scripts: profiling: Add stackcollapse script

Samples, that were obtained by profiling perf tool, can be be translated
into flamegraph using stackcollapse.py script.

Originally-by: Yonatan Goldschmidt <[email protected]>
Signed-off-by: Mikhail Kushnerov <[email protected]>

Author: Mikhail Kushnerov

scripts/profiling/stackcollapse.py

@@ -0,0 +1,65 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2023 KNS Group LLC (YADRO)
+# Copyright (c) 2020 Yonatan Goldschmidt <[email protected]>
+#
+# SPDX-License-Identifier: Apache-2.0
+
+"""
+Stack compressor for FlameGraph
+
+This translate stack samples captured by perf subsystem into format
+used by flamegraph.pl. Translation uses .elf file to get function names
+from addresses
+
+Usage:
+    ./script/perf/stackcollapse.py <file with perf printbuf output> <ELF file>
+"""
+
+import re
+import sys
+import struct
+import binascii
+from functools import lru_cache
+from elftools.elf.elffile import ELFFile
+
+
+@lru_cache(maxsize=None)
+def addr_to_sym(addr, elf):
+    symtab = elf.get_section_by_name(".symtab")
+    for sym in symtab.iter_symbols():
+        if sym.entry.st_info.type == "STT_FUNC" and sym.entry.st_value <= addr < sym.entry.st_value + sym.entry.st_size:
+            return sym.name
+    if addr == 0:
+        return "nullptr"
+    return "[unknown]"
+
+
+def collapse(buf, elf):
+    while buf:
+        count, = struct.unpack_from(">Q", buf)
+        assert count > 0
+        addrs = struct.unpack_from(f">{count}Q", buf, 8)
+
+        func_trace = reversed(list(map(lambda a: addr_to_sym(a, elf), addrs)))
+        prev_func = next(func_trace)
+        line = prev_func
+        # merge dublicate functions
+        for func in func_trace:
+            if prev_func != func:
+                prev_func = func
+                line += ";" + func
+
+        print(line, 1)
+        buf = buf[8 + 8 * count:]
+
+
+if __name__ == "__main__":
+    elf = ELFFile(open(sys.argv[2], "rb"))
+    with open(sys.argv[1], "r") as f:
+        inp = f.read()
+
+    lines = inp.splitlines()
+    assert int(re.match(r"Perf buf length (\d+)", lines[0]).group(1)) == len(lines) - 1
+    buf = binascii.unhexlify("".join(lines[1:]))
+    collapse(buf, elf)