scripts: gdb: Added some useful GDB scripts to test.py --gdb

These just invoke the existing dbg*.py python scripts, but allow quick
references to variables in the debugginged process:

  (gdb) dbgflags o file->b.o.flags
  LFS3_O_RDWR    0x00000002  Open a file as read and write
  LFS3_o_REG     0x10000000  Type = regular-file
  LFS3_o_UNSYNC  0x01000000  File's metadata does not match disk

Quite neat and useful!

This works by injecting dbg.gdb.py via gdb -x, which includes the
necessary python hooks to add these commands to gdb. This can be
overridden/extended with test.py/bench.py's --gdb-script flag.

Currently limited to scripts that seem the most useful for process
internals:

- dbgerr - Decode littlefs error codes
- dbgflags - Decode littlefs flags
- dbgtag - Decode littlefs tags

scripts/bench.py

@@ -40,6 +40,7 @@ RUNNER_PATH = ['./runners/bench_runner']
 HEADER_PATH = 'runners/bench_runner.h'
 
 GDB_PATH = ['gdb']
+GDB_SCRIPTS = ['./scripts/dbg.gdb.py']
 VALGRIND_PATH = ['valgrind']
 PERF_SCRIPT = ['./scripts/perf.py']
 
@@ -1469,12 +1470,16 @@ def run(runner, bench_ids=[], **args):
             or args.get('gdb_main')):
         failure = failures[0]
         cmd = find_runner(runner, failure.id, **args)
+        gdb_path = args['gdb_path']
+        gdb_scripts = (args.get('gdb_script') or GDB_SCRIPTS)
 
         if args.get('gdb_main'):
             # we don't really need the case breakpoint here, but it
             # can be helpful
             path, lineno = find_path(runner, failure.id, **args)
-            cmd[:0] = args['gdb_path'] + [
+            cmd[:0] = [
+                    *gdb_path,
+                    *it.chain.from_iterable(['-x', s] for s in gdb_scripts),
                     '-q',
                     '-ex', 'break main',
                     '-ex', 'break %s:%d' % (path, lineno),
@@ -1482,13 +1487,17 @@ def run(runner, bench_ids=[], **args):
                     '--args']
         elif args.get('gdb_perm'):
             path, lineno = find_path(runner, failure.id, **args)
-            cmd[:0] = args['gdb_path'] + [
+            cmd[:0] = [
+                    *gdb_path,
+                    *it.chain.from_iterable(['-x', s] for s in gdb_scripts),
                     '-q',
                     '-ex', 'break %s:%d' % (path, lineno),
                     '-ex', 'run',
                     '--args']
         else:
-            cmd[:0] = args['gdb_path'] + [
+            cmd[:0] = [
+                    *gdb_path,
+                    *it.chain.from_iterable(['-x', s] for s in gdb_scripts),
                     '-q',
                     '-ex', 'run',
                     '--args']
@@ -1693,6 +1702,11 @@ if __name__ == "__main__":
             default=GDB_PATH,
             help="Path to the gdb executable, may include flags. "
                 "Defaults to %r." % GDB_PATH)
+    bench_parser.add_argument(
+            '--gdb-script',
+            action='append',
+            help="Paths to scripts to execute when dropping into gdb. "
+                "Defaults to %r." % GDB_SCRIPTS)
     bench_parser.add_argument(
             '-e', '--exec',
             type=lambda e: e.split(),