[PATCH v1 32/58] perf arm-cs-trace-disasm: Port arm-cs-trace-disasm to use python module

Ian Rogers
2026-04-20T00:00:35Z

Add a port of the arm-cs-trace-disasm script that uses the perf python
module directly. This approach is significantly faster than using perf
script callbacks as it avoids creating intermediate dictionaries for
all event fields. Update the testing to use the ported script.

Assisted-by: Gemini:gemini-3.1-pro-preview
Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/python/arm-cs-trace-disasm.py | 333 ++++++++++++++++++
.../tests/shell/test_arm_coresight_disasm.sh | 10 +-
2 files changed, 339 insertions(+), 4 deletions(-)
create mode 100755 tools/perf/python/arm-cs-trace-disasm.py

diff --git a/tools/perf/python/arm-cs-trace-disasm.py b/tools/perf/python/arm-cs-trace-disasm.py
new file mode 100755
index 000000000000..3557a02b03fb
--- /dev/null
+++ b/tools/perf/python/arm-cs-trace-disasm.py
@@ -0,0 +1,333 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+"""
+arm-cs-trace-disasm.py: ARM CoreSight Trace Dump With Disassember using perf python module
+"""
+
+import os
+from os import path
+import re
+from subprocess import check_output
+import argparse
+import platform
+import sys
+from typing import Dict, List, Optional
+
+# Initialize global dicts and regular expression
+DISASM_CACHE: Dict[str, List[str]] = {}
+CPU_DATA: Dict[str, int] = {}
+DISASM_RE = re.compile(r"^\s*([0-9a-fA-F]+):")
+DISASM_FUNC_RE = re.compile(r"^\s*([0-9a-fA-F]+)\s.*:")
+CACHE_SIZE = 64*1024
+SAMPLE_IDX = -1
+
+GLB_SOURCE_FILE_NAME: Optional[str] = None
+GLB_LINE_NUMBER: Optional[int] = None
+GLB_DSO: Optional[str] = None
+
+KVER = platform.release()
+VMLINUX_PATHS = [
+ f"/usr/lib/debug/boot/vmlinux-{KVER}.debug",
+ f"/usr/lib/debug/lib/modules/{KVER}/vmlinux",
+ f"/lib/modules/{KVER}/build/vmlinux",
+ f"/usr/lib/debug/boot/vmlinux-{KVER}",
+ f"/boot/vmlinux-{KVER}",
+ "/boot/vmlinux",
+ "vmlinux"
+]
+
+def default_objdump() -> str:
+ """Return the default objdump path from perf config or 'objdump'."""
+ try:
+ config = perf.config_get("annotate.objdump")
+ return str(config) if config else "objdump"
+ except (AttributeError, TypeError):
+ return "objdump"
+
+def find_vmlinux() -> Optional[str]:
+ """Find the vmlinux file in standard paths."""
+ if hasattr(find_vmlinux, "path"):
+ return getattr(find_vmlinux, "path")
+
+ for v in VMLINUX_PATHS:
+ if os.access(v, os.R_OK):
+ setattr(find_vmlinux, "path", v)
+ return v
+ setattr(find_vmlinux, "path", None)
+ return None
+
+def get_dso_file_path(dso_name: str, dso_build_id: str, vmlinux: Optional[str]) -> str:
+ """Return the path to the DSO file."""
+ if dso_name in ("[kernel.kallsyms]", "vmlinux"):
+ if vmlinux:
+ return vmlinux
+ return find_vmlinux() or dso_name
+
+ if dso_name == "[vdso]":
+ append = "/vdso"
+ else:
+ append = "/elf"
+
+ buildid_dir = os.environ.get('PERF_BUILDID_DIR')
+ if not buildid_dir:
+ buildid_dir = os.path.join(os.environ.get('HOME', ''), '.debug')
+
+ dso_path = buildid_dir + "/" + dso_name + "/" + dso_build_id + append
+ # Replace duplicate slash chars to single slash char
+ dso_path = dso_path.replace('//', '/', 1)
+ return dso_path
+
+def read_disam(dso_fname: str, dso_start: int, start_addr: int,
+ stop_addr: int, objdump: str) -> List[str]:
+ """Read disassembly from a DSO file using objdump."""
+ addr_range = f"{start_addr}:{stop_addr}:{dso_fname}"
+
+ # Don't let the cache get too big, clear it when it hits max size
+ if len(DISASM_CACHE) > CACHE_SIZE:
+ DISASM_CACHE.clear()
+
+ if addr_range in DISASM_CACHE:
+ disasm_output = DISASM_CACHE[addr_range]
+ else:
+ start_addr = start_addr - dso_start
+ stop_addr = stop_addr - dso_start
+ disasm = [objdump, "-d", "-z",
+ f"--start-address={start_addr:#x}",
+ f"--stop-address={stop_addr:#x}"]
+ disasm += [dso_fname]
+ disasm_output = check_output(disasm).decode('utf-8').split('\n')
+ DISASM_CACHE[addr_range] = disasm_output
+
+ return disasm_output
+
+def print_disam(dso_fname: str, dso_start: int, start_addr: int,
+ stop_addr: int, objdump: str) -> None:
+ """Print disassembly for a given address range."""
+ for line in read_disam(dso_fname, dso_start, start_addr, stop_addr, objdump):
+ m = DISASM_FUNC_RE.search(line)
+ if m is None:
+ m = DISASM_RE.search(line)
+ if m is None:
+ continue
+ print(f"\t{line}")
+
+def print_sample(sample: perf.sample_event) -> None:
+ """Print sample details."""
+ print(f"Sample = {{ cpu: {sample.sample_cpu:04d} addr: {sample.sample_addr:016x} "
+ f"phys_addr: {sample.sample_phys_addr:016x} ip: {sample.sample_ip:016x} "
+ f"pid: {sample.sample_pid} tid: {sample.sample_tid} period: {sample.sample_period} "
+ f"time: {sample.sample_time} index: {SAMPLE_IDX}}}")
+
+def common_start_str(comm: str, sample: perf.sample_event) -> str:
+ """Return common start string for sample output."""
+ sec = int(sample.sample_time / 1000000000)
+ ns = sample.sample_time % 1000000000
+ cpu = sample.sample_cpu
+ pid = sample.sample_pid
+ tid = sample.sample_tid
+ return f"{comm:>16s} {pid:5u}/{tid:<5u} [{cpu:04d}] {sec:9d}.{ns:09d} "
+
+def print_srccode(comm: str, sample: perf.sample_event, symbol: str, dso: str) -> None:
+ """Print source code and symbols for a sample."""
+ ip = sample.sample_ip
+ if symbol == "[unknown]":
+ start_str = common_start_str(comm, sample) + f"{ip:x}".rjust(16).ljust(40)
+ else:
+ symoff = 0
+ sym_start = sample.sym_start
+ if sym_start is not None:
+ symoff = ip - sym_start
+ offs = f"+{symoff:#x}" if symoff != 0 else ""
+ start_str = common_start_str(comm, sample) + (symbol + offs).ljust(40)
+
+ global GLB_SOURCE_FILE_NAME, GLB_LINE_NUMBER, GLB_DSO
+
+ source_file_name, line_number, source_line, _ = sample.srccode()
+ if source_file_name:
+ if GLB_LINE_NUMBER == line_number and GLB_SOURCE_FILE_NAME == source_file_name:
+ src_str = ""
+ else:
+ if len(source_file_name) > 40:
+ src_file = f"...{source_file_name[-37:]} "
+ else:
+ src_file = source_file_name.ljust(41)
+
+ if source_line is None:
+ src_str = f"{src_file}{line_number:>4d} "
+ else:
+ src_str = f"{src_file}{line_number:>4d} {source_line}"
+ GLB_DSO = None
+ elif dso == GLB_DSO:
+ src_str = ""
+ else:
+ src_str = dso
+ GLB_DSO = dso
+
+ GLB_LINE_NUMBER = line_number
+ GLB_SOURCE_FILE_NAME = source_file_name
+
+ print(start_str, src_str)
+
+class TraceDisasm:
+ """Class to handle trace disassembly."""
+ def __init__(self, cli_options: argparse.Namespace):
+ self.options = cli_options
+ self.sample_idx = -1
+ self.session: Optional[perf.session] = None
+
+ def process_event(self, sample: perf.sample_event) -> None:
+ """Process a single perf event."""
+ self.sample_idx += 1
+ global SAMPLE_IDX
+ SAMPLE_IDX = self.sample_idx
+
+ if self.options.start_time and sample.sample_time < self.options.start_time:
+ return
+ if self.options.stop_time and sample.sample_time > self.options.stop_time:
+ return
+ if self.options.start_sample and self.sample_idx < self.options.start_sample:
+ return
+ if self.options.stop_sample and self.sample_idx > self.options.stop_sample:
+ return
+
+ ev_name = str(sample.evsel)
+ if self.options.verbose:
+ print(f"Event type: {ev_name}")
+ print_sample(sample)
+
+ dso = sample.dso or '[unknown]'
+ symbol = sample.symbol or '[unknown]'
+ dso_bid = sample.dso_bid or '[unknown]'
+ dso_start = sample.map_start
+ dso_end = sample.map_end
+ map_pgoff = sample.map_pgoff or 0
+
+ try:
+ thread_info = self.session.process(sample.sample_tid)
+ comm = thread_info.comm()
+ except Exception:
+ comm = "[unknown]"
+
+ cpu = sample.sample_cpu
+ addr = sample.sample_addr
+
+ if CPU_DATA.get(str(cpu) + 'addr') is None:
+ CPU_DATA[str(cpu) + 'addr'] = addr
+ return
+
+ if dso == '[unknown]':
+ return
+
+ if dso_start is None or dso_end is None:
+ print(f"Failed to find valid dso map for dso {dso}")
+ return
+
+ if ev_name.startswith("instructions"):
+ print_srccode(comm, sample, symbol, dso)
+ return
+
+ if not ev_name.startswith("branches"):
+ return
+
+ self._process_branch(sample, comm, symbol, dso, dso_bid, dso_start, dso_end, map_pgoff)
+
+ def _process_branch(self, sample: perf.sample_event, comm: str, symbol: str, dso: str,
+ dso_bid: str, dso_start: int, dso_end: int, map_pgoff: int) -> None:
+ """Helper to process branch events."""
+ cpu = sample.sample_cpu
+ ip = sample.sample_ip
+ addr = sample.sample_addr
+
+ start_addr = CPU_DATA[str(cpu) + 'addr']
+ stop_addr = ip + 4
+
+ # Record for previous sample packet
+ CPU_DATA[str(cpu) + 'addr'] = addr
+
+ # Filter out zero start_address. Optionally identify CS_ETM_TRACE_ON packet
+ if start_addr == 0:
+ if stop_addr == 4 and self.options.verbose:
+ print(f"CPU{cpu}: CS_ETM_TRACE_ON packet is inserted")
+ return
+
+ if start_addr < dso_start or start_addr > dso_end:
+ print(f"Start address {start_addr:#x} is out of range [ {dso_start:#x} .. "
+ f"{dso_end:#x} ] for dso {dso}")
+ return
+
+ if stop_addr < dso_start or stop_addr > dso_end:
+ print(f"Stop address {stop_addr:#x} is out of range [ {dso_start:#x} .. "
+ f"{dso_end:#x} ] for dso {dso}")
+ return
+
+ if self.options.objdump is not None:
+ if dso == "[kernel.kallsyms]" or dso_start == 0x400000:
+ dso_vm_start = 0
+ map_pgoff_local = 0
+ else:
+ dso_vm_start = dso_start
+ map_pgoff_local = map_pgoff
+
+ dso_fname = get_dso_file_path(dso, dso_bid, self.options.vmlinux)
+ if path.exists(dso_fname):
+ print_disam(dso_fname, dso_vm_start, start_addr + map_pgoff_local,
+ stop_addr + map_pgoff_local, self.options.objdump)
+ else:
+ print(f"Failed to find dso {dso} for address range [ "
+ f"{start_addr + map_pgoff_local:#x} .. {stop_addr + map_pgoff_local:#x} ]")
+
+ print_srccode(comm, sample, symbol, dso)
+
+ def run(self) -> None:
+ """Run the trace disassembly session."""
+ input_file = self.options.input or "perf.data"
+ if not os.path.exists(input_file):
+ print(f"Error: {input_file} not found.", file=sys.stderr)
+ sys.exit(1)
+
+ print('ARM CoreSight Trace Data Assembler Dump')
+ try:
+ self.session = perf.session(perf.data(input_file), sample=self.process_event)
+ except Exception as e:
+ print(f"Error opening session: {e}", file=sys.stderr)
+ sys.exit(1)
+
+ self.session.process_events()
+ print('End')
+
+if __name__ == "__main__":
+ def int_arg(v: str) -> int:
+ """Helper for integer command line arguments."""
+ val = int(v)
+ if val < 0:
+ raise argparse.ArgumentTypeError("Argument must be a positive integer")
+ return val
+
+ arg_parser = argparse.ArgumentParser(description="ARM CoreSight Trace Dump With Disassembler")
+ arg_parser.add_argument("-i", "--input", help="input perf.data file")
+ arg_parser.add_argument("-k", "--vmlinux",
+ help="Set path to vmlinux file. Omit to autodetect")
+ arg_parser.add_argument("-d", "--objdump", nargs="?", const=default_objdump(),
+ help="Show disassembly. Can also be used to change the objdump path")
+ arg_parser.add_argument("-v", "--verbose", action="store_true", help="Enable debugging log")
+ arg_parser.add_argument("--start-time", type=int_arg,
+ help="Monotonic clock time of sample to start from.")
+ arg_parser.add_argument("--stop-time", type=int_arg,
+ help="Monotonic clock time of sample to stop at.")
+ arg_parser.add_argument("--start-sample", type=int_arg,
+ help="Index of sample to start from.")
+ arg_parser.add_argument("--stop-sample", type=int_arg,
+ help="Index of sample to stop at.")
+
+ parsed_options = arg_parser.parse_args()
+ if (parsed_options.start_time and parsed_options.stop_time and \
+ parsed_options.start_time >= parsed_options.stop_time):
+ print("--start-time must less than --stop-time")
+ sys.exit(2)
+ if (parsed_options.start_sample and parsed_options.stop_sample and \
+ parsed_options.start_sample >= parsed_options.stop_sample):
+ print("--start-sample must less than --stop-sample")
+ sys.exit(2)
+
+ td = TraceDisasm(parsed_options)
+ td.run()
diff --git a/tools/perf/tests/shell/test_arm_coresight_disasm.sh b/tools/perf/tests/shell/test_arm_coresight_disasm.sh
index 0dfb4fadf531..9749501cbf78 100755
--- a/tools/perf/tests/shell/test_arm_coresight_disasm.sh
+++ b/tools/perf/tests/shell/test_arm_coresight_disasm.sh
@@ -45,8 +45,9 @@ branch_search="\sbl${sep}b${sep}b.ne${sep}b.eq${sep}cbz\s"
if [ -e /proc/kcore ]; then
echo "Testing kernel disassembly"
perf record -o ${perfdata} -e cs_etm//k --kcore -- touch $file > /dev/null 2>&1
- perf script -i ${perfdata} -s python:${script_path} -- \
- -d --stop-sample=30 2> /dev/null > ${file}
+ # shellcheck source=lib/setup_python.sh
+ . "$(dirname "$0")"/lib/setup_python.sh
+ $PYTHON ${script_path} -i ${perfdata} -d --stop-sample=30 2> /dev/null > ${file}
grep -q -e ${branch_search} ${file}
echo "Found kernel branches"
else
@@ -57,8 +58,9 @@ fi
## Test user ##
echo "Testing userspace disassembly"
perf record -o ${perfdata} -e cs_etm//u -- touch $file > /dev/null 2>&1
-perf script -i ${perfdata} -s python:${script_path} -- \
- -d --stop-sample=30 2> /dev/null > ${file}
+# shellcheck source=lib/setup_python.sh
+. "$(dirname "$0")"/lib/setup_python.sh
+$PYTHON ${script_path} -i ${perfdata} -d --stop-sample=30 2> /dev/null > ${file}
grep -q -e ${branch_search} ${file}
echo "Found userspace branches"

--
2.54.0.rc1.513.gad8abe7a5a-goog