[PATCH v6 00/22] tracing: bootconfig: Boot-time tracing and Extra boot config

Masami Hiramatsu
2020-01-10T16:03:29Z

Hello,

This is the 6th version of the series for the boot-time tracing.

Previous version is here.

https://lkml.kernel.org/r/157736902773.11126.2531161235817081873.stgit@devnote2

Thanks Steve for reivew. I fixed issues in this version.

- [1/22] Remove "!!" from xbc_node_is_value().
Redefine xbc_node_is_key() as "!xbc_node_is_value()".
Fix a memory leak and a bug in __xbc_parse_value().
Add xbc_destroy_all() to clean up the parsed data.
Fix to treat comment right after value as a newline.

- [3/22] Fix memory leaks.
Fix to cleanup old bootconfig on memory before load new one.
Show applying message.
Suppress parse error with wrong data in initrd for delete_xbc().

- [4/22] Add some testcases for value parser
Add a test case for checking delete old bootconfig

- [9/22] Add a note about comment after value.

- [21/22] Fix to depend on CONFIG_DYNAMIC_FTRACE instead
of CONFIG_FUNCTION_TRACER.

This series can be applied on v5.5-rc5 or directly available at;

https://github.com/mhiramat/linux.git ftrace-boottrace-v6

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.

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

Documentation/admin-guide/bootconfig.rst | 186 +++++
Documentation/admin-guide/index.rst | 1
Documentation/trace/boottime-trace.rst | 184 +++++
Documentation/trace/index.rst | 1
MAINTAINERS | 9
fs/proc/Makefile | 1
fs/proc/bootconfig.c | 89 ++
include/linux/bootconfig.h | 224 ++++++
include/linux/trace_events.h | 1
init/Kconfig | 12
init/main.c | 213 +++++
kernel/trace/Kconfig | 9
kernel/trace/Makefile | 1
kernel/trace/trace.c | 63 +-
kernel/trace/trace_boot.c | 353 +++++++++
kernel/trace/trace_events.c | 1
kernel/trace/trace_events_hist.c | 14
kernel/trace/trace_events_trigger.c | 2
kernel/trace/trace_kprobe.c | 81 +-
lib/Kconfig | 3
lib/Makefile | 2
lib/bootconfig.c | 803 ++++++++++++++++++++
tools/Makefile | 11
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 | 17
tools/bootconfig/include/linux/string.h | 32 +
tools/bootconfig/main.c | 354 +++++++++
.../samples/bad-array-space-comment.bconf | 5
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
.../samples/good-array-space-comment.bconf | 4
.../samples/good-comment-after-value.bconf | 1
tools/bootconfig/samples/good-printables.bconf | 2
tools/bootconfig/samples/good-simple.bconf | 11
tools/bootconfig/samples/good-single.bconf | 4
.../samples/good-space-after-value.bconf | 1
tools/bootconfig/samples/good-tree.bconf | 12
tools/bootconfig/test-bootconfig.sh | 105 +++
54 files changed, 2836 insertions(+), 79 deletions(-)
create mode 100644 Documentation/admin-guide/bootconfig.rst
create mode 100644 Documentation/trace/boottime-trace.rst
create mode 100644 fs/proc/bootconfig.c
create mode 100644 include/linux/bootconfig.h
create mode 100644 kernel/trace/trace_boot.c
create mode 100644 lib/bootconfig.c
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-space-comment.bconf
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-array-space-comment.bconf
create mode 100644 tools/bootconfig/samples/good-comment-after-value.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-space-after-value.bconf
create mode 100644 tools/bootconfig/samples/good-tree.bconf
create mode 100755 tools/bootconfig/test-bootconfig.sh

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