Merge tag 'bootconfig-v7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull bootconfig updates from Masami Hiramatsu:

 - Support build-time command line building for embedded bootconfig

 - Fix xbc_snprint_cmdline() to render descendant keys when the root has
   both a value and subkeys, and treats empty subtrees correctly.

 - Add build-time pipeline using tools/bootconfig -C to render the
   embedded bootconfig "kernel" subtree into .init.rodata as a cmdline
   string.

 - Clean build-time tools/bootconfig from make clean

 - Add helper to prepend embedded bootconfig cmdline into
   boot_command_line early before parse_early_param()

 - Wire early prepend helper in x86 setup_arch() so early_param handlers
   see values from the embedded bootconfig (currently x86 only)

 - Avoid duplicating "kernel" keys in setup_boot_config()

 - Refactor setup_boot_config() to share bootconfig_cmdline_requested()

 - Document CONFIG_CMDLINE_FROM_BOOTCONFIG usage, requirements, and
   precedence

* tag 'bootconfig-v7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  init/main.c: use bootconfig_cmdline_requested() for the runtime opt-in
  bootconfig: skip runtime kernel.* render once prepended early
  x86/setup: prepend embedded bootconfig cmdline before parse_early_param
  Documentation: bootconfig: document build-time cmdline rendering
  bootconfig: add xbc_prepend_embedded_cmdline() helper
  bootconfig: clean build-time tools/bootconfig from make clean
  bootconfig: render embedded bootconfig as a kernel cmdline at build time
  bootconfig: render descendant keys when xbc_snprint_cmdline() root has a value

2 files changed, 64 insertions, 24 deletions

diff --git a/init/Kconfig b/init/Kconfig
index f63bf5e05e79..8583d9f06c52 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1578,6 +1578,42 @@ config BOOT_CONFIG_EMBED_FILE
 	  This bootconfig will be used if there is no initrd or no other
 	  bootconfig in the initrd.
 
+config ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG
+	bool
+	help
+	  Silent symbol; no C code reads it directly. Architectures
+	  select it once their setup_arch() calls
+	  xbc_prepend_embedded_cmdline() before parse_early_param().
+	  Its only role is to gate the user-visible
+	  CMDLINE_FROM_BOOTCONFIG option per-arch, the same
+	  ARCH_SUPPORTS_* idiom used by ARCH_SUPPORTS_CFI, etc.
+
+config CMDLINE_FROM_BOOTCONFIG
+	bool "Render embedded bootconfig as kernel cmdline at build time"
+	depends on BOOT_CONFIG_EMBED_FILE != ""
+	depends on ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG
+	depends on CMDLINE = ""
+	default n
+	help
+	  Render the "kernel" subtree of the embedded bootconfig file into a
+	  flat cmdline string at kernel build time and prepend it to
+	  boot_command_line during early architecture setup. This makes
+	  early_param() handlers (e.g. mem=, earlycon=, loglevel=) see the
+	  values supplied via the embedded bootconfig.
+
+	  The runtime bootconfig parser is unaffected, so tree-structured
+	  consumers such as ftrace boot-time tracing keep working.
+
+	  Note: when an initrd also carries a bootconfig, its "kernel"
+	  subtree is still parsed at runtime, but the embedded "kernel"
+	  keys remain in boot_command_line for parse_early_param() and
+	  end up later than the initrd keys in saved_command_line, so
+	  parse_args() last-wins favors the embedded values. If you need
+	  initrd to override embedded kernel.* keys, leave this option
+	  off.
+
+	  If unsure, say N.
+
 config CMDLINE_LOG_WRAP_IDEAL_LEN
 	int "Length to try to wrap the cmdline when logged at boot"
 	default 1021
diff --git a/init/main.c b/init/main.c
index 92d34e496a33..2613d3f9b3ce 100644
--- a/init/main.c
+++ b/init/main.c
@@ -357,45 +357,33 @@ static char * __init xbc_make_cmdline(const char *key)
 	return new_cmdline;
 }
 
-static int __init bootconfig_params(char *param, char *val,
-				    const char *unused, void *arg)
-{
-	if (strcmp(param, "bootconfig") == 0) {
-		bootconfig_found = true;
-	}
-	return 0;
-}
-
 static int __init warn_bootconfig(char *str)
 {
-	/* The 'bootconfig' has been handled by bootconfig_params(). */
+	/* The 'bootconfig' option is handled by setup_boot_config(). */
 	return 0;
 }
 
 static void __init setup_boot_config(void)
 {
-	static char tmp_cmdline[COMMAND_LINE_SIZE] __initdata;
 	const char *msg, *data;
-	int pos, ret;
+	int pos, ret, offs;
 	size_t size;
-	char *err;
+	bool from_embedded = false;
 
 	/* Cut out the bootconfig data even if we have no bootconfig option */
 	data = get_boot_config_from_initrd(&size);
 	/* If there is no bootconfig in initrd, try embedded one. */
-	if (!data)
+	if (!data) {
 		data = xbc_get_embedded_bootconfig(&size);
+		from_embedded = true;
+	}
 
-	strscpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
-	err = parse_args("bootconfig", tmp_cmdline, NULL, 0, 0, 0, NULL,
-			 bootconfig_params);
-
-	if (IS_ERR(err) || !(bootconfig_found || IS_ENABLED(CONFIG_BOOT_CONFIG_FORCE)))
+	bootconfig_found = bootconfig_cmdline_requested(boot_command_line, &offs);
+	if (!(bootconfig_found || IS_ENABLED(CONFIG_BOOT_CONFIG_FORCE)))
 		return;
 
-	/* parse_args() stops at the next param of '--' and returns an address */
-	if (err)
-		initargs_offs = err - tmp_cmdline;
+	/* Offset of the init arguments after a "--", located by the helper. */
+	initargs_offs = offs;
 
 	if (!data) {
 		/* If user intended to use bootconfig, show an error level message */
@@ -422,8 +410,24 @@ static void __init setup_boot_config(void)
 	} else {
 		xbc_get_info(&ret, NULL);
 		pr_info("Load bootconfig: %ld bytes %d nodes\n", (long)size, ret);
-		/* keys starting with "kernel." are passed via cmdline */
-		extra_command_line = xbc_make_cmdline("kernel");
+		/*
+		 * keys starting with "kernel." are passed via cmdline. When
+		 * this bootconfig came from the embedded source and
+		 * setup_arch() already prepended the rendered "kernel" subtree
+		 * to boot_command_line, rendering again here would duplicate
+		 * the keys in saved_command_line and make accumulating handlers
+		 * (console=, earlycon=, ...) re-register the same value. Skip
+		 * only when the prepend really happened.
+		 *
+		 * On arches that do not select ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG,
+		 * CONFIG_CMDLINE_FROM_BOOTCONFIG is unselectable and
+		 * xbc_embedded_cmdline_applied() collapses to a stub returning
+		 * false, so this path still runs and the embedded "kernel"
+		 * keys reach the cmdline via the runtime parser exactly as
+		 * before this series.
+		 */
+		if (!from_embedded || !xbc_embedded_cmdline_applied())
+			extra_command_line = xbc_make_cmdline("kernel");
 		/* Also, "init." keys are init arguments */
 		extra_init_args = xbc_make_cmdline("init");
 	}