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Date:   Tue, 9 Mar 2021 13:40:51 -0800
From:   Daniel Walker <danielwa@cisco.com>
To:     Christophe Leroy <christophe.leroy@csgroup.eu>
Cc:     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>,
        Ruslan Ruslichenko <rruslich@cisco.com>,
        Ruslan Bilovol <rbilovol@cisco.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 4/7] CMDLINE: powerpc: convert to generic builtin
 command line
Message-ID: <20210309214051.GS109100@zorba>
References: <20210309000247.2989531-5-danielwa@cisco.com>
 <c5c8b57e-7954-ec02-188a-7f85cb0af731@csgroup.eu>
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On Tue, Mar 09, 2021 at 08:56:47AM +0100, Christophe Leroy wrote:
> 
> 
> Le 09/03/2021 ? 01:02, Daniel Walker a ?crit?:
> > 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 ?
 
Must have been a mistake, I don't think it's needed.


> >   #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().

strscpy() is very large. I'm not sure it's compatible with this prom_init.c
environment.

> >   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.

powerpc is a special case, there's no other users like this. The reason is
because of all the difficulty in this prom_init.c code. A lot of the generic
code has similar kind of changes to work across architectures.


> >   	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.

I can move it, I missed that from the first round.

Daniel