[PATCH 3/3] init: move embedded bootconfig parsing before setup_arch()

Breno Leitao
2026-04-15T10:51:32Z

Split setup_boot_config() into setup_boot_config_from_embedded() for
embedded bootconfig and setup_boot_config_from_initrd() for initrd
bootconfig.

The embedded bootconfig data lives in .init.rodata (compiled into the
kernel via bootconfig-data.S), so it requires no memory allocation to
access. Combined with the previous patches that replaced memblock
allocations with static buffers, this allows embedded bootconfig to
be parsed before setup_arch(), making bootconfig parameters available
during architecture-specific setup.

The initrd bootconfig path remains at its original position since it
needs initrd_start/initrd_end set up by setup_arch().

Signed-off-by: Breno Leitao <leitao@debian.org>
---
init/main.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 55 insertions(+), 12 deletions(-)

diff --git a/init/main.c b/init/main.c
index b9feca55e01f9..20fded9bfbdd0 100644
--- a/init/main.c
+++ b/init/main.c
@@ -416,20 +416,17 @@ static int __init warn_bootconfig(char *str)
return 0;
}

-static void __init setup_boot_config(void)
+/*
+ * Parse bootconfig data and extract kernel/init command line parameters.
+ * Shared by both the early embedded path and the late initrd path.
+ */
+static void __init __boot_config_load(const char *data, size_t size)
{
static char tmp_cmdline[COMMAND_LINE_SIZE] __initdata;
- const char *msg, *data;
+ const char *msg;
int pos, ret;
- size_t size;
char *err;

- /* 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)
- data = xbc_get_embedded_bootconfig(&size);
-
strscpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
err = parse_args("bootconfig", tmp_cmdline, NULL, 0, 0, 0, NULL,
bootconfig_params);
@@ -471,7 +468,50 @@ static void __init setup_boot_config(void)
/* Also, "init." keys are init arguments */
extra_init_args = xbc_make_cmdline("init", extra_initargs_buf);
}
- return;
+}
+
+/*
+ * Load embedded bootconfig before setup_arch(). This runs before memblock
+ * is available, relying on static buffers in the bootconfig parser.
+ * The embedded data lives in .init.rodata so no allocation is needed
+ * to access it.
+ */
+static void __init setup_boot_config_from_embedded(void)
+{
+ const char *data;
+ size_t size;
+
+ data = xbc_get_embedded_bootconfig(&size);
+ if (!data)
+ return;
+
+ pr_info("Load embedded bootconfig early\n");
+ __boot_config_load(data, size);
+}
+
+/*
+ * Load bootconfig from initrd. This MUST run after setup_arch() when initrd
+ * boundaries are known. If initrd bootconfig exists, it overrides any embedded
+ * bootconfig that was loaded early, preserving the original priority (initrd
+ * > embedded).
+ */
+static void __init setup_boot_config_from_initrd(void)
+{
+ const char *data;
+ size_t size;
+
+ /* Cut out the bootconfig data even if we have no bootconfig option */
+ data = get_boot_config_from_initrd(&size);
+
+ /* No initrd bootconfig — keep embedded if already loaded */
+ if (!data)
+ return;
+
+ /* Initrd overrides embedded — tear down and re-parse */
+ if (xbc_get_info(NULL, NULL) == 0)
+ _xbc_exit(true);
+
+ __boot_config_load(data, size);
}

static void __init exit_boot_config(void)
@@ -481,7 +521,9 @@ static void __init exit_boot_config(void)

#else /* !CONFIG_BOOT_CONFIG */

-static void __init setup_boot_config(void)
+static void __init setup_boot_config_from_embedded(void) { }
+
+static void __init setup_boot_config_from_initrd(void)
{
/* Remove bootconfig data from initrd */
get_boot_config_from_initrd(NULL);
@@ -1036,13 +1078,14 @@ void start_kernel(void)
boot_cpu_init();
page_address_init();
pr_notice("%s", linux_banner);
+ setup_boot_config_from_embedded();
setup_arch(&command_line);
mm_core_init_early();
/* Static keys and static calls are needed by LSMs */
jump_label_init();
static_call_init();
early_security_init();
- setup_boot_config();
+ setup_boot_config_from_initrd();
setup_command_line(command_line);
setup_nr_cpu_ids();
setup_per_cpu_areas();

--
2.52.0