[PATCH v2 1/1] kbuild: record real-prereqs in .cmd files

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

Record $(real-prereqs), the non-phony prerequisites of the target, in a
new metadata field:

    make_prereqs_<target> := <prerequisites>

Write the field from both cmd_and_savecmd and cmd_and_fixdep.

Update scripts/make_fit.py to read only savedcmd_* instead of parsing the
complete .cmd file.

Ignore make_prereqs_* in KernelSbom.

Link: https://lore.kernel.org/r/a01233b9-23a2-4666-91ed-f1cf030dcb9f@tngtech.com
Assisted-by: Cursor:GPT-5.6 Sol
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/Kbuild.include                  |   9 +-
 scripts/basic/fixdep.c                  | 159 ++++++++++++++++++++----
 scripts/make_fit.py                     |   2 +-
 scripts/sbom/sbom/cmd_graph/cmd_file.py |   4 +
 4 files changed, 148 insertions(+), 26 deletions(-)

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 8c311b997e2..6daa244ba0e 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -181,6 +181,9 @@ endif
 # (needed for the shell)
 make-cmd = $(call escsq,$(subst $(pound),$$(pound),$(subst $$,$$$$,$(cmd_$(1)))))
 
+# prerequisites to record in .cmd files, excluding those covered in deps_*
+cmd-prereqs = $(call escsq,$(filter-out $(deps_$@), $(real-prereqs)))
+
 # Find any prerequisites that are newer than target or that do not exist.
 # PHONY targets skipped in both cases.
 # If there is no prerequisite other than phony targets, $(newer-prereqs) becomes
@@ -198,14 +201,16 @@ if_changed = $(if $(if-changed-cond),$(cmd_and_savecmd),@:)
 
 cmd_and_savecmd =                                                            \
 	$(cmd);                                                              \
-	printf '%s\n' 'savedcmd_$@ := $(make-cmd)' > $(dot-target).cmd
+	printf '%s\n\n%s\n' 'savedcmd_$@ := $(make-cmd)'                    \
+		'make_prereqs_$@ := $(cmd-prereqs)' > $(dot-target).cmd
 
 # Execute the command and also postprocess generated .d dependencies file.
 if_changed_dep = $(if $(if-changed-cond),$(cmd_and_fixdep),@:)
 
 cmd_and_fixdep =                                                             \
 	$(cmd);                                                              \
-	$(objtree)/scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).cmd;\
+	$(objtree)/scripts/basic/fixdep $(depfile) $@ '$(make-cmd)'          \
+		'$(cmd-prereqs)' > $(dot-target).cmd;                        \
 	rm -f $(depfile)
 
 # Usage: $(call if_changed_rule,foo)
diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c
index cdd5da7e009..e644c1590a9 100644
--- a/scripts/basic/fixdep.c
+++ b/scripts/basic/fixdep.c
@@ -62,15 +62,17 @@
  *
  * It is invoked as
  *
- *   fixdep <depfile> <target> <cmdline>
+ *   fixdep <depfile> <target> <cmdline> <prereqs>
  *
  * and will read the dependency file <depfile>
  *
  * The transformed dependency snipped is written to stdout.
  *
- * It first generates a line
+ * It first generates the lines
  *
- *   savedcmd_<target> = <cmdline>
+ *   savedcmd_<target> := <cmdline>
+ *
+ *   make_prereqs_<target> := <prereqs_without_deps>
  *
  * and then basically copies the .<target>.d file to stdout, in the
  * process filtering out the dependency on autoconf.h and adding
@@ -103,7 +105,7 @@
 
 static void usage(void)
 {
-	fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
+	fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline> <prereqs>\n");
 	exit(1);
 }
 
@@ -114,6 +116,17 @@ struct item {
 	char		name[];
 };
 
+struct dep_item {
+	struct dep_item	*next;
+	char		name[];
+};
+
+struct dep_info {
+	char			*source;
+	struct dep_item		*deps;
+	struct dep_item		*last_dep;
+};
+
 #define HASHSZ 256
 static struct item *config_hashtab[HASHSZ], *file_hashtab[HASHSZ];
 
@@ -163,16 +176,42 @@ static bool in_hashtable(const char *name, int len, struct item *hashtab[])
 	return false;
 }
 
+/*
+ * Append a dependency or include/config/<SYM> path to the info linked list.
+ */
+static void dep_info_add(struct dep_info *info, const char *name, int len)
+{
+	struct dep_item *dep = xmalloc(sizeof(*dep) + len + 1);
+
+	memcpy(dep->name, name, len);
+	dep->name[len] = '\0';
+	dep->next = NULL;
+
+	if (info->last_dep)
+		info->last_dep->next = dep;
+	else
+		info->deps = dep;
+	info->last_dep = dep;
+}
+
 /*
  * Record the use of a CONFIG_* word.
  */
-static void use_config(const char *m, int slen)
+static void use_config(const char *m, int slen, struct dep_info *info)
 {
 	if (in_hashtable(m, slen, config_hashtab))
 		return;
 
-	/* Print out a dependency path from a symbol name. */
-	printf("    $(wildcard include/config/%.*s) \\\n", slen, m);
+	/* Build a dependency path from a symbol name. */
+	static const char config_path[] = "include/config/";
+	char *path;
+	int path_len = sizeof(config_path) - 1 + slen;
+
+	path = xmalloc(path_len);
+	memcpy(path, config_path, sizeof(config_path) - 1);
+	memcpy(path + sizeof(config_path) - 1, m, slen);
+	dep_info_add(info, path, path_len);
+	free(path);
 }
 
 /* test if s ends in sub */
@@ -186,7 +225,12 @@ static int str_ends_with(const char *s, int slen, const char *sub)
 	return !memcmp(s + slen - sublen, sub, sublen);
 }
 
-static void parse_config_file(const char *p)
+/*
+ * Scan dependency p for CONFIG_ words, map each to an
+ * include/config/ path and append to the dep_info list if not
+ * already included.
+ */
+static void parse_config_file(const char *p, struct dep_info *info)
 {
 	const char *q, *r;
 	const char *start = p;
@@ -205,7 +249,7 @@ static void parse_config_file(const char *p)
 		else
 			r = q;
 		if (r > p)
-			use_config(p, r - p);
+			use_config(p, r - p, info);
 		p = q;
 	}
 }
@@ -253,13 +297,9 @@ static int is_no_parse_file(const char *s, int len)
 	       str_ends_with(s, len, ".so");
 }
 
-/*
- * Important: The below generated source_foo.o and deps_foo.o variable
- * assignments are parsed not only by make, but also by the rather simple
- * parser in scripts/mod/sumversion.c.
- */
-static void parse_dep_file(char *p, const char *target)
+static struct dep_info parse_dep_file(char *p)
 {
+	struct dep_info info = {};
 	bool saw_any_target = false;
 	bool is_target = true;
 	bool is_source = false;
@@ -375,13 +415,12 @@ static void parse_dep_file(char *p, const char *target)
 			 */
 			if (!saw_any_target) {
 				saw_any_target = true;
-				printf("source_%s := %s\n\n", target, p);
-				printf("deps_%s := \\\n", target);
+				info.source = xstrdup(p);
 				need_parse = true;
 			}
 		} else if (!is_ignored_file(p, q - p) &&
 			   !in_hashtable(p, q - p, file_hashtab)) {
-			printf("  %s \\\n", p);
+			dep_info_add(&info, p, q - p);
 			need_parse = true;
 		}
 
@@ -389,7 +428,7 @@ static void parse_dep_file(char *p, const char *target)
 			void *buf;
 
 			buf = read_file(p);
-			parse_config_file(buf);
+			parse_config_file(buf, &info);
 			free(buf);
 		}
 
@@ -403,26 +442,100 @@ static void parse_dep_file(char *p, const char *target)
 		exit(1);
 	}
 
+	return info;
+}
+
+static void free_dep_info(struct dep_info *info)
+{
+	struct dep_item *dep, *next;
+
+	for (dep = info->deps; dep; dep = next) {
+		next = dep->next;
+		free(dep);
+	}
+	free(info->source);
+}
+
+/*
+ * Important: The below generated source_foo.o and deps_foo.o variable
+ * assignments are parsed not only by make, but also by the rather simple
+ * parser in scripts/mod/sumversion.c.
+ */
+static void print_dep_file(const char *target, const struct dep_info *info)
+{
+	static const char config_path[] = "include/config/";
+	const struct dep_item *dep;
+
+	printf("source_%s := %s\n\n", target, info->source);
+	printf("deps_%s := \\\n", target);
+
+	for (dep = info->deps; dep; dep = dep->next) {
+		if (!strncmp(dep->name, config_path, sizeof(config_path) - 1))
+			printf("    $(wildcard %s) \\\n", dep->name);
+		else
+			printf("  %s \\\n", dep->name);
+	}
+
 	printf("\n%s: $(deps_%s)\n\n", target, target);
 	printf("$(deps_%s):\n", target);
 }
 
+static void print_make_prereqs(const char *target, const char *prereqs,
+			       const struct dep_info *info)
+{
+	struct item *seen_prereqs_hashtab[HASHSZ] = {};
+	const struct dep_item *dep;
+	const char *p = prereqs;
+
+	for (dep = info->deps; dep; dep = dep->next)
+		in_hashtable(dep->name, strlen(dep->name),
+			     seen_prereqs_hashtab);
+
+	printf("make_prereqs_%s :=", target);
+
+	while (*p) {
+		const char *start;
+		int len;
+
+		while (*p == ' ' || *p == '\t')
+			p++;
+		if (!*p)
+			break;
+
+		start = p;
+		while (*p && *p != ' ' && *p != '\t')
+			p++;
+		len = p - start;
+
+		if (!in_hashtable(start, len, seen_prereqs_hashtab))
+			printf(" %.*s", len, start);
+	}
+
+	printf("\n\n");
+}
+
 int main(int argc, char *argv[])
 {
-	const char *depfile, *target, *cmdline;
+	const char *depfile, *target, *cmdline, *prereqs;
+	struct dep_info info;
 	void *buf;
 
-	if (argc != 4)
+	if (argc != 5)
 		usage();
 
 	depfile = argv[1];
 	target = argv[2];
 	cmdline = argv[3];
+	prereqs = argv[4];
+
+	buf = read_file(depfile);
+	info = parse_dep_file(buf);
 
 	printf("savedcmd_%s := %s\n\n", target, cmdline);
+	print_make_prereqs(target, prereqs, &info);
+	print_dep_file(target, &info);
 
-	buf = read_file(depfile);
-	parse_dep_file(buf, target);
+	free_dep_info(&info);
 	free(buf);
 
 	fflush(stdout);
diff --git a/scripts/make_fit.py b/scripts/make_fit.py
index 15ba26974fd..346e8a7ec12 100755
--- a/scripts/make_fit.py
+++ b/scripts/make_fit.py
@@ -288,7 +288,7 @@ def process_dtb(fname, args):
         path, basename = os.path.split(fname)
         cmd_fname = os.path.join(path, f'.{basename}.cmd')
         with open(cmd_fname, 'r', encoding='ascii') as inf:
-            cmd = inf.read()
+            cmd = inf.readline()
 
         if 'scripts/dtc/fdtoverlay' in cmd:
             # This depends on the structure of the composite DTB command
diff --git a/scripts/sbom/sbom/cmd_graph/cmd_file.py b/scripts/sbom/sbom/cmd_graph/cmd_file.py
index dcd63e284a3..08819b4d117 100644
--- a/scripts/sbom/sbom/cmd_graph/cmd_file.py
+++ b/scripts/sbom/sbom/cmd_graph/cmd_file.py
@@ -50,6 +50,10 @@ class CmdFile:
         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
         match = SAVEDCMD_PATTERN.match(lines[0] if lines else "")
         if match is None:
-- 
2.43.0