#!/usr/bin/env bpftrace
// statsnoop	Trace stat() syscalls.
// 		For Linux, uses bpftrace and eBPF.
//
// This traces the tracepoints for statfs(), statx(), newstat(), and
// newlstat(). These aren't the only the stat syscalls: if you are missing
// activity, you may need to add more variants.
//
// Example of usage:
//
// # ./statsnoop.bt
// Attaching 9 probes...
// Tracing stat syscalls... Hit Ctrl-C to end.
// PID    COMM             ERR PATH
// 27835  bash               0 .
// 27835  bash               2 /usr/local/sbin/iconfig
// 27835  bash               2 /usr/local/bin/iconfig
// 27835  bash               2 /usr/sbin/iconfig
// 27835  bash               2 /usr/bin/iconfig
// 27835  bash               2 /sbin/iconfig
// 27835  bash               2 /bin/iconfig
// 27835  bash               2 /usr/games/iconfig
// 27835  bash               2 /usr/local/games/iconfig
// 27835  bash               2 /snap/bin/iconfig
// 27835  bash               2 /apps/python/bin/iconfig
// 30573  command-not-fou    2 /usr/bin/Modules/Setup
// 30573  command-not-fou    2 /usr/bin/lib/python3.5/os.py
// 30573  command-not-fou    2 /usr/bin/lib/python3.5/os.pyc
// 30573  command-not-fou    0 /usr/lib/python3.5/os.py
// 30573  command-not-fou    2 /usr/bin/pybuilddir.txt
// 30573  command-not-fou    2 /usr/bin/lib/python3.5/lib-dynload
// 30573  command-not-fou    0 /usr/lib/python3.5/lib-dynload
// 30573  command-not-fou    2 /usr/lib/python35.zip
// 30573  command-not-fou    0 /usr/lib
// 30573  command-not-fou    2 /usr/lib/python35.zip
// 30573  command-not-fou    0 /usr/lib/python3.5/
// 30573  command-not-fou    0 /usr/lib/python3.5/
// 30573  command-not-fou    0 /usr/lib/python3.5/
// 30573  command-not-fou    2 /usr/lib/python3.5/encodings/__init__.cpython-35m-x86_64-linux-
// 30573  command-not-fou    2 /usr/lib/python3.5/encodings/__init__.abi3.so
// 30573  command-not-fou    2 /usr/lib/python3.5/encodings/__init__.so
// 30573  command-not-fou    0 /usr/lib/python3.5/encodings/__init__.py
// 30573  command-not-fou    0 /usr/lib/python3.5/encodings/__init__.py
//
// This output has caught me mistyping a command in another shell, "iconfig"
// instead of "ifconfig". The first several lines show the bash shell searching
// the $PATH (why is games in my $PATH??), and failing to find it (ERR == 2 is
// file not found). Then, a "command-not-found" program executes (the name is
// truncated to 16 characters in the COMM field, including the NULL), which
// begins the process of searching for and suggesting a package. ie, this:
//
// # iconfig
// The program 'iconfig' is currently not installed. You can install it by typing:
// apt install ipmiutil
//
// statsnoop can be used for general debugging, to see what file information has
// been requested, and whether those files exist. It can be used as a companion
// to opensnoop, which shows what files were actually opened.
//
// This is a bpftrace version of the bcc tool of the same name.
// The bcc version provides options to customize the output.
//
// Copyright 2018 Netflix, Inc.
//
// 08-Sep-2018	Brendan Gregg	Created this.

config = {
  missing_probes = warn;
}

BEGIN
{
  printf("Tracing stat syscalls... Hit Ctrl-C to end.\n");
  printf("%-6s %-16s %3s %s\n", "PID", "COMM", "ERR", "PATH");
}

tracepoint:syscalls:sys_enter_statfs
{
  @filename[tid] = args.pathname;
}

tracepoint:syscalls:sys_enter_statx,
tracepoint:syscalls:sys_enter_newstat,
tracepoint:syscalls:sys_enter_newlstat
{
  @filename[tid] = args.filename;
}

tracepoint:syscalls:sys_exit_statfs,
tracepoint:syscalls:sys_exit_statx,
tracepoint:syscalls:sys_exit_newstat,
tracepoint:syscalls:sys_exit_newlstat
/@filename[tid]/
{
  $ret = args.ret;
  $errno = ($ret >= 0) ? 0 : (-$ret);

  printf("%-6d %-16s %3d %s\n", pid, comm, $errno, str(@filename[tid]));
  delete(@filename, tid);
}

END
{
  clear(@filename);
}