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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: Tyler Hicks <tyhicks@linux.microsoft.com>
Link: https://lore.kernel.org/r/20200921191557.350256-3-tyhicks@linux.microsoft.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Tyler Hicks 2020-09-21 14:15:57 -05:00 committed by Catalin Marinas
parent 52ec03f75d
commit 1e40d105da
2 changed files with 30 additions and 2 deletions
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23
arch/arm64/Kconfig
View File

@ -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

9
arch/arm64/kernel/kaslr.c
View File

@ -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);