Re: [PATCH V4 00/13] perf/x86: Add perf text poke events

Adrian Hunter
2020-03-16T07:08:19Z

On 4/03/20 11:06 am, Adrian Hunter wrote:
> 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, kprobes and ftrace trampolines.
>
> The first 8 patches make the kernel changes and the subsequent patches are
> tools changes.
>
> The next 4 patches add support for updating perf tools' data cache
> with the changed bytes.
>
> The last patch is an Intel PT specific tools change.
>
> Patches also here:
>
> git://git.infradead.org/users/ahunter/linux-perf.git text_poke

Any comments?

>
>
> Changes in V4
>
> kprobes: Add symbols for kprobe insn pages
>
> Change "module name" from kprobe to __builtin__kprobes
> Added comment about "module name" use
>
> ftrace: Add symbols for ftrace trampolines
>
> Change "module name" from ftrace to __builtin__ftrace
> Move calls of ftrace_add_trampoline_to_kallsyms() and
> ftrace_remove_trampoline_from_kallsyms() into
> kernel/trace/ftrace.c
> Added comment about "module name" use
>
> ftrace: Add perf ksymbol events for ftrace trampolines
>
> Move changes into kernel/trace/ftrace.c
>
> ftrace: Add perf text poke events for ftrace trampolines
>
> Move changes into kernel/trace/ftrace.c
>
> Changes in V3:
>
> perf: Add perf text poke event
>
> To prevent warning, cast pointer to (unsigned long) not (u64)
>
> kprobes: Add symbols for kprobe insn pages
>
> Expand commit message
> Remove un-needed declarations of kprobe_cache_get_kallsym() and arch_kprobe_get_kallsym() when !CONFIG_KPROBES
>
> ftrace: Add symbols for ftrace trampolines
>
> Expand commit message
> Make ftrace_get_trampoline_kallsym() static
>
> Changes in V2:
>
> perf: Add perf text poke event
>
> Separate out x86 changes
> The text poke event now has old len and new len
> Revised commit message
>
> perf/x86: Add support for perf text poke event for text_poke_bp_batch() callers
>
> New patch containing x86 changes from original first patch
>
> kprobes: Add symbols for kprobe insn pages
> kprobes: Add perf ksymbol events for kprobe insn pages
> perf/x86: Add perf text poke events for kprobes
> ftrace: Add symbols for ftrace trampolines
> ftrace: Add perf ksymbol events for ftrace trampolines
> ftrace: Add perf text poke events for ftrace trampolines
> perf kcore_copy: Fix module map when there are no modules loaded
> perf evlist: Disable 'immediate' events last
>
> New patches
>
> perf tools: Add support for PERF_RECORD_TEXT_POKE
>
> The text poke event now has old len and new len
> Also select ksymbol events with text poke events
>
> perf tools: Add support for PERF_RECORD_KSYMBOL_TYPE_OOL
>
> New patch
>
> perf intel-pt: Add support for text poke events
>
> The text poke event now has old len and new len
> Allow for the address not having a map yet
>
>
> Changes since RFC:
>
> Dropped 'flags' from the new event. The consensus seemed to be that text
> pokes should employ a scheme similar to x86's INT3 method instead.
>
> dropped tools patches already applied.
>
>
> 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
> CONFIG_SCHED_DEBUG=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 (13):
> perf: Add perf text poke event
> perf/x86: Add support for perf text poke event for text_poke_bp_batch() callers
> kprobes: Add symbols for kprobe insn pages
> kprobes: Add perf ksymbol events for kprobe insn pages
> perf/x86: Add perf text poke events for kprobes
> ftrace: Add symbols for ftrace trampolines
> ftrace: Add perf ksymbol events for ftrace trampolines
> ftrace: Add perf text poke events for ftrace trampolines
> perf kcore_copy: Fix module map when there are no modules loaded
> perf evlist: Disable 'immediate' events last
> perf tools: Add support for PERF_RECORD_TEXT_POKE
> perf tools: Add support for PERF_RECORD_KSYMBOL_TYPE_OOL
> perf intel-pt: Add support for text poke events
>
> arch/x86/include/asm/kprobes.h | 4 ++
> arch/x86/include/asm/text-patching.h | 2 +
> arch/x86/kernel/alternative.c | 70 +++++++++++++++++----
> arch/x86/kernel/kprobes/core.c | 7 +++
> arch/x86/kernel/kprobes/opt.c | 18 +++++-
> include/linux/ftrace.h | 12 ++--
> include/linux/kprobes.h | 15 +++++
> include/linux/perf_event.h | 8 +++
> include/uapi/linux/perf_event.h | 26 +++++++-
> kernel/events/core.c | 90 +++++++++++++++++++++++++-
> kernel/kallsyms.c | 42 +++++++++++--
> kernel/kprobes.c | 57 +++++++++++++++++
> kernel/trace/ftrace.c | 101 +++++++++++++++++++++++++++++-
> tools/include/uapi/linux/perf_event.h | 26 +++++++-
> tools/lib/perf/include/perf/event.h | 9 +++
> tools/perf/arch/x86/util/intel-pt.c | 4 ++
> tools/perf/builtin-record.c | 45 +++++++++++++
> tools/perf/util/dso.c | 3 +
> tools/perf/util/dso.h | 1 +
> tools/perf/util/event.c | 40 ++++++++++++
> tools/perf/util/event.h | 5 ++
> tools/perf/util/evlist.c | 31 ++++++---
> tools/perf/util/evlist.h | 1 +
> tools/perf/util/evsel.c | 7 ++-
> tools/perf/util/intel-pt.c | 75 ++++++++++++++++++++++
> tools/perf/util/machine.c | 49 +++++++++++++++
> tools/perf/util/machine.h | 3 +
> tools/perf/util/map.c | 5 ++
> tools/perf/util/map.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 | 23 +++++++
> tools/perf/util/symbol-elf.c | 7 +++
> tools/perf/util/symbol.c | 1 +
> tools/perf/util/tool.h | 3 +-
> 36 files changed, 765 insertions(+), 40 deletions(-)
>
>
> Regards
> Adrian
>