testing: probe gdb for supported architectures ahead of time

Currently when we encounter a gdb that is old or not built with
multiarch in mind we fail rather messily. Try and improve the
situation by probing ahead of time and setting
HOST_GDB_SUPPORTS_ARCH=y in the relevant tcg configs. We can then skip
and give a more meaningful message if we don't run the test.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230302190846.2593720-24-alex.bennee@linaro.org>
Message-Id: <20230303025805.625589-24-richard.henderson@linaro.org>

scripts/probe-gdb-support.py

@@ -0,0 +1,88 @@
+#!/usr/bin/env python3
+# coding: utf-8
+#
+# Probe gdb for supported architectures.
+#
+# This is required to support testing of the gdbstub as its hard to
+# handle errors gracefully during the test. Instead this script when
+# passed a GDB binary will probe its architecture support and return a
+# string of supported arches, stripped of guff.
+#
+# Copyright 2023 Linaro Ltd
+#
+# Author: Alex Bennée <alex.bennee@linaro.org>
+#
+# This work is licensed under the terms of the GNU GPL, version 2 or later.
+# See the COPYING file in the top-level directory.
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+import argparse
+import re
+from subprocess import check_output, STDOUT
+
+# mappings from gdb arch to QEMU target
+mappings = {
+    "alpha" : "alpha",
+    "aarch64" : ["aarch64", "aarch64_be"],
+    "armv7": "arm",
+    "armv8-a" : ["aarch64", "aarch64_be"],
+    "avr" : "avr",
+    "cris" : "cris",
+    # no hexagon in upstream gdb
+    "hppa1.0" : "hppa",
+    "i386" : "i386",
+    "i386:x86-64" : "x86_64",
+    "Loongarch64" : "loongarch64",
+    "m68k" : "m68k",
+    "MicroBlaze" : "microblaze",
+    "mips:isa64" : ["mips64", "mips64el"],
+    "nios2" : "nios2",
+    "or1k" : "or1k",
+    "powerpc:common" : "ppc",
+    "powerpc:common64" : ["ppc64", "ppc64le"],
+    "riscv:rv32" : "riscv32",
+    "riscv:rv64" : "riscv64",
+    "s390:64-bit" : "s390x",
+    "sh4" : ["sh4", "sh4eb"],
+    "sparc": "sparc",
+    "sparc:v8plus": "sparc32plus",
+    "sparc:v9a" : "sparc64",
+    # no tricore in upstream gdb
+    "xtensa" : ["xtensa", "xtensaeb"]
+}
+
+def do_probe(gdb):
+    gdb_out = check_output([gdb,
+                            "-ex", "set architecture",
+                            "-ex", "quit"], stderr=STDOUT)
+
+    m = re.search(r"Valid arguments are (.*)",
+                  gdb_out.decode("utf-8"))
+
+    valid_arches = set()
+
+    if m.group(1):
+        for arch in m.group(1).split(", "):
+            if arch in mappings:
+                mapping = mappings[arch]
+                if isinstance(mapping, str):
+                    valid_arches.add(mapping)
+                else:
+                    for entry in mapping:
+                        valid_arches.add(entry)
+
+    return valid_arches
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description='Probe GDB Architectures')
+    parser.add_argument('gdb', help='Path to GDB binary.')
+
+    args = parser.parse_args()
+
+    supported = do_probe(args.gdb)
+
+    print(" ".join(supported))
+
+if __name__ == '__main__':
+    main()