Commit 1e40d105 authored by Tyler Hicks's avatar Tyler Hicks Committed by Catalin Marinas
Browse files

arm64: Extend the kernel command line from the bootloader 



Provide support for additional kernel command line parameters to be
concatenated onto the end of the command line provided by the
bootloader. Additional parameters are specified in the CONFIG_CMDLINE
option when CONFIG_CMDLINE_EXTEND is selected, matching other
architectures and leveraging existing support in the FDT and EFI stub
code.

Special care must be taken for the arch-specific nokaslr parsing. Search
the bootargs FDT property and the CONFIG_CMDLINE when
CONFIG_CMDLINE_EXTEND is in use.

There are a couple of known use cases for this feature:

1) Switching between stable and development kernel versions, where one
   of the versions benefits from additional command line parameters,
   such as debugging options.
2) Specifying additional command line parameters, for additional tuning
   or debugging, when the bootloader does not offer an interactive mode.

Signed-off-by: default avatarTyler Hicks <tyhicks@linux.microsoft.com>
Link: https://lore.kernel.org/r/20200921191557.350256-3-tyhicks@linux.microsoft.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 52ec03f7

arch/arm64/Kconfig

+22 −1
Original line number Diff line number Diff line
@@ -1846,15 +1846,36 @@ config CMDLINE 
	  entering them here. As a minimum, you should specify the the

	  root device (e.g. root=/dev/nfs).



choice

	prompt "Kernel command line type" if CMDLINE != ""

	default CMDLINE_FROM_BOOTLOADER

	help

	  Choose how the kernel will handle the provided default kernel

	  command line string.



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 != ""

	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 EFI_STUB

	bool

arch/arm64/kernel/kaslr.c

+8 −1
Original line number Diff line number Diff line
@@ -71,7 +71,14 @@ static __init bool is_kaslr_disabled_cmdline(void *fdt) 
		prop = fdt_getprop(fdt, node, "bootargs", NULL);

		if (!prop)

			goto out;

		return cmdline_contains_nokaslr(prop);



		if (cmdline_contains_nokaslr(prop))

			return true;



		if (IS_ENABLED(CONFIG_CMDLINE_EXTEND))

			goto out;



		return false;

	}

out:

	return cmdline_contains_nokaslr(CONFIG_CMDLINE);