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Subject[PATCH RFC 0/6] perf/x86: Add perf text poke event
Date
Hi

Here are patches to add a text poke event to record changes to kernel text
(i.e. self-modifying code) in order to support tracers like Intel PT
decoding through jump labels.

One question is whether this approach can be of use to other architectures,
particularly ARM-CS.

The first patch makes the kernel change and the subsequent patches are
tools changes.

The first 3 tools patches add support for updating perf tools' data cache
with the changed bytes.

The last 2 patches are Intel PT specific tools changes.

The patches are based on Arnaldo's tree perf/core branch.

Example:

For jump labels, the kernel needs
CONFIG_JUMP_LABEL=y
and also an easy to flip jump label is in sysctl_schedstats() which needs
CONFIG_SCHEDSTATS=y
CONFIG_PROC_SYSCTL=y

Also note the 'sudo perf record' is put into the background which, as
written, needs sudo credential caching (otherwise the background task
will stop awaiting the sudo password), hence the 'sudo echo' to start.

Before:

$ sudo echo
$ sudo perf record -o perf.data.before --kcore -a -e intel_pt//k -m,64M &
[1] 1640
$ cat /proc/sys/kernel/sched_schedstats
0
$ sudo bash -c 'echo 1 > /proc/sys/kernel/sched_schedstats'
$ cat /proc/sys/kernel/sched_schedstats
1
$ sudo bash -c 'echo 0 > /proc/sys/kernel/sched_schedstats'
$ cat /proc/sys/kernel/sched_schedstats
0
$ sudo kill 1640
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 16.635 MB perf.data.before ]
$ perf script -i perf.data.before --itrace=e >/dev/null
Warning:
1946 instruction trace errors

After:

$ sudo echo
$ sudo perf record -o perf.data.after --kcore -a -e intel_pt//k -m,64M &
[1] 1882
$ cat /proc/sys/kernel/sched_schedstats
0
$ sudo bash -c 'echo 1 > /proc/sys/kernel/sched_schedstats'
$ cat /proc/sys/kernel/sched_schedstats
1
$ sudo bash -c 'echo 0 > /proc/sys/kernel/sched_schedstats'
$ cat /proc/sys/kernel/sched_schedstats
0
$ sudo kill 1882
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 10.893 MB perf.data.after ]
$ perf script -i perf.data.after --itrace=e
$


Adrian Hunter (6):
perf/x86: Add perf text poke event
perf dso: Refactor dso_cache__read()
perf dso: Add dso__data_write_cache_addr()
perf tools: Add support for PERF_RECORD_TEXT_POKE
perf auxtrace: Add auxtrace_cache__remove()
perf intel-pt: Add support for text poke events

arch/x86/include/asm/text-patching.h | 1 +
arch/x86/kernel/alternative.c | 39 ++++++++-
include/linux/perf_event.h | 6 ++
include/uapi/linux/perf_event.h | 28 ++++++-
kernel/events/core.c | 90 +++++++++++++++++++-
tools/include/uapi/linux/perf_event.h | 28 ++++++-
tools/perf/arch/x86/util/intel-pt.c | 5 ++
tools/perf/builtin-record.c | 45 ++++++++++
tools/perf/lib/include/perf/event.h | 9 ++
tools/perf/util/auxtrace.c | 28 +++++++
tools/perf/util/auxtrace.h | 1 +
tools/perf/util/dso.c | 135 +++++++++++++++++++++---------
tools/perf/util/dso.h | 7 ++
tools/perf/util/event.c | 39 +++++++++
tools/perf/util/event.h | 5 ++
tools/perf/util/evlist.h | 1 +
tools/perf/util/intel-pt.c | 71 ++++++++++++++++
tools/perf/util/machine.c | 38 +++++++++
tools/perf/util/machine.h | 3 +
tools/perf/util/perf_event_attr_fprintf.c | 1 +
tools/perf/util/record.c | 10 +++
tools/perf/util/record.h | 1 +
tools/perf/util/session.c | 22 +++++
tools/perf/util/tool.h | 3 +-
24 files changed, 570 insertions(+), 46 deletions(-)


Regards
Adrian

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