syscount: Use ausyscalls if available to get syscall list

If ausyscall is installed, it can provide a clean, up-to-date list of
syscall numbers for the current architecture. This is much more useful
than the default hardcoded list for x86-64, which is currently used by
syscount.

Try to run `ausyscall --dump` and parse the output before resorting to
the static list. Tested on FC/Linux 4.9 and produces 327 syscalls.

Resolves #1001.

tools/syscount.py

@@ -13,6 +13,7 @@ from bcc import BPF
 from itertools import izip_longest
 from time import sleep, strftime
 import argparse
+import subprocess
 import sys
 
 #
@@ -343,6 +344,21 @@ syscalls = {
     313: "finit_module",
 }
 
+# Try to use ausyscall if it is available, because it can give us an up-to-date
+# list of syscalls for various architectures, rather than the x86-64 hardcoded
+# list above.
+def parse_syscall(line):
+    parts = line.split()
+    return (int(parts[0]), parts[1].strip())
+
+try:
+    # Skip the first line, which is a header. The rest of the lines are simply
+    # SYSCALL_NUM\tSYSCALL_NAME pairs.
+    out = subprocess.check_output('ausyscall --dump | tail -n +2', shell=True)
+    syscalls = dict(map(parse_syscall, out.strip().split('\n')))
+except Exception as e:
+    pass
+
 parser = argparse.ArgumentParser(
     description="Summarize syscall counts and latencies.")
 parser.add_argument("-p", "--pid", type=int, help="trace only this pid")