09 Jan, 2015

1 commit


07 Jan, 2015

2 commits


23 Dec, 2014

1 commit

  • On 32-bit:

    execveat.c: In function 'check_execveat_pathmax':
    execveat.c:183: warning: format '%lu' expects type 'long unsigned int', but argument 3 has type 'size_t'
    execveat.c:187: warning: format '%lu' expects type 'long unsigned int', but argument 2 has type 'size_t'

    Signed-off-by: Geert Uytterhoeven
    Signed-off-by: Shuah Khan

    Geert Uytterhoeven
     

19 Dec, 2014

1 commit


18 Dec, 2014

1 commit

  • Pull user namespace related fixes from Eric Biederman:
    "As these are bug fixes almost all of thes changes are marked for
    backporting to stable.

    The first change (implicitly adding MNT_NODEV on remount) addresses a
    regression that was created when security issues with unprivileged
    remount were closed. I go on to update the remount test to make it
    easy to detect if this issue reoccurs.

    Then there are a handful of mount and umount related fixes.

    Then half of the changes deal with the a recently discovered design
    bug in the permission checks of gid_map. Unix since the beginning has
    allowed setting group permissions on files to less than the user and
    other permissions (aka ---rwx---rwx). As the unix permission checks
    stop as soon as a group matches, and setgroups allows setting groups
    that can not later be dropped, results in a situtation where it is
    possible to legitimately use a group to assign fewer privileges to a
    process. Which means dropping a group can increase a processes
    privileges.

    The fix I have adopted is that gid_map is now no longer writable
    without privilege unless the new file /proc/self/setgroups has been
    set to permanently disable setgroups.

    The bulk of user namespace using applications even the applications
    using applications using user namespaces without privilege remain
    unaffected by this change. Unfortunately this ix breaks a couple user
    space applications, that were relying on the problematic behavior (one
    of which was tools/selftests/mount/unprivileged-remount-test.c).

    To hopefully prevent needing a regression fix on top of my security
    fix I rounded folks who work with the container implementations mostly
    like to be affected and encouraged them to test the changes.

    > So far nothing broke on my libvirt-lxc test bed. :-)
    > Tested with openSUSE 13.2 and libvirt 1.2.9.
    > Tested-by: Richard Weinberger

    > Tested on Fedora20 with libvirt 1.2.11, works fine.
    > Tested-by: Chen Hanxiao

    > Ok, thanks - yes, unprivileged lxc is working fine with your kernels.
    > Just to be sure I was testing the right thing I also tested using
    > my unprivileged nsexec testcases, and they failed on setgroup/setgid
    > as now expected, and succeeded there without your patches.
    > Tested-by: Serge Hallyn

    > I tested this with Sandstorm. It breaks as is and it works if I add
    > the setgroups thing.
    > Tested-by: Andy Lutomirski # breaks things as designed :("

    * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
    userns: Unbreak the unprivileged remount tests
    userns; Correct the comment in map_write
    userns: Allow setting gid_maps without privilege when setgroups is disabled
    userns: Add a knob to disable setgroups on a per user namespace basis
    userns: Rename id_map_mutex to userns_state_mutex
    userns: Only allow the creator of the userns unprivileged mappings
    userns: Check euid no fsuid when establishing an unprivileged uid mapping
    userns: Don't allow unprivileged creation of gid mappings
    userns: Don't allow setgroups until a gid mapping has been setablished
    userns: Document what the invariant required for safe unprivileged mappings.
    groups: Consolidate the setgroups permission checks
    mnt: Clear mnt_expire during pivot_root
    mnt: Carefully set CL_UNPRIVILEGED in clone_mnt
    mnt: Move the clear of MNT_LOCKED from copy_tree to it's callers.
    umount: Do not allow unmounting rootfs.
    umount: Disallow unprivileged mount force
    mnt: Update unprivileged remount test
    mnt: Implicitly add MNT_NODEV on remount when it was implicitly added by mount

    Linus Torvalds
     

17 Dec, 2014

1 commit

  • …l/git/shuah/linux-kselftest

    Pull kselftest update from Shuah Khan:
    "kselftest updates for 3.19-rc1:

    - kcmp test include file cleanup
    - kcmp change to build on all architectures
    - A light weight kselftest framework that provides a set of
    interfaces for tests to use to report results. In addition,
    several tests are updated to use the framework.
    - A new runtime system size test that prints the amount of RAM that
    the currently running system is using"

    * tag 'linux-kselftest-3.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest:
    selftest: size: Add size test for Linux kernel
    selftests/kcmp: Always try to build the test
    selftests/kcmp: Don't include kernel headers
    kcmp: Move kcmp.h into uapi
    selftests/timers: change test to use ksft framework
    selftests/kcmp: change test to use ksft framework
    selftests/ipc: change test to use ksft framework
    selftests/breakpoints: change test to use ksft framework
    selftests: add kselftest framework for uniform test reporting
    selftests/user: move test out of Makefile into a shell script
    selftests/net: move test out of Makefile into a shell script

    Linus Torvalds
     

14 Dec, 2014

2 commits

  • Merge second patchbomb from Andrew Morton:
    - the rest of MM
    - misc fs fixes
    - add execveat() syscall
    - new ratelimit feature for fault-injection
    - decompressor updates
    - ipc/ updates
    - fallocate feature creep
    - fsnotify cleanups
    - a few other misc things

    * emailed patches from Andrew Morton : (99 commits)
    cgroups: Documentation: fix trivial typos and wrong paragraph numberings
    parisc: percpu: update comments referring to __get_cpu_var
    percpu: update local_ops.txt to reflect this_cpu operations
    percpu: remove __get_cpu_var and __raw_get_cpu_var macros
    fsnotify: remove destroy_list from fsnotify_mark
    fsnotify: unify inode and mount marks handling
    fallocate: create FAN_MODIFY and IN_MODIFY events
    mm/cma: make kmemleak ignore CMA regions
    slub: fix cpuset check in get_any_partial
    slab: fix cpuset check in fallback_alloc
    shmdt: use i_size_read() instead of ->i_size
    ipc/shm.c: fix overly aggressive shmdt() when calls span multiple segments
    ipc/msg: increase MSGMNI, remove scaling
    ipc/sem.c: increase SEMMSL, SEMMNI, SEMOPM
    ipc/sem.c: change memory barrier in sem_lock() to smp_rmb()
    lib/decompress.c: consistency of compress formats for kernel image
    decompress_bunzip2: off by one in get_next_block()
    usr/Kconfig: make initrd compression algorithm selection not expert
    fault-inject: add ratelimit option
    ratelimit: add initialization macro
    ...

    Linus Torvalds
     
  • Signed-off-by: David Drysdale
    Cc: Meredydd Luff
    Cc: Shuah Khan
    Cc: "Eric W. Biederman"
    Cc: Andy Lutomirski
    Cc: Alexander Viro
    Cc: Thomas Gleixner
    Cc: Ingo Molnar
    Cc: "H. Peter Anvin"
    Cc: Kees Cook
    Cc: Arnd Bergmann
    Cc: Rich Felker
    Cc: Christoph Hellwig
    Cc: Michael Kerrisk
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Drysdale
     

13 Dec, 2014

1 commit

  • Pull documentation update from Jonathan Corbet:
    "Here's my set of accumulated documentation changes for 3.19.

    It includes a couple of additions to the coding style document, some
    fixes for minor build problems within the documentation tree, the
    relocation of the kselftest docs, and various tweaks and additions.

    A couple of changes reach outside of Documentation/; they only make
    trivial comment changes and I did my best to get the required acks.

    Complete with a shiny signed tag this time around"

    * tag 'docs-for-linus' of git://git.lwn.net/linux-2.6:
    kobject: grammar fix
    Input: xpad - update docs to reflect current state
    Documentation: Build mic/mpssd only for x86_64
    cgroups: Documentation: fix wrong cgroupfs paths
    Documentation/email-clients.txt: add info about Claws Mail
    CodingStyle: add some more error handling guidelines
    kselftest: Move the docs to the Documentation dir
    Documentation: fix formatting to make 's' happy
    Documentation: power: Fix typo in Documentation/power
    Documentation: vm: Add 1GB large page support information
    ipv4: add kernel parameter tcpmhash_entries
    Documentation: Fix a typo in mailbox.txt
    treewide: Fix typo in Documentation/DocBook/device-drivers
    CodingStyle: Add a chapter on conditional compilation

    Linus Torvalds
     

12 Dec, 2014

1 commit


11 Dec, 2014

2 commits

  • Pull ktest changes from Steven Rostedt:
    "The following ktest updates were done:

    - Fix handling the make kernelrelease change
    - Fix make_min_config that was broken by new bisect_config changes
    - Allow tests to undefine default options (not just being able to
    override them)
    - Print name of test (if defined) to start of test output"

    * tag 'ktest-v3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-ktest:
    ktest: Add back "tail -1" to kernelrelease make
    ktest: Add name to running title
    ktest: Allow tests to undefine default options
    ktest: Fix make_min_config to handle new assign_configs call
    ktest: Use make -s kernelrelease

    Linus Torvalds
     
  • Pull ftrace self-test updates from Steven Rostedt:
    "Updates for the ftrace self tests:

    - Added kprobes on ftrace testcase
    - Sort test cases
    - Add file to hold helper functions
    - Use logfile name supported by busybox's mktemp
    - Clear trace buffer after running kprobe test
    - Fix show descriptions when run on dash shell
    - Add --verbose option for showing echo output"

    * tag 'ftracetest-3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
    ftracetest: Add --verbose option for showing echo output
    ftracetest: Fix to show descriptions on dash
    ftracetest: Add basic event tracing test cases
    ftracetest: Clear trace buffer after running kprobe testcases
    ftracetest: Use logfile name supported by busybox's mktemp
    ftracetest: Add a couple of ftrace test cases
    ftracetest: Add functions file that holds helper functions
    ftracetest: Sort testcases
    ftracetest: Add kprobes on ftrace testcase

    Linus Torvalds
     

04 Dec, 2014

3 commits

  • Add --verbose/-v option for showing echo output in testcases.
    This is good for checking the progress of testcases which
    take a longer time to run.

    To implement this feature, all the testcase failures are
    captured in ftracetest and send signal to set SIG_RESULT=FAIL.

    Link: http://lkml.kernel.org/r/20141204194123.7376.22964.stgit@localhost.localdomain

    Suggested-by: Steven Rostedt
    Signed-off-by: Masami Hiramatsu
    Signed-off-by: Steven Rostedt

    Masami Hiramatsu
     
  • The ftracetest doesn't show testcase's descriptions when
    it is executed on dash. This fixes that to show the
    descriptions on dash correctly by passing it via a variable
    instead of directly passing the grep command output.

    Link: http://lkml.kernel.org/r/20141204194116.7376.78940.stgit@localhost.localdomain

    Signed-off-by: Masami Hiramatsu
    Signed-off-by: Steven Rostedt

    Masami Hiramatsu
     
  • This test shows the amount of memory used by the system.
    Note that this is dependent on the user-space that is loaded
    when this program runs. Optimally, this program would be
    run as the init program itself.

    The program is optimized for size itself, to avoid conflating
    its own execution with that of the system software.
    The code is compiled statically, with no stdlibs. On my x86_64 system,
    this results in a statically linked binary of less than 5K.

    Signed-off-by: Tim Bird
    Reviewed-by: Josh Triplett
    Signed-off-by: Shuah Khan

    Tim Bird
     

03 Dec, 2014

3 commits

  • Don't prevent the test building on non-x86. Just try and build it and
    let the chips fall where they may.

    Add support for CROSS_COMPILE while we're at it. Also we don't need a
    custom rule for building kcmp_test.

    Signed-off-by: Michael Ellerman
    Reviewed-by: Christopher Covington
    Signed-off-by: Shuah Khan

    Michael Ellerman
     
  • The kcmp test mucks with the include path to bring in the kernel
    headers, and x86 headers too for reasons that are not clear.

    Now that kcmp.h is exported none of that should be necessary.

    Signed-off-by: Michael Ellerman
    Acked-by: Cyrill Gorcunov
    Signed-off-by: Shuah Khan

    Michael Ellerman
     
  • - MNT_NODEV should be irrelevant except when reading back mount flags,
    no longer specify MNT_NODEV on remount.

    - Test MNT_NODEV on devpts where it is meaningful even for unprivileged mounts.

    - Add a test to verify that remount of a prexisting mount with the same flags
    is allowed and does not change those flags.

    - Cleanup up the definitions of MS_REC, MS_RELATIME, MS_STRICTATIME that are used
    when the code is built in an environment without them.

    - Correct the test error messages when tests fail. There were not 5 tests
    that tested MS_RELATIME.

    Cc: stable@vger.kernel.org
    Signed-off-by: Eric W. Biederman

    Eric W. Biederman
     

25 Nov, 2014

1 commit


24 Nov, 2014

1 commit

  • Commit 52d21580b362 "ktest: Use make -s kernelrelease" fixed commit
    7ff525712acf "kbuild: fake the "Entering directory ..." message more simply"
    as that commit added output after the make kernelrelease. But there's still
    some build scripts that are used by ktest that has output before the make
    is executed, and requires that only the last line is printed.

    Cc: Michal Marek
    Signed-off-by: Steven Rostedt

    Steven Rostedt (Red Hat)
     

22 Nov, 2014

4 commits

  • Instead of just showing the test type of test in the start of the
    test, like this:

    RUNNING TEST 1 of 26 with option build defconfig

    Add the name (if it is defined) as well, like this:

    RUNNING TEST 1 of 26 (arm64 aarch64-linux) with option build defconfig

    Signed-off-by: Steven Rostedt

    Steven Rostedt (Red Hat)
     
  • Tests can set options that override the default ones. But if a test
    tries to undefine a default option, it is simply ignored and the
    default option stays as is.

    For example, if you want to have a test that defines no MIN_CONFIG
    then the test should be able to do that with:

    TEST_START
    MIN_CONFIG =

    Which should make MIN_CONFIG not defined for that test. But the way
    the code currently works, undefined options in tests are dropped.
    This is because the NULL options are evaluated during the reading of
    the config file and since one can disable default options in the default
    section with this method, it is evaluated there (the option turns to a
    undef). But undef options in the test section mean to use the default
    option.

    To fix this, keep the empty string in the option during the reading
    of the config file, and then evaluate it when running the test. This
    will allow tests to null out default options.

    Signed-off-by: Steven Rostedt

    Steven Rostedt (Red Hat)
     
  • Commit 6071c22e1755 "ktest: Rewrite the config-bisect to actually work"
    fixed the config-bisect to work nicely but in doing so it broke
    make_min_config by changing the way assign_configs works.

    The assign_configs function now adds the config to the hash even if
    it is disabled, but changes the hash value to be that of the
    line "# CONFIG_FOO is not set". Unfortunately, the make_min_config
    test only checks to see if the config is removed. It now needs to
    check if the config is in the hash and not set to be disabled.

    Cc: stable@vger.kernel.org # 3.17+
    Signed-off-by: Steven Rostedt

    Steven Rostedt (Red Hat)
     
  • The previous tail -1 broke with commit 7ff525712acf ("kbuild: fake the
    "Entering directory ..." message more simply")

    Link: http://lkml.kernel.org/r/20141022194408.GA20989@pobox.suse.cz

    Reported-by: Steven Rostedt
    Signed-off-by: Michal Marek
    Signed-off-by: Steven Rostedt

    Michal Marek
     

20 Nov, 2014

1 commit


18 Nov, 2014

6 commits


14 Nov, 2014

2 commits

  • Pull networking fixes from David Miller:

    1) sunhme driver lacks DMA mapping error checks, based upon a report by
    Meelis Roos.

    2) Fix memory leak in mvpp2 driver, from Sudip Mukherjee.

    3) DMA memory allocation sizes are wrong in systemport ethernet driver,
    fix from Florian Fainelli.

    4) Fix use after free in mac80211 defragmentation code, from Johannes
    Berg.

    5) Some networking uapi headers missing from Kbuild file, from Stephen
    Hemminger.

    6) TUN driver gets csum_start offset wrong when VLAN accel is enabled,
    and macvtap has a similar bug, from Herbert Xu.

    7) Adjust several tunneling drivers to set dev->iflink after registry,
    because registry sets that to -1 overwriting whatever we did. From
    Steffen Klassert.

    8) Geneve forgets to set inner tunneling type, causing GSO segmentation
    to fail on some NICs. From Jesse Gross.

    9) Fix several locking bugs in stmmac driver, from Fabrice Gasnier and
    Giuseppe CAVALLARO.

    10) Fix spurious timeouts with NewReno on low traffic connections, from
    Marcelo Leitner.

    11) Fix descriptor updates in enic driver, from Govindarajulu
    Varadarajan.

    12) PPP calls bpf_prog_create() with locks held, which isn't kosher.
    Fix from Takashi Iwai.

    13) Fix NULL deref in SCTP with malformed INIT packets, from Daniel
    Borkmann.

    14) psock_fanout selftest accesses past the end of the mmap ring, fix
    from Shuah Khan.

    15) Fix PTP timestamping for VLAN packets, from Richard Cochran.

    16) netlink_unbind() calls in netlink pass wrong initial argument, from
    Hiroaki SHIMODA.

    17) vxlan socket reuse accidently reuses a socket when the address
    family is different, so we have to explicitly check this, from
    Marcelo Lietner.

    18) Fix missing include in nft_reject_bridge.c breaking the build on ppc
    and other architectures, from Guenter Roeck.

    * git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (75 commits)
    vxlan: Do not reuse sockets for a different address family
    smsc911x: power-up phydev before doing a software reset.
    lib: rhashtable - Remove weird non-ASCII characters from comments
    net/smsc911x: Fix delays in the PHY enable/disable routines
    net/smsc911x: Fix rare soft reset timeout issue due to PHY power-down mode
    netlink: Properly unbind in error conditions.
    net: ptp: fix time stamp matching logic for VLAN packets.
    cxgb4 : dcb open-lldp interop fixes
    selftests/net: psock_fanout seg faults in sock_fanout_read_ring()
    net: bcmgenet: apply MII configuration in bcmgenet_open()
    net: bcmgenet: connect and disconnect from the PHY state machine
    net: qualcomm: Fix dependency
    ixgbe: phy: fix uninitialized status in ixgbe_setup_phy_link_tnx
    net: phy: Correctly handle MII ioctl which changes autonegotiation.
    ipv6: fix IPV6_PKTINFO with v4 mapped
    net: sctp: fix memory leak in auth key management
    net: sctp: fix NULL pointer dereference in af->from_addr_param on malformed packet
    net: ppp: Don't call bpf_prog_create() in ppp_lock
    net/mlx4_en: Advertize encapsulation offloads features only when VXLAN tunnel is set
    cxgb4 : Fix bug in DCB app deletion
    ...

    Linus Torvalds
     
  • …es.2014.11.13a', 'signal.2014.10.29a' and 'rt.2014.10.29a' into HEAD

    cpu.2014.11.03a: Changes for per-CPU variables.
    doc.2014.11.13a: Documentation updates.
    fixes.2014.11.13a: Miscellaneous fixes.
    signal.2014.10.29a: Signal changes.
    rt.2014.10.29a: Real-time changes.
    torture.2014.11.03a: torture-test changes.

    Paul E. McKenney
     

12 Nov, 2014

1 commit

  • The while loop in sock_fanout_read_ring() checks mmap region
    bounds after access, causing it to segfault. Fix it to check
    count before accessing header->tp_status. This problem can be
    reproduced consistently when the test in run as follows:

    make -C tools/testing/selftests TARGETS=net run_tests
    or
    make run_tests from tools/testing/selftests
    or
    make run_test from tools/testing/selftests/net

    Signed-off-by: Shuah Khan
    Signed-off-by: David S. Miller

    Shuah Khan
     

06 Nov, 2014

5 commits

  • This patch adds basic event tracing tests like enable/disable with
    top-level, subsystem-level and individual event files.

    # ./ftracetest
    === Ftrace unit tests ===
    [1] Basic trace file check [PASS]
    [2] Basic trace clock test [PASS]
    [3] Basic event tracing check [PASS]
    [4] Basic test for tracers [PASS]
    [5] event tracing - enable/disable with top level files [PASS]
    [6] event tracing - enable/disable with subsystem level files [PASS]
    [7] event tracing - enable/disable with event level files [PASS]
    [8] ftrace - function graph filters [PASS]
    [9] ftrace - function profiler with function tracing [PASS]
    [10] ftrace - function graph filters with stack tracer [PASS]
    [11] Kretprobe dynamic event with arguments [PASS]
    [12] Kprobe dynamic event - busy event check [PASS]
    [13] Kprobe dynamic event with arguments [PASS]
    [14] Kprobe dynamic event - adding and removing [PASS]

    # of passed: 14
    # of failed: 0
    # of unresolved: 0
    # of untested: 0
    # of unsupported: 0
    # of xfailed: 0
    # of undefined(test bug): 0

    Link: http://lkml.kernel.org/r/1415239470-28705-3-git-send-email-namhyung@kernel.org

    Acked-by: Masami Hiramatsu
    Signed-off-by: Namhyung Kim
    Signed-off-by: Steven Rostedt

    Namhyung Kim
     
  • The kprobe testcases create, use and delete dynamic events during the
    test but didn't clear the trace buffer so it'll leave the result after
    it finishes.

    # ./ftracetest
    ...

    # cat trace
    # tracer: nop
    #
    # entries-in-buffer/entries-written: 2/2 #P:12
    #
    # _-----=> irqs-off
    # / _----=> need-resched
    # | / _---=> hardirq/softirq
    # || / _--=> preempt-depth
    # ||| / delay
    # TASK-PID CPU# |||| TIMESTAMP FUNCTION
    # | | | |||| | |
    ftracetest-26474 [009] d..1 79417.143782: Unknown type 1099
    ftracetest-26498 [009] d..1 79417.208034: Unknown type 1101

    Link: http://lkml.kernel.org/r/1415239470-28705-2-git-send-email-namhyung@kernel.org

    Acked-by: Masami Hiramatsu
    Signed-off-by: Namhyung Kim
    Signed-off-by: Steven Rostedt

    Namhyung Kim
     
  • When I run the ftracetest in a busybox docker container, I saw
    following error. Make the logfile template to comply with busybox's
    mktemp. It also keep the logfiles under the logs directory.

    # /linux/tools/testing/selftests/ftrace/ftracetest
    === Ftrace unit tests ===
    mktemp: unrecognized option `--tmpdir=/linux/tools/testing/selftests/ftrace/logs/20141106-003624/'
    BusyBox v1.22.1 (2014-05-22 23:22:11 UTC) multi-call binary.

    Usage: mktemp [-dt] [-p DIR] [TEMPLATE]

    Create a temporary file with name based on TEMPLATE and print its name.
    TEMPLATE must end with XXXXXX (e.g. [/dir/]nameXXXXXX).
    Without TEMPLATE, -t tmp.XXXXXX is assumed.

    -d Make directory, not file
    -q Fail silently on errors
    -t Prepend base directory name to TEMPLATE
    -p DIR Use DIR as a base directory (implies -t)
    -u Do not create anything; print a name

    Base directory is: -p DIR, else $TMPDIR, else /tmp

    [1] Basic trace file check/linux/tools/testing/selftests/ftrace/ftracetest: line 244: can't create : nonexistent directory
    /linux/tools/testing/selftests/ftrace/ftracetest: line 244: can't create : nonexistent directory
    [FAIL]

    Link: http://lkml.kernel.org/r/1415239470-28705-1-git-send-email-namhyung@kernel.org

    Acked-by: Masami Hiramatsu
    Signed-off-by: Namhyung Kim
    Signed-off-by: Steven Rostedt

    Namhyung Kim
     
  • Added three test cases to get the feel of adding tests to ftracetest.
    The three cases are:

    function profiling test, to make sure function profiling still works
    with function tracing (was a regression)

    function graph filter test to make sure that function graph filtering works.

    function graph filter with stack tracing test to make sure that the function
    graph filter does filter and also continues to filter when another function tracer
    is running (like the stack tracer)

    Link: http://lkml.kernel.org/r/20141103212737.696365174@goodmis.org
    Link: http://lkml.kernel.org/r/20141104153028.602754370@goodmis.org

    Acked-by: Masami Hiramatsu
    Acked-by: Namhyung Kim
    Signed-off-by: Steven Rostedt

    Steven Rostedt (Red Hat)
     
  • Created the file tools/testing/ftrace/test.d/functions that will
    hold helper functions.

    Current helper functions include:

    Add clear_trace() helper to reset the trace file

    Used as a descriptive name to show that "echo > trace" is clearing
    the trace file.

    Add disable/enable_tracing() helper calls

    Add calls that disable and enable tracing respectively by echoing
    0 or 1 into tracing_on.

    Add helper reset_tracer() function

    Add a helper function reset_tracer() that will clear the current_tracer
    (echo nop > current_tracer).

    Link: http://lkml.kernel.org/r/20141103212737.696365174@goodmis.org
    Link: http://lkml.kernel.org/r/20141104153028.465517119@goodmis.org

    Acked-by: Masami Hiramatsu
    Acked-by: Namhyung Kim
    Signed-off-by: Steven Rostedt

    Steven Rostedt (Red Hat)