perf trace: Augment the 'open' syscall 'filename' arg

As described in the previous cset, all we had to do was to touch the
augmented_syscalls.c eBPF program, fire up 'perf trace' with that new
eBPF script in system wide mode and wait for 'open' syscalls, in
addition to 'openat' ones to see that it works:

  # perf trace -e tools/perf/examples/bpf/augmented_syscalls.c
       0.000 StreamT~s #200/16150 openat(dfd: CWD, filename: /home/acme/.mozilla/firefox/fqxhj76d.default/prefs.js, flags: CREAT|EXCL|TRUNC|WRONLY, mode: IRUSR|IWUSR)
       0.065 StreamT~s #200/16150 openat(dfd: CWD, filename: /home/acme/.mozilla/firefox/fqxhj76d.default/prefs-1.js, flags: CREAT|EXCL|TRUNC|WRONLY, mode: IRUSR|IWUSR)
       0.435 StreamT~s #200/16150 openat(dfd: CWD, filename: /home/acme/.mozilla/firefox/fqxhj76d.default/prefs-1.js, flags: CREAT|TRUNC|WRONLY, mode: IRUSR|IWUSR)
       1.875 perf/16772 openat(dfd: CWD, filename: /sys/kernel/debug/tracing/events/syscalls/sys_enter_openat/form)
    1227.260 gnome-shell/1463 openat(dfd: CWD, filename: /proc/self/stat)
    1227.397 gnome-shell/2125 openat(dfd: CWD, filename: /proc/self/stat)
    7227.619 gnome-shell/1463 openat(dfd: CWD, filename: /proc/self/stat)
    7227.661 gnome-shell/2125 openat(dfd: CWD, filename: /proc/self/stat)
   10018.079 gnome-shell/1463 openat(dfd: CWD, filename: /proc/self/stat)
   10018.514 perf/16772 openat(dfd: CWD, filename: /proc/1237/status)
   10018.568 perf/16772 openat(dfd: CWD, filename: /proc/1237/status)
   10022.409 gnome-shell/2125 openat(dfd: CWD, filename: /proc/self/stat)
   10090.044 NetworkManager/1237 openat(dfd: CWD, filename: /proc/2125/stat)
   10090.351 NetworkManager/1237 open(filename: /etc/passwd, flags: CLOEXEC)
   10090.407 perf/16772 openat(dfd: CWD, filename: /sys/kernel/debug/tracing/events/syscalls/sys_enter_open/format)
   10091.763 NetworkManager/1237 openat(dfd: CWD, filename: /proc/2125/stat)
   10091.812 NetworkManager/1237 open(filename: /etc/passwd, flags: CLOEXEC)
   10092.807 NetworkManager/1237 openat(dfd: CWD, filename: /proc/2125/stat)
   10092.851 NetworkManager/1237 open(filename: /etc/passwd, flags: CLOEXEC)
   10094.650 NetworkManager/1237 openat(dfd: CWD, filename: /proc/1463/stat)
   10094.926 NetworkManager/1237 open(filename: /etc/passwd, flags: CLOEXEC)
   10096.010 NetworkManager/1237 openat(dfd: CWD, filename: /proc/1463/stat)
   10096.057 NetworkManager/1237 open(filename: /etc/passwd, flags: CLOEXEC)
   10097.056 NetworkManager/1237 openat(dfd: CWD, filename: /proc/1463/stat)
   10097.099 NetworkManager/1237 open(filename: /etc/passwd, flags: CLOEXEC)
   13228.345 gnome-shell/1463 openat(dfd: CWD, filename: /proc/self/stat)
   13232.734 gnome-shell/2125 openat(dfd: CWD, filename: /proc/self/stat)
   15198.956 lighttpd/16748 open(filename: /proc/loadavg, mode: ISGID|IXOTH)
  ^C#

It even catches 'perf' itself looking at the sys_enter_open and
sys_enter_openat tracefs format dictionaries when it first finds them in
the trace... :-)

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-upmogc57uatljr6el6u8537l@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/examples/bpf/augmented_syscalls.c

@@ -61,4 +61,31 @@ int syscall_enter(openat)(struct syscall_enter_openat_args *args)
 	return 0;
 }
 
+struct syscall_enter_open_args {
+	unsigned long long common_tp_fields;
+	long		   syscall_nr;
+	char		   *filename_ptr;
+	long		   flags;
+	long		   mode;
+};
+
+struct augmented_enter_open_args {
+	struct syscall_enter_open_args args;
+	struct augmented_filename      filename;
+};
+
+int syscall_enter(open)(struct syscall_enter_open_args *args)
+{
+	struct augmented_enter_open_args augmented_args = { .filename.reserved = 0, };
+
+	probe_read(&augmented_args.args, sizeof(augmented_args.args), args);
+	augmented_args.filename.size = probe_read_str(&augmented_args.filename.value,
+						      sizeof(augmented_args.filename.value),
+						      args->filename_ptr);
+	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU,
+			  &augmented_args,
+			  sizeof(augmented_args) - sizeof(augmented_args.filename.value) + augmented_args.filename.size);
+	return 0;
+}
+
 license(GPL);