Re: [PATCH v1] perf script flamegraph: Avoid d3-flame-graph package dependency

From: Andreas Gerstmayr
Date: Wed Jan 11 2023 - 08:19:18 EST

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On 10.01.23 20:51, Ian Rogers wrote:

On Tue, Jan 10, 2023 at 10:02 AM Andreas Gerstmayr
<agerstmayr@xxxxxxxxxx> wrote:

On 05.01.23 10:24, Ian Rogers wrote:

On Wed, Jan 4, 2023 at 7:04 PM Ian Rogers <irogers@xxxxxxxxxx> wrote:

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 warn and download it from
jsdelivr CDN. If downloading fails generate a minimal flame graph
again with the javascript coming from jsdelivr CDN.

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

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>

I'm not entirely convinced that this perf script should make a network
request. In my opinion

* best would be if this template gets packaged in Debian
* alternatively print instructions how to install the template:

sudo mkdir /usr/share/d3-flame-graph
sudo wget -O /usr/share/d3-flame-graph/d3-flamegraph-base.html
https://cdn.jsdelivr.net/npm/d3-flame-graph@4/dist/templates/d3-flamegraph-base.html

* or eventually just embed the entire template (66 KB) in the Python
file (not sure if this is permissible though, it's basically a minified
HTML/JS blob)?
* if the above options don't work, I'd recommend asking the user before
making the network request, and eventually persist the template
somewhere so it doesn't need to be downloaded every time

What do you think?

So the script following this patch is going to try 3 things:
1) look for a local template HTML,
2) if a local template isn't found warn and switch to downloading the
CDN version,
3) if the CDN version fails to download then use a minimal (embedded
in the script) HTML file with JS dependencies coming from the CDN.

For (1) there are references in the generated HTML to www.w3.org,
meaning the HTML isn't fully hermetic - although these references may
not matter.

The references to w3.org are XML namespace names. As far as I'm aware they do not matter, as they are merely identifiers and are never accessed [1,2]. Therefore the generated HTML file in its current form is hermetic.

This was a design decision from the start - the flame graph generation and the resulting HTML file should not use any external resources loaded over the network (the external host could be inaccessible or compromised at any time). I understand that this requirement may not apply to every user or company.

For (2) there will be a download from the CDN of the template during
the execution of flamegraph. The template is better than (3) as it
features additional buttons letting you zoom out, etc. The HTML will
contain CDN references.
For (3) the generated HTML isn't hermetic and will use the CDN.

For (2) we could give a prompt before trying to download the template,
or we could change it so that we give the wget command. I wouldn't
have the wget command require root privileges, I'd say that the
template could be downloaded and then the path of the download given
as an option to the flamegraph program. Downloading the file and then
adding an option to flamegraph seems inconvenient to the user,
something that the use of urllib in the patch avoids - it is
essentially just doing this for the user without storing the file on
disk. I think I prefer to be less inconvenient, and so the state of
the code at the moment looks best to me. Given that no choice results
in a fully hermetic HTML file, they seem similar in this regard. Is it
okay to try a download with urllib? Should there be a prompt? I think
the warning is enough and allows scripts, etc. using flamegraph to
more easily function across differing distributions.

I fully agree, your changes make the flame graph generation more convenient in case the template is not installed. Also, downloading the template to a local directory and having to specify the path to the template every time is an inconvenience.

I think it is a tradeoff between convenience and security/privacy. jsdelivr can get compromised, serving malicious JS (well, in that case, printing instructions to jsdelivr is also flawed :|).
In the end it's up to the maintainers to decide.

An aside, Namhyung pointed out to me that there is a "perf report -g
folded" option, that was added in part to simplify creating
flamegraphs:
http://lkml.kernel.org/r/1447047946-1691-2-git-send-email-namhyung@xxxxxxxxxx
Building off of perf report may improve/simplify the flamegraph code,
or avoid the requirement that libpython be linked against perf.

Yep, in this case another tool is required to generate the flame graph visualization, for example [3].

[1] https://www.w3.org/TR/xml-names11/
[2] https://developer.mozilla.org/en-US/docs/Web/SVG/Namespaces_Crash_Course
[3] https://github.com/brendangregg/FlameGraph

Cheers,
Andreas

Thanks,
Ian

Cheers,
Andreas

---
tools/perf/scripts/python/flamegraph.py | 63 ++++++++++++++++++-------
1 file changed, 45 insertions(+), 18 deletions(-)

diff --git a/tools/perf/scripts/python/flamegraph.py b/tools/perf/scripts/python/flamegraph.py
index b6af1dd5f816..808b0e1c9be5 100755
--- a/tools/perf/scripts/python/flamegraph.py
+++ b/tools/perf/scripts/python/flamegraph.py
@@ -25,6 +25,27 @@ import io
import argparse
import json
import subprocess
+import urllib.request
+
+minimal_html = """<head>
+ <link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/npm/d3-flame-graph@4.1.3/dist/d3-flamegraph.css";>

(hopefully fixed Martin Spier's e-mail address)

The @4.1.3 comes from the README.md:
https://github.com/spiermar/d3-flame-graph/blob/master/README.md
Does it make sense just to drop it or use @latest ? It'd be nice not
to patch this file for every d3-flame-graph update.

Thanks,
Ian

+</head>
+<body>
+ <div id="chart"></div>
+ <script type="text/javascript" src="https://d3js.org/d3.v7.js";></script>
+ <script type="text/javascript" src="https://cdn.jsdelivr.net/npm/d3-flame-graph@4.1.3/dist/d3-flamegraph.min.js";></script>
+ <script type="text/javascript">
+ const stacks = [/** @flamegraph_json **/];
+ // Note, options is unused.
+ const options = [/** @options_json **/];
+
+ var chart = flamegraph();
+ d3.select("#chart")
+ .datum(stacks[0])
+ .call(chart);
+ </script>
+</body>
+"""

# pylint: disable=too-few-public-methods
class Node:
@@ -50,15 +71,18 @@ class FlameGraphCLI:
self.args = args
self.stack = Node("all", "root")

- if self.args.format == "html" and \
- not os.path.isfile(self.args.template):
- print("Flame Graph template {} does not exist. Please install "
- "the js-d3-flame-graph (RPM) or libjs-d3-flame-graph (deb) "
- "package, specify an existing flame graph template "
- "(--template PATH) or another output format "
- "(--format FORMAT).".format(self.args.template),
- file=sys.stderr)
- sys.exit(1)
+ if self.args.format == "html":
+ if os.path.isfile(self.args.template):
+ self.template = f"file://{self.args.template}"
+ else:
+ print(f"""
+Warning: Flame Graph template '{self.args.template}'
+does not exist, a template will be downloaded via http. To avoid this
+please install a package such as the js-d3-flame-graph or
+libjs-d3-flame-graph, specify an existing flame graph template
+(--template PATH) or another output format (--format FORMAT).
+""", file=sys.stderr)
+ self.template = "https://cdn.jsdelivr.net/npm/d3-flame-graph@4.1.3/dist/templates/d3-flamegraph-base.html";

@staticmethod
def get_libtype_from_dso(dso):
@@ -129,15 +153,18 @@ class FlameGraphCLI:
options_json = json.dumps(options)

try:
- with io.open(self.args.template, encoding="utf-8") as template:
- output_str = (
- template.read()
- .replace("/** @options_json **/", options_json)
- .replace("/** @flamegraph_json **/", stacks_json)
- )
- except IOError as err:
- print("Error reading template file: {}".format(err), file=sys.stderr)
- sys.exit(1)
+ with urllib.request.urlopen(self.template) as template:
+ output_str = '\n'.join([
+ l.decode('utf-8') for l in template.readlines()
+ ])
+ except Exception as err:
+ print(f"Error reading template {self.template}: {err}\n"
+ "a minimal flame graph will be generated", file=sys.stderr)
+ output_str = minimal_html
+
+ output_str = output_str.replace("/** @options_json **/", options_json)
+ output_str = output_str.replace("/** @flamegraph_json **/", stacks_json)
+
output_fn = self.args.output or "flamegraph.html"
else:
output_str = stacks_json
--
2.39.0.314.g84b9a713c41-goog

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Commercial register: Commercial Court Vienna, FN 479668w

Next message: Vernon Yang: "[PATCH v2] mm/mmap: fix comment of unmapped_area{_topdown}"
Previous message: Simon Horman: "Re: [PATCH] net: remove redundant config PCI dependency for some network driver configs"
In reply to: Ian Rogers: "Re: [PATCH v1] perf script flamegraph: Avoid d3-flame-graph package dependency"
Next in thread: Ian Rogers: "Re: [PATCH v1] perf script flamegraph: Avoid d3-flame-graph package dependency"
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