perf script flamegraph: Avoid d3-flame-graph package dependency

Currently flame graph generation requires a d3-flame-graph template to
be installed. Unfortunately this is hard to come by for things like
Debian [1].

If the template isn't installed then ask if it should be downloaded from
jsdelivr CDN. The downloaded HTML file is validated against an md5sum.
If the download fails, generate a minimal flame graph with the
javascript coming from links to jsdelivr CDN.

v3. Adds a warning message and quits before download in live mode.
v2. Change the warning to a prompt about downloading and add the
--allow-download command line flag. Add an md5sum check for the
downloaded HTML.

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=996839

Reviewed-by: Andreas Gerstmayr <agerstmayr@redhat.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: 996839@bugs.debian.org
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Brendan Gregg <brendan@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin Spier <spiermar@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230118072409.147786-1-irogers@google.com # v3 discussion
Link: https://lore.kernel.org/r/20230112220024.32709-1-irogers@google.com # v2 discussion
Link: https://lore.kernel.org/r/CAP-5=fXi_9zdhTAoYApiFQoLURAvpEatFzU3uL23o3zs=z25ZQ@mail.gmail.com # v1 discussion
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

perf flamegraph: flamegraph.py script improvements

* display perf.data header
* display PIDs of user stacks
* added option to change color scheme
* default to blue/green color scheme to improve accessibility
* correctly identify kernel stacks when kernel-debuginfo is installed

Signed-off-by: Andreas Gerstmayr <agerstmayr@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20210830164729.116049-1-agerstmayr@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

perf flamegraph: Explicitly set utf-8 encoding

On some platforms the default encoding is not utf-8, which causes an
UnicodeDecodeError when reading the flamegraph template and writing the
flamegraph

Signed-off-by: Andreas Gerstmayr <agerstmayr@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200619153232.203537-1-agerstmayr@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

perf script: Add flamegraph.py script

This script works in tandem with d3-flame-graph to generate flame graphs
from perf. It supports two output formats: JSON and HTML (the default).
The HTML format will look for a standalone d3-flame-graph template file
in /usr/share/d3-flame-graph/d3-flamegraph-base.html and fill in the
collected stacks.

Usage:

perf record -a -g -F 99 sleep 60
perf script report flamegraph

Combined:

perf script flamegraph -a -F 99 sleep 60

Committer testing:

Tested both with "PYTHON=python3" and with the default, that uses
python2-devel:

Complete set of instructions:

$ mkdir /tmp/build/perf
$ make PYTHON=python3 -C tools/perf O=/tmp/build/perf install-bin
$ export PATH=~/bin:$PATH
$ perf record -a -g -F 99 sleep 60
$ perf script report flamegraph

Now go and open the generated flamegraph.html file in a browser.

At first this required building with PYTHON=python3, but after I
reported this Andreas was kind enough to send a patch making it work
with both python and python3.

Signed-off-by: Andreas Gerstmayr <agerstmayr@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Brendan Gregg <bgregg@netflix.com>
Cc: Martin Spier <mspier@netflix.com>
Link: http://lore.kernel.org/lkml/20200320151355.66302-1-agerstmayr@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>