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zephyr/lib/libc/Kconfig
Keith Packard d0c75f3b96 lib/libc: Add picolibc support (aarch32, aarch64 and RISC-V) [v21] 
Picolibc is a fork of newlib designed and tested on embedded systems. It
offers a smaller memory footprint (both ROM and RAM), and native TLS
support, which uses the Zephyr TLS support.

By default, the full printf version is included in the executable, which
includes exact floating point and long long input and output. A
configuration option has been added to switch to the integer-only
version (which also omits long long support).

Here are some size comparisons using qemu-cortex-m3 and this application
(parameters passed to printf to avoid GCC optimizing it into puts):

void main(void)
{
    printf("Hello World! %s %d\n", CONFIG_BOARD, 12);
}

                       FLASH    SRAM
    minimal             8696    3952
    picolibc int        7600    3960
    picolibc float     12304    3960
    newlib-nano int    11696    4128
    newlib-nano float  30516    4496
    newlib             34800    6112

---

v2:
	Include picolibc-tls.ld

v3:
	Document usage in guides/c_library.rst and
	getting_started/toolchain_other_x_compilers.rst

v4:
	Lost the lib/libc/picolibc directory somehow!

v5:
	Add PICOLIBC_ALIGNED_HEAP_SIZE configuration option.
	Delete PICOLIBC_SEMIHOST option support code

v6:
	Don't allocate static RAM for TLS values; TLS
	values only need to be allocated for each thread.

v7:
	Use arm coprocessor for TLS pointer storage where supported for
	compatibility with the -mtp=cp15 compiler option (or when the
	target cpu type selects this option)

	Add a bunch of tests

	Round TLS segment up to stack alignment so that overall stack
	remains correctly aligned

	Add aarch64 support

	Rebase to upstream head

v8:
	Share NEWLIB, NEWLIB_NANO and PICOLIBC library configuration
	variables in a single LIBC_PARTITIONS variable instead of
	having separate PICOLIBC_PART and NEWLIB_PART variables.

v9:
	Update docs to reference pending sdk-ng support for picolibc

v10:
	Support memory protection by creating a partition for
	picolibc shared data and any pre-defined picolibc heap.

v11:
	Fix formatting in arch/arm/core/aarch64/switch.S

v12:
	Remove TLS support from this patch now that TLS is upstream
	Require THREAD_LOCAL_STORAGE when using PICOLIBC for architectures
	that support it.

v13:
	Merge errno changes as they're only needed for picolibc.
	Adapt cmake changes suggested by Torsten Tejlmand Rasmussen

v14:
	Update to picolibc 1.7 and newer (new stdin/stdout/stderr ABI)

v15:
	Respond to comments from dcpleung:
	* switch kernel/errno to use CONFIG_LIBC_ERRNO instead of
          CONFIG_PICOLIBC
	* Add comment to test/lib/sprintf as to why the %n test
	  was disabled for picolibc.

v16:
	Switch picolibc to a module built with Zephyr. This eliminates
	toolchain dependencies and allows compiler settings for Zephyr
	to also be applied to picolibc.

v17:
	Provide Zephyr-specific 'abort' implementation.
	Support systems with MMU

v18:
	Allow use of toolchain picolibc version.

v19:
	Use zephyr/ for zephyr headers

v20:
	Add locking
	Use explicit commit for picolibc module

v21:
	Create PICOLIBC_SUPPORTED config param. Set on arc, arm, arm64,
	mips and riscv architectures.

Signed-off-by: Keith Packard <keithp@keithp.com>
2022-06-22 13:15:55 +02:00

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# C library
# Copyright (c) 2016 Intel Corporation
# SPDX-License-Identifier: Apache-2.0
menu "C Library"
config REQUIRES_FULL_LIBC
bool
help
Helper symbol to indicate some feature requires a C library implementation
with more functionality than what MINIMAL_LIBC provides
config SUPPORT_MINIMAL_LIBC
bool
default y
config PICOLIBC_SUPPORTED
bool
depends on ARC || ARM || ARM64 || MIPS || RISCV
default y
help
Selected when the target has support for picolibc.
choice LIBC_IMPLEMENTATION
prompt "C Library Implementation"
default EXTERNAL_LIBC if NATIVE_APPLICATION
default NEWLIB_LIBC if REQUIRES_FULL_LIBC
default MINIMAL_LIBC
config MINIMAL_LIBC
bool "Minimal C library"
depends on !NATIVE_APPLICATION
depends on !REQUIRES_FULL_LIBC
depends on SUPPORT_MINIMAL_LIBC
help
Build with minimal C library.
config PICOLIBC
bool "Picolibc library"
select LIBC_ERRNO
select THREAD_LOCAL_STORAGE if ARCH_HAS_THREAD_LOCAL_STORAGE
depends on !NATIVE_APPLICATION
help
Build with picolibc library. The picolibc library is built as
a module if PICOLIBC_MODULE is set, otherwise picolibc is
expected to be provided by the toolchain.
config NEWLIB_LIBC
bool "Newlib C library"
depends on !NATIVE_APPLICATION
help
Build with newlib library. The newlib library is expected to be
part of the SDK in this case.
config ARCMWDT_LIBC
bool "ARC MWDT C library"
depends on !NATIVE_APPLICATION
depends on "$(ZEPHYR_TOOLCHAIN_VARIANT)" = "arcmwdt"
help
C library provided by ARC MWDT toolchain.
config EXTERNAL_LIBC
bool "External C library"
help
Build with external/user provided C library.
endchoice # LIBC_IMPLEMENTATION
config HAS_NEWLIB_LIBC_NANO
bool
if PICOLIBC
source "lib/libc/picolibc/Kconfig"
endif # PICOLIBC
if NEWLIB_LIBC
config NEWLIB_LIBC_NANO
bool "Build with newlib-nano C library"
depends on HAS_NEWLIB_LIBC_NANO
default y
help
Build with newlib-nano library, for small embedded apps.
The newlib-nano library for ARM embedded processors is a part of the
GNU Tools for ARM Embedded Processors.
config NEWLIB_LIBC_MAX_MAPPED_REGION_SIZE
int "Maximum memory mapped for newlib heap"
depends on MMU
default 1048576
help
On MMU-based systems, indicates the maximum amount of memory which
will be used for the newlib malloc() heap. The actual amount of
memory used will be the minimum of this value and the amount of
free physical memory at kernel boot.
config NEWLIB_LIBC_MIN_REQUIRED_HEAP_SIZE
int "Newlib minimum required heap size"
default 2048 if NEWLIB_LIBC_NANO
default 8192 if !NEWLIB_LIBC_NANO
help
Specifies the amount of memory space that must be available for the
newlib heap. An assertion failure message will be displayed during
initialization if the memory space available for the newlib heap is
smaller than this value.
config NEWLIB_LIBC_ALIGNED_HEAP_SIZE
int "Newlib aligned heap size"
depends on MPU_REQUIRES_POWER_OF_TWO_ALIGNMENT
depends on USERSPACE
default 0
help
If user mode is enabled, and MPU hardware has requirements that
regions be sized to a power of two and aligned to their size,
and user mode threads need to access this heap, then this is necessary
to properly define an MPU region for the heap.
If this is left at 0, then remaining system RAM will be used for this
area and it may not be possible to program it as an MPU region.
config NEWLIB_LIBC_FLOAT_PRINTF
bool "Build with newlib float printf"
help
Build with floating point printf enabled. This will increase the size of
the image.
config NEWLIB_LIBC_FLOAT_SCANF
bool "Build with newlib float scanf"
help
Build with floating point scanf enabled. This will increase the size of
the image.
config NEWLIB_LIBC_HEAP_LISTENER
bool "Notify heap listeners of newlib libc heap events"
select HEAP_LISTENER
help
Notify registered heap listeners upon certain events related to the newlib
libc heap usage, such as the heap resize.
endif # NEWLIB_LIBC
if MINIMAL_LIBC
config MINIMAL_LIBC_NON_REENTRANT_FUNCTIONS
bool "Non-reentrant functions"
default y if !USERSPACE
select NEED_LIBC_MEM_PARTITION
help
Enable non-reentrant functions that make use of the globals; e.g.
rand() and gmtime(). The globals must be put into a dedicated C
library memory partition when CONFIG_USERSPACE=y, and enabling this
option may require an additional memory protection region.
config MINIMAL_LIBC_MALLOC
bool "Minimal libc malloc implementation"
default y
help
Enable the minimal libc's implementation of malloc, free, and realloc.
Disable if you wish to provide your own implementations of these functions.
config MINIMAL_LIBC_MALLOC_ARENA_SIZE
int "Size of the minimal libc malloc arena"
default 0
depends on MINIMAL_LIBC_MALLOC
help
Indicate the size in bytes of the memory arena used for
minimal libc's malloc() implementation.
config MINIMAL_LIBC_CALLOC
bool "Minimal libc trivial calloc implementation"
default y
help
Enable the minimal libc's trivial implementation of calloc, which
forwards to malloc and memset.
config MINIMAL_LIBC_REALLOCARRAY
bool "Minimal libc trivial reallocarray implementation"
default y
help
Enable the minimal libc's trivial implementation of reallocarray, which
forwards to realloc.
config MINIMAL_LIBC_LL_PRINTF
bool "Build with minimal libc long long printf" if !64BIT
default y if 64BIT
help
Build with long long printf enabled. This will increase the size of
the image.
config MINIMAL_LIBC_OPTIMIZE_STRING_FOR_SIZE
bool "Use size optimized string functions"
default y if SIZE_OPTIMIZATIONS
help
Enable smaller but potentially slower implementations of memcpy and
memset. On the Cortex-M0+ this reduces the total code size by 120 bytes.
config MINIMAL_LIBC_RAND
bool "Rand and srand functions"
help
Enable rand_r() for the minimal libc.
In order to make use of the non-reentrant rand() and srand(), it is
necessary to set CONFIG_MINIMAL_LIBC_NON_REENTRANT_FUNCTIONS=y.
config MINIMAL_LIBC_TIME
bool "Time functions"
default y
help
Enable time() and gmtime_r() for the minimal libc.
time() requires CONFIG_POSIX_CLOCK=y because it relies on the POSIX
clock_gettime() function.
In order to make use of the non-reentrant gmtime(), it is necessary
to set CONFIG_MINIMAL_LIBC_NON_REENTRANT_FUNCTIONS=y.
endif # MINIMAL_LIBC
config STDOUT_CONSOLE
bool "Send stdout to console"
depends on CONSOLE_HAS_DRIVER
depends on !NATIVE_APPLICATION
default y
help
This option directs standard output (e.g. printf) to the console
device, rather than suppressing it entirely. See also EARLY_CONSOLE
option.
config NEED_LIBC_MEM_PARTITION
bool
help
Hidden option to signal that a memory partition is needed for
the C library even though it would not have been enabled
otherwise.
endmenu
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