migrated statsnoop to use bpf_perf_event_output

man/man8/statsnoop.8

@@ -12,6 +12,10 @@ applications that are failing, especially on startup.
 This works by tracing various kernel sys_stat() functions using dynamic
 tracing, and will need updating to match any changes to these functions.
 
+This makes use of a Linux 4.5 feature (bpf_perf_event_output());
+for kernels older than 4.5, see the version under tools/old,
+which uses an older mechanism.
+
 Since this uses BPF, only the root user can use this tool.
 .SH REQUIREMENTS
 CONFIG_BPF and bcc.

tools/old/statsnoop.py

+#!/usr/bin/python
+# @lint-avoid-python-3-compatibility-imports
+#
+# statsnoop Trace stat() syscalls.
+#           For Linux, uses BCC, eBPF. Embedded C.
+#
+# USAGE: statsnoop [-h] [-t] [-x] [-p PID]
+#
+# Copyright 2016 Netflix, Inc.
+# Licensed under the Apache License, Version 2.0 (the "License")
+#
+# 08-Feb-2016   Brendan Gregg   Created this.
+
+from __future__ import print_function
+from bcc import BPF
+import argparse
+
+# arguments
+examples = """examples:
+    ./statsnoop           # trace all stat() syscalls
+    ./statsnoop -t        # include timestamps
+    ./statsnoop -x        # only show failed stats
+    ./statsnoop -p 181    # only trace PID 181
+"""
+parser = argparse.ArgumentParser(
+    description="Trace stat() syscalls",
+    formatter_class=argparse.RawDescriptionHelpFormatter,
+    epilog=examples)
+parser.add_argument("-t", "--timestamp", action="store_true",
+    help="include timestamp on output")
+parser.add_argument("-x", "--failed", action="store_true",
+    help="only show failed stats")
+parser.add_argument("-p", "--pid",
+    help="trace this PID only")
+args = parser.parse_args()
+debug = 0
+
+# define BPF program
+bpf_text = """
+#include <uapi/linux/ptrace.h>
+
+BPF_HASH(args_filename, u32, const char *);
+
+int trace_entry(struct pt_regs *ctx, const char __user *filename)
+{
+    u32 pid = bpf_get_current_pid_tgid();
+
+    FILTER
+    args_filename.update(&pid, &filename);
+
+    return 0;
+};
+
+int trace_return(struct pt_regs *ctx)
+{
+    const char **filenamep;
+    int ret = ctx->ax;
+    u32 pid = bpf_get_current_pid_tgid();
+
+    filenamep = args_filename.lookup(&pid);
+    if (filenamep == 0) {
+        // missed entry
+        return 0;
+    }
+
+    bpf_trace_printk("%d %s\\n", ret, *filenamep);
+    args_filename.delete(&pid);
+
+    return 0;
+}
+"""
+if args.pid:
+    bpf_text = bpf_text.replace('FILTER',
+        '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="sys_stat", fn_name="trace_entry")
+b.attach_kprobe(event="sys_statfs", fn_name="trace_entry")
+b.attach_kprobe(event="sys_newstat", fn_name="trace_entry")
+b.attach_kretprobe(event="sys_stat", fn_name="trace_return")
+b.attach_kretprobe(event="sys_statfs", fn_name="trace_return")
+b.attach_kretprobe(event="sys_newstat", fn_name="trace_return")
+
+# header
+if args.timestamp:
+    print("%-14s" % ("TIME(s)"), end="")
+print("%-6s %-16s %4s %3s %s" % ("PID", "COMM", "FD", "ERR", "PATH"))
+
+start_ts = 0
+
+# format output
+while 1:
+    (task, pid, cpu, flags, ts, msg) = b.trace_fields()
+    (ret_s, filename) = msg.split(" ", 1)
+
+    ret = int(ret_s)
+    if (args.failed and (ret >= 0)):
+        continue
+
+    # split return value into FD and errno columns
+    if ret >= 0:
+        fd_s = ret
+        err = 0
+    else:
+        fd_s = "-1"
+        err = - ret
+
+    # print columns
+    if args.timestamp:
+        if start_ts == 0:
+            start_ts = ts
+        print("%-14.9f" % (ts - start_ts), end="")
+    print("%-6d %-16s %4s %3s %s" % (pid, task, fd_s, err, filename))

tools/statsnoop.py

@@ -10,10 +10,12 @@
 # Licensed under the Apache License, Version 2.0 (the "License")
 #
 # 08-Feb-2016   Brendan Gregg   Created this.
+# 17-Feb-2016   Allan McAleavy updated for BPF_PERF_OUTPUT
 
 from __future__ import print_function
 from bcc import BPF
 import argparse
+import ctypes as ct
 
 # arguments
 examples = """examples:
@@ -38,32 +40,67 @@ debug = 0
 # define BPF program
 bpf_text = """
 #include <uapi/linux/ptrace.h>
+#include <uapi/linux/limits.h>
+#include <linux/sched.h>
+
+struct val_t {
+    u32 pid;
+    u64 ts;
+    char comm[TASK_COMM_LEN];
+    const char *fname;
+};
+
+struct data_t {
+    u32 pid;
+    u64 ts;
+    u64 delta;
+    int ret;
+    char comm[TASK_COMM_LEN];
+    char fname[NAME_MAX];
+};
 
 BPF_HASH(args_filename, u32, const char *);
+BPF_HASH(infotmp, u32,struct val_t);
+BPF_PERF_OUTPUT(events);
 
 int trace_entry(struct pt_regs *ctx, const char __user *filename)
 {
+    struct val_t val = {};
     u32 pid = bpf_get_current_pid_tgid();
 
     FILTER
-    args_filename.update(&pid, &filename);
+    if (bpf_get_current_comm(&val.comm, sizeof(val.comm)) == 0) {
+        val.pid = bpf_get_current_pid_tgid();
+        val.ts = bpf_ktime_get_ns();
+        val.fname = filename;
+        infotmp.update(&pid, &val);
+    }
 
     return 0;
 };
 
 int trace_return(struct pt_regs *ctx)
 {
-    const char **filenamep;
-    int ret = ctx->ax;
     u32 pid = bpf_get_current_pid_tgid();
+    struct val_t *valp;
+    struct data_t data = {};
+
+    u64 tsp = bpf_ktime_get_ns();
 
-    filenamep = args_filename.lookup(&pid);
-    if (filenamep == 0) {
+    valp = infotmp.lookup(&pid);
+    if (valp == 0) {
         // missed entry
         return 0;
     }
-
-    bpf_trace_printk("%d %s\\n", ret, *filenamep);
+    bpf_probe_read(&data.comm,sizeof(data.comm), valp->comm);
+    bpf_probe_read(&data.fname,sizeof(data.fname),(void *)valp->fname);
+    data.pid = valp->pid;
+    data.delta = tsp - valp->ts;
+    data.ts = tsp /1000;
+    data.ret = ctx->ax;
+
+    events.perf_submit(ctx,&data,sizeof(data));
+    infotmp.delete(&pid);
     args_filename.delete(&pid);
 
     return 0;
@@ -86,33 +123,65 @@ b.attach_kretprobe(event="sys_stat", fn_name="trace_return")
 b.attach_kretprobe(event="sys_statfs", fn_name="trace_return")
 b.attach_kretprobe(event="sys_newstat", fn_name="trace_return")
 
+TASK_COMM_LEN = 16    # linux/sched.h
+NAME_MAX = 255        # linux/limits.h
+
+class Data(ct.Structure):
+    _fields_ = [
+        ("pid", ct.c_ulonglong),
+        ("ts", ct.c_ulonglong),
+        ("delta", ct.c_ulonglong),
+        ("ret", ct.c_int),
+        ("comm", ct.c_char * TASK_COMM_LEN),
+        ("fname", ct.c_char * NAME_MAX)
+    ]
+
+start_ts = 0
+prev_ts = 0
+delta = 0
+
 # header
 if args.timestamp:
     print("%-14s" % ("TIME(s)"), end="")
 print("%-6s %-16s %4s %3s %s" % ("PID", "COMM", "FD", "ERR", "PATH"))
 
-start_ts = 0
-
-# format output
-while 1:
-    (task, pid, cpu, flags, ts, msg) = b.trace_fields()
-    (ret_s, filename) = msg.split(" ", 1)
-
-    ret = int(ret_s)
-    if (args.failed and (ret >= 0)):
-        continue
+# process event
+def print_event(cpu, data, size):
+    event = ct.cast(data, ct.POINTER(Data)).contents
+    global start_ts
+    global prev_ts
+    global delta
+    global cont
 
     # split return value into FD and errno columns
-    if ret >= 0:
-        fd_s = ret
+    if event.ret >= 0:
+        fd_s = event.ret
         err = 0
     else:
-        fd_s = "-1"
-        err = - ret
+        fd_s = -1
+        err = - event.ret
+
+    if start_ts == 0:
+        prev_ts = start_ts
+
+    if start_ts == 1:
+        delta = float(delta) + (event.ts - prev_ts)
+
+    if (args.failed and (event.ret >= 0)):
+        start_ts = 1
+        prev_ts = event.ts
+        return
 
-    # print columns
     if args.timestamp:
-        if start_ts == 0:
-            start_ts = ts
-        print("%-14.9f" % (ts - start_ts), end="")
-    print("%-6d %-16s %4s %3s %s" % (pid, task, fd_s, err, filename))
+        print("%-14.9f" % (delta / 1000000), end="")
+
+    print("%-6d %-16s %4d %3d %s" % (event.pid, event.comm,
+        fd_s, err, event.fname))
+
+    prev_ts = event.ts
+    start_ts = 1
+
+# loop with callback to print_event
+b["events"].open_perf_buffer(print_event)
+while 1:
+    b.kprobe_poll()