linux-kernel - Re: [PATCH v2 4/7] cmdline: Add capability to prepend the command line

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Date:   Wed, 3 Mar 2021 18:19:04 +0000
From:   Will Deacon <will@...nel.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, danielwa@...co.com,
        robh@...nel.org, daniel@...pelevich.san-francisco.ca.us,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-arch@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 4/7] cmdline: Add capability to prepend the command
 line

On Tue, Mar 02, 2021 at 05:25:20PM +0000, Christophe Leroy wrote:
> This patchs adds an option of prepend a text to the command
> line instead of appending it.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  include/linux/cmdline.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/cmdline.h b/include/linux/cmdline.h
> index ae3610bb0ee2..144346051e01 100644
> --- a/include/linux/cmdline.h
> +++ b/include/linux/cmdline.h
> @@ -31,7 +31,7 @@ static __always_inline size_t cmdline_strlcat(char *dest, const char *src, size_
>  }
>  
>  /*
> - * This function will append a builtin command line to the command
> + * This function will append or prepend a builtin command line to the command
>   * line provided by the bootloader. Kconfig options can be used to alter
>   * the behavior of this builtin command line.
>   * @dest: The destination of the final appended/prepended string.
> @@ -50,6 +50,9 @@ static __always_inline void cmdline_build(char *dest, const char *src, size_t le
>  		cmdline_strlcat(dest, CONFIG_CMDLINE, length);
>  		return;
>  	}
> +
> +	if (IS_ENABLED(CONFIG_CMDLINE_PREPEND) && sizeof(CONFIG_CMDLINE) > 1)
> +		cmdline_strlcat(dest, CONFIG_CMDLINE " ", length);

Same comment as the other patch: I don't think we need to worry about the
sizeof() here.

Will