gdbstub: Add num_regs member to GDBFeature

Currently the number of registers exposed to GDB is written as magic
numbers in code. Derive the number of registers GDB actually see from
XML files to replace the magic numbers in code later.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231025093128.33116-2-akihiko.odaki@daynix.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231106185112.2755262-9-alex.bennee@linaro.org>

include/exec/gdbstub.h

@@ -13,6 +13,7 @@
 typedef struct GDBFeature {
     const char *xmlname;
     const char *xml;
+    int num_regs;
 } GDBFeature;
 
 

scripts/feature_to_c.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0-or-later
 
-import os, sys
+import os, sys, xml.etree.ElementTree
 
 def writeliteral(indent, bytes):
     sys.stdout.write(' ' * indent)
@@ -39,10 +39,52 @@ def writeliteral(indent, bytes):
     with open(input, 'rb') as file:
         read = file.read()
 
+    parser = xml.etree.ElementTree.XMLPullParser(['start', 'end'])
+    parser.feed(read)
+    events = parser.read_events()
+    event, element = next(events)
+    if event != 'start':
+        sys.stderr.write(f'unexpected event: {event}\n')
+        exit(1)
+    if element.tag != 'feature':
+        sys.stderr.write(f'unexpected start tag: {element.tag}\n')
+        exit(1)
+
+    regnum = 0
+    regnums = []
+    tags = ['feature']
+    for event, element in events:
+        if event == 'end':
+            if element.tag != tags[len(tags) - 1]:
+                sys.stderr.write(f'unexpected end tag: {element.tag}\n')
+                exit(1)
+
+            tags.pop()
+            if element.tag == 'feature':
+                break
+        elif event == 'start':
+            if len(tags) < 2 and element.tag == 'reg':
+                if 'regnum' in element.attrib:
+                    regnum = int(element.attrib['regnum'])
+
+                regnums.append(regnum)
+                regnum += 1
+
+            tags.append(element.tag)
+        else:
+            raise Exception(f'unexpected event: {event}\n')
+
+    if len(tags):
+        sys.stderr.write('unterminated feature tag\n')
+        exit(1)
+
+    base_reg = min(regnums)
+    num_regs = max(regnums) - base_reg + 1 if len(regnums) else 0
+
     sys.stdout.write('    {\n')
     writeliteral(8, bytes(os.path.basename(input), 'utf-8'))
     sys.stdout.write(',\n')
     writeliteral(8, read)
-    sys.stdout.write('\n    },\n')
+    sys.stdout.write(f',\n        {num_regs},\n    }},\n')
 
 sys.stdout.write('    { NULL }\n};\n')