556 lines
16 KiB
Plaintext
556 lines
16 KiB
Plaintext
# Kconfig - kernel configuration options
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#
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# Copyright (c) 2014-2015 Wind River Systems, Inc.
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#
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# SPDX-License-Identifier: Apache-2.0
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#
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menu "General Kernel Options"
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config MULTITHREADING
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bool
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prompt "Multi-threading"
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default y
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help
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If disabled, only the main thread is available, so a main() function
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must be provided. Interrupts are available. Kernel objects will most
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probably not behave as expected, especially with regards to pending,
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since the main thread cannot pend, it being the only thread in the
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system.
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Many drivers and subsystems will not work with this option; use only
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when you REALLY know what you are doing.
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config NUM_COOP_PRIORITIES
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int
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prompt "Number of coop priorities" if MULTITHREADING
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default 16
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default 1 if !MULTITHREADING
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range 0 128
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help
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Number of cooperative priorities configured in the system. Gives access
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to priorities:
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K_PRIO_COOP(0) to K_PRIO_COOP(CONFIG_NUM_COOP_PRIORITIES - 1)
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or seen another way, priorities:
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-CONFIG_NUM_COOP_PRIORITIES to -1
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This can be set to zero to disable cooperative scheduling. Cooperative
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threads always preempt preemptible threads.
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Each priority requires an extra 8 bytes of RAM. Each set of 32 extra
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total priorities require an extra 4 bytes and add one possible
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iteration to loops that search for the next thread to run.
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The total number of priorities is
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NUM_COOP_PRIORITIES + NUM_PREEMPT_PRIORITIES + 1
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The extra one is for the idle thread, which must run at the lowest
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priority, and be the only thread at that priority.
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config NUM_PREEMPT_PRIORITIES
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int
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prompt "Number of preemptible priorities" if MULTITHREADING
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default 15
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default 0 if !MULTITHREADING
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range 0 128
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help
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Number of preemptible priorities available in the system. Gives access
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to priorities 0 to CONFIG_NUM_PREEMPT_PRIORITIES - 1.
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This can be set to 0 to disable preemptible scheduling.
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Each priority requires an extra 8 bytes of RAM. Each set of 32 extra
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total priorities require an extra 4 bytes and add one possible
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iteration to loops that search for the next thread to run.
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The total number of priorities is
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NUM_COOP_PRIORITIES + NUM_PREEMPT_PRIORITIES + 1
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The extra one is for the idle thread, which must run at the lowest
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priority, and be the only thread at that priority.
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config MAIN_THREAD_PRIORITY
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int
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prompt "Priority of initialization/main thread"
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default 0
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default -2 if !PREEMPT_ENABLED
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help
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Priority at which the initialization thread runs, including the start
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of the main() function. main() can then change its priority if desired.
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config COOP_ENABLED
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bool
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default y
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default n if (NUM_COOP_PRIORITIES = 0)
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config PREEMPT_ENABLED
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bool
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default y
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default n if (NUM_PREEMPT_PRIORITIES = 0)
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config PRIORITY_CEILING
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int
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prompt "Priority inheritance ceiling"
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default 0
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config MAIN_STACK_SIZE
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int
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prompt "Size of stack for initialization and main thread"
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default 1024
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default 512 if ZTEST
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help
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When the initialization is complete, the thread executing it then
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executes the main() routine, so as to reuse the stack used by the
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initialization, which would be wasted RAM otherwise.
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After initialization is complete, the thread runs main().
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config IDLE_STACK_SIZE
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int
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prompt "Size of stack for idle thread"
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default 256
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default 320 if ARC || (ARM && CPU_HAS_FPU)
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default 512 if RISCV32
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default 1024 if XTENSA
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help
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Depending on the work that the idle task must do, most likely due to
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power management but possibly to other features like system event
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logging (e.g. logging when the system goes to sleep), the idle thread
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may need more stack space than the default value.
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config ISR_STACK_SIZE
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int
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prompt "ISR and initialization stack size (in bytes)"
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default 2048
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help
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This option specifies the size of the stack used by interrupt
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service routines (ISRs), and during kernel initialization.
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config THREAD_STACK_INFO
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bool
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prompt "Thread stack info"
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default n
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help
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This option allows each thread to store the thread stack info into
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the k_thread data structure.
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config THREAD_CUSTOM_DATA
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bool
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prompt "Thread custom data"
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default n
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help
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This option allows each thread to store 32 bits of custom data,
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which can be accessed using the k_thread_custom_data_xxx() APIs.
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config ERRNO
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bool
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prompt "Enable errno support"
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default y
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help
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Enable per-thread errno in the kernel. Application and library code must
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include errno.h provided by the C library (libc) to use the errno
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symbol. The C library must access the per-thread errno via the
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_get_errno() symbol.
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config APPLICATION_MEMORY
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bool
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prompt "Split kernel and application memory"
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default n
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help
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For all read-write memory sections (namely bss, noinit, data),
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separate them into application and kernel areas. The application area
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will have the project-level application objects and any libraries
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including the C library in it.
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menu "Kernel Debugging and Metrics"
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config KERNEL_DEBUG
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bool
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prompt "Kernel debugging"
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default n
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select INIT_STACKS
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help
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Enable kernel debugging.
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Note that debugging the kernel internals can be very verbose.
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config BOOT_BANNER
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bool
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prompt "Boot banner"
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default n
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depends on CONSOLE_HAS_DRIVER
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select PRINTK
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select EARLY_CONSOLE
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help
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This option outputs a banner to the console device during boot up. It
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also embeds a date & time stamp in the kernel if the BUILD_TIMESTAMP
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option is enabled.
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config BOOT_DELAY
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int
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prompt "Boot delay in milliseconds"
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default 0
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help
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This option delays bootup for the specified amount of
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milliseconds. This is used to allow serial ports to get ready
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before starting to print information on them during boot, as
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some systems might boot to fast for a receiving endpoint to
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detect the new USB serial bus, enumerate it and get ready to
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receive before it actually gets data. A similar effect can be
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achieved by waiting for DCD on the serial port--however, not
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all serial ports have DCD.
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config BUILD_TIMESTAMP
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bool
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prompt "Build Timestamp"
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help
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Build timestamp and add it to the boot banner.
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config INT_LATENCY_BENCHMARK
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bool
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prompt "Interrupt latency metrics [EXPERIMENTAL]"
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default n
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depends on ARCH="x86"
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help
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This option enables the tracking of interrupt latency metrics;
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the exact set of metrics being tracked is board-dependent.
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Tracking begins when int_latency_init() is invoked by an application.
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The metrics are displayed (and a new sampling interval is started)
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each time int_latency_show() is called thereafter.
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config EXECUTION_BENCHMARKING
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bool
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prompt "Timing metrics "
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default n
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help
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This option enables the tracking of various times inside the kernel
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the exact set of metrics being tracked is board-dependent.
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All timing measurements are enabled for X86 and ARM based architectures.
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In other architectures only a subset are enabled.
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config THREAD_MONITOR
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bool
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prompt "Thread monitoring [EXPERIMENTAL]"
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default n
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help
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This option instructs the kernel to maintain a list of all threads
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(excluding those that have not yet started or have already
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terminated).
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endmenu
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menu "Work Queue Options"
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config SYSTEM_WORKQUEUE_STACK_SIZE
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int "System workqueue stack size"
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default 1024
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config SYSTEM_WORKQUEUE_PRIORITY
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int "System workqueue priority"
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default -1
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default 0 if !COOP_ENABLED
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default -2 if COOP_ENABLED && !PREEMPT_ENABLED
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config OFFLOAD_WORKQUEUE_STACK_SIZE
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int "Workqueue stack size for thread offload requests"
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default 1024
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config OFFLOAD_WORKQUEUE_PRIORITY
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int "Offload requests workqueue priority"
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default -1
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endmenu
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menu "Atomic Operations"
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config ATOMIC_OPERATIONS_BUILTIN
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bool
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help
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Use the compiler builtin functions for atomic operations. This is
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the preferred method. However, support for all arches in GCC is
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incomplete.
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config ATOMIC_OPERATIONS_CUSTOM
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bool
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help
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Use when there isn't support for compiler built-ins, but you have
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written optimized assembly code under arch/ which implements these.
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config ATOMIC_OPERATIONS_C
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bool
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help
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Use atomic operations routines that are implemented entirely
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in C by locking interrupts. Selected by architectures which either
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do not have support for atomic operations in their instruction
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set, or haven't been implemented yet during bring-up, and also
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the compiler does not have support for the atomic __sync_* builtins.
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endmenu
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menu "Timer API Options"
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config TIMESLICING
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bool "Thread time slicing"
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default y
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depends on SYS_CLOCK_EXISTS && (NUM_PREEMPT_PRIORITIES != 0)
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help
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This option enables time slicing between preemptible threads of
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equal priority.
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config TIMESLICE_SIZE
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int "Time slice size (in ms)"
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default 0
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range 0 2147483647
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depends on TIMESLICING
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help
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This option specifies the maximum amount of time a thread can execute
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before other threads of equal priority are given an opportunity to run.
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A time slice size of zero means "no limit" (i.e. an infinitely large
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time slice).
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config TIMESLICE_PRIORITY
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int "Time slicing thread priority ceiling"
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default 0
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range 0 NUM_PREEMPT_PRIORITIES
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depends on TIMESLICING
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help
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This option specifies the thread priority level at which time slicing
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takes effect; threads having a higher priority than this ceiling are
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not subject to time slicing.
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config POLL
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bool
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prompt "async I/O framework"
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default n
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help
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Asynchronous notification framework. Enable the k_poll() and
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k_poll_signal() APIs. The former can wait on multiple events
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concurrently, which can be either directly triggered or triggered by
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the availability of some kernel objects (semaphores and fifos).
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endmenu
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menu "Other Kernel Object Options"
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config NUM_MBOX_ASYNC_MSGS
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int "Maximum number of in-flight asynchronous mailbox messages"
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default 10
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help
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This option specifies the total number of asynchronous mailbox
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messages that can exist simultaneously, across all mailboxes
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in the system.
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Setting this option to 0 disables support for asynchronous
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mailbox messages.
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config NUM_PIPE_ASYNC_MSGS
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int "Maximum number of in-flight asynchronous pipe messages"
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default 10
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help
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This option specifies the total number of asynchronous pipe
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messages that can exist simultaneously, across all pipes in
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the system.
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Setting this option to 0 disables support for asynchronous
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pipe messages.
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endmenu
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menu "Memory Pool Options"
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config HEAP_MEM_POOL_SIZE
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int
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prompt "Heap memory pool size (in bytes)"
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default 0
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help
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This option specifies the size of the heap memory pool used when
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dynamically allocating memory using k_malloc(). Supported values
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are: 256, 1024, 4096, and 16384. A size of zero means that no
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heap memory pool is defined.
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endmenu
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config ARCH_HAS_CUSTOM_SWAP_TO_MAIN
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bool
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# hidden
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default n
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help
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It's possible that an architecture port cannot use _Swap() to swap to
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the _main() thread, but instead must do something custom. It must
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enable this option in that case.
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config ARCH_HAS_CUSTOM_BUSY_WAIT
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bool
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# hidden
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default n
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help
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It's possible that an architecture port cannot or does not want to use
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the provided k_busy_wait(), but instead must do something custom. It must
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enable this option in that case.
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config SYS_CLOCK_TICKS_PER_SEC
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int
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prompt "System tick frequency (in ticks/second)"
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default 100
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help
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This option specifies the frequency of the system clock in Hz.
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Depending on the choice made, an amount of possibly expensive math must
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occur when converting ticks to milliseconds and vice-versa. Some values
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are optimized, and yield significantly less math.
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The optimal values from a computational point-of-view are 1000, 500,
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250 and 125, since in these cases there is either no computation
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required, or it is all done via bit-shifting. These also give a
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granularity from 1ms to 8ms.
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Other good values are 100, 50, 25, 20 and 10. In this case, some math
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is required but is minimized. These are also values that necessitate a
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reduced number of clock interrupts per second, at the cost of
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granularity (10ms to 100ms).
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All other values require some extensive 64-bit math, and in some
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configurations even require calls to compiler built-in functions, and
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can require a non-trivial extra amount of stack space (e.g. around 80
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bytes on x86).
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config SYS_CLOCK_HW_CYCLES_PER_SEC
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int "System clock's h/w timer frequency"
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help
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This option specifies the frequency of the hardware timer used for the
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system clock (in Hz). This option is set by the board's Kconfig file
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and the user should generally avoid modifying it via the menu configuration.
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config SYS_CLOCK_EXISTS
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bool
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# omit prompt to signify a "hidden" option
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default y
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default n if (SYS_CLOCK_TICKS_PER_SEC = 0)
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help
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This option specifies that the kernel lacks timer support.
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config INIT_STACKS
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bool
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prompt "Initialize stack areas"
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default n
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help
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This option instructs the kernel to initialize stack areas with a
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known value (0xaa) before they are first used, so that the high
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water mark can be easily determined. This applies to the stack areas
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for threads.
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config XIP
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bool
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prompt "Execute in place"
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help
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This option allows the kernel to operate with its text and read-only
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sections residing in ROM (or similar read-only memory). Not all boards
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support this option so it must be used with care; you must also
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supply a linker command file when building your image. Enabling this
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option increases both the code and data footprint of the image.
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config RING_BUFFER
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bool
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prompt "Enable ring buffers"
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default n
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help
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Enable usage of ring buffers. This is similar to kernel FIFOs but ring
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buffers manage their own buffer memory and can store arbitrary data.
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For optimal performance, use buffer sizes that are a power of 2.
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menu "Initialization Priorities"
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config KERNEL_INIT_PRIORITY_OBJECTS
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int
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prompt "Kernel objects initialization priority"
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default 30
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help
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Kernel objects use this priority for initialization. This
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priority needs to be higher than minimal default initialization
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priority.
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config KERNEL_INIT_PRIORITY_DEFAULT
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int
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prompt "Default init priority"
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default 40
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help
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Default minimal init priority for each init level.
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config KERNEL_INIT_PRIORITY_DEVICE
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int
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prompt "Default init priority for device drivers"
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default 50
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help
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Device driver, that depends on common components, such as
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interrupt controller, but does not depend on other devices,
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uses this init priority.
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config APPLICATION_INIT_PRIORITY
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int
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prompt "Default init priority for application level drivers"
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default 90
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help
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This priority level is for end-user drivers such as sensors and display
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which have no inward dependencies.
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config PTHREAD_IPC
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bool
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prompt "POSIX pthread IPC API"
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default n
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help
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This enables a mostly-standards-compliant implementation of
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the pthread mutex, condition variable and barrier IPC
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mechanisms.
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endmenu
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menu "Security Options"
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config STACK_CANARIES
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bool
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prompt "Compiler stack canaries"
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default n
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help
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This option enables compiler stack canaries support kernel functions.
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If stack canaries are supported by the compiler, it will emit
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extra code that inserts a canary value into the stack frame when
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a function is entered and validates this value upon exit.
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Stack corruption (such as that caused by buffer overflow) results
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in a fatal error condition for the running entity.
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Enabling this option can result in a significant increase
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in footprint and an associated decrease in performance.
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If stack canaries are not supported by the compiler, enabling this
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option has no effect.
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config EXECUTE_XOR_WRITE
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bool "Enable W^X for memory partitions"
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depends on USERSPACE
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depends on ARCH_HAS_EXECUTABLE_PAGE_BIT
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default y
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help
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When enabled, will enforce that a writable page isn't executable
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and vice versa. This might not be acceptable in all scenarios,
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so this option is given for those unafraid of shooting themselves
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in the foot.
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If unsure, say Y.
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endmenu
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config MAX_DOMAIN_PARTITIONS
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int
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prompt "Maximum number of partitions per memory domain"
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default 16
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range 0 255
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depends on USERSPACE
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help
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Configure the maximum number of partitions per memory domain.
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source "kernel/Kconfig.event_logger"
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source "kernel/Kconfig.power_mgmt"
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endmenu
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