Re: [PATCH v2 6/6] x86/setup: prepend embedded bootconfig cmdline before parse_early_param

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Mon, 8 Jun 2026 07:41:05 -0700
Breno Leitao <leitao@debian.org> wrote:

> On Mon, Jun 08, 2026 at 07:19:28PM +0900, Masami Hiramatsu wrote:
> > On Fri, 05 Jun 2026 05:03:37 -0700
> > Breno Leitao <leitao@debian.org> 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.

Ah, OK. I missed the 3/6, which defined the dependency.

Thanks!

-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>