are no (task) events, every task ctx is inactive
      and disabling the context switch hooks is harmless.
      
      This leaves two places that need attention (and already had
      accumulated weird and wonderful hacks to work around, without
      recognising this actual problem).
      
      Namely:
      
       - perf_install_in_context() will need to deal with installing events
         in an inactive context, meaning it cannot rely on ctx-is_active for
         its IPIs.
      
       - perf_remove_from_context() will have to mark a context as inactive
         when it removes the last event.
      
      For specific detail, see the patch/comments.
      Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
      Cc: David Ahern <dsahern@gmail.com>
      Cc: Dmitry Vyukov <dvyukov@google.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>
      39a43640
    • P
      perf: Make ctx->is_active and cpuctx->task_ctx consistent · 63e30d3e
      Peter Zijlstra 提交于
      For no apparent reason and to great confusion the rules for
      ctx->is_active and cpuctx->task_ctx are different. This means that its
      not always possible to find all active (task) contexts.
      
      Fix this such that if ctx->is_active gets set, we also set (or verify)
      cpuctx->task_ctx.
      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>
      63e30d3e
    • P
      perf: Optimize perf_sched_events() usage · 25432ae9
      Peter Zijlstra 提交于
      It doesn't make sense to take up-to _4_ references on
      perf_sched_events() per event, avoid doing this.
      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>
      25432ae9
    • P
      perf: Simplify/fix perf_event_enable() event scheduling · aee7dbc4
      Peter Zijlstra 提交于
      Like perf_enable_on_exec(), perf_event_enable() event scheduling has problems
      respecting the context hierarchy when trying to schedule events (for
      example, it will try and add a pinned event without first removing
      existing flexible events).
      
      So simplify it by using the new ctx_resched() call which will DTRT.
      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>
      aee7dbc4
    • P
      perf: Use task_ctx_sched_out() · 8833d0e2
      Peter Zijlstra 提交于
      We have a function that does exactly what we want here, use it. This
      reduces the amount of cpuctx->task_ctx muckery.
      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>
      8833d0e2
    • P
      perf: Fix perf_enable_on_exec() event scheduling · 3e349507
      Peter Zijlstra 提交于
      There are two problems with the current perf_enable_on_exec() event
      scheduling:
      
        - the newly enabled events will be immediately scheduled
          irrespective of their ctx event list order.
      
        - there's a hole in the ctx->lock between scheduling the events
          out and putting them back on.
      
      Esp. the latter issue is a real problem because a hole in event
      scheduling leaves the thing in an observable inconsistent state,
      confusing things.
      
      Fix both issues by first doing the enable iteration and at the end,
      when there are newly enabled events, reschedule the ctx in one go.
      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>
      3e349507
    • P
      perf: Remove stale comment · 5947f657
      Peter Zijlstra 提交于
      The comment here is horribly out of date, remove it.
      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>
      5947f657
    • P
      perf: Fix cgroup scheduling in perf_enable_on_exec() · 70a01657
      Peter Zijlstra 提交于
      There is a comment that states that perf_event_context_sched_in() will
      also switch in the cgroup events, I cannot find it does so. Therefore
      all the resulting logic goes out the window too.
      
      Clean that up.
      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>
      70a01657
    • P
      perf: Fix cgroup event scheduling · 7e41d177
      Peter Zijlstra 提交于
      There appears to be a problem in __perf_event_task_sched_in() wrt
      cgroup event scheduling.
      
      The normal event scheduling order is:
      
      	CPU pinned
      	Task pinned
      	CPU flexible
      	Task flexible
      
      And since perf_cgroup_sched*() only schedules the cpu context, we must
      call this _before_ adding the task events.
      
      Note: double check what happens on the ctx switch optimization where
      the task ctx isn't scheduled.
      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>
      7e41d177
    • P
      perf: Add lockdep assertions · c994d613
      Peter Zijlstra 提交于
      Make various bugs easier to see.
      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>
      c994d613
  8. 19 1月, 2016 1 次提交
    • I
      Merge tag 'perf-core-for-mingo' of... · f5540ecb
      Ingo Molnar 提交于
      Merge tag 'perf-core-for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/urgent
      
      Pull perf tools improvements and fixes from Arnaldo Carvalho de Melo:
      
      User visible bug fixes:
      
        - Fix reading of build-id from vDSO (Ben Hutchings)
      
        - Fix processing samples for guests, noticed with 'perf kvm',
          but noticeable as well via other tools, such as 'perf top'
          (Ravi Bangoria)
      
      Build infrastructure:
      
        - Add feature-dump target and FEATURES_DUMP make variable, to
          allow reusing the feature detection results among multiple
          tools/ living codebases, such as perf and lib/bpf (Jiri Olsa)
      
        - 'make -C tools/perf build-test' improvements, making it more
          paralelizable and allowing building it outside of the source
          tree, using O= (Wang Nan)
      Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      f5540ecb