[PATCH v3 5/7] scripts/sbom: parse make_prereqs from .cmd files

[Luis Augenstein <luis.augenstein@tngtech.com>]

Add support for parsing the make_prereqs_<target> field recorded by
kbuild in .cmd files.

Refactor CmdFile.create() to collect the required fields by name
instead of deriving the file structure from the number of lines and
the position.

The source_ entry is no longer parsed, because it is always also
included in make_prereqs_<target> and therefore redundant for
KernelSbom.

Assisted-by: LLM
Co-developed-by: Maximilian Huber <maximilian.huber@tngtech.com>
Signed-off-by: Maximilian Huber <maximilian.huber@tngtech.com>
Signed-off-by: Luis Augenstein <luis.augenstein@tngtech.com>
---
 scripts/sbom/sbom/cmd_graph/cmd_file.py | 103 +++++++++---------------
 1 file changed, 36 insertions(+), 67 deletions(-)

diff --git a/scripts/sbom/sbom/cmd_graph/cmd_file.py b/scripts/sbom/sbom/cmd_graph/cmd_file.py
index 08819b4d117..cc576c7c6be 100644
--- a/scripts/sbom/sbom/cmd_graph/cmd_file.py
+++ b/scripts/sbom/sbom/cmd_graph/cmd_file.py
@@ -10,97 +10,66 @@ import sbom.sbom_logging as sbom_logging
 from sbom.path_utils import PathStr
 
 SAVEDCMD_PATTERN = re.compile(r"^(saved)?cmd_.*?:=\s*(?P<full_command>.+)$")
-SOURCE_PATTERN = re.compile(r"^source.*?:=\s*(?P<source_file>.+)$")
+MAKE_PREREQS_PATTERN = re.compile(r"^make_prereqs_.*?:=\s*(?P<prereqs>.+)$")
+DEPS_ASSIGNMENT_PATTERN = re.compile(r"^deps_.*?:=")
 
 
 @dataclass
 class CmdFile:
     cmd_file_path: PathStr
     savedcmd: str
-    source: PathStr | None = None
+    make_prereqs: list[str] = field(default_factory=list)
     deps: list[str] = field(default_factory=list)
-    make_rules: list[str] = field(default_factory=list)
 
     @classmethod
     def create(cls, cmd_file_path: PathStr) -> "CmdFile | None":
-        """
-        Parses a .cmd file.
-        .cmd files are assumed to have one of the following structures:
-        1. Full Cmd File
-            (saved)?cmd_<output> := <command>
-            source_<output> := <main_input>
-            deps_<output> := \
-            <dependencies>
-            <output> := $(deps_<output>)
-            $(deps_<output>):
-
-        2. Command Only Cmd File
-            (saved)?cmd_<output> := <command>
-
-        3. Single Dependency Cmd File
-            (saved)?cmd_<output> := <command>
-            <output> : <dependency>
+        r"""
+        Parse the following fields from a `.cmd` file:
+
+        * `(saved)?cmd_<target> := <shell command>` (required) —
+          the shell command Kbuild ran to produce the build target.
+        * `make_prereqs_<target> := <prerequisites>` (required but can be empty) —
+          the non-phony make prerequisites.
+        * `deps_<target> := \` (optional) —
+          additional dependencies not covered by make prerequisites, e.g., headers.
 
         Args:
-            cmd_file_path (Path): absolute Path to a .cmd file
+            cmd_file_path (Path): absolute Path to a `.cmd` file.
 
         Returns:
-            cmd_file (CmdFile): Parsed cmd file.
+            cmd_file (CmdFile): Parsed `.cmd` file or `None` if no `savedcmd` line was found.
         """
         with open(cmd_file_path, "rt", encoding="utf-8") as f:
             lines = [line.strip() for line in f.readlines() if line.strip() != "" and not line.startswith("#")]
 
-        # make_prereqs_* is recorded for future use. Ignore it for now to
-        # preserve the existing parser behavior.
-        lines = [line for line in lines if not line.startswith("make_prereqs_")]
+        savedcmd: str | None = None
+        make_prereqs: list[str] = []
+        deps: list[str] = []
+
+        for i, line in enumerate(lines):
+            match = SAVEDCMD_PATTERN.match(line)
+            if match is not None:
+                savedcmd = match.group("full_command")
+                continue
+
+            match = MAKE_PREREQS_PATTERN.match(line)
+            if match is not None:
+                make_prereqs = match.group("prereqs").split()
+                continue
 
-        # savedcmd
-        match = SAVEDCMD_PATTERN.match(lines[0] if lines else "")
-        if match is None:
+            if DEPS_ASSIGNMENT_PATTERN.match(line):
+                j = i + 1
+                while j < len(lines) and lines[j].endswith("\\"):
+                    deps.append(lines[j].removesuffix("\\").strip())
+                    j += 1
+
+        if savedcmd is None:
             sbom_logging.error(
                 "Skip parsing '{cmd_file_path}' because no 'savedcmd_' command was found.", cmd_file_path=cmd_file_path
             )
             return None
-        savedcmd = match.group("full_command")
-
-        # Command Only Cmd File
-        if len(lines) == 1:
-            return CmdFile(cmd_file_path, savedcmd)
-
-        # Single Dependency Cmd File
-        if len(lines) == 2:
-            parts = lines[1].split(":", 1)
-            if len(parts) != 2:
-                sbom_logging.error(
-                    "Skip parsing '{cmd_file_path}'. Expected dependency line '<output>: <dependency>' but got {second_line}", cmd_file_path=cmd_file_path, second_line=lines[1]
-                )
-                return None
-            dep = parts[1].strip()
-            return CmdFile(cmd_file_path, savedcmd, deps=[dep])
-
-        # Full Cmd File
-        # source
-        line1 = SOURCE_PATTERN.match(lines[1])
-        if line1 is None:
-            sbom_logging.error(
-                "Skip parsing '{cmd_file_path}' because no 'source_' entry was found.", cmd_file_path=cmd_file_path
-            )
-            return CmdFile(cmd_file_path, savedcmd)
-        source = line1.group("source_file")
-
-        # deps
-        deps: list[str] = []
-        i = 3  # lines[2] includes the variable assignment but no actual dependency, so we need to start at lines[3].
-        while i < len(lines):
-            if not lines[i].endswith("\\"):
-                break
-            deps.append(lines[i][:-1].strip())
-            i += 1
-
-        # make_rules
-        make_rules = lines[i:]
 
-        return CmdFile(cmd_file_path, savedcmd, source, deps, make_rules)
+        return CmdFile(cmd_file_path, savedcmd, make_prereqs, deps)
 
     def get_dependencies(
         self: "CmdFile", target_path: PathStr, obj_tree: PathStr, fail_on_unknown_build_command: bool
-- 
2.43.0