netdev - [PATCH net-next v2 1/4] selftests: drv-net: add helper/wrapper for bpftrace

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Message-Id: <20250625-netpoll_test-v2-1-47d27775222c@debian.org>
Date: Wed, 25 Jun 2025 04:39:46 -0700
From: Breno Leitao <leitao@...ian.org>
To: Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Shuah Khan <shuah@...nel.org>, Simon Horman <horms@...nel.org>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>, bpf@...r.kernel.org, 
 gustavold@...il.com, Breno Leitao <leitao@...ian.org>
Subject: [PATCH net-next v2 1/4] selftests: drv-net: add helper/wrapper for
 bpftrace

From: Jakub Kicinski <kuba@...nel.org>

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>
Signed-off-by: Breno Leitao <leitao@...ian.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 34470d65d871a..760ccf6fccccc 100644
--- a/tools/testing/selftests/net/lib/py/utils.py
+++ b/tools/testing/selftests/net/lib/py/utils.py
@@ -185,6 +185,39 @@ def ethtool(args, json=None, ns=None, host=None):
     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.

-- 
2.47.1