| #!/usr/bin/python |
| # |
| # stacksnoop Trace a kernel function and print all kernel stack traces. |
| # For Linux, uses BCC, eBPF, and currently x86_64 only. Inline C. |
| # |
| # USAGE: stacksnoop [-h] [-p PID] [-s] [-v] function |
| # |
| # Copyright 2016 Netflix, Inc. |
| # Licensed under the Apache License, Version 2.0 (the "License") |
| # |
| # 12-Jan-2016 Brendan Gregg Created this. |
| |
| from __future__ import print_function |
| from bcc import BPF |
| import argparse |
| import ctypes as ct |
| import time |
| |
| # arguments |
| examples = """examples: |
| ./stacksnoop ext4_sync_fs # print kernel stack traces for ext4_sync_fs |
| ./stacksnoop -s ext4_sync_fs # ... also show symbol offsets |
| ./stacksnoop -v ext4_sync_fs # ... show extra columns |
| ./stacksnoop -p 185 ext4_sync_fs # ... only when PID 185 is on-CPU |
| """ |
| parser = argparse.ArgumentParser( |
| description="Trace and print kernel stack traces for a kernel function", |
| formatter_class=argparse.RawDescriptionHelpFormatter, |
| epilog=examples) |
| parser.add_argument("-p", "--pid", |
| help="trace this PID only") |
| parser.add_argument("-s", "--offset", action="store_true", |
| help="show address offsets") |
| parser.add_argument("-v", "--verbose", action="store_true", |
| help="print more fields") |
| parser.add_argument("function", |
| help="kernel function name") |
| args = parser.parse_args() |
| function = args.function |
| offset = args.offset |
| verbose = args.verbose |
| debug = 0 |
| |
| # define BPF program |
| bpf_text = """ |
| #include <uapi/linux/ptrace.h> |
| #include <linux/sched.h> |
| |
| struct data_t { |
| u64 stack_id; |
| u32 pid; |
| char comm[TASK_COMM_LEN]; |
| }; |
| |
| BPF_STACK_TRACE(stack_traces, 128); |
| BPF_PERF_OUTPUT(events); |
| |
| void trace_stack(struct pt_regs *ctx) { |
| u32 pid = bpf_get_current_pid_tgid(); |
| FILTER |
| struct data_t data = {}; |
| data.stack_id = stack_traces.get_stackid(ctx, BPF_F_REUSE_STACKID), |
| data.pid = pid; |
| bpf_get_current_comm(&data.comm, sizeof(data.comm)); |
| events.perf_submit(ctx, &data, sizeof(data)); |
| } |
| """ |
| if args.pid: |
| bpf_text = bpf_text.replace('FILTER', |
| 'if (pid != %s) { return; }' % args.pid) |
| else: |
| bpf_text = bpf_text.replace('FILTER', '') |
| if debug: |
| print(bpf_text) |
| |
| # initialize BPF |
| b = BPF(text=bpf_text) |
| b.attach_kprobe(event=function, fn_name="trace_stack") |
| |
| TASK_COMM_LEN = 16 # linux/sched.h |
| |
| class Data(ct.Structure): |
| _fields_ = [ |
| ("stack_id", ct.c_ulonglong), |
| ("pid", ct.c_uint), |
| ("comm", ct.c_char * TASK_COMM_LEN), |
| ] |
| |
| matched = b.num_open_kprobes() |
| if matched == 0: |
| print("Function \"%s\" not found. Exiting." % function) |
| exit() |
| |
| stack_traces = b.get_table("stack_traces") |
| start_ts = time.time() |
| |
| # header |
| if verbose: |
| print("%-18s %-12s %-6s %-3s %s" % |
| ("TIME(s)", "COMM", "PID", "CPU", "FUNCTION")) |
| else: |
| print("%-18s %s" % ("TIME(s)", "FUNCTION")) |
| |
| def print_event(cpu, data, size): |
| event = ct.cast(data, ct.POINTER(Data)).contents |
| |
| ts = time.time() - start_ts |
| |
| if verbose: |
| print("%-18.9f %-12.12s %-6d %-3d %s" % |
| (ts, event.comm.decode(), event.pid, cpu, function)) |
| else: |
| print("%-18.9f %s" % (ts, function)) |
| |
| for addr in stack_traces.walk(event.stack_id): |
| sym = b.ksym(addr, show_offset=offset) |
| print("\t%s" % sym) |
| |
| print() |
| |
| b["events"].open_perf_buffer(print_event) |
| while 1: |
| b.kprobe_poll() |