[RFC PATCH v2 3/8] [WIP]xen/scripts: add codestyle.py script

[Luca Fancellu <luca.fancellu@arm.com>]

This script finds every .c and .h file in the xen hypervisor
codebase, takes the exclusion list from docs/misra, removes the
file excluded from the list and for the remaining files is
calling clang-format on them.

TBD: write it better

Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
---
 xen/scripts/codestyle.py | 265 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 265 insertions(+)
 create mode 100755 xen/scripts/codestyle.py

diff --git a/xen/scripts/codestyle.py b/xen/scripts/codestyle.py
new file mode 100755
index 000000000000..ab3df66fc2e2
--- /dev/null
+++ b/xen/scripts/codestyle.py
@@ -0,0 +1,265 @@
+#!/usr/bin/env python3
+
+import glob
+import os
+import re
+import sys
+from xen_analysis.settings import xen_dir, repo_dir
+from xen_analysis import utils
+from xen_analysis import exclusion_file_list
+from xen_analysis.exclusion_file_list import ExclusionFileListError
+
+# The Xen codestyle states that labels needs to be indented by at least one
+# blank, but clang-format doesn't have an option for that and if it encounters
+# a label indented by blank characters that are less than its indent
+# configuration, it removes the indentation.
+# So this action is meant as post step and checks every label syntax match and
+# it adds one blank before the label
+def action_fix_label_indent(filename, file_lines):
+    label_rgx = re.compile('^[a-zA-Z_][a-zA-Z0-9_]*\s*:.*$')
+
+    for i in range(0, len(file_lines)):
+        if label_rgx.match(file_lines[i]):
+            file_lines[i] = ' ' + file_lines[i]
+
+    return file_lines
+
+
+# clang-format most of the time breaks the content of asm(...) instructions,
+# so with this function, we protect all the asm sections using the special
+# in code comments that tells clang-format to don't touch the block.
+# asm(...) instruction could be also inside macros, so in that case we protect
+# the entire macro that is enclosing the instruction, in the un-protect stage
+# however, we need to do clang-format's job at least on the tab-space conversion
+# and to put the backslash on the right side.
+def action_protect_asm(filename, file_lines, protect):
+    opening_asm = False
+    cf_off_comment = '/* clang-format off */'
+    cf_on_comment = '/* clang-format on */'
+    asm_stx = '(?:asm|__asm__)(?:\s(?:volatile|__volatile__))?\s?\('
+    asm_stx_close = ');'
+
+    if protect:
+        # Look for closing parenthesis with semicolon ');'
+        closing_asm_rgx_rule = rf'^.*{re.escape(asm_stx_close)}.*$'
+        # Look for opening asm syntax
+        opening_asm_rgx_rule = rf'^\s*{asm_stx}.*$'
+        macro_start_rgx_rule = r'^\s?#\s?define.*\\$'
+        opening_asm_find = rf'({asm_stx})'
+        opening_asm_replace = cf_off_comment + r'\1'
+        opening_def_find = r'#\s?define'
+        opening_def_replace = f'{cf_off_comment}#define'
+        closing_asm_find    = re.escape(asm_stx_close)
+        closing_asm_replace = asm_stx_close + cf_on_comment
+        closing_def_find    = '\n'
+        closing_def_replace = cf_on_comment + '\n'
+    else:
+        # Look for closing parenthesis with semicolon ');' and with the
+        # special clang-format comment
+        closing_asm_rgx_rule = \
+            rf'^.*{re.escape(asm_stx_close)}.*{re.escape(cf_on_comment)}.*$'
+        # Look for opening asm syntax preceded by the special clang-format
+        # comment, the comment is optional to generalise the algorithm to
+        # un-protect asm outside and inside macros. The case outside is easy
+        # because we will find '/* clang-format off */asm', instead the case
+        # inside is more tricky and we are going to find only 'asm' and then
+        # go backwards until we find '/* clang-format off */#define'
+        opening_asm_rgx_rule = \
+            rf'^\s*({re.escape(cf_off_comment)})?{asm_stx}.*$'
+        # Look for the define just before the asm invocation, here we look for
+        # '/* clang-format off */#define' or '#define', this is to handle a rare
+        # corner case where an asm invocation is inside a macro, but was not
+        # protected in the 'protect stage', because it was on the same line
+        # of the define and was not ending with backslash but it was exceeding
+        # line width so clang-format formatted anyway.
+        # It's safe because we won't change code that has no clang-format
+        # comments, but at least the tool won't complain
+        macro_start_rgx_rule = \
+            rf'^\s?(?:{re.escape(cf_off_comment)})?#\s?define.*\\$'
+        opening_asm_find = rf'({re.escape(cf_off_comment)}({asm_stx}))'
+        opening_asm_replace = r'\2'
+        opening_def_find = rf'(?:{re.escape(cf_off_comment)})?#\s?define'
+        opening_def_replace = '#define'
+        closing_asm_find \
+            = rf'{re.escape(asm_stx_close)}.*{re.escape(cf_on_comment)}'
+        closing_asm_replace = asm_stx_close
+        closing_def_find    = cf_on_comment + '\n'
+        closing_def_replace = '\n'
+
+    opening_asm_rgx = re.compile(opening_asm_rgx_rule)
+    closing_asm_rgx = re.compile(closing_asm_rgx_rule)
+    macro_start_rgx = re.compile(macro_start_rgx_rule)
+
+    i = 0
+    i_max = len(file_lines)
+    macro_begin = -1
+    while i < i_max:
+        # Keep track of the last define we found
+        if macro_start_rgx.match(file_lines[i]):
+            macro_begin = i
+        # Try to find in the current line the asm syntax opening, but don't
+        # touch asm syntax inside macros that usually have the line ended by
+        # a backslash, this is because insert stuff in them will have issues
+        # when later clang-format will format the macro itself
+        if (not opening_asm) and opening_asm_rgx.match(file_lines[i]):
+            line_before = (i > 0) and file_lines[i-1].endswith('\\\n')
+            if file_lines[i].endswith('\\\n') or line_before:
+                # This should never happen, but if it does, it means an
+                # unexpected syntax is found in the file
+                if macro_begin < 0:
+                    raise Exception("Begin of macro not found in {}\n"
+                                    "The asm invocation is on line {}"
+                                    .format(filename, i))
+
+                # asm invocation inside macro, need to protect the entire macro,
+                # macro_begin should point to this define
+                file_lines[macro_begin] = re.sub(opening_def_find,
+                                                 opening_def_replace,
+                                                 file_lines[macro_begin])
+
+                # now go to the end of the macro, it's easy as the first line
+                # without a backslash will be the end
+                for j in range(i, len(file_lines)):
+                    if not file_lines[j].endswith('\\\n'):
+                        file_lines[j] = \
+                            file_lines[j].replace(closing_def_find,
+                                                  closing_def_replace, 1)
+                        # Advance i index, as j is the last line checked
+                        i = j
+                        break
+
+                # In the un-protect stage, we need to do clang-format's job,
+                # so convert tabs to 4 spaces and for macros put the backslash
+                # at the end of the line
+                if not protect:
+                    for j in range(macro_begin, i+1):
+                        # Tab replacement
+                        file_lines[j] = file_lines[j].replace('\t', '    ')
+                        # backslash indentation
+                        line_len = len(file_lines[j])
+                        # 81 counting also the newline character
+                        if file_lines[j].endswith('\\\n') and line_len < 81:
+                            spaces = ' ' * (81 - line_len)
+                            file_lines[j] = \
+                                file_lines[j].replace('\\\n', spaces + '\\\n',
+                                                      1)
+
+                macro_begin = -1
+            else:
+                # asm invocation is not inside a macro, protect the asm syntax
+                opening_asm = True
+                file_lines[i] = re.sub(opening_asm_find, opening_asm_replace,
+                                       file_lines[i])
+
+        # Try to find in the current line the asm closing syntax, only if a
+        # previous line already found an opening asm syntax
+        if opening_asm and closing_asm_rgx.match(file_lines[i]):
+            opening_asm = False
+            file_lines[i] = re.sub(closing_asm_find, closing_asm_replace,
+                                   file_lines[i])
+
+        i += 1
+
+    # This should never happen, but if it does, it means an unexpected syntax
+    # is found in the file
+    if opening_asm:
+        raise Exception("Unbalanced asm parenthesis in {}".format(filename))
+
+    return file_lines
+
+
+# This function runs a set of actions on the passed file name, the actions needs
+# to have a specific interface: action(filename, file_lines), filename will be
+# the name of the file where the script is working, file_lines will be the
+# content of the file expressed as an array of lines in string format.
+# The action function must return this array back to the caller and every
+# possible modifications done on that
+def stage(filename, actions):
+
+    if len(actions) == 0:
+        return
+
+    try:
+        with open(filename, "rt") as infile:
+            file_lines = infile.readlines()
+    except OSError as e:
+        raise Exception("Issue with reading file {}: {}".format(filename, e))
+
+    for task in actions:
+        file_lines = task(filename, file_lines)
+
+    try:
+        with open(filename, "wt") as outfile:
+            outfile.writelines(file_lines)
+    except OSError as e:
+        raise Exception("Issue writing file {}: {}".format(filename, e))
+
+
+def main(argv):
+    # Setup actions for pre-stage and post-stage
+    pre_stage_asm_protect = \
+        lambda file, file_lines: action_protect_asm(file, file_lines, True)
+    post_stage_asm_unprotect = \
+        lambda file, file_lines: action_protect_asm(file, file_lines, False)
+    pre_stage_actions = [pre_stage_asm_protect]
+    post_stage_actions = [post_stage_asm_unprotect, action_fix_label_indent]
+
+    len_args = len(argv)
+    if len_args > 0:
+        c_files = []
+        for i in range(0, len_args):
+            if not argv[i].startswith('/'):
+                # Assume a relative path to Xen
+                abs_path = os.getcwd() + "/" + argv[i]
+                check_path = [abs_path]
+                if '*' in abs_path:
+                    check_path = glob.glob(abs_path)
+                for path in check_path:
+                    if os.path.exists(path):
+                        c_files.append(path)
+                    else:
+                        raise Exception("Malformed path {} solved from {}"
+                                        .format(path, argv[i]))
+    else:
+        # Find all files with .c and .h extension
+        c_files = utils.recursive_find_file(xen_dir, r'.*\.(?:c|h)$')
+
+    try:
+        exclusion_file = \
+                "{}/docs/misra/exclude-list.json".format(repo_dir)
+        exclusion_list = \
+                exclusion_file_list.load_exclusion_file_list(exclusion_file,
+                                                             "codestyle")
+    except ExclusionFileListError as e:
+        print("ERROR: Issue with reading file {}: {}".format(exclusion_file, e))
+        sys.exit(1)
+
+    # Transform the lists of absolute path in the second element of the
+    # exclusion_list into a plain list of absolute path to be exluded
+    excluded_c_files = [j for i in exclusion_list for j in i[1]]
+
+    file_to_format = []
+    for file in c_files:
+        add_to_list = True
+        for excl in excluded_c_files:
+            if excl in file:
+                add_to_list = False
+                break
+        if add_to_list:
+            file_to_format.append(file)
+        elif len_args > 0:
+            print("ERROR: file {} is excluded!".format(file))
+            sys.exit(1)
+
+    for file in file_to_format:
+        try:
+            stage(file, pre_stage_actions)
+            utils.invoke_command("clang-format -i {}".format(file), False,
+                                 Exception, "Error occured invoking: {}\n")
+            stage(file, post_stage_actions)
+        except Exception as e:
+            print("ERROR: {}\n".format(e))
+
+
+if __name__ == "__main__":
+    main(sys.argv[1:])
-- 
2.34.1