Re: [PATCH] bootup: Add built-in kernel command line for x86 (v2)

2008-08-12 Thread Tim Bird
Allow x86 to support a built-in kernel command line.  The built-in
command line can override the one provided by the boot loader, for
those cases where the boot loader is broken or it is difficult
to change the command line in the the boot loader.

Signed-off-by: Tim Bird [EMAIL PROTECTED]
---
 arch/x86/Kconfig|   45 +
 arch/x86/kernel/setup.c |   16 
 2 files changed, 61 insertions(+), 0 deletions(-)

H. Peter Anvin wrote:
 Ingo Molnar wrote:
 Best would be to make it really apparent in the code that nothing
 changes if this config option is not set. Preferably there should be
 no extra code at all in that case.


 I would like to see this:
[...Nested ifdefs...]

OK. This version changes absolutely nothing if CONFIG_CMDLINE_BOOL is not
set (the default).  Also, no space is appended even when CONFIG_CMDLINE_BOOL
is set, but the builtin string is empty.  This is less sloppy all the way
around, IMHO.

Note that I use the same option names as on other arches for
this feature.

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 3d0f2b6..f7bbbd7 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1393,6 +1393,51 @@ config COMPAT_VDSO

  If unsure, say Y.

+config CMDLINE_BOOL
+   bool Built-in kernel command line
+   default n
+   help
+ Allow for specifying boot arguments to the kernel at
+ build time.  On some systems (e.g. embedded ones), it is
+ necessary or convenient to provide some or all of the
+ kernel boot arguments with the kernel itself (that is,
+ to not rely on the boot loader to provide them.)
+
+ To compile command line arguments into the kernel,
+ set this option to 'Y', then fill in the
+ the boot arguments in CONFIG_CMDLINE.
+
+ Systems with fully functional boot loaders (i.e. non-embedded)
+ should leave this option set to 'N'.
+
+config CMDLINE
+   string Built-in kernel command string
+   depends on CMDLINE_BOOL
+   default 
+   help
+ Enter arguments here that should be compiled into the kernel
+ image and used at boot time.  If the boot loader provides a
+ command line at boot time, it is appended to this string to
+ form the full kernel command line, when the system boots.
+
+ However, you can use the CONFIG_CMDLINE_OVERRIDE option to
+ change this behavior.
+
+ In most cases, the command line (whether built-in or provided
+ by the boot loader) should specify the device for the root
+ file system.
+
+config CMDLINE_OVERRIDE
+   bool Built-in command line overrides boot loader arguments
+   default n
+   depends on CMDLINE_BOOL
+   help
+ Set this option to 'Y' to have the kernel ignore the boot loader
+ command line, and use ONLY the built-in command line.
+
+ This is used to work around broken boot loaders.  This should
+ be set to 'N' under normal conditions.
+
 endmenu

 config ARCH_ENABLE_MEMORY_HOTPLUG
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 2d88858..492610c 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -223,6 +223,9 @@ unsigned long saved_video_mode;
 #define RAMDISK_LOAD_FLAG  0x4000

 static char __initdata command_line[COMMAND_LINE_SIZE];
+#ifdef CONFIG_CMDLINE_BOOL
+static char __initdata builtin_cmdline[COMMAND_LINE_SIZE] = CONFIG_CMDLINE;
+#endif

 #if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
 struct edd edd;
@@ -665,6 +668,19 @@ void __init setup_arch(char **cmdline_p)
bss_resource.start = virt_to_phys(__bss_start);
bss_resource.end = virt_to_phys(__bss_stop)-1;

+#ifdef CONFIG_CMDLINE_BOOL
+#ifdef CONFIG_CMDLINE_OVERRIDE
+   strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
+#else
+   if (builtin_cmdline[0]) {
+   /* append boot loader cmdline to builtin */
+   strlcat(builtin_cmdline,  , COMMAND_LINE_SIZE);
+   strlcat(builtin_cmdline, boot_command_line, COMMAND_LINE_SIZE);
+   strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
+   }
+#endif
+#endif
+
strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
*cmdline_p = command_line;

-- 
1.5.6

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Re: [PATCH] bootup: Add built-in kernel command line for x86

2008-08-11 Thread Ingo Molnar

* Tim Bird [EMAIL PROTECTED] wrote:

 Add support for a built-in command line for x86 architectures. The 
 Kconfig help gives the major rationale for this addition.

i have actually used a local hack quite similar to this to inject boot 
options into bzImages via randconfig - so i would find this feature 
rather useful.

a small observation:

 + /* append boot loader cmdline to builtin, unless builtin overrides it */
 + if (builtin_cmdline[0] != '!') {
 + strlcat(builtin_cmdline,  , COMMAND_LINE_SIZE);
 + strlcat(builtin_cmdline, boot_command_line, COMMAND_LINE_SIZE);
 + strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
 + } else {
 + strlcpy(boot_command_line, builtin_cmdline[1],
 + COMMAND_LINE_SIZE);
 + }

the default branch changes existing command lines slightly: it appends a 
space to them. This could break scripts that rely on the precise 
contents of /proc/cmdline output. (i have some - they are arguably 
dodgy)

Best would be to make it really apparent in the code that nothing 
changes if this config option is not set. Preferably there should be no 
extra code at all in that case.

Ingo
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Re: [PATCH] bootup: Add built-in kernel command line for x86

2008-08-11 Thread H. Peter Anvin

Ingo Molnar wrote:

* Tim Bird [EMAIL PROTECTED] wrote:

Add support for a built-in command line for x86 architectures. The 
Kconfig help gives the major rationale for this addition.


i have actually used a local hack quite similar to this to inject boot 
options into bzImages via randconfig - so i would find this feature 
rather useful.


a small observation:


+   /* append boot loader cmdline to builtin, unless builtin overrides it */
+   if (builtin_cmdline[0] != '!') {
+   strlcat(builtin_cmdline,  , COMMAND_LINE_SIZE);
+   strlcat(builtin_cmdline, boot_command_line, COMMAND_LINE_SIZE);
+   strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
+   } else {
+   strlcpy(boot_command_line, builtin_cmdline[1],
+   COMMAND_LINE_SIZE);
+   }


the default branch changes existing command lines slightly: it appends a 
space to them. This could break scripts that rely on the precise 
contents of /proc/cmdline output. (i have some - they are arguably 
dodgy)


Best would be to make it really apparent in the code that nothing 
changes if this config option is not set. Preferably there should be no 
extra code at all in that case.




I would like to see this:

#ifdef CONFIG_BUILTIN_CMDLINE
# ifdef CONFIG_BUILTIN_CMDLINE_OVERRIDE
strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
# else
if (boot_command_line) {
strlcat(builtin_cmdline,  , COMMAND_LINE_SIZE);
strlcat(builtin_cmdline, boot_command_line, COMMAND_LINE_SIZE);
}
# endif
#endif

-hpa


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Re: [PATCH] bootup: Add built-in kernel command line for x86

2008-08-11 Thread Tim Bird
H. Peter Anvin wrote:
 Ingo Molnar wrote:
 * Tim Bird [EMAIL PROTECTED] wrote:

 Add support for a built-in command line for x86 architectures. The
 Kconfig help gives the major rationale for this addition.

 i have actually used a local hack quite similar to this to inject boot
 options into bzImages via randconfig - so i would find this feature
 rather useful.

 a small observation:

 +/* append boot loader cmdline to builtin, unless builtin
 overrides it */
 +if (builtin_cmdline[0] != '!') {
 +strlcat(builtin_cmdline,  , COMMAND_LINE_SIZE);
 +strlcat(builtin_cmdline, boot_command_line, COMMAND_LINE_SIZE);
 +strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
 +} else {
 +strlcpy(boot_command_line, builtin_cmdline[1],
 +COMMAND_LINE_SIZE);
 +}

 the default branch changes existing command lines slightly: it appends
 a space to them. This could break scripts that rely on the precise
 contents of /proc/cmdline output. (i have some - they are arguably dodgy)

Yeah, I wasn't too comfortable with that.

 Best would be to make it really apparent in the code that nothing
 changes if this config option is not set. Preferably there should be
 no extra code at all in that case.

Agreed.

 
 I would like to see this:
 
 #ifdef CONFIG_BUILTIN_CMDLINE
 # ifdef CONFIG_BUILTIN_CMDLINE_OVERRIDE
 strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
 # else
 if (boot_command_line) {
 strlcat(builtin_cmdline,  , COMMAND_LINE_SIZE);
 strlcat(builtin_cmdline, boot_command_line, COMMAND_LINE_SIZE);
 }
 # endif
 #endif

You missed copying builtin_cmdline back to boot_command_line, but
in general this looks OK to me.  If nobody objects to the ifdef
multiplicity, I'll work up a version tomorrow for review.  (Sorry,
I'm a bit swamped today.)
 -- Tim

=
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Corporation of America
=

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Re: [PATCH] bootup: Add built-in kernel command line for x86

2008-08-06 Thread Robert Schwebel
On Wed, Aug 06, 2008 at 02:31:48PM -0700, Tim Bird wrote:
 Add support for a built-in command line for x86 architectures.
 The Kconfig help gives the major rationale for this addition.

If this feature is desired on all architectures, shouldn't it go out of
arch/?

rsc
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Re: [PATCH] bootup: Add built-in kernel command line for x86

2008-08-06 Thread Matt Mackall

On Wed, 2008-08-06 at 14:31 -0700, Tim Bird wrote:
 The default behavior is to append the boot loader string
 to this one.  However, there is a mechanism (leading '!')
 to force the built-in string to override the boot loader
 string.

Nice solution.

Where is this relative to early boot option checking?

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Re: [PATCH] bootup: Add built-in kernel command line for x86

2008-08-06 Thread Tim Bird
Matt Mackall wrote:
 On Wed, 2008-08-06 at 14:31 -0700, Tim Bird wrote:
 The default behavior is to append the boot loader string
 to this one.  However, there is a mechanism (leading '!')
 to force the built-in string to override the boot loader
 string.
 
 Nice solution.
 
 Where is this relative to early boot option checking?

parse_early_param() is right AFTER this in the x86 setup_arch()
function (in arch/x86/kernel/setup.c).  All the other command-line
handling I could find is after this in init/main.c:start_kernel().

There is some stuff earlier in the setup_arch() routine about
boot_params, but that looks like it's related to the old(?)
binary data points you can jam into the kernel image.  (That is,
it doesn't look like it's related to the command line handling).
 -- Tim

=
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Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Corporation of America
=

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Re: [PATCH] bootup: Add built-in kernel command line for x86

2008-08-06 Thread H. Peter Anvin

Tim Bird wrote:


One difficulty is that the other arches' command lines
are not currently broken, so there's no real incentive
to change them.

The only thing novel thing I'm adding here is the addition of
the leading '!' to allow for an override.  This is needed
in some x86 cases I'm familiar with, but I've haven't seen
any cases where it would be useful for other arches.
(not to say they don't exist - I just haven't seen them.)



Note that it could just as easily be done with a CONFIG_CMDLINE_OVERRIDE 
option, since the initial reason for a magic character was to be able to 
provide both prefix and suffix splicing.


CONFIG_CMDLINE_OVERRIDE is probably more palatable to other architectures.

-hpa
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Re: [PATCH] bootup: Add built-in kernel command line for x86

2008-08-06 Thread Matt Mackall

On Wed, 2008-08-06 at 15:31 -0700, Tim Bird wrote:
 Matt Mackall wrote:
  On Wed, 2008-08-06 at 14:31 -0700, Tim Bird wrote:
  The default behavior is to append the boot loader string
  to this one.  However, there is a mechanism (leading '!')
  to force the built-in string to override the boot loader
  string.
  
  Nice solution.
  
  Where is this relative to early boot option checking?
 
 parse_early_param() is right AFTER this in the x86 setup_arch()
 function (in arch/x86/kernel/setup.c).  All the other command-line
 handling I could find is after this in init/main.c:start_kernel().

Ok, there are a couple weird outliers outside of that still, but that
should make most people satisfied.

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Re: [PATCH] bootup: Add built-in kernel command line for x86

2008-08-06 Thread Matt Mackall

On Wed, 2008-08-06 at 15:48 -0700, H. Peter Anvin wrote:
 Tim Bird wrote:
  
  One difficulty is that the other arches' command lines
  are not currently broken, so there's no real incentive
  to change them.
  
  The only thing novel thing I'm adding here is the addition of
  the leading '!' to allow for an override.  This is needed
  in some x86 cases I'm familiar with, but I've haven't seen
  any cases where it would be useful for other arches.
  (not to say they don't exist - I just haven't seen them.)
  
 
 Note that it could just as easily be done with a CONFIG_CMDLINE_OVERRIDE 
 option, since the initial reason for a magic character was to be able to 
 provide both prefix and suffix splicing.

You're right, I had forgotten about the suffix splicing and my brain is
a bit foggy on what motivated it.

 CONFIG_CMDLINE_OVERRIDE is probably more palatable to other architectures.

Yes, though I doubt we're in danger of introducing any real backwards
compatibility issues with the magic '!' at the beginning.

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Re: [PATCH] bootup: Add built-in kernel command line for x86

2008-08-06 Thread Tim Bird
H. Peter Anvin wrote:
 Tim Bird wrote:
 The only thing novel thing I'm adding here is the addition of
 the leading '!' to allow for an override.  This is needed
 in some x86 cases I'm familiar with, but I've haven't seen
 any cases where it would be useful for other arches.
 (not to say they don't exist - I just haven't seen them.)

 
 Note that it could just as easily be done with a CONFIG_CMDLINE_OVERRIDE
 option, since the initial reason for a magic character was to be able to
 provide both prefix and suffix splicing.
Agreed.

 
 CONFIG_CMDLINE_OVERRIDE is probably more palatable to other architectures.

I'd be OK implementing it with an option, rather than a magic char.
I was trying to avoid adding too many options, since many kernel
developers prefer fewer options where possible.  But the magic
char makes the code less straightforward.

If we ever move towards supporting both prefix and suffice splicing (or
even complicated in-the-middle splicing), then the magic char is
easier to develop into that.  But so far, I can only come up with
reasonable cases for append and override, and I don't want to add
superfluous handling for non-existent use cases.
 -- Tim

=
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Corporation of America
=

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Re: [PATCH] bootup: Add built-in kernel command line for x86

2008-08-06 Thread H. Peter Anvin

Matt Mackall wrote:

On Wed, 2008-08-06 at 15:48 -0700, H. Peter Anvin wrote:

Tim Bird wrote:

One difficulty is that the other arches' command lines
are not currently broken, so there's no real incentive
to change them.

The only thing novel thing I'm adding here is the addition of
the leading '!' to allow for an override.  This is needed
in some x86 cases I'm familiar with, but I've haven't seen
any cases where it would be useful for other arches.
(not to say they don't exist - I just haven't seen them.)

Note that it could just as easily be done with a CONFIG_CMDLINE_OVERRIDE 
option, since the initial reason for a magic character was to be able to 
provide both prefix and suffix splicing.


You're right, I had forgotten about the suffix splicing and my brain is
a bit foggy on what motivated it.



Well, prefix = bootloader overrides; suffix = builtin overrides.


CONFIG_CMDLINE_OVERRIDE is probably more palatable to other architectures.


Yes, though I doubt we're in danger of introducing any real backwards
compatibility issues with the magic '!' at the beginning.


Well, it does if we want to make this a generic feature, which I believe 
we should.


-hpa

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Re: [PATCH] bootup: Add built-in kernel command line for x86

2008-08-06 Thread H. Peter Anvin

Tim Bird wrote:



CONFIG_CMDLINE_OVERRIDE is probably more palatable to other architectures.


I'd be OK implementing it with an option, rather than a magic char.
I was trying to avoid adding too many options, since many kernel
developers prefer fewer options where possible.  But the magic
char makes the code less straightforward.

If we ever move towards supporting both prefix and suffice splicing (or
even complicated in-the-middle splicing), then the magic char is
easier to develop into that.  But so far, I can only come up with
reasonable cases for append and override, and I don't want to add
superfluous handling for non-existent use cases.


I think I agree, and the override option would make it easier to make 
generic.


-hpa

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