mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-03 17:40:04 +00:00
![Nicholas Piggin](/assets/img/avatar_default.png)
On big systems, the mm refcount can become highly contented when doing a lot of context switching with threaded applications. user<->idle switch is one of the important cases. Abandoning lazy tlb entirely slows this switching down quite a bit in the common uncontended case, so that is not viable. Implement a scheme where lazy tlb mm references do not contribute to the refcount, instead they get explicitly removed when the refcount reaches zero. The final mmdrop() sends IPIs to all CPUs in the mm_cpumask and they switch away from this mm to init_mm if it was being used as the lazy tlb mm. Enabling the shoot lazies option therefore requires that the arch ensures that mm_cpumask contains all CPUs that could possibly be using mm. A DEBUG_VM option IPIs every CPU in the system after this to ensure there are no references remaining before the mm is freed. Shootdown IPIs cost could be an issue, but they have not been observed to be a serious problem with this scheme, because short-lived processes tend not to migrate CPUs much, therefore they don't get much chance to leave lazy tlb mm references on remote CPUs. There are a lot of options to reduce them if necessary, described in comments. The near-worst-case can be benchmarked with will-it-scale: context_switch1_threads -t $(($(nproc) / 2)) This will create nproc threads (nproc / 2 switching pairs) all sharing the same mm that spread over all CPUs so each CPU does thread->idle->thread switching. [ Rik came up with basically the same idea a few years ago, so credit to him for that. ] Link: https://lore.kernel.org/linux-mm/20230118080011.2258375-1-npiggin@gmail.com/ Link: https://lore.kernel.org/all/20180728215357.3249-11-riel@surriel.com/ Link: https://lkml.kernel.org/r/20230203071837.1136453-5-npiggin@gmail.com Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nadav Amit <nadav.amit@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
1497 lines
44 KiB
Text
1497 lines
44 KiB
Text
# SPDX-License-Identifier: GPL-2.0
|
||
#
|
||
# General architecture dependent options
|
||
#
|
||
|
||
#
|
||
# Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can
|
||
# override the default values in this file.
|
||
#
|
||
source "arch/$(SRCARCH)/Kconfig"
|
||
|
||
menu "General architecture-dependent options"
|
||
|
||
config CRASH_CORE
|
||
bool
|
||
|
||
config KEXEC_CORE
|
||
select CRASH_CORE
|
||
bool
|
||
|
||
config KEXEC_ELF
|
||
bool
|
||
|
||
config HAVE_IMA_KEXEC
|
||
bool
|
||
|
||
config ARCH_HAS_SUBPAGE_FAULTS
|
||
bool
|
||
help
|
||
Select if the architecture can check permissions at sub-page
|
||
granularity (e.g. arm64 MTE). The probe_user_*() functions
|
||
must be implemented.
|
||
|
||
config HOTPLUG_SMT
|
||
bool
|
||
|
||
config GENERIC_ENTRY
|
||
bool
|
||
|
||
config KPROBES
|
||
bool "Kprobes"
|
||
depends on MODULES
|
||
depends on HAVE_KPROBES
|
||
select KALLSYMS
|
||
select TASKS_RCU if PREEMPTION
|
||
help
|
||
Kprobes allows you to trap at almost any kernel address and
|
||
execute a callback function. register_kprobe() establishes
|
||
a probepoint and specifies the callback. Kprobes is useful
|
||
for kernel debugging, non-intrusive instrumentation and testing.
|
||
If in doubt, say "N".
|
||
|
||
config JUMP_LABEL
|
||
bool "Optimize very unlikely/likely branches"
|
||
depends on HAVE_ARCH_JUMP_LABEL
|
||
select OBJTOOL if HAVE_JUMP_LABEL_HACK
|
||
help
|
||
This option enables a transparent branch optimization that
|
||
makes certain almost-always-true or almost-always-false branch
|
||
conditions even cheaper to execute within the kernel.
|
||
|
||
Certain performance-sensitive kernel code, such as trace points,
|
||
scheduler functionality, networking code and KVM have such
|
||
branches and include support for this optimization technique.
|
||
|
||
If it is detected that the compiler has support for "asm goto",
|
||
the kernel will compile such branches with just a nop
|
||
instruction. When the condition flag is toggled to true, the
|
||
nop will be converted to a jump instruction to execute the
|
||
conditional block of instructions.
|
||
|
||
This technique lowers overhead and stress on the branch prediction
|
||
of the processor and generally makes the kernel faster. The update
|
||
of the condition is slower, but those are always very rare.
|
||
|
||
( On 32-bit x86, the necessary options added to the compiler
|
||
flags may increase the size of the kernel slightly. )
|
||
|
||
config STATIC_KEYS_SELFTEST
|
||
bool "Static key selftest"
|
||
depends on JUMP_LABEL
|
||
help
|
||
Boot time self-test of the branch patching code.
|
||
|
||
config STATIC_CALL_SELFTEST
|
||
bool "Static call selftest"
|
||
depends on HAVE_STATIC_CALL
|
||
help
|
||
Boot time self-test of the call patching code.
|
||
|
||
config OPTPROBES
|
||
def_bool y
|
||
depends on KPROBES && HAVE_OPTPROBES
|
||
select TASKS_RCU if PREEMPTION
|
||
|
||
config KPROBES_ON_FTRACE
|
||
def_bool y
|
||
depends on KPROBES && HAVE_KPROBES_ON_FTRACE
|
||
depends on DYNAMIC_FTRACE_WITH_REGS
|
||
help
|
||
If function tracer is enabled and the arch supports full
|
||
passing of pt_regs to function tracing, then kprobes can
|
||
optimize on top of function tracing.
|
||
|
||
config UPROBES
|
||
def_bool n
|
||
depends on ARCH_SUPPORTS_UPROBES
|
||
help
|
||
Uprobes is the user-space counterpart to kprobes: they
|
||
enable instrumentation applications (such as 'perf probe')
|
||
to establish unintrusive probes in user-space binaries and
|
||
libraries, by executing handler functions when the probes
|
||
are hit by user-space applications.
|
||
|
||
( These probes come in the form of single-byte breakpoints,
|
||
managed by the kernel and kept transparent to the probed
|
||
application. )
|
||
|
||
config HAVE_64BIT_ALIGNED_ACCESS
|
||
def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
|
||
help
|
||
Some architectures require 64 bit accesses to be 64 bit
|
||
aligned, which also requires structs containing 64 bit values
|
||
to be 64 bit aligned too. This includes some 32 bit
|
||
architectures which can do 64 bit accesses, as well as 64 bit
|
||
architectures without unaligned access.
|
||
|
||
This symbol should be selected by an architecture if 64 bit
|
||
accesses are required to be 64 bit aligned in this way even
|
||
though it is not a 64 bit architecture.
|
||
|
||
See Documentation/core-api/unaligned-memory-access.rst for
|
||
more information on the topic of unaligned memory accesses.
|
||
|
||
config HAVE_EFFICIENT_UNALIGNED_ACCESS
|
||
bool
|
||
help
|
||
Some architectures are unable to perform unaligned accesses
|
||
without the use of get_unaligned/put_unaligned. Others are
|
||
unable to perform such accesses efficiently (e.g. trap on
|
||
unaligned access and require fixing it up in the exception
|
||
handler.)
|
||
|
||
This symbol should be selected by an architecture if it can
|
||
perform unaligned accesses efficiently to allow different
|
||
code paths to be selected for these cases. Some network
|
||
drivers, for example, could opt to not fix up alignment
|
||
problems with received packets if doing so would not help
|
||
much.
|
||
|
||
See Documentation/core-api/unaligned-memory-access.rst for more
|
||
information on the topic of unaligned memory accesses.
|
||
|
||
config ARCH_USE_BUILTIN_BSWAP
|
||
bool
|
||
help
|
||
Modern versions of GCC (since 4.4) have builtin functions
|
||
for handling byte-swapping. Using these, instead of the old
|
||
inline assembler that the architecture code provides in the
|
||
__arch_bswapXX() macros, allows the compiler to see what's
|
||
happening and offers more opportunity for optimisation. In
|
||
particular, the compiler will be able to combine the byteswap
|
||
with a nearby load or store and use load-and-swap or
|
||
store-and-swap instructions if the architecture has them. It
|
||
should almost *never* result in code which is worse than the
|
||
hand-coded assembler in <asm/swab.h>. But just in case it
|
||
does, the use of the builtins is optional.
|
||
|
||
Any architecture with load-and-swap or store-and-swap
|
||
instructions should set this. And it shouldn't hurt to set it
|
||
on architectures that don't have such instructions.
|
||
|
||
config KRETPROBES
|
||
def_bool y
|
||
depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK)
|
||
|
||
config KRETPROBE_ON_RETHOOK
|
||
def_bool y
|
||
depends on HAVE_RETHOOK
|
||
depends on KRETPROBES
|
||
select RETHOOK
|
||
|
||
config USER_RETURN_NOTIFIER
|
||
bool
|
||
depends on HAVE_USER_RETURN_NOTIFIER
|
||
help
|
||
Provide a kernel-internal notification when a cpu is about to
|
||
switch to user mode.
|
||
|
||
config HAVE_IOREMAP_PROT
|
||
bool
|
||
|
||
config HAVE_KPROBES
|
||
bool
|
||
|
||
config HAVE_KRETPROBES
|
||
bool
|
||
|
||
config HAVE_OPTPROBES
|
||
bool
|
||
|
||
config HAVE_KPROBES_ON_FTRACE
|
||
bool
|
||
|
||
config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
|
||
bool
|
||
help
|
||
Since kretprobes modifies return address on the stack, the
|
||
stacktrace may see the kretprobe trampoline address instead
|
||
of correct one. If the architecture stacktrace code and
|
||
unwinder can adjust such entries, select this configuration.
|
||
|
||
config HAVE_FUNCTION_ERROR_INJECTION
|
||
bool
|
||
|
||
config HAVE_NMI
|
||
bool
|
||
|
||
config HAVE_FUNCTION_DESCRIPTORS
|
||
bool
|
||
|
||
config TRACE_IRQFLAGS_SUPPORT
|
||
bool
|
||
|
||
config TRACE_IRQFLAGS_NMI_SUPPORT
|
||
bool
|
||
|
||
#
|
||
# An arch should select this if it provides all these things:
|
||
#
|
||
# task_pt_regs() in asm/processor.h or asm/ptrace.h
|
||
# arch_has_single_step() if there is hardware single-step support
|
||
# arch_has_block_step() if there is hardware block-step support
|
||
# asm/syscall.h supplying asm-generic/syscall.h interface
|
||
# linux/regset.h user_regset interfaces
|
||
# CORE_DUMP_USE_REGSET #define'd in linux/elf.h
|
||
# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit}
|
||
# TIF_NOTIFY_RESUME calls resume_user_mode_work()
|
||
#
|
||
config HAVE_ARCH_TRACEHOOK
|
||
bool
|
||
|
||
config HAVE_DMA_CONTIGUOUS
|
||
bool
|
||
|
||
config GENERIC_SMP_IDLE_THREAD
|
||
bool
|
||
|
||
config GENERIC_IDLE_POLL_SETUP
|
||
bool
|
||
|
||
config ARCH_HAS_FORTIFY_SOURCE
|
||
bool
|
||
help
|
||
An architecture should select this when it can successfully
|
||
build and run with CONFIG_FORTIFY_SOURCE.
|
||
|
||
#
|
||
# Select if the arch provides a historic keepinit alias for the retain_initrd
|
||
# command line option
|
||
#
|
||
config ARCH_HAS_KEEPINITRD
|
||
bool
|
||
|
||
# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
|
||
config ARCH_HAS_SET_MEMORY
|
||
bool
|
||
|
||
# Select if arch has all set_direct_map_invalid/default() functions
|
||
config ARCH_HAS_SET_DIRECT_MAP
|
||
bool
|
||
|
||
#
|
||
# Select if the architecture provides the arch_dma_set_uncached symbol to
|
||
# either provide an uncached segment alias for a DMA allocation, or
|
||
# to remap the page tables in place.
|
||
#
|
||
config ARCH_HAS_DMA_SET_UNCACHED
|
||
bool
|
||
|
||
#
|
||
# Select if the architectures provides the arch_dma_clear_uncached symbol
|
||
# to undo an in-place page table remap for uncached access.
|
||
#
|
||
config ARCH_HAS_DMA_CLEAR_UNCACHED
|
||
bool
|
||
|
||
# Select if arch init_task must go in the __init_task_data section
|
||
config ARCH_TASK_STRUCT_ON_STACK
|
||
bool
|
||
|
||
# Select if arch has its private alloc_task_struct() function
|
||
config ARCH_TASK_STRUCT_ALLOCATOR
|
||
bool
|
||
|
||
config HAVE_ARCH_THREAD_STRUCT_WHITELIST
|
||
bool
|
||
depends on !ARCH_TASK_STRUCT_ALLOCATOR
|
||
help
|
||
An architecture should select this to provide hardened usercopy
|
||
knowledge about what region of the thread_struct should be
|
||
whitelisted for copying to userspace. Normally this is only the
|
||
FPU registers. Specifically, arch_thread_struct_whitelist()
|
||
should be implemented. Without this, the entire thread_struct
|
||
field in task_struct will be left whitelisted.
|
||
|
||
# Select if arch has its private alloc_thread_stack() function
|
||
config ARCH_THREAD_STACK_ALLOCATOR
|
||
bool
|
||
|
||
# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
|
||
config ARCH_WANTS_DYNAMIC_TASK_STRUCT
|
||
bool
|
||
|
||
config ARCH_WANTS_NO_INSTR
|
||
bool
|
||
help
|
||
An architecture should select this if the noinstr macro is being used on
|
||
functions to denote that the toolchain should avoid instrumenting such
|
||
functions and is required for correctness.
|
||
|
||
config ARCH_32BIT_OFF_T
|
||
bool
|
||
depends on !64BIT
|
||
help
|
||
All new 32-bit architectures should have 64-bit off_t type on
|
||
userspace side which corresponds to the loff_t kernel type. This
|
||
is the requirement for modern ABIs. Some existing architectures
|
||
still support 32-bit off_t. This option is enabled for all such
|
||
architectures explicitly.
|
||
|
||
# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
|
||
config ARCH_32BIT_USTAT_F_TINODE
|
||
bool
|
||
|
||
config HAVE_ASM_MODVERSIONS
|
||
bool
|
||
help
|
||
This symbol should be selected by an architecture if it provides
|
||
<asm/asm-prototypes.h> to support the module versioning for symbols
|
||
exported from assembly code.
|
||
|
||
config HAVE_REGS_AND_STACK_ACCESS_API
|
||
bool
|
||
help
|
||
This symbol should be selected by an architecture if it supports
|
||
the API needed to access registers and stack entries from pt_regs,
|
||
declared in asm/ptrace.h
|
||
For example the kprobes-based event tracer needs this API.
|
||
|
||
config HAVE_RSEQ
|
||
bool
|
||
depends on HAVE_REGS_AND_STACK_ACCESS_API
|
||
help
|
||
This symbol should be selected by an architecture if it
|
||
supports an implementation of restartable sequences.
|
||
|
||
config HAVE_RUST
|
||
bool
|
||
help
|
||
This symbol should be selected by an architecture if it
|
||
supports Rust.
|
||
|
||
config HAVE_FUNCTION_ARG_ACCESS_API
|
||
bool
|
||
help
|
||
This symbol should be selected by an architecture if it supports
|
||
the API needed to access function arguments from pt_regs,
|
||
declared in asm/ptrace.h
|
||
|
||
config HAVE_HW_BREAKPOINT
|
||
bool
|
||
depends on PERF_EVENTS
|
||
|
||
config HAVE_MIXED_BREAKPOINTS_REGS
|
||
bool
|
||
depends on HAVE_HW_BREAKPOINT
|
||
help
|
||
Depending on the arch implementation of hardware breakpoints,
|
||
some of them have separate registers for data and instruction
|
||
breakpoints addresses, others have mixed registers to store
|
||
them but define the access type in a control register.
|
||
Select this option if your arch implements breakpoints under the
|
||
latter fashion.
|
||
|
||
config HAVE_USER_RETURN_NOTIFIER
|
||
bool
|
||
|
||
config HAVE_PERF_EVENTS_NMI
|
||
bool
|
||
help
|
||
System hardware can generate an NMI using the perf event
|
||
subsystem. Also has support for calculating CPU cycle events
|
||
to determine how many clock cycles in a given period.
|
||
|
||
config HAVE_HARDLOCKUP_DETECTOR_PERF
|
||
bool
|
||
depends on HAVE_PERF_EVENTS_NMI
|
||
help
|
||
The arch chooses to use the generic perf-NMI-based hardlockup
|
||
detector. Must define HAVE_PERF_EVENTS_NMI.
|
||
|
||
config HAVE_NMI_WATCHDOG
|
||
depends on HAVE_NMI
|
||
bool
|
||
help
|
||
The arch provides a low level NMI watchdog. It provides
|
||
asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
|
||
|
||
config HAVE_HARDLOCKUP_DETECTOR_ARCH
|
||
bool
|
||
select HAVE_NMI_WATCHDOG
|
||
help
|
||
The arch chooses to provide its own hardlockup detector, which is
|
||
a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
|
||
interfaces and parameters provided by hardlockup detector subsystem.
|
||
|
||
config HAVE_PERF_REGS
|
||
bool
|
||
help
|
||
Support selective register dumps for perf events. This includes
|
||
bit-mapping of each registers and a unique architecture id.
|
||
|
||
config HAVE_PERF_USER_STACK_DUMP
|
||
bool
|
||
help
|
||
Support user stack dumps for perf event samples. This needs
|
||
access to the user stack pointer which is not unified across
|
||
architectures.
|
||
|
||
config HAVE_ARCH_JUMP_LABEL
|
||
bool
|
||
|
||
config HAVE_ARCH_JUMP_LABEL_RELATIVE
|
||
bool
|
||
|
||
config MMU_GATHER_TABLE_FREE
|
||
bool
|
||
|
||
config MMU_GATHER_RCU_TABLE_FREE
|
||
bool
|
||
select MMU_GATHER_TABLE_FREE
|
||
|
||
config MMU_GATHER_PAGE_SIZE
|
||
bool
|
||
|
||
config MMU_GATHER_NO_RANGE
|
||
bool
|
||
select MMU_GATHER_MERGE_VMAS
|
||
|
||
config MMU_GATHER_NO_FLUSH_CACHE
|
||
bool
|
||
|
||
config MMU_GATHER_MERGE_VMAS
|
||
bool
|
||
|
||
config MMU_GATHER_NO_GATHER
|
||
bool
|
||
depends on MMU_GATHER_TABLE_FREE
|
||
|
||
config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
|
||
bool
|
||
help
|
||
Temporary select until all architectures can be converted to have
|
||
irqs disabled over activate_mm. Architectures that do IPI based TLB
|
||
shootdowns should enable this.
|
||
|
||
# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references.
|
||
# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching
|
||
# to/from kernel threads when the same mm is running on a lot of CPUs (a large
|
||
# multi-threaded application), by reducing contention on the mm refcount.
|
||
#
|
||
# This can be disabled if the architecture ensures no CPUs are using an mm as a
|
||
# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm
|
||
# or its kernel page tables). This could be arranged by arch_exit_mmap(), or
|
||
# final exit(2) TLB flush, for example.
|
||
#
|
||
# To implement this, an arch *must*:
|
||
# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating
|
||
# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been
|
||
# converted already).
|
||
config MMU_LAZY_TLB_REFCOUNT
|
||
def_bool y
|
||
depends on !MMU_LAZY_TLB_SHOOTDOWN
|
||
|
||
# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an
|
||
# mm as a lazy tlb beyond its last reference count, by shooting down these
|
||
# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may
|
||
# be using the mm as a lazy tlb, so that they may switch themselves to using
|
||
# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs
|
||
# may be using mm as a lazy tlb mm.
|
||
#
|
||
# To implement this, an arch *must*:
|
||
# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains
|
||
# at least all possible CPUs in which the mm is lazy.
|
||
# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above).
|
||
config MMU_LAZY_TLB_SHOOTDOWN
|
||
bool
|
||
|
||
config ARCH_HAVE_NMI_SAFE_CMPXCHG
|
||
bool
|
||
|
||
config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
|
||
bool
|
||
|
||
config HAVE_ALIGNED_STRUCT_PAGE
|
||
bool
|
||
help
|
||
This makes sure that struct pages are double word aligned and that
|
||
e.g. the SLUB allocator can perform double word atomic operations
|
||
on a struct page for better performance. However selecting this
|
||
might increase the size of a struct page by a word.
|
||
|
||
config HAVE_CMPXCHG_LOCAL
|
||
bool
|
||
|
||
config HAVE_CMPXCHG_DOUBLE
|
||
bool
|
||
|
||
config ARCH_WEAK_RELEASE_ACQUIRE
|
||
bool
|
||
|
||
config ARCH_WANT_IPC_PARSE_VERSION
|
||
bool
|
||
|
||
config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
|
||
bool
|
||
|
||
config ARCH_WANT_OLD_COMPAT_IPC
|
||
select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
|
||
bool
|
||
|
||
config HAVE_ARCH_SECCOMP
|
||
bool
|
||
help
|
||
An arch should select this symbol to support seccomp mode 1 (the fixed
|
||
syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
|
||
and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
|
||
- __NR_seccomp_read_32
|
||
- __NR_seccomp_write_32
|
||
- __NR_seccomp_exit_32
|
||
- __NR_seccomp_sigreturn_32
|
||
|
||
config HAVE_ARCH_SECCOMP_FILTER
|
||
bool
|
||
select HAVE_ARCH_SECCOMP
|
||
help
|
||
An arch should select this symbol if it provides all of these things:
|
||
- all the requirements for HAVE_ARCH_SECCOMP
|
||
- syscall_get_arch()
|
||
- syscall_get_arguments()
|
||
- syscall_rollback()
|
||
- syscall_set_return_value()
|
||
- SIGSYS siginfo_t support
|
||
- secure_computing is called from a ptrace_event()-safe context
|
||
- secure_computing return value is checked and a return value of -1
|
||
results in the system call being skipped immediately.
|
||
- seccomp syscall wired up
|
||
- if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
|
||
SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
|
||
COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
|
||
|
||
config SECCOMP
|
||
prompt "Enable seccomp to safely execute untrusted bytecode"
|
||
def_bool y
|
||
depends on HAVE_ARCH_SECCOMP
|
||
help
|
||
This kernel feature is useful for number crunching applications
|
||
that may need to handle untrusted bytecode during their
|
||
execution. By using pipes or other transports made available
|
||
to the process as file descriptors supporting the read/write
|
||
syscalls, it's possible to isolate those applications in their
|
||
own address space using seccomp. Once seccomp is enabled via
|
||
prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
|
||
disabled and the task is only allowed to execute a few safe
|
||
syscalls defined by each seccomp mode.
|
||
|
||
If unsure, say Y.
|
||
|
||
config SECCOMP_FILTER
|
||
def_bool y
|
||
depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
|
||
help
|
||
Enable tasks to build secure computing environments defined
|
||
in terms of Berkeley Packet Filter programs which implement
|
||
task-defined system call filtering polices.
|
||
|
||
See Documentation/userspace-api/seccomp_filter.rst for details.
|
||
|
||
config SECCOMP_CACHE_DEBUG
|
||
bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
|
||
depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
|
||
depends on PROC_FS
|
||
help
|
||
This enables the /proc/pid/seccomp_cache interface to monitor
|
||
seccomp cache data. The file format is subject to change. Reading
|
||
the file requires CAP_SYS_ADMIN.
|
||
|
||
This option is for debugging only. Enabling presents the risk that
|
||
an adversary may be able to infer the seccomp filter logic.
|
||
|
||
If unsure, say N.
|
||
|
||
config HAVE_ARCH_STACKLEAK
|
||
bool
|
||
help
|
||
An architecture should select this if it has the code which
|
||
fills the used part of the kernel stack with the STACKLEAK_POISON
|
||
value before returning from system calls.
|
||
|
||
config HAVE_STACKPROTECTOR
|
||
bool
|
||
help
|
||
An arch should select this symbol if:
|
||
- it has implemented a stack canary (e.g. __stack_chk_guard)
|
||
|
||
config STACKPROTECTOR
|
||
bool "Stack Protector buffer overflow detection"
|
||
depends on HAVE_STACKPROTECTOR
|
||
depends on $(cc-option,-fstack-protector)
|
||
default y
|
||
help
|
||
This option turns on the "stack-protector" GCC feature. This
|
||
feature puts, at the beginning of functions, a canary value on
|
||
the stack just before the return address, and validates
|
||
the value just before actually returning. Stack based buffer
|
||
overflows (that need to overwrite this return address) now also
|
||
overwrite the canary, which gets detected and the attack is then
|
||
neutralized via a kernel panic.
|
||
|
||
Functions will have the stack-protector canary logic added if they
|
||
have an 8-byte or larger character array on the stack.
|
||
|
||
This feature requires gcc version 4.2 or above, or a distribution
|
||
gcc with the feature backported ("-fstack-protector").
|
||
|
||
On an x86 "defconfig" build, this feature adds canary checks to
|
||
about 3% of all kernel functions, which increases kernel code size
|
||
by about 0.3%.
|
||
|
||
config STACKPROTECTOR_STRONG
|
||
bool "Strong Stack Protector"
|
||
depends on STACKPROTECTOR
|
||
depends on $(cc-option,-fstack-protector-strong)
|
||
default y
|
||
help
|
||
Functions will have the stack-protector canary logic added in any
|
||
of the following conditions:
|
||
|
||
- local variable's address used as part of the right hand side of an
|
||
assignment or function argument
|
||
- local variable is an array (or union containing an array),
|
||
regardless of array type or length
|
||
- uses register local variables
|
||
|
||
This feature requires gcc version 4.9 or above, or a distribution
|
||
gcc with the feature backported ("-fstack-protector-strong").
|
||
|
||
On an x86 "defconfig" build, this feature adds canary checks to
|
||
about 20% of all kernel functions, which increases the kernel code
|
||
size by about 2%.
|
||
|
||
config ARCH_SUPPORTS_SHADOW_CALL_STACK
|
||
bool
|
||
help
|
||
An architecture should select this if it supports the compiler's
|
||
Shadow Call Stack and implements runtime support for shadow stack
|
||
switching.
|
||
|
||
config SHADOW_CALL_STACK
|
||
bool "Shadow Call Stack"
|
||
depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
|
||
depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
|
||
help
|
||
This option enables the compiler's Shadow Call Stack, which
|
||
uses a shadow stack to protect function return addresses from
|
||
being overwritten by an attacker. More information can be found
|
||
in the compiler's documentation:
|
||
|
||
- Clang: https://clang.llvm.org/docs/ShadowCallStack.html
|
||
- GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
|
||
|
||
Note that security guarantees in the kernel differ from the
|
||
ones documented for user space. The kernel must store addresses
|
||
of shadow stacks in memory, which means an attacker capable of
|
||
reading and writing arbitrary memory may be able to locate them
|
||
and hijack control flow by modifying the stacks.
|
||
|
||
config DYNAMIC_SCS
|
||
bool
|
||
help
|
||
Set by the arch code if it relies on code patching to insert the
|
||
shadow call stack push and pop instructions rather than on the
|
||
compiler.
|
||
|
||
config LTO
|
||
bool
|
||
help
|
||
Selected if the kernel will be built using the compiler's LTO feature.
|
||
|
||
config LTO_CLANG
|
||
bool
|
||
select LTO
|
||
help
|
||
Selected if the kernel will be built using Clang's LTO feature.
|
||
|
||
config ARCH_SUPPORTS_LTO_CLANG
|
||
bool
|
||
help
|
||
An architecture should select this option if it supports:
|
||
- compiling with Clang,
|
||
- compiling inline assembly with Clang's integrated assembler,
|
||
- and linking with LLD.
|
||
|
||
config ARCH_SUPPORTS_LTO_CLANG_THIN
|
||
bool
|
||
help
|
||
An architecture should select this option if it can support Clang's
|
||
ThinLTO mode.
|
||
|
||
config HAS_LTO_CLANG
|
||
def_bool y
|
||
depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM
|
||
depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
|
||
depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
|
||
depends on ARCH_SUPPORTS_LTO_CLANG
|
||
depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
|
||
depends on !KASAN || KASAN_HW_TAGS
|
||
depends on !GCOV_KERNEL
|
||
help
|
||
The compiler and Kconfig options support building with Clang's
|
||
LTO.
|
||
|
||
choice
|
||
prompt "Link Time Optimization (LTO)"
|
||
default LTO_NONE
|
||
help
|
||
This option enables Link Time Optimization (LTO), which allows the
|
||
compiler to optimize binaries globally.
|
||
|
||
If unsure, select LTO_NONE. Note that LTO is very resource-intensive
|
||
so it's disabled by default.
|
||
|
||
config LTO_NONE
|
||
bool "None"
|
||
help
|
||
Build the kernel normally, without Link Time Optimization (LTO).
|
||
|
||
config LTO_CLANG_FULL
|
||
bool "Clang Full LTO (EXPERIMENTAL)"
|
||
depends on HAS_LTO_CLANG
|
||
depends on !COMPILE_TEST
|
||
select LTO_CLANG
|
||
help
|
||
This option enables Clang's full Link Time Optimization (LTO), which
|
||
allows the compiler to optimize the kernel globally. If you enable
|
||
this option, the compiler generates LLVM bitcode instead of ELF
|
||
object files, and the actual compilation from bitcode happens at
|
||
the LTO link step, which may take several minutes depending on the
|
||
kernel configuration. More information can be found from LLVM's
|
||
documentation:
|
||
|
||
https://llvm.org/docs/LinkTimeOptimization.html
|
||
|
||
During link time, this option can use a large amount of RAM, and
|
||
may take much longer than the ThinLTO option.
|
||
|
||
config LTO_CLANG_THIN
|
||
bool "Clang ThinLTO (EXPERIMENTAL)"
|
||
depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
|
||
select LTO_CLANG
|
||
help
|
||
This option enables Clang's ThinLTO, which allows for parallel
|
||
optimization and faster incremental compiles compared to the
|
||
CONFIG_LTO_CLANG_FULL option. More information can be found
|
||
from Clang's documentation:
|
||
|
||
https://clang.llvm.org/docs/ThinLTO.html
|
||
|
||
If unsure, say Y.
|
||
endchoice
|
||
|
||
config ARCH_SUPPORTS_CFI_CLANG
|
||
bool
|
||
help
|
||
An architecture should select this option if it can support Clang's
|
||
Control-Flow Integrity (CFI) checking.
|
||
|
||
config ARCH_USES_CFI_TRAPS
|
||
bool
|
||
|
||
config CFI_CLANG
|
||
bool "Use Clang's Control Flow Integrity (CFI)"
|
||
depends on ARCH_SUPPORTS_CFI_CLANG
|
||
depends on $(cc-option,-fsanitize=kcfi)
|
||
help
|
||
This option enables Clang’s forward-edge Control Flow Integrity
|
||
(CFI) checking, where the compiler injects a runtime check to each
|
||
indirect function call to ensure the target is a valid function with
|
||
the correct static type. This restricts possible call targets and
|
||
makes it more difficult for an attacker to exploit bugs that allow
|
||
the modification of stored function pointers. More information can be
|
||
found from Clang's documentation:
|
||
|
||
https://clang.llvm.org/docs/ControlFlowIntegrity.html
|
||
|
||
config CFI_PERMISSIVE
|
||
bool "Use CFI in permissive mode"
|
||
depends on CFI_CLANG
|
||
help
|
||
When selected, Control Flow Integrity (CFI) violations result in a
|
||
warning instead of a kernel panic. This option should only be used
|
||
for finding indirect call type mismatches during development.
|
||
|
||
If unsure, say N.
|
||
|
||
config HAVE_ARCH_WITHIN_STACK_FRAMES
|
||
bool
|
||
help
|
||
An architecture should select this if it can walk the kernel stack
|
||
frames to determine if an object is part of either the arguments
|
||
or local variables (i.e. that it excludes saved return addresses,
|
||
and similar) by implementing an inline arch_within_stack_frames(),
|
||
which is used by CONFIG_HARDENED_USERCOPY.
|
||
|
||
config HAVE_CONTEXT_TRACKING_USER
|
||
bool
|
||
help
|
||
Provide kernel/user boundaries probes necessary for subsystems
|
||
that need it, such as userspace RCU extended quiescent state.
|
||
Syscalls need to be wrapped inside user_exit()-user_enter(), either
|
||
optimized behind static key or through the slow path using TIF_NOHZ
|
||
flag. Exceptions handlers must be wrapped as well. Irqs are already
|
||
protected inside ct_irq_enter/ct_irq_exit() but preemption or signal
|
||
handling on irq exit still need to be protected.
|
||
|
||
config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
|
||
bool
|
||
help
|
||
Architecture neither relies on exception_enter()/exception_exit()
|
||
nor on schedule_user(). Also preempt_schedule_notrace() and
|
||
preempt_schedule_irq() can't be called in a preemptible section
|
||
while context tracking is CONTEXT_USER. This feature reflects a sane
|
||
entry implementation where the following requirements are met on
|
||
critical entry code, ie: before user_exit() or after user_enter():
|
||
|
||
- Critical entry code isn't preemptible (or better yet:
|
||
not interruptible).
|
||
- No use of RCU read side critical sections, unless ct_nmi_enter()
|
||
got called.
|
||
- No use of instrumentation, unless instrumentation_begin() got
|
||
called.
|
||
|
||
config HAVE_TIF_NOHZ
|
||
bool
|
||
help
|
||
Arch relies on TIF_NOHZ and syscall slow path to implement context
|
||
tracking calls to user_enter()/user_exit().
|
||
|
||
config HAVE_VIRT_CPU_ACCOUNTING
|
||
bool
|
||
|
||
config HAVE_VIRT_CPU_ACCOUNTING_IDLE
|
||
bool
|
||
help
|
||
Architecture has its own way to account idle CPU time and therefore
|
||
doesn't implement vtime_account_idle().
|
||
|
||
config ARCH_HAS_SCALED_CPUTIME
|
||
bool
|
||
|
||
config HAVE_VIRT_CPU_ACCOUNTING_GEN
|
||
bool
|
||
default y if 64BIT
|
||
help
|
||
With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
|
||
Before enabling this option, arch code must be audited
|
||
to ensure there are no races in concurrent read/write of
|
||
cputime_t. For example, reading/writing 64-bit cputime_t on
|
||
some 32-bit arches may require multiple accesses, so proper
|
||
locking is needed to protect against concurrent accesses.
|
||
|
||
config HAVE_IRQ_TIME_ACCOUNTING
|
||
bool
|
||
help
|
||
Archs need to ensure they use a high enough resolution clock to
|
||
support irq time accounting and then call enable_sched_clock_irqtime().
|
||
|
||
config HAVE_MOVE_PUD
|
||
bool
|
||
help
|
||
Architectures that select this are able to move page tables at the
|
||
PUD level. If there are only 3 page table levels, the move effectively
|
||
happens at the PGD level.
|
||
|
||
config HAVE_MOVE_PMD
|
||
bool
|
||
help
|
||
Archs that select this are able to move page tables at the PMD level.
|
||
|
||
config HAVE_ARCH_TRANSPARENT_HUGEPAGE
|
||
bool
|
||
|
||
config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
|
||
bool
|
||
|
||
config HAVE_ARCH_HUGE_VMAP
|
||
bool
|
||
|
||
#
|
||
# Archs that select this would be capable of PMD-sized vmaps (i.e.,
|
||
# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag
|
||
# must be used to enable allocations to use hugepages.
|
||
#
|
||
config HAVE_ARCH_HUGE_VMALLOC
|
||
depends on HAVE_ARCH_HUGE_VMAP
|
||
bool
|
||
|
||
config ARCH_WANT_HUGE_PMD_SHARE
|
||
bool
|
||
|
||
config HAVE_ARCH_SOFT_DIRTY
|
||
bool
|
||
|
||
config HAVE_MOD_ARCH_SPECIFIC
|
||
bool
|
||
help
|
||
The arch uses struct mod_arch_specific to store data. Many arches
|
||
just need a simple module loader without arch specific data - those
|
||
should not enable this.
|
||
|
||
config MODULES_USE_ELF_RELA
|
||
bool
|
||
help
|
||
Modules only use ELF RELA relocations. Modules with ELF REL
|
||
relocations will give an error.
|
||
|
||
config MODULES_USE_ELF_REL
|
||
bool
|
||
help
|
||
Modules only use ELF REL relocations. Modules with ELF RELA
|
||
relocations will give an error.
|
||
|
||
config ARCH_WANTS_MODULES_DATA_IN_VMALLOC
|
||
bool
|
||
help
|
||
For architectures like powerpc/32 which have constraints on module
|
||
allocation and need to allocate module data outside of module area.
|
||
|
||
config HAVE_IRQ_EXIT_ON_IRQ_STACK
|
||
bool
|
||
help
|
||
Architecture doesn't only execute the irq handler on the irq stack
|
||
but also irq_exit(). This way we can process softirqs on this irq
|
||
stack instead of switching to a new one when we call __do_softirq()
|
||
in the end of an hardirq.
|
||
This spares a stack switch and improves cache usage on softirq
|
||
processing.
|
||
|
||
config HAVE_SOFTIRQ_ON_OWN_STACK
|
||
bool
|
||
help
|
||
Architecture provides a function to run __do_softirq() on a
|
||
separate stack.
|
||
|
||
config SOFTIRQ_ON_OWN_STACK
|
||
def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT
|
||
|
||
config ALTERNATE_USER_ADDRESS_SPACE
|
||
bool
|
||
help
|
||
Architectures set this when the CPU uses separate address
|
||
spaces for kernel and user space pointers. In this case, the
|
||
access_ok() check on a __user pointer is skipped.
|
||
|
||
config PGTABLE_LEVELS
|
||
int
|
||
default 2
|
||
|
||
config ARCH_HAS_ELF_RANDOMIZE
|
||
bool
|
||
help
|
||
An architecture supports choosing randomized locations for
|
||
stack, mmap, brk, and ET_DYN. Defined functions:
|
||
- arch_mmap_rnd()
|
||
- arch_randomize_brk()
|
||
|
||
config HAVE_ARCH_MMAP_RND_BITS
|
||
bool
|
||
help
|
||
An arch should select this symbol if it supports setting a variable
|
||
number of bits for use in establishing the base address for mmap
|
||
allocations, has MMU enabled and provides values for both:
|
||
- ARCH_MMAP_RND_BITS_MIN
|
||
- ARCH_MMAP_RND_BITS_MAX
|
||
|
||
config HAVE_EXIT_THREAD
|
||
bool
|
||
help
|
||
An architecture implements exit_thread.
|
||
|
||
config ARCH_MMAP_RND_BITS_MIN
|
||
int
|
||
|
||
config ARCH_MMAP_RND_BITS_MAX
|
||
int
|
||
|
||
config ARCH_MMAP_RND_BITS_DEFAULT
|
||
int
|
||
|
||
config ARCH_MMAP_RND_BITS
|
||
int "Number of bits to use for ASLR of mmap base address" if EXPERT
|
||
range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
|
||
default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
|
||
default ARCH_MMAP_RND_BITS_MIN
|
||
depends on HAVE_ARCH_MMAP_RND_BITS
|
||
help
|
||
This value can be used to select the number of bits to use to
|
||
determine the random offset to the base address of vma regions
|
||
resulting from mmap allocations. This value will be bounded
|
||
by the architecture's minimum and maximum supported values.
|
||
|
||
This value can be changed after boot using the
|
||
/proc/sys/vm/mmap_rnd_bits tunable
|
||
|
||
config HAVE_ARCH_MMAP_RND_COMPAT_BITS
|
||
bool
|
||
help
|
||
An arch should select this symbol if it supports running applications
|
||
in compatibility mode, supports setting a variable number of bits for
|
||
use in establishing the base address for mmap allocations, has MMU
|
||
enabled and provides values for both:
|
||
- ARCH_MMAP_RND_COMPAT_BITS_MIN
|
||
- ARCH_MMAP_RND_COMPAT_BITS_MAX
|
||
|
||
config ARCH_MMAP_RND_COMPAT_BITS_MIN
|
||
int
|
||
|
||
config ARCH_MMAP_RND_COMPAT_BITS_MAX
|
||
int
|
||
|
||
config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
|
||
int
|
||
|
||
config ARCH_MMAP_RND_COMPAT_BITS
|
||
int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
|
||
range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
|
||
default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
|
||
default ARCH_MMAP_RND_COMPAT_BITS_MIN
|
||
depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
|
||
help
|
||
This value can be used to select the number of bits to use to
|
||
determine the random offset to the base address of vma regions
|
||
resulting from mmap allocations for compatible applications This
|
||
value will be bounded by the architecture's minimum and maximum
|
||
supported values.
|
||
|
||
This value can be changed after boot using the
|
||
/proc/sys/vm/mmap_rnd_compat_bits tunable
|
||
|
||
config HAVE_ARCH_COMPAT_MMAP_BASES
|
||
bool
|
||
help
|
||
This allows 64bit applications to invoke 32-bit mmap() syscall
|
||
and vice-versa 32-bit applications to call 64-bit mmap().
|
||
Required for applications doing different bitness syscalls.
|
||
|
||
config PAGE_SIZE_LESS_THAN_64KB
|
||
def_bool y
|
||
depends on !ARM64_64K_PAGES
|
||
depends on !IA64_PAGE_SIZE_64KB
|
||
depends on !PAGE_SIZE_64KB
|
||
depends on !PARISC_PAGE_SIZE_64KB
|
||
depends on PAGE_SIZE_LESS_THAN_256KB
|
||
|
||
config PAGE_SIZE_LESS_THAN_256KB
|
||
def_bool y
|
||
depends on !PAGE_SIZE_256KB
|
||
|
||
# This allows to use a set of generic functions to determine mmap base
|
||
# address by giving priority to top-down scheme only if the process
|
||
# is not in legacy mode (compat task, unlimited stack size or
|
||
# sysctl_legacy_va_layout).
|
||
# Architecture that selects this option can provide its own version of:
|
||
# - STACK_RND_MASK
|
||
config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
|
||
bool
|
||
depends on MMU
|
||
select ARCH_HAS_ELF_RANDOMIZE
|
||
|
||
config HAVE_OBJTOOL
|
||
bool
|
||
|
||
config HAVE_JUMP_LABEL_HACK
|
||
bool
|
||
|
||
config HAVE_NOINSTR_HACK
|
||
bool
|
||
|
||
config HAVE_NOINSTR_VALIDATION
|
||
bool
|
||
|
||
config HAVE_UACCESS_VALIDATION
|
||
bool
|
||
select OBJTOOL
|
||
|
||
config HAVE_STACK_VALIDATION
|
||
bool
|
||
help
|
||
Architecture supports objtool compile-time frame pointer rule
|
||
validation.
|
||
|
||
config HAVE_RELIABLE_STACKTRACE
|
||
bool
|
||
help
|
||
Architecture has either save_stack_trace_tsk_reliable() or
|
||
arch_stack_walk_reliable() function which only returns a stack trace
|
||
if it can guarantee the trace is reliable.
|
||
|
||
config HAVE_ARCH_HASH
|
||
bool
|
||
default n
|
||
help
|
||
If this is set, the architecture provides an <asm/hash.h>
|
||
file which provides platform-specific implementations of some
|
||
functions in <linux/hash.h> or fs/namei.c.
|
||
|
||
config HAVE_ARCH_NVRAM_OPS
|
||
bool
|
||
|
||
config ISA_BUS_API
|
||
def_bool ISA
|
||
|
||
#
|
||
# ABI hall of shame
|
||
#
|
||
config CLONE_BACKWARDS
|
||
bool
|
||
help
|
||
Architecture has tls passed as the 4th argument of clone(2),
|
||
not the 5th one.
|
||
|
||
config CLONE_BACKWARDS2
|
||
bool
|
||
help
|
||
Architecture has the first two arguments of clone(2) swapped.
|
||
|
||
config CLONE_BACKWARDS3
|
||
bool
|
||
help
|
||
Architecture has tls passed as the 3rd argument of clone(2),
|
||
not the 5th one.
|
||
|
||
config ODD_RT_SIGACTION
|
||
bool
|
||
help
|
||
Architecture has unusual rt_sigaction(2) arguments
|
||
|
||
config OLD_SIGSUSPEND
|
||
bool
|
||
help
|
||
Architecture has old sigsuspend(2) syscall, of one-argument variety
|
||
|
||
config OLD_SIGSUSPEND3
|
||
bool
|
||
help
|
||
Even weirder antique ABI - three-argument sigsuspend(2)
|
||
|
||
config OLD_SIGACTION
|
||
bool
|
||
help
|
||
Architecture has old sigaction(2) syscall. Nope, not the same
|
||
as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
|
||
but fairly different variant of sigaction(2), thanks to OSF/1
|
||
compatibility...
|
||
|
||
config COMPAT_OLD_SIGACTION
|
||
bool
|
||
|
||
config COMPAT_32BIT_TIME
|
||
bool "Provide system calls for 32-bit time_t"
|
||
default !64BIT || COMPAT
|
||
help
|
||
This enables 32 bit time_t support in addition to 64 bit time_t support.
|
||
This is relevant on all 32-bit architectures, and 64-bit architectures
|
||
as part of compat syscall handling.
|
||
|
||
config ARCH_NO_PREEMPT
|
||
bool
|
||
|
||
config ARCH_EPHEMERAL_INODES
|
||
def_bool n
|
||
help
|
||
An arch should select this symbol if it doesn't keep track of inode
|
||
instances on its own, but instead relies on something else (e.g. the
|
||
host kernel for an UML kernel).
|
||
|
||
config ARCH_SUPPORTS_RT
|
||
bool
|
||
|
||
config CPU_NO_EFFICIENT_FFS
|
||
def_bool n
|
||
|
||
config HAVE_ARCH_VMAP_STACK
|
||
def_bool n
|
||
help
|
||
An arch should select this symbol if it can support kernel stacks
|
||
in vmalloc space. This means:
|
||
|
||
- vmalloc space must be large enough to hold many kernel stacks.
|
||
This may rule out many 32-bit architectures.
|
||
|
||
- Stacks in vmalloc space need to work reliably. For example, if
|
||
vmap page tables are created on demand, either this mechanism
|
||
needs to work while the stack points to a virtual address with
|
||
unpopulated page tables or arch code (switch_to() and switch_mm(),
|
||
most likely) needs to ensure that the stack's page table entries
|
||
are populated before running on a possibly unpopulated stack.
|
||
|
||
- If the stack overflows into a guard page, something reasonable
|
||
should happen. The definition of "reasonable" is flexible, but
|
||
instantly rebooting without logging anything would be unfriendly.
|
||
|
||
config VMAP_STACK
|
||
default y
|
||
bool "Use a virtually-mapped stack"
|
||
depends on HAVE_ARCH_VMAP_STACK
|
||
depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
|
||
help
|
||
Enable this if you want the use virtually-mapped kernel stacks
|
||
with guard pages. This causes kernel stack overflows to be
|
||
caught immediately rather than causing difficult-to-diagnose
|
||
corruption.
|
||
|
||
To use this with software KASAN modes, the architecture must support
|
||
backing virtual mappings with real shadow memory, and KASAN_VMALLOC
|
||
must be enabled.
|
||
|
||
config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
|
||
def_bool n
|
||
help
|
||
An arch should select this symbol if it can support kernel stack
|
||
offset randomization with calls to add_random_kstack_offset()
|
||
during syscall entry and choose_random_kstack_offset() during
|
||
syscall exit. Careful removal of -fstack-protector-strong and
|
||
-fstack-protector should also be applied to the entry code and
|
||
closely examined, as the artificial stack bump looks like an array
|
||
to the compiler, so it will attempt to add canary checks regardless
|
||
of the static branch state.
|
||
|
||
config RANDOMIZE_KSTACK_OFFSET
|
||
bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT
|
||
default y
|
||
depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
|
||
depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
|
||
help
|
||
The kernel stack offset can be randomized (after pt_regs) by
|
||
roughly 5 bits of entropy, frustrating memory corruption
|
||
attacks that depend on stack address determinism or
|
||
cross-syscall address exposures.
|
||
|
||
The feature is controlled via the "randomize_kstack_offset=on/off"
|
||
kernel boot param, and if turned off has zero overhead due to its use
|
||
of static branches (see JUMP_LABEL).
|
||
|
||
If unsure, say Y.
|
||
|
||
config RANDOMIZE_KSTACK_OFFSET_DEFAULT
|
||
bool "Default state of kernel stack offset randomization"
|
||
depends on RANDOMIZE_KSTACK_OFFSET
|
||
help
|
||
Kernel stack offset randomization is controlled by kernel boot param
|
||
"randomize_kstack_offset=on/off", and this config chooses the default
|
||
boot state.
|
||
|
||
config ARCH_OPTIONAL_KERNEL_RWX
|
||
def_bool n
|
||
|
||
config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
|
||
def_bool n
|
||
|
||
config ARCH_HAS_STRICT_KERNEL_RWX
|
||
def_bool n
|
||
|
||
config STRICT_KERNEL_RWX
|
||
bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
|
||
depends on ARCH_HAS_STRICT_KERNEL_RWX
|
||
default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
|
||
help
|
||
If this is set, kernel text and rodata memory will be made read-only,
|
||
and non-text memory will be made non-executable. This provides
|
||
protection against certain security exploits (e.g. executing the heap
|
||
or modifying text)
|
||
|
||
These features are considered standard security practice these days.
|
||
You should say Y here in almost all cases.
|
||
|
||
config ARCH_HAS_STRICT_MODULE_RWX
|
||
def_bool n
|
||
|
||
config STRICT_MODULE_RWX
|
||
bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
|
||
depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
|
||
default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
|
||
help
|
||
If this is set, module text and rodata memory will be made read-only,
|
||
and non-text memory will be made non-executable. This provides
|
||
protection against certain security exploits (e.g. writing to text)
|
||
|
||
# select if the architecture provides an asm/dma-direct.h header
|
||
config ARCH_HAS_PHYS_TO_DMA
|
||
bool
|
||
|
||
config HAVE_ARCH_COMPILER_H
|
||
bool
|
||
help
|
||
An architecture can select this if it provides an
|
||
asm/compiler.h header that should be included after
|
||
linux/compiler-*.h in order to override macro definitions that those
|
||
headers generally provide.
|
||
|
||
config HAVE_ARCH_PREL32_RELOCATIONS
|
||
bool
|
||
help
|
||
May be selected by an architecture if it supports place-relative
|
||
32-bit relocations, both in the toolchain and in the module loader,
|
||
in which case relative references can be used in special sections
|
||
for PCI fixup, initcalls etc which are only half the size on 64 bit
|
||
architectures, and don't require runtime relocation on relocatable
|
||
kernels.
|
||
|
||
config ARCH_USE_MEMREMAP_PROT
|
||
bool
|
||
|
||
config LOCK_EVENT_COUNTS
|
||
bool "Locking event counts collection"
|
||
depends on DEBUG_FS
|
||
help
|
||
Enable light-weight counting of various locking related events
|
||
in the system with minimal performance impact. This reduces
|
||
the chance of application behavior change because of timing
|
||
differences. The counts are reported via debugfs.
|
||
|
||
# Select if the architecture has support for applying RELR relocations.
|
||
config ARCH_HAS_RELR
|
||
bool
|
||
|
||
config RELR
|
||
bool "Use RELR relocation packing"
|
||
depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
|
||
default y
|
||
help
|
||
Store the kernel's dynamic relocations in the RELR relocation packing
|
||
format. Requires a compatible linker (LLD supports this feature), as
|
||
well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
|
||
are compatible).
|
||
|
||
config ARCH_HAS_MEM_ENCRYPT
|
||
bool
|
||
|
||
config ARCH_HAS_CC_PLATFORM
|
||
bool
|
||
|
||
config HAVE_SPARSE_SYSCALL_NR
|
||
bool
|
||
help
|
||
An architecture should select this if its syscall numbering is sparse
|
||
to save space. For example, MIPS architecture has a syscall array with
|
||
entries at 4000, 5000 and 6000 locations. This option turns on syscall
|
||
related optimizations for a given architecture.
|
||
|
||
config ARCH_HAS_VDSO_DATA
|
||
bool
|
||
|
||
config HAVE_STATIC_CALL
|
||
bool
|
||
|
||
config HAVE_STATIC_CALL_INLINE
|
||
bool
|
||
depends on HAVE_STATIC_CALL
|
||
select OBJTOOL
|
||
|
||
config HAVE_PREEMPT_DYNAMIC
|
||
bool
|
||
|
||
config HAVE_PREEMPT_DYNAMIC_CALL
|
||
bool
|
||
depends on HAVE_STATIC_CALL
|
||
select HAVE_PREEMPT_DYNAMIC
|
||
help
|
||
An architecture should select this if it can handle the preemption
|
||
model being selected at boot time using static calls.
|
||
|
||
Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a
|
||
preemption function will be patched directly.
|
||
|
||
Where an architecture does not select HAVE_STATIC_CALL_INLINE, any
|
||
call to a preemption function will go through a trampoline, and the
|
||
trampoline will be patched.
|
||
|
||
It is strongly advised to support inline static call to avoid any
|
||
overhead.
|
||
|
||
config HAVE_PREEMPT_DYNAMIC_KEY
|
||
bool
|
||
depends on HAVE_ARCH_JUMP_LABEL
|
||
select HAVE_PREEMPT_DYNAMIC
|
||
help
|
||
An architecture should select this if it can handle the preemption
|
||
model being selected at boot time using static keys.
|
||
|
||
Each preemption function will be given an early return based on a
|
||
static key. This should have slightly lower overhead than non-inline
|
||
static calls, as this effectively inlines each trampoline into the
|
||
start of its callee. This may avoid redundant work, and may
|
||
integrate better with CFI schemes.
|
||
|
||
This will have greater overhead than using inline static calls as
|
||
the call to the preemption function cannot be entirely elided.
|
||
|
||
config ARCH_WANT_LD_ORPHAN_WARN
|
||
bool
|
||
help
|
||
An arch should select this symbol once all linker sections are explicitly
|
||
included, size-asserted, or discarded in the linker scripts. This is
|
||
important because we never want expected sections to be placed heuristically
|
||
by the linker, since the locations of such sections can change between linker
|
||
versions.
|
||
|
||
config HAVE_ARCH_PFN_VALID
|
||
bool
|
||
|
||
config ARCH_SUPPORTS_DEBUG_PAGEALLOC
|
||
bool
|
||
|
||
config ARCH_SUPPORTS_PAGE_TABLE_CHECK
|
||
bool
|
||
|
||
config ARCH_SPLIT_ARG64
|
||
bool
|
||
help
|
||
If a 32-bit architecture requires 64-bit arguments to be split into
|
||
pairs of 32-bit arguments, select this option.
|
||
|
||
config ARCH_HAS_ELFCORE_COMPAT
|
||
bool
|
||
|
||
config ARCH_HAS_PARANOID_L1D_FLUSH
|
||
bool
|
||
|
||
config ARCH_HAVE_TRACE_MMIO_ACCESS
|
||
bool
|
||
|
||
config DYNAMIC_SIGFRAME
|
||
bool
|
||
|
||
# Select, if arch has a named attribute group bound to NUMA device nodes.
|
||
config HAVE_ARCH_NODE_DEV_GROUP
|
||
bool
|
||
|
||
config ARCH_HAS_NONLEAF_PMD_YOUNG
|
||
bool
|
||
help
|
||
Architectures that select this option are capable of setting the
|
||
accessed bit in non-leaf PMD entries when using them as part of linear
|
||
address translations. Page table walkers that clear the accessed bit
|
||
may use this capability to reduce their search space.
|
||
|
||
source "kernel/gcov/Kconfig"
|
||
|
||
source "scripts/gcc-plugins/Kconfig"
|
||
|
||
config FUNCTION_ALIGNMENT_4B
|
||
bool
|
||
|
||
config FUNCTION_ALIGNMENT_8B
|
||
bool
|
||
|
||
config FUNCTION_ALIGNMENT_16B
|
||
bool
|
||
|
||
config FUNCTION_ALIGNMENT_32B
|
||
bool
|
||
|
||
config FUNCTION_ALIGNMENT_64B
|
||
bool
|
||
|
||
config FUNCTION_ALIGNMENT
|
||
int
|
||
default 64 if FUNCTION_ALIGNMENT_64B
|
||
default 32 if FUNCTION_ALIGNMENT_32B
|
||
default 16 if FUNCTION_ALIGNMENT_16B
|
||
default 8 if FUNCTION_ALIGNMENT_8B
|
||
default 4 if FUNCTION_ALIGNMENT_4B
|
||
default 0
|
||
|
||
endmenu
|