netdev - [RFC net-next 21/22] selftests: drv-net: add helper/wrapper for bpftrace

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Message-ID: <20250421222827.283737-22-kuba@kernel.org>
Date: Mon, 21 Apr 2025 15:28:26 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
	edumazet@...gle.com,
	pabeni@...hat.com,
	andrew+netdev@...n.ch,
	horms@...nel.org,
	donald.hunter@...il.com,
	sdf@...ichev.me,
	almasrymina@...gle.com,
	dw@...idwei.uk,
	asml.silence@...il.com,
	ap420073@...il.com,
	jdamato@...tly.com,
	dtatulea@...dia.com,
	michael.chan@...adcom.com,
	Jakub Kicinski <kuba@...nel.org>
Subject: [RFC net-next 21/22] selftests: drv-net: add helper/wrapper for bpftrace

bpftrace is very useful for low level driver testing. perf or trace-cmd
would also do for collecting data from tracepoints, but they require
much more post-processing.

Add a wrapper for running bpftrace and sanitizing its output.
bpftrace has JSON output, which is great, but it prints loose objects
and in a slightly inconvenient format. We have to read the objects
line by line, and while at it return them indexed by the map name.

Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
 tools/testing/selftests/net/lib/py/utils.py | 33 +++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/tools/testing/selftests/net/lib/py/utils.py b/tools/testing/selftests/net/lib/py/utils.py
index 34470d65d871..760ccf6fcccc 100644
--- a/tools/testing/selftests/net/lib/py/utils.py
+++ b/tools/testing/selftests/net/lib/py/utils.py
@@ -185,6 +185,39 @@ global_defer_queue = []
     return tool('ethtool', args, json=json, ns=ns, host=host)
 
 
+def bpftrace(expr, json=None, ns=None, host=None, timeout=None):
+    """
+    Run bpftrace and return map data (if json=True).
+    The output of bpftrace is inconvenient, so the helper converts
+    to a dict indexed by map name, e.g.:
+     {
+       "@":     { ... },
+       "@map2": { ... },
+     }
+    """
+    cmd_arr = ['bpftrace']
+    # Throw in --quiet if json, otherwise the output has two objects
+    if json:
+        cmd_arr += ['-f', 'json', '-q']
+    if timeout:
+        expr += ' interval:s:' + str(timeout) + ' { exit(); }'
+    cmd_arr += ['-e', expr]
+    cmd_obj = cmd(cmd_arr, ns=ns, host=host, shell=False)
+    if json:
+        # bpftrace prints objects as lines
+        ret = {}
+        for l in cmd_obj.stdout.split('\n'):
+            if not l.strip():
+                continue
+            one = _json.loads(l)
+            if one.get('type') != 'map':
+                continue
+            for k, v in one["data"].items():
+                ret[k] = v
+        return ret
+    return cmd_obj
+
+
 def rand_port(type=socket.SOCK_STREAM):
     """
     Get a random unprivileged port.
-- 
2.49.0