Message-Id: <157736902773.11126.2531161235817081873.stgit@devnote2>
Date:   Thu, 26 Dec 2019 23:03:48 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Frank Rowand <frowand.list@...il.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Tim Bird <Tim.Bird@...y.com>, Jiri Olsa <jolsa@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Rob Herring <robh+dt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-doc@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v5 00/22] tracing: bootconfig: Boot-time tracing and Extra boot config

Hello,

This is the 5th version of the series for the boot-time tracing.

Previous version is here.

https://lkml.kernel.org/r/157528159833.22451.14878731055438721716.stgit@devnote2

In this version, I removed RFC tag from the series.
Changes from the v4 are here, updating bootconfig things.

 - [1/22] Fix help comment and indent of Kconfig.
          Restrict available characters in values(*)
          Drop backslash escape from quoted value(**)
 - [3/22] Fix Makefile to compile tool correctly
          Remove unused pattern from Makefile
 - [4/22] Show test target bootconfig
          Add printable value testcases
          Add bad array testcase
 - [9/22] Fix TOC list
          Add notes about available characters.
          Fix to use correct quotes (``) for .rst.

(*) this is for preventing admin from shoot himself.
(**) this rule is from legacy command line.

Boot-time tracing features are not modified. I know Tom is working
on exporting synthetic event (and dynamic events) APIs for module.
If that APIs are merged first, I will update my series on top
of that.

This series can be applied on v5.5-rc3 or directly available at;

https://github.com/mhiramat/linux.git ftrace-boottrace-v5


Extra Boot Config
=================

Extra boot config allows admin to pass a tree-structured key-value
list when booting up the kernel. This expands the kernel command
line in an efficient way.

Each key is described as a dot-jointed-words. And user can write
the key-words in tree stlye. (In this version, the tailing ';'
becomes optional. See Documentation/admin-guide/bootconfig.rst)

For example,

 feature.option.foo = 1
 feature.option.bar = 2

can be also written in

 feature.option {
    foo = 1
    bar = 2
 }

or more compact,

 feature.option{foo=1;bar=2}

(Note that in both style, the same words are merged automatically
 and make a single tree)
All values are treated as a string, or array of strings, e.g.

 feature.options = "foo", "bar"

User can see the loaded key-value list via /proc/bootconfig.
The size is limited upto 32KB and 1024 key-words and values
in total.

Boot with a Boot Config
=======================

This version doesn't require to modify boot loaders anymore.
The boot config is loaded with initrd, and there is new "bootconfig"
command under tools/bootconfig.
To add (append) a bootconfig file to an initrd, you can use the
bootconfig command like:

 # tools/bootconfig/bootconfig -a your-config /boot/initrd.img-X.Y.Z

This verifies the configuration file too. 


Boot-time Tracing
=================

Boot-time tracing supports following boot configs. Please read
Documentation/trace/boottime-trace.rst for details.

     - kernel.dump_on_oops [= MODE]
     - kernel.traceoff_on_warning
     - kernel.tp_printk
     - kernel.fgraph_filters = FILTER[, FILTER2...]
     - kernel.fgraph_notraces = FILTER[, FILTER2...]
     - kernel.fgraph_max_depth = MAX_DEPTH
     - ftrace.[instance.INSTANCE.]options = OPT1[,OPT2...]
     - ftrace.[instance.INSTANCE.]trace_clock = CLOCK
     - ftrace.[instance.INSTANCE.]buffer_size = SIZE
     - ftrace.[instance.INSTANCE.]alloc_snapshot
     - ftrace.[instance.INSTANCE.]cpumask = CPUMASK
     - ftrace.[instance.INSTANCE.]events = EVENT[, EVENT2...]
     - ftrace.[instance.INSTANCE.]tracer = TRACER
     - ftrace.[instance.INSTANCE.]ftrace.filters
     - ftrace.[instance.INSTANCE.]ftrace.notraces
     - ftrace.[instance.INSTANCE.]event.GROUP.EVENT.filter = FILTER
     - ftrace.[instance.INSTANCE.]event.GROUP.EVENT.actions = ACTION[, ACTION2...]
     - ftrace.[instance.INSTANCE.]event.GROUP.EVENT.enable
     - ftrace.[instance.INSTANCE.]event.kprobes.EVENT.probes = PROBE[, PROBE2...]
     - ftrace.[instance.INSTANCE.]event.synthetic.EVENT.fields = FIELD[, FIELD2...]

Kernel and Init Command Line
============================

Boot config also supports kernel and init command line parameters
except for early kernel parameters.

In boot config, all key-values start with "kernel." are automatically
merged into user passed boot command line, and key-values which
start with "init." are also passed to init. These options are visible
on /proc/cmdline.

For example,

kernel {
  audit = on
  audit_backlog_limit = 256
}
init.systemd.unified_cgroup_hierarchy = 1


Usage
=====

With this series, we can setup new kprobe and synthetic events, more
complicated event filters and trigger actions including histogram
via supplemental kernel cmdline.

We can add filter and actions for each event, define kprobe events,
and synthetic events with histogram like below.

ftrace.event {
	task.task_newtask {
		filter = "pid < 128"
		enable
	}
	kprobes.vfs_read {
		probes = "vfs_read $arg1 $arg2"
		filter = "common_pid < 200"
		enable
	}
	synthetic.initcall_latency {
		fields = "unsigned long func", "u64 lat"
		actions = "hist:keys=func.sym,lat:vals=lat:sort=lat"
	}
	initcall.initcall_start {
		actions = "hist:keys=func:ts0=common_timestamp.usecs"
	}
	initcall.initcall_finish {
		actions = "hist:keys=func:lat=common_timestamp.usecs-$ts0:onmatch(initcall.initcall_start).initcall_latency(func,$lat)"
	}
}

Also, this supports "instance" node, which allows us to run several
tracers for different purpose at once. For example, one tracer is for
tracing functions start with "user_", and others tracing "kernel_",
you can write boot config as:

ftrace.instance {
	foo {
		tracer = "function"
		ftrace-filters = "user_*"
	}
	bar {
		tracer = "function"
		ftrace-filters = "function_*"
	}
}

The instance node also accepts event nodes so that each instance
can customize its event tracing.

This boot-time trace also supports ftrace kernel parameters.
For example, following kernel parameters

trace_options=sym-addr trace_event=initcall:* tp_printk trace_buf_size=1M ftrace=function ftrace_filter="vfs*"

it can be written in boot config like below.

ftrace {
	options = sym-addr;
	events = "initcall:*";
	tp-printk;
	buffer-size = 1MB;
	ftrace-filters = "vfs*";
}

However, since the initialization timing is different, if you need
to trace very early boot, please use normal kernel parameters.

Some Notes
==========

- To align the legacy command line rule, I made the quotes (double
  quotes or single quotes) not able to be escaped.
  Also, this rejects non-printable chars (except for space). Actually
  legacy cmdline accepts any of them, but it might confuse users if
  they put a control code by mistake. Imagine that they put a "\b"
  on it...

- Since it is not easy to write boot-time tracing without any bug
  in bootconfig, a user-helper command will be needed.
  That command will generate a boot config file from current ftrace
  settings, or try to apply given boot config setting to the ftrace.

- It is also possible to embed boot config file into the kernel
  image for the environment which doesn't use initrd. But in that
  case, user can not update the boot config.

- As you can see, the EVENT.actions value is a bit ugly since histogram
  interface settings are bit complicated. Maybe we can introduce more
  abstractive syntax for that. e.g.

ftrace.event.synthetic.initcall_latency {
	fields = "unsigned long func", "u64 lat"
	hist {
		from {
			event = initcall.initcall_start
			key = func
			assigns = "ts0=common_timestamp.usecs"
		}
		to {
			event = initcall.initcall_finish
			key = func
			assigns = "lat=common_timestamp.usecs-$ts0"
			onmatch = func, $lat
		}
		keys = func.sym, lat
		vals = lat
		sort = lat
	}
}

Any suggestions, thoughts?

Thank you,

---

Masami Hiramatsu (22):
      bootconfig: Add Extra Boot Config support
      bootconfig: Load boot config from the tail of initrd
      tools: bootconfig: Add bootconfig command
      tools: bootconfig: Add bootconfig test script
      proc: bootconfig: Add /proc/bootconfig to show boot config list
      init/main.c: Alloc initcall_command_line in do_initcall() and free it
      bootconfig: init: Allow admin to use bootconfig for kernel command line
      bootconfig: init: Allow admin to use bootconfig for init command line
      Documentation: bootconfig: Add a doc for extended boot config
      tracing: Apply soft-disabled and filter to tracepoints printk
      tracing: kprobes: Output kprobe event to printk buffer
      tracing: kprobes: Register to dynevent earlier stage
      tracing: Accept different type for synthetic event fields
      tracing: Add NULL trace-array check in print_synth_event()
      tracing/boot: Add boot-time tracing
      tracing/boot: Add per-event settings
      tracing/boot Add kprobe event support
      tracing/boot: Add synthetic event support
      tracing/boot: Add instance node support
      tracing/boot: Add cpu_mask option support
      tracing/boot: Add function tracer filter options
      Documentation: tracing: Add boot-time tracing document


 tools/bootconfig/.gitignore                     |    1 
 tools/bootconfig/Makefile                       |   23 ++
 tools/bootconfig/include/linux/bootconfig.h     |    7 
 tools/bootconfig/include/linux/bug.h            |   12 +
 tools/bootconfig/include/linux/ctype.h          |    7 
 tools/bootconfig/include/linux/errno.h          |    7 
 tools/bootconfig/include/linux/kernel.h         |   18 +
 tools/bootconfig/include/linux/printk.h         |   13 +
 tools/bootconfig/include/linux/string.h         |   32 ++
 tools/bootconfig/main.c                         |  337 +++++++++++++++++++++++
 tools/bootconfig/samples/bad-array.bconf        |    2 
 tools/bootconfig/samples/bad-dotword.bconf      |    4 
 tools/bootconfig/samples/bad-empty.bconf        |    1 
 tools/bootconfig/samples/bad-keyerror.bconf     |    2 
 tools/bootconfig/samples/bad-longkey.bconf      |    1 
 tools/bootconfig/samples/bad-manywords.bconf    |    1 
 tools/bootconfig/samples/bad-no-keyword.bconf   |    2 
 tools/bootconfig/samples/bad-nonprintable.bconf |    2 
 tools/bootconfig/samples/bad-spaceword.bconf    |    2 
 tools/bootconfig/samples/bad-tree.bconf         |    5 
 tools/bootconfig/samples/bad-value.bconf        |    3 
 tools/bootconfig/samples/escaped.bconf          |    3 
 tools/bootconfig/samples/good-printables.bconf  |    2 
 tools/bootconfig/samples/good-simple.bconf      |   11 +
 tools/bootconfig/samples/good-single.bconf      |    4 
 tools/bootconfig/samples/good-tree.bconf        |   12 +
 tools/bootconfig/test-bootconfig.sh             |   80 +++++
 27 files changed, 594 insertions(+)
 create mode 100644 tools/bootconfig/.gitignore
 create mode 100644 tools/bootconfig/Makefile
 create mode 100644 tools/bootconfig/include/linux/bootconfig.h
 create mode 100644 tools/bootconfig/include/linux/bug.h
 create mode 100644 tools/bootconfig/include/linux/ctype.h
 create mode 100644 tools/bootconfig/include/linux/errno.h
 create mode 100644 tools/bootconfig/include/linux/kernel.h
 create mode 100644 tools/bootconfig/include/linux/printk.h
 create mode 100644 tools/bootconfig/include/linux/string.h
 create mode 100644 tools/bootconfig/main.c
 create mode 100644 tools/bootconfig/samples/bad-array.bconf
 create mode 100644 tools/bootconfig/samples/bad-dotword.bconf
 create mode 100644 tools/bootconfig/samples/bad-empty.bconf
 create mode 100644 tools/bootconfig/samples/bad-keyerror.bconf
 create mode 100644 tools/bootconfig/samples/bad-longkey.bconf
 create mode 100644 tools/bootconfig/samples/bad-manywords.bconf
 create mode 100644 tools/bootconfig/samples/bad-no-keyword.bconf
 create mode 100644 tools/bootconfig/samples/bad-nonprintable.bconf
 create mode 100644 tools/bootconfig/samples/bad-spaceword.bconf
 create mode 100644 tools/bootconfig/samples/bad-tree.bconf
 create mode 100644 tools/bootconfig/samples/bad-value.bconf
 create mode 100644 tools/bootconfig/samples/escaped.bconf
 create mode 100644 tools/bootconfig/samples/good-printables.bconf
 create mode 100644 tools/bootconfig/samples/good-simple.bconf
 create mode 100644 tools/bootconfig/samples/good-single.bconf
 create mode 100644 tools/bootconfig/samples/good-tree.bconf
 create mode 100755 tools/bootconfig/test-bootconfig.sh

--
Masami Hiramatsu (Linaro) <mhiramat@...nel.org>

Powered by blists - more mailing lists