linux-kernel - Re: [PATCH v3] powerpc: Support CMDLINE

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Message-ID: <9262a291-161f-e172-9d13-88a717da9de4@c-s.fr>
Date:   Fri, 2 Aug 2019 06:40:54 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Chris Packham <chris.packham@...iedtelesis.co.nz>,
        benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        malat@...ian.org
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] powerpc: Support CMDLINE_EXTEND



Le 02/08/2019 à 00:50, Chris Packham a écrit :
> Bring powerpc in line with other architectures that support extending or
> overriding the bootloader provided command line.
> 
> The current behaviour is most like CMDLINE_FROM_BOOTLOADER where the
> bootloader command line is preferred but the kernel config can provide a
> fallback so CMDLINE_FROM_BOOTLOADER is the default. CMDLINE_EXTEND can
> be used to append the CMDLINE from the kernel config to the one provided
> by the bootloader.
> 
> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>

Reviewed-by: Christophe Leroy <christophe.leroy@....fr>

> ---
> Changes in v3:
> - don't use BUG_ON in prom_strlcat
> - rearrange things to eliminate prom_strlcpy
> 
> Changes in v2:
> - incorporate ideas from Christope's patch https://patchwork.ozlabs.org/patch/1074126/
> - support CMDLINE_FORCE
> 
>   arch/powerpc/Kconfig            | 20 +++++++++++++++++-
>   arch/powerpc/kernel/prom_init.c | 36 ++++++++++++++++++++++-----------
>   2 files changed, 43 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 77f6ebf97113..d413fe1b4058 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -852,15 +852,33 @@ config CMDLINE
>   	  some command-line options at build time by entering them here.  In
>   	  most cases you will need to specify the root device here.
>   
> +choice
> +	prompt "Kernel command line type" if CMDLINE != ""
> +	default CMDLINE_FROM_BOOTLOADER
> +
> +config CMDLINE_FROM_BOOTLOADER
> +	bool "Use bootloader kernel arguments if available"
> +	help
> +	  Uses the command-line options passed by the boot loader. If
> +	  the boot loader doesn't provide any, the default kernel command
> +	  string provided in CMDLINE will be used.
> +
> +config CMDLINE_EXTEND
> +	bool "Extend bootloader kernel arguments"
> +	help
> +	  The command-line arguments provided by the boot loader will be
> +	  appended to the default kernel command string.
> +
>   config CMDLINE_FORCE
>   	bool "Always use the default kernel command string"
> -	depends on CMDLINE_BOOL
>   	help
>   	  Always use the default kernel command string, even if the boot
>   	  loader passes other arguments to the kernel.
>   	  This is useful if you cannot or don't want to change the
>   	  command-line options your boot loader passes to the kernel.
>   
> +endchoice
> +
>   config EXTRA_TARGETS
>   	string "Additional default image types"
>   	help
> diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
> index 514707ef6779..1c7010cc6ec9 100644
> --- a/arch/powerpc/kernel/prom_init.c
> +++ b/arch/powerpc/kernel/prom_init.c
> @@ -298,16 +298,24 @@ static char __init *prom_strstr(const char *s1, const char *s2)
>   	return NULL;
>   }
>   
> -static size_t __init prom_strlcpy(char *dest, const char *src, size_t size)
> -{
> -	size_t ret = prom_strlen(src);
> +static size_t __init prom_strlcat(char *dest, const char *src, size_t count)
> +{
> +	size_t dsize = prom_strlen(dest);
> +	size_t len = prom_strlen(src);
> +	size_t res = dsize + len;
> +
> +	/* This would be a bug */
> +	if (dsize >= count)
> +		return count;
> +
> +	dest += dsize;
> +	count -= dsize;
> +	if (len >= count)
> +		len = count-1;
> +	memcpy(dest, src, len);
> +	dest[len] = 0;
> +	return res;
>   
> -	if (size) {
> -		size_t len = (ret >= size) ? size - 1 : ret;
> -		memcpy(dest, src, len);
> -		dest[len] = '\0';
> -	}
> -	return ret;
>   }
>   
>   #ifdef CONFIG_PPC_PSERIES
> @@ -759,10 +767,14 @@ static void __init early_cmdline_parse(void)
>   
>   	prom_cmd_line[0] = 0;
>   	p = prom_cmd_line;
> -	if ((long)prom.chosen > 0)
> +
> +	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && (long)prom.chosen > 0)
>   		l = prom_getprop(prom.chosen, "bootargs", p, COMMAND_LINE_SIZE-1);
> -	if (IS_ENABLED(CONFIG_CMDLINE_BOOL) && (l <= 0 || p[0] == '\0')) /* dbl check */
> -		prom_strlcpy(prom_cmd_line, CONFIG_CMDLINE, sizeof(prom_cmd_line));
> +
> +	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) || l <= 0 || p[0] == '\0')
> +		prom_strlcat(prom_cmd_line, " " CONFIG_CMDLINE,
> +			     sizeof(prom_cmd_line));
> +
>   	prom_printf("command line: %s\n", prom_cmd_line);
>   
>   #ifdef CONFIG_PPC64
>