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Commit 516cbf37 authored by Tim Bird's avatar Tim Bird Committed by Ingo Molnar
Browse files

x86, bootup: add built-in kernel command line for x86 (v2) 



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.

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.

[ mingo@elte.hu: build fix ]

Signed-off-by: default avatarTim Bird <tim.bird@am.sony.com>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent b635acec

arch/x86/Kconfig

+45 −0
Original line number Diff line number Diff line
@@ -1392,6 +1392,51 @@ 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

arch/x86/kernel/setup.c

+16 −0
Original line number Diff line number Diff line
@@ -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;
@@ -673,6 +676,19 @@ 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;