stack walking scripts
diff --git a/tools/stacksnoop b/tools/stacksnoop
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+++ b/tools/stacksnoop
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+#!/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
+#
+# The current implementation uses an unrolled loop for x86_64, and was written
+# as a proof of concept. This implementation should be replaced in the future
+# with an appropriate bpf_ call, when available.
+#
+# The stack depth is limited to 10 (+1 for the current instruction pointer).
+# This could be tunable in a future version.
+#
+# 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
+
+# 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>
+
+static int print_frame(u64 *bp, int *depth) {
+ if (*bp) {
+ // The following stack walker is x86_64 specific
+ u64 ret = 0;
+ if (bpf_probe_read(&ret, sizeof(ret), (void *)(*bp+8)))
+ return 0;
+ if (!ret || ret < __START_KERNEL_map)
+ return 0;
+ bpf_trace_printk("r%d: %llx\\n", *depth, ret);
+ if (bpf_probe_read(bp, sizeof(*bp), (void *)*bp))
+ return 0;
+ *depth += 1;
+ return 1;
+ }
+ return 0;
+}
+
+void trace_stack(struct pt_regs *ctx) {
+ FILTER
+ u64 bp = 0;
+ int depth = 0;
+
+ bpf_trace_printk("\\n");
+ if (ctx->ip)
+ bpf_trace_printk("ip: %llx\\n", ctx->ip);
+ bp = ctx->bp;
+
+ // unrolled loop, 10 frames deep:
+ if (!print_frame(&bp, &depth)) return;
+ if (!print_frame(&bp, &depth)) return;
+ if (!print_frame(&bp, &depth)) return;
+ if (!print_frame(&bp, &depth)) return;
+ if (!print_frame(&bp, &depth)) return;
+ if (!print_frame(&bp, &depth)) return;
+ if (!print_frame(&bp, &depth)) return;
+ if (!print_frame(&bp, &depth)) return;
+ if (!print_frame(&bp, &depth)) return;
+ if (!print_frame(&bp, &depth)) return;
+};
+"""
+if args.pid:
+ bpf_text = bpf_text.replace('FILTER',
+ ('u32 pid; pid = bpf_get_current_pid_tgid(); ' +
+ 'if (pid != %s) { return 0; }') % (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")
+matched = b.num_open_kprobes()
+if matched == 0:
+ print("Function \"%s\" not found. Exiting." % function)
+ exit()
+
+# header
+if verbose:
+ print("%-18s %-12s %-6s %-3s %s" % ("TIME(s)", "COMM", "PID", "CPU",
+ "STACK"))
+else:
+ print("%-18s %s" % ("TIME(s)", "STACK"))
+
+# format output
+while 1:
+ (task, pid, cpu, flags, ts, msg) = b.trace_fields()
+ if msg != "":
+ (reg, addr) = msg.split(" ")
+ if offset:
+ ip = b.ksymaddr(int(addr, 16))
+ else:
+ ip = b.ksym(int(addr, 16))
+ msg = msg + " " + ip
+ if verbose:
+ print("%-18.9f %-12.12s %-6d %-3d %s" % (ts, task, pid, cpu, msg))
+ else:
+ print("%-18.9f %s" % (ts, msg))