linux-kernel - Re: [PATCH 2/2] bootconfig: Apply early options from embedded config

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Message-ID: <4a67b4bb-d211-4726-8f43-d3f159127dd9@infradead.org>
Date:   Wed, 22 Nov 2023 14:47:30 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Petr Malat <oss@...at.biz>, linux-kernel@...r.kernel.org
Cc:     mhiramat@...nel.org, paulmck@...nel.org, rostedt@...dmis.org
Subject: Re: [PATCH 2/2] bootconfig: Apply early options from embedded config

Hi--

On 11/21/23 15:13, Petr Malat wrote:
> Eliminate all allocations in embedded config handling to allow calling
> it from arch_setup and applying early options.
> 
> Config stored in initrd can't be used for early options, because initrd
> is set up after early options are processed.
> 
> Add this information to the documentation and also to the option
> description.
> 
> Signed-off-by: Petr Malat <oss@...at.biz>
> ---
>  Documentation/admin-guide/bootconfig.rst |   3 +
>  init/Kconfig                             |   4 +-
>  init/main.c                              | 141 ++++++++++++++++++-----
>  lib/bootconfig.c                         |  20 +++-
>  4 files changed, 132 insertions(+), 36 deletions(-)
> 
> diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst
> index 91339efdcb54..fb085f696f9b 100644
> --- a/Documentation/admin-guide/bootconfig.rst
> +++ b/Documentation/admin-guide/bootconfig.rst
> @@ -161,6 +161,9 @@ Boot Kernel With a Boot Config
>  There are two options to boot the kernel with bootconfig: attaching the
>  bootconfig to the initrd image or embedding it in the kernel itself.
>  
> +Early options may be specified only in the embedded bootconfig, because
> +they are processed before the initrd.
> +

I'm confused by which options are early options. Are they specified or
described somewhere?
How does a user know which options are "early" options?


>  Attaching a Boot Config to Initrd
>  ---------------------------------
>  
> diff --git a/init/Kconfig b/init/Kconfig
> index 9161d2dbad0c..04de756c935e 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1310,7 +1310,9 @@ config BOOT_CONFIG
>  	  Extra boot config allows system admin to pass a config file as
>  	  complemental extension of kernel cmdline when booting.
>  	  The boot config file must be attached at the end of initramfs
> -	  with checksum, size and magic word.
> +	  with checksum, size and magic word. Note that early options may
> +	  be specified in the embedded bootconfig only. Early options
> +	  specified in initrd bootconfig will not be applied.
>  	  See <file:Documentation/admin-guide/bootconfig.rst> for details.
>  
>  	  If unsure, say Y.
> diff --git a/init/main.c b/init/main.c
> index 0cd738f7f0cf..9aac59673a3a 100644
> --- a/init/main.c
> +++ b/init/main.c

[]

> +
> +static int __init setup_boot_config_early(void)
>  {
>  	static char tmp_cmdline[COMMAND_LINE_SIZE] __initdata;
> -	const char *msg, *initrd_data;
> -	int pos, ret;
> -	size_t initrd_size, embeded_size = 0;
> -	char *err, *embeded_data = NULL;
> +	static int prev_rtn __initdata;
> +	struct xbc_node *root, *knode, *vnode;
> +	char *embeded_data, *err;
> +	const char *val, *msg;
> +	size_t embeded_size;
> +	int ret, pos;

It hurts my eyes to see "embeded" here.

Thanks.
-- 
~Randy