bootconfig: skip runtime kernel.* render once prepended early

setup_boot_config() folds the embedded bootconfig "kernel" subtree into
the command line via xbc_make_cmdline("kernel"). A subsequent patch lets
an architecture prepend the build-time-rendered embedded "kernel" keys
to boot_command_line early in setup_arch(); rendering them again here
would then duplicate every key in saved_command_line and make
accumulating handlers (console=, earlycon=, ...) re-register the same
value.

Track whether the bootconfig data came from the embedded source
(from_embedded) and skip the runtime render only when the early prepend
actually happened, as reported by xbc_embedded_cmdline_applied(). On
architectures that do not select ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG
that helper is a stub returning false, so this path is unchanged and the
embedded "kernel" keys still reach the cmdline via the runtime parser
exactly as before.

Link: https://lore.kernel.org/all/20260626-bootconfig_using_tools-v7-8-24ab72139c29@debian.org/

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

1 files changed, 22 insertions, 3 deletions

diff --git a/init/main.c b/init/main.c
index e363232b428b..260bd5242f94 100644
--- a/init/main.c
+++ b/init/main.c
@@ -378,12 +378,15 @@ static void __init setup_boot_config(void)
 	int pos, ret;
 	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,
@@ -421,8 +424,24 @@ 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");
 	}