On Mon, Jun 08, 2026 at 07:19:28PM +0900, Masami Hiramatsu wrote:
> On Fri, 05 Jun 2026 05:03:37 -0700
> Breno Leitao <[email protected]> wrote:
>
> > Call xbc_prepend_embedded_cmdline() in setup_arch() right after the
> > CONFIG_CMDLINE merge and before strscpy(command_line, ...) so the
> > build-time-rendered embedded bootconfig "kernel" subtree is part of
> > boot_command_line by the time parse_early_param() runs. early_param()
> > handlers (mem=, earlycon=, loglevel=, ...) now see values supplied via
> > CONFIG_BOOT_CONFIG_EMBED_FILE without parsing bootconfig at runtime.
> >
> > Gate the prepend on the bootconfig opt-in: only fold in the embedded
> > kernel.* keys when "bootconfig" is present on the command line, or
> > CONFIG_BOOT_CONFIG_FORCE is set. Applying the embedded cmdline
> > unconditionally would (a) diverge from how embedded init.* keys are
> > treated and (b) break fail-safe recovery: a malformed embedded
> > console=/mem= could panic the boot with no way for the admin to disable
> > it by dropping "bootconfig" from the bootloader cmdline.
> > cmdline_find_option_bool() runs before parse_early_param(), so the gate
> > is cheap and correctly ordered.
> >
> > Select ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG so the user-visible
> > CONFIG_BOOT_CONFIG_EMBED_CMDLINE option becomes selectable on x86.
>
> This seems like a dummy config. what code does depend on this flag?
No C code reads ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG directly — it's
a silent gating symbol, the same ARCH_SUPPORTS_* idiom as
ARCH_SUPPORTS_CFI, ARCH_SUPPORTS_LTO_CLANG, etc.
Its only role is the depends on line of BOOT_CONFIG_EMBED_CMDLINE: an
arch selects it once its setup_arch() calls
xbc_prepend_embedded_cmdline(), and that makes the user-visible
BOOT_CONFIG_EMBED_CMDLINE selectable.
Right now, only x86 supports embedded bootconfig, thus, only x86 does
the following (last patch):
config X86
+ select ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG
So, no other platform can see CONFIG_BOOT_CONFIG_EMBED_CMDLINE.
> > --- 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;
>
> Even from embedded bootconfig, if the arch set
> ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG=n, this must be applied to
> the cmdline as we are doing.
Right — that path is preserved. When the arch doesn't select
ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG, BOOT_CONFIG_EMBED_CMDLINE is
unselectable, so xbc_embedded_cmdline_applied() is the no-op stub
returning false.
> > strscpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
> > err = parse_args("bootconfig", tmp_cmdline, NULL, 0, 0, 0, NULL,
> > @@ -421,8 +424,17 @@ 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.
>
> Also, this should mention ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG=n case.
Ack, I will update
Thanks for the review,
--breno
