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Subject: Re: [PATCH v2 4/7] CMDLINE: powerpc: convert to generic builtin
 command line
To:     Daniel Walker <danielwa@cisco.com>, Will Deacon <will@kernel.org>,
        Rob Herring <robh@kernel.org>,
        Daniel Gimpelevich <daniel@gimpelevich.san-francisco.ca.us>,
        Andrew Morton <akpm@linux-foundation.org>, x86@kernel.org,
        linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        xe-linux-external@cisco.com, Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>
Cc:     Ruslan Ruslichenko <rruslich@cisco.com>,
        Ruslan Bilovol <rbilovol@cisco.com>,
        linux-kernel@vger.kernel.org
References: <20210309000247.2989531-5-danielwa@cisco.com>
From:   Christophe Leroy <christophe.leroy@csgroup.eu>
Message-ID: <c5c8b57e-7954-ec02-188a-7f85cb0af731@csgroup.eu>
Date:   Tue, 9 Mar 2021 08:56:47 +0100
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Le 09/03/2021 à 01:02, Daniel Walker a écrit :
> This updates the powerpc code to use the CONFIG_GENERIC_CMDLINE
> option.
> 
> Cc: xe-linux-external@cisco.com
> Signed-off-by: Ruslan Ruslichenko <rruslich@cisco.com>
> Signed-off-by: Ruslan Bilovol <rbilovol@cisco.com>
> Signed-off-by: Daniel Walker <danielwa@cisco.com>
> ---
>   arch/powerpc/Kconfig            | 37 +--------------------------------
>   arch/powerpc/kernel/prom.c      |  1 +
>   arch/powerpc/kernel/prom_init.c | 35 ++++++++++++++++++-------------
>   3 files changed, 23 insertions(+), 50 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 107bb4319e0e..276b06d5c961 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -167,6 +167,7 @@ config PPC
>   	select EDAC_SUPPORT
>   	select GENERIC_ATOMIC64			if PPC32
>   	select GENERIC_CLOCKEVENTS_BROADCAST	if SMP
> +	select GENERIC_CMDLINE
>   	select GENERIC_CMOS_UPDATE
>   	select GENERIC_CPU_AUTOPROBE
>   	select GENERIC_CPU_VULNERABILITIES	if PPC_BARRIER_NOSPEC
> @@ -906,42 +907,6 @@ config PPC_DENORMALISATION
>   	  Add support for handling denormalisation of single precision
>   	  values.  Useful for bare metal only.  If unsure say Y here.
>   
> -config CMDLINE
> -	string "Initial kernel command string"
> -	default ""
> -	help
> -	  On some platforms, there is currently no way for the boot loader to
> -	  pass arguments to the kernel. For these platforms, you can supply
> -	  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"
> -	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.c b/arch/powerpc/kernel/prom.c
> index ae3c41730367..96d0a01be1b4 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -27,6 +27,7 @@
>   #include <linux/irq.h>
>   #include <linux/memblock.h>
>   #include <linux/of.h>
> +#include <linux/cmdline.h>

Why is this needed in prom.c ?

>   #include <linux/of_fdt.h>
>   #include <linux/libfdt.h>
>   #include <linux/cpu.h>
> diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
> index e9d4eb6144e1..657241534d69 100644
> --- a/arch/powerpc/kernel/prom_init.c
> +++ b/arch/powerpc/kernel/prom_init.c
> @@ -27,6 +27,7 @@
>   #include <linux/initrd.h>
>   #include <linux/bitops.h>
>   #include <linux/pgtable.h>
> +#include <linux/cmdline.h>
>   #include <asm/prom.h>
>   #include <asm/rtas.h>
>   #include <asm/page.h>
> @@ -242,15 +243,6 @@ static int __init prom_strcmp(const char *cs, const char *ct)
>   	return 0;
>   }
>   
> -static char __init *prom_strcpy(char *dest, const char *src)
> -{
> -	char *tmp = dest;
> -
> -	while ((*dest++ = *src++) != '\0')
> -		/* nothing */;
> -	return tmp;
> -}
> -

This game with prom_strcpy() should go a separate preceeding patch.

Also, it looks like checkpatch.pl recommends to use strscpy() instead of strlcpy().

>   static int __init prom_strncmp(const char *cs, const char *ct, size_t count)
>   {
>   	unsigned char c1, c2;
> @@ -276,6 +268,20 @@ static size_t __init prom_strlen(const char *s)
>   	return sc - s;
>   }
>   
> +static size_t __init prom_strlcpy(char *dest, const char *src, size_t size)
> +{
> +	size_t ret = prom_strlen(src);
> +
> +	if (size) {
> +		size_t len = (ret >= size) ? size - 1 : ret;
> +
> +		memcpy(dest, src, len);
> +		dest[len] = '\0';
> +	}
> +	return ret;
> +}
> +
> +
>   static int __init prom_memcmp(const void *cs, const void *ct, size_t count)
>   {
>   	const unsigned char *su1, *su2;
> @@ -304,6 +310,7 @@ static char __init *prom_strstr(const char *s1, const char *s2)
>   	return NULL;
>   }
>   
> +#ifdef GENERIC_CMDLINE_NEED_STRLCAT
>   static size_t __init prom_strlcat(char *dest, const char *src, size_t count)
>   {
>   	size_t dsize = prom_strlen(dest);
> @@ -323,6 +330,7 @@ static size_t __init prom_strlcat(char *dest, const char *src, size_t count)
>   	return res;
>   
>   }
> +#endif
>   
>   #ifdef CONFIG_PPC_PSERIES
>   static int __init prom_strtobool(const char *s, bool *res)
> @@ -775,12 +783,11 @@ static void __init early_cmdline_parse(void)
>   	prom_cmd_line[0] = 0;
>   	p = prom_cmd_line;
>   
> -	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && (long)prom.chosen > 0)
> +	if ((long)prom.chosen > 0)
>   		l = prom_getprop(prom.chosen, "bootargs", p, COMMAND_LINE_SIZE-1);
>   
> -	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) || l <= 0 || p[0] == '\0')
> -		prom_strlcat(prom_cmd_line, " " CONFIG_CMDLINE,
> -			     sizeof(prom_cmd_line));
> +	cmdline_add_builtin_custom(prom_cmd_line, (l > 0 ? p : NULL), sizeof(prom_cmd_line),
> +					__prombss, prom_strlcpy, prom_strlcat);

So we are referencing a function that doesn't exist (namely prom_strlcat).
But it works because cmdline_add_builtin_custom() looks like a function but is in fact an obscure 
macro that doesn't use prom_strlcat() unless GENERIC_CMDLINE_NEED_STRLCAT is defined.

IMHO that's awful for readability and code maintenance.

>   
>   	prom_printf("command line: %s\n", prom_cmd_line);
>   
> @@ -2706,7 +2713,7 @@ static void __init flatten_device_tree(void)
>   
>   	/* Add "phandle" in there, we'll need it */
>   	namep = make_room(&mem_start, &mem_end, 16, 1);
> -	prom_strcpy(namep, "phandle");
> +	prom_strlcpy(namep, "phandle", 8);

Should be in a separate patch.

>   	mem_start = (unsigned long)namep + prom_strlen(namep) + 1;
>   
>   	/* Build string array */
> 

Christophe