Linux: Add tables with system call numbers

The new tables are currently only used for consistency checks
with the installed kernel headers and the architecture-independent
system call names table.  They are based on Linux 5.4.

The goal is to use these architecture-specific tables to ensure
that system call wrappers are available irrespective of the version
of the installed kernel headers.

The tables are formatted in the form of C header files so that they
can be used directly in an #include directive, without external
preprocessing.  (External preprocessing of a plain table file
would introduce cross-subdirectory dependency issues.)  However,
the intent is that they can still be treated as tables and can be
processed by simple tools.

The irregular system call names on 32-bit arm add a complication.
The <fixup-asm-unistd.h> header is introduced to work around that,
and the system calls are listed under regular names in the
<arch-syscall.h> file.

A make target, update-syscalls-list, is added to patch the glibc
sources with data from the current kernel headers.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

sysdeps/unix/sysv/linux/tst-glibcsyscalls.py

@@ -0,0 +1,88 @@
+#!/usr/bin/python3
+# Consistency checks for glibc system call lists.
+# Copyright (C) 2020 Free Software Foundation, Inc.
+# This file is part of the GNU C Library.
+#
+# The GNU C Library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# The GNU C Library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with the GNU C Library; if not, see
+# <http://www.gnu.org/licenses/>.
+
+import argparse
+import sys
+
+import glibcextract
+import glibcsyscalls
+
+def main():
+    """The main entry point."""
+    parser = argparse.ArgumentParser(
+        description="System call list consistency checks")
+    parser.add_argument('--cc', metavar='CC', required=True,
+                        help='C compiler (including options) to use')
+    parser.add_argument('syscall_numbers_list', metavar='PATH',
+                        help='Path to the list of system call numbers')
+    parser.add_argument('syscall_names_list', metavar='PATH',
+                        help='Path to the list of system call names')
+
+    args = parser.parse_args()
+
+    glibc_constants = glibcsyscalls.load_arch_syscall_header(
+        args.syscall_numbers_list)
+    with open(args.syscall_names_list) as inp:
+        glibc_names = glibcsyscalls.SyscallNamesList(inp)
+    kernel_constants = glibcsyscalls.kernel_constants(args.cc)
+    kernel_version = glibcsyscalls.linux_kernel_version(args.cc)
+
+    errors = 0
+    warnings = False
+    for name in glibc_constants.keys() & kernel_constants.keys():
+        if glibc_constants[name] != kernel_constants[name]:
+            print("error: syscall {!r} number mismatch: glibc={!r} kernel={!r}"
+                  .format(name, glibc_constants[name], kernel_constants[name]))
+            errors = 1
+
+    # The architecture-specific list in the glibc tree must be a
+    # subset of the global list of system call names.
+    for name in glibc_constants.keys() - set(glibc_names.syscalls):
+        print("error: architecture syscall {!r} missing from global names list"
+              .format(name))
+        errors = 1
+
+    for name in glibc_constants.keys() - kernel_constants.keys():
+        print("info: glibc syscall {!r} not known to kernel".format(name))
+        warnings = True
+
+    # If the glibc-recorded kernel version is not older than the
+    # installed kernel headers, the glibc system call set must be a
+    # superset of the kernel system call set.
+    if glibc_names.kernel_version >= kernel_version:
+        for name in kernel_constants.keys() - glibc_constants.keys():
+            print("error: kernel syscall {!r} ({}) not known to glibc"
+                  .format(name, kernel_constants[name]))
+            errors = 1
+    else:
+        for name in kernel_constants.keys() - glibc_constants.keys():
+            print("warning: kernel syscall {!r} ({}) not known to glibc"
+                  .format(name, kernel_constants[name]))
+            warnings = True
+
+    if errors > 0 or warnings:
+        print("info: glibc tables are based on kernel version {}".format(
+            ".".join(map(str, glibc_names.kernel_version))))
+        print("info: installed kernel headers are version {}".format(
+            ".".join(map(str, kernel_version))))
+
+    sys.exit(errors)
+
+if __name__ == '__main__':
+    main()