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Currently, s390 has the ability to configure the maximum kernel command
line size via Kconfig (CONFIG_COMMAND_LINE_SIZE). Other architectures
define a hardcoded COMMAND_LINE_SIZE macro in their setup.h headers.
In some use cases, such as netboot kernels, rootfs configurations, or
larger initramfs setups, a larger command line size is required. While
for embedded workloads, it can be reduced to save memory.
Move CONFIG_COMMAND_LINE_SIZE out of arch/s390/Kconfig and into
init/Kconfig under General setup, and update every architecture's setup.h
header to define COMMAND_LINE_SIZE as CONFIG_COMMAND_LINE_SIZE.
For user-space API (uapi) headers, wrap the definition in an `#ifdef
__KERNEL__` guard and retain the historical hardcoded default in the
`#else` block. When user-space headers are installed via `make
headers_install`, unifdef strips out the kernel section, ensuring the same
value as before for user-space applications including `<asm/setup.h>`.
For S390, the range is kept the same, but other architectures have varying
constraints. S390 requires a minimum of 896 bytes to protect legacy
bootloaders from overwriting the .text section. ARM, M68K, and NIOS2
allocate the command line directly on severely constrained decompressor
stacks, so their ranges are strictly capped at 2048 bytes to prevent
deterministic stack exhaustion and boot panics. PowerPC (PPC) boot
wrappers silently truncate arguments past 2048 bytes, so it is also capped
at 2048 to prevent silent parameter loss.
The SuperH (SUPERH) boot parameter page allocates exactly PAGE_SIZE
(typically 4096 bytes), and placing a 4096-byte command line starting at
offset 256 would cause strscpy() to read out of bounds; it is capped at
3840 bytes. Alpha physically limits its boot parameter block to 256
bytes, so its limit is strictly locked to 256. All other architectures
are capped at 4096 bytes to prevent unreasonable allocations.
Link: https://lore.kernel.org/20260818231646.804507-2-wfelipe@google.com
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Wilson Felipe Pereira <wfelipe@google.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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license
Many user space API headers are missing licensing information, which
makes it hard for compliance tools to determine the correct license.
By default are files without license information under the default
license of the kernel, which is GPLV2. Marking them GPLV2 would exclude
them from being included in non GPLV2 code, which is obviously not
intended. The user space API headers fall under the syscall exception
which is in the kernels COPYING file:
NOTE! This copyright does *not* cover user programs that use kernel
services by normal system calls - this is merely considered normal use
of the kernel, and does *not* fall under the heading of "derived work".
otherwise syscall usage would not be possible.
Update the files which contain no license information with an SPDX
license identifier. The chosen identifier is 'GPL-2.0 WITH
Linux-syscall-note' which is the officially assigned identifier for the
Linux syscall exception. SPDX license identifiers are a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne. See the previous patch in this series for the
methodology of how this patch was researched.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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