Syscall table rework (#245)

* Script for generating syscall tables from Linux src (pulled from kernel.org)

* Add generated syscall table

* Update syscall names to match extracted entries

* Move to new syscall dispatcher

* Add machine def to x86 cpus

scripts/extract_syscalls.py

@@ -0,0 +1,60 @@
+#!/usr/bin/env python
+
+'''
+Generate syscall tables from the Linux source. Used to generate
+manticore/platforms/linux_syscalls.py.
+
+This fetches the tables from kernel.org.
+
+Usage:
+
+    ./extract_syscalls.py [--linux_version linux_version] linux_syscalls.py
+
+'''
+
+import os
+import sys
+import urllib
+import argparse
+
+base_url = 'https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/{}?id=refs/tags/v{}'
+
+arch_tables = {
+    'armv7': 'arch/arm/tools/syscall.tbl',
+    'i386':  'arch/x86/entry/syscalls/syscall_32.tbl',
+    'amd64': 'arch/x86/entry/syscalls/syscall_64.tbl',
+}
+
+
+if __name__=='__main__':
+    parser = argparse.ArgumentParser(description='Generate syscall tables')
+    parser.add_argument('output', help='Python output to generate tables')
+    parser.add_argument('--linux_version', help='Major version of the Linux kernel to use', default='4.11')
+    args = parser.parse_args()
+
+    output = open(args.output, 'w+')
+    output.write('#\n#\n# AUTOGENERATED, DO NOT EDIT\n#\n')
+    output.write('# From version: {}\n#\n\n'.format(args.linux_version))
+
+    for arch, path in arch_tables.items():
+        url = base_url.format(path, args.linux_version)
+        tbl = urllib.urlopen(url)
+
+        if tbl.code // 100 != 2:
+            sys.stderr.write("Failed retrieving table; check version and connection.\n")
+            sys.stderr.write("Url: {}\n".format(url))
+            sys.exit(1)
+
+        output.write('{} = {{\n'.format(arch))
+        for line in tbl.readlines():
+            line = line.strip()
+            if line.startswith('#'):
+                continue
+            columns = line.split()
+            if len(columns) < 4:
+                continue
+            num, abi, name, entry = columns[:4]
+            output.write('    {}: "{}",\n'.format(num, entry))
+        output.write('}\n')
+        
+