[PATCH v2] powerpc: Support CMDLINE_EXTEND

[PATCH v2] powerpc: Support CMDLINE_EXTEND

[Chris Packham]

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@alliedtelesis.co.nz>
---
While I'm at it does anyone think it's worth getting rid of the default CMDLINE
value if CMDLINE_BOOL and maybe CMDLINE_BOOL? Every defconfig in the kernel
that sets CMDLINE_BOOL=y also sets CMDLINE to something other than
"console=ttyS0,9600 console=tty0 root=/dev/sda2". Removing CMDLINE_BOOL and
unconditionally setting the default value of CMDLINE to "" would clean up the
Kconfig even more.

Changes in v2:
- incorporate ideas from Christope's patch https://patchwork.ozlabs.org/patch/1074126/

 arch/powerpc/Kconfig            | 20 +++++++++++++++++++-
 arch/powerpc/kernel/prom_init.c | 26 +++++++++++++++++++++++++-
 2 files changed, 44 insertions(+), 2 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..df29f141dbd2 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -310,6 +310,25 @@ static size_t __init prom_strlcpy(char *dest, const char *src, size_t size)
 	return ret;
 }
 
+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 */
+	BUG_ON(dsize >= count);
+
+	dest += dsize;
+	count -= dsize;
+	if (len >= count)
+		len = count-1;
+	memcpy(dest, src, len);
+	dest[len] = 0;
+	return res;
+
+}
+
 #ifdef CONFIG_PPC_PSERIES
 static int __init prom_strtobool(const char *s, bool *res)
 {
@@ -761,8 +780,13 @@ static void __init early_cmdline_parse(void)
 	p = prom_cmd_line;
 	if ((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 */
+
+	if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || l <= 0 || p[0] == '\0')
 		prom_strlcpy(prom_cmd_line, CONFIG_CMDLINE, sizeof(prom_cmd_line));
+	else if (IS_ENABLED(CONFIG_CMDLINE_EXTEND))
+		prom_strlcat(prom_cmd_line, " " CONFIG_CMDLINE,
+			     sizeof(prom_cmd_line));
+
 	prom_printf("command line: %s\n", prom_cmd_line);
 
 #ifdef CONFIG_PPC64
-- 
2.22.0

Re: [PATCH v2] powerpc: Support CMDLINE_EXTEND

[Christophe Leroy]

Le 01/08/2019 à 04:12, 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@alliedtelesis.co.nz>
> ---
> While I'm at it does anyone think it's worth getting rid of the default CMDLINE
> value if CMDLINE_BOOL and maybe CMDLINE_BOOL? Every defconfig in the kernel
> that sets CMDLINE_BOOL=y also sets CMDLINE to something other than
> "console=ttyS0,9600 console=tty0 root=/dev/sda2". Removing CMDLINE_BOOL and
> unconditionally setting the default value of CMDLINE to "" would clean up the
> Kconfig even more.

Note 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cbe46bd4f5104552b612505b73d366f66efc2341 
which is already a step forward.

I guess that default is for users selecting this option manually to get 
a first sensitive CMDLINE. But is it really worth it ?

> 
> Changes in v2:
> - incorporate ideas from Christope's patch https://patchwork.ozlabs.org/patch/1074126/
> 
>   arch/powerpc/Kconfig            | 20 +++++++++++++++++++-
>   arch/powerpc/kernel/prom_init.c | 26 +++++++++++++++++++++++++-
>   2 files changed, 44 insertions(+), 2 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..df29f141dbd2 100644
> --- a/arch/powerpc/kernel/prom_init.c
> +++ b/arch/powerpc/kernel/prom_init.c
> @@ -310,6 +310,25 @@ static size_t __init prom_strlcpy(char *dest, const char *src, size_t size)
>   	return ret;
>   }
>   
> +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 */
> +	BUG_ON(dsize >= count);

Has you pointed in another mail, BUG_ON() should be avoided here.
I guess if the destination is already full, just return count:

if (dsize >= count)
	return count;

> +
> +	dest += dsize;
> +	count -= dsize;
> +	if (len >= count)
> +		len = count-1;
> +	memcpy(dest, src, len);
> +	dest[len] = 0;
> +	return res;
> +
> +}
> +
>   #ifdef CONFIG_PPC_PSERIES
>   static int __init prom_strtobool(const char *s, bool *res)
>   {
> @@ -761,8 +780,13 @@ static void __init early_cmdline_parse(void)
>   	p = prom_cmd_line;
>   	if ((long)prom.chosen > 0)
>   		l = prom_getprop(prom.chosen, "bootargs", p, COMMAND_LINE_SIZE-1);

The above is pointless in case CONFIG_CMDLINE_FORCE is selected.


> -	if (IS_ENABLED(CONFIG_CMDLINE_BOOL) && (l <= 0 || p[0] == '\0')) /* dbl check */
> +
> +	if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || l <= 0 || p[0] == '\0')
>   		prom_strlcpy(prom_cmd_line, CONFIG_CMDLINE, sizeof(prom_cmd_line));

If we can ensure that prom_cmd_line remains empty when 
CONFIG_CMDLINE_FORCE is selected (see above comment), then 
prom_strlcat() can be used in lieu of prom_strlcpy()

> +	else if (IS_ENABLED(CONFIG_CMDLINE_EXTEND))
> +		prom_strlcat(prom_cmd_line, " " CONFIG_CMDLINE,
> +			     sizeof(prom_cmd_line));
> +
>   	prom_printf("command line: %s\n", prom_cmd_line);
>   
>   #ifdef CONFIG_PPC64
> 

Christophe

Re: [PATCH v2] powerpc: Support CMDLINE_EXTEND

[Chris Packham]

On Thu, 2019-08-01 at 08:14 +0200, Christophe Leroy wrote:
> 
> Le 01/08/2019 à 04:12, 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@alliedtelesis.co.nz>
> > ---
> > While I'm at it does anyone think it's worth getting rid of the
> > default CMDLINE
> > value if CMDLINE_BOOL and maybe CMDLINE_BOOL? Every defconfig in
> > the kernel
> > that sets CMDLINE_BOOL=y also sets CMDLINE to something other than
> > "console=ttyS0,9600 console=tty0 root=/dev/sda2". Removing
> > CMDLINE_BOOL and
> > unconditionally setting the default value of CMDLINE to "" would
> > clean up the
> > Kconfig even more.
> Note 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/co
> mmit/?id=cbe46bd4f5104552b612505b73d366f66efc2341 
> which is already a step forward.
> 
> I guess that default is for users selecting this option manually to
> get 
> a first sensitive CMDLINE. But is it really worth it ?
> 

I'm not even sure if it is working as intended right now. Even without
my changes if I use menuconfig and select CMDLINE_BOOL I end up with 
CONFIG_CMDLINE="" in the resulting .config.

> > 
> > 
> > Changes in v2:
> > - incorporate ideas from Christope's patch https://patchwork.ozlabs
> > .org/patch/1074126/
> > 
> >   arch/powerpc/Kconfig            | 20 +++++++++++++++++++-
> >   arch/powerpc/kernel/prom_init.c | 26 +++++++++++++++++++++++++-
> >   2 files changed, 44 insertions(+), 2 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..df29f141dbd2 100644
> > --- a/arch/powerpc/kernel/prom_init.c
> > +++ b/arch/powerpc/kernel/prom_init.c
> > @@ -310,6 +310,25 @@ static size_t __init prom_strlcpy(char *dest,
> > const char *src, size_t size)
> >   	return ret;
> >   }
> >   
> > +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 */
> > +	BUG_ON(dsize >= count);
> Has you pointed in another mail, BUG_ON() should be avoided here.
> I guess if the destination is already full, just return count:
> 
> if (dsize >= count)
> 	return count;
> 

Will fix in v3.

> > 
> > +
> > +	dest += dsize;
> > +	count -= dsize;
> > +	if (len >= count)
> > +		len = count-1;
> > +	memcpy(dest, src, len);
> > +	dest[len] = 0;
> > +	return res;
> > +
> > +}
> > +
> >   #ifdef CONFIG_PPC_PSERIES
> >   static int __init prom_strtobool(const char *s, bool *res)
> >   {
> > @@ -761,8 +780,13 @@ static void __init early_cmdline_parse(void)
> >   	p = prom_cmd_line;
> >   	if ((long)prom.chosen > 0)
> >   		l = prom_getprop(prom.chosen, "bootargs", p,
> > COMMAND_LINE_SIZE-1);
> The above is pointless in case CONFIG_CMDLINE_FORCE is selected.
> 

Will fix in v3.

> > 
> > -	if (IS_ENABLED(CONFIG_CMDLINE_BOOL) && (l <= 0 || p[0] ==
> > '\0')) /* dbl check */
> > +
> > +	if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || l <= 0 || p[0] ==
> > '\0')
> >   		prom_strlcpy(prom_cmd_line, CONFIG_CMDLINE,
> > sizeof(prom_cmd_line));
> If we can ensure that prom_cmd_line remains empty when 
> CONFIG_CMDLINE_FORCE is selected (see above comment), then 
> prom_strlcat() can be used in lieu of prom_strlcpy()
> 
> > 
> > +	else if (IS_ENABLED(CONFIG_CMDLINE_EXTEND))
> > +		prom_strlcat(prom_cmd_line, " " CONFIG_CMDLINE,
> > +			     sizeof(prom_cmd_line));
> > +
> >   	prom_printf("command line: %s\n", prom_cmd_line);
> >   
> >   #ifdef CONFIG_PPC64
> > 
> Christophe

Re: [PATCH v2] powerpc: Support CMDLINE_EXTEND

[Christophe Leroy]

Le 02/08/2019 à 00:32, Chris Packham a écrit :
> On Thu, 2019-08-01 at 08:14 +0200, Christophe Leroy wrote:
>>
>> Le 01/08/2019 à 04:12, 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@alliedtelesis.co.nz>
>>> ---
>>> While I'm at it does anyone think it's worth getting rid of the
>>> default CMDLINE
>>> value if CMDLINE_BOOL and maybe CMDLINE_BOOL? Every defconfig in
>>> the kernel
>>> that sets CMDLINE_BOOL=y also sets CMDLINE to something other than
>>> "console=ttyS0,9600 console=tty0 root=/dev/sda2". Removing
>>> CMDLINE_BOOL and
>>> unconditionally setting the default value of CMDLINE to "" would
>>> clean up the
>>> Kconfig even more.
>> Note
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/co
>> mmit/?id=cbe46bd4f5104552b612505b73d366f66efc2341
>> which is already a step forward.
>>
>> I guess that default is for users selecting this option manually to
>> get
>> a first sensitive CMDLINE. But is it really worth it ?
>>
> 
> I'm not even sure if it is working as intended right now. Even without
> my changes if I use menuconfig and select CMDLINE_BOOL I end up with
> CONFIG_CMDLINE="" in the resulting .config.

I guess if the CONFIG_CMDLINE doesn't exist yet, it will get the default 
value. But if it is already there allthough empty, it will remain empty.
So yes I guess you could just drop it for this reason and the other 
reasons you said.

Christophe