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libkernaux
==========
[![Build status](https://github.com/tailix/libkernaux/actions/workflows/main.yml/badge.svg)](https://github.com/tailix/libkernaux/actions/workflows/main.yml)
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Auxiliary library for kernel development.
[Topic on OSDev.org forum](https://forum.osdev.org/viewtopic.php?f=1&t=37958).
Table of contents
-----------------
* [Overview](#libkernaux)
* [Table of contents](#table-of-contents)
* [API](#api)
* [Headers](#headers)
* [Definitions](#definitions)
* [Global variables](#global-variables)
* [Configuration](#configuration)
* [Non-default options](#non-default-options)
* [Default options](#default-options)
* [Tips](#tips)
* [Installation](#installation)
* [Development](#development)
* [Cross](#cross)
API
---
### Headers
We use [semantic versioning](https://semver.org) for stable APIs. Stable APIs
can only change when major version number is increased (or minor while major is
zero). Work-in-progress APIs can change at any time.
* Runtime environment
* [Feature macros](/include/kernaux/version.h.in) (*work in progress*)
* [Assertions](/include/kernaux/assert.h) (*non-breaking since* **0.4.0**)
* [Example: Assert](/examples/assert.c)
* [Example: Panic](/examples/panic.c)
* Stack trace *(planned)*
* Architecture-specific code (*work in progress*)
* [Declarations](/include/kernaux/arch/)
* [Functions](/include/kernaux/asm/)
* Generic types
* [File](/include/kernaux/generic/file.h) (*non-breaking since* **?.?.?**)
* [Example](/examples/generic_file.c)
* [Memory allocator](/include/kernaux/generic/malloc.h) (*non-breaking since* **?.?.?**)
* [Example](/examples/generic_malloc.c)
* [Mutex](/include/kernaux/generic/mutex.h) (*non-breaking since* **?.?.?**)
* [Example](/examples/generic_mutex.c)
* Algorithms
* [Free list memory allocator](/include/kernaux/free_list.h) (*non-breaking since* **?.?.?**)
* [Simple command line parser](/include/kernaux/cmdline.h) (*non-breaking since* **0.2.0**)
* [Example](/examples/cmdline.c)
* [Page Frame Allocator](/include/kernaux/pfa.h) (*work in progress*)
* [Example](/examples/pfa.c)
* Data formats
* [ELF](/include/kernaux/elf.h) (*work in progress*)
* [MBR](/include/kernaux/mbr.h) (*work in progress*)
* [Multiboot 2 (GRUB 2)](/include/kernaux/multiboot2.h) (*work in progress*)
* Utilities
* [Measurement units utils](/include/kernaux/units.h) (*work in progress*)
* [Example: To human](/examples/units_human.c)
* [Memory map](/include/kernaux/memmap.h.in) (*non-breaking since* **0.4.0**)
* [Example](/examples/memmap.c)
* [printf format parser](/include/kernaux/printf_fmt.h) (*work in progress*)
* [Example](/examples/printf_fmt.c)
* Usual functions
* [itoa/ftoa replacement](/include/kernaux/ntoa.h) (*non-breaking since* **0.4.0**)
* [Example](/examples/ntoa.c)
* [printf replacement](/include/kernaux/printf.h.in) (*non-breaking since* **?.?.?**)
* [Example: fprintf](/examples/printf_file.c)
* [Example: vfprintf](/examples/printf_file_va.c)
* [Example: snprintf](/examples/printf_str.c)
* [Example: vsnprintf](/examples/printf_str_va.c)
* libc replacement (*work in progress*)
* [ctype.h](/libc/include/ctype.h)
* [inttypes.h](/libc/include/inttypes.h)
* [setjmp.h](/libc/include/setjmp.h)
* [stdlib.h](/libc/include/stdlib.h)
* [string.h](/libc/include/string.h)
* [sys/types.h](/libc/include/sys/types.h)
* Device drivers (for debugging only)
* [Serial console](/include/kernaux/drivers/console.h) (*work in progress*)
* [Framebuffer](/include/kernaux/drivers/framebuffer.h) (*planned*)
* [Intel 8253-compatible PIT](/include/kernaux/drivers/intel_8253_pit.h) (*work in progress*)
* [Intel 8259-compatible PIC](/include/kernaux/drivers/intel_8259_pic.h) (*work in progress*)
* USB (*planned*)
### Definitions
`#define` the following C preprocessor macros before including `<kernaux.h>` and
`<kernaux/*.h>` files. They have effect on your code, not the library code.
* `KERNAUX_DEBUG` - enable assertions.
* `KERNAUX_ACCESS_PRIVATE` - disable access modifier "private". Don't do this!
* `KERNAUX_ACCESS_PROTECTED` - disable access modifier "protected". Only do this
in a file where you implement an inherited type.
### Global variables
```c
// in <kernaux/assert.h>
void (*kernaux_assert_cb)(const char *file, int line, const char *msg)
```
Assertion callback. It's better to always set it to some function which always
interrupts the execution, even when debugging is disabled. It may for example
call `abort()` in hosted environment, raise an exception in Ruby, panic in Rust
or power off the machine in freestanding environment. It may also log the error
location and message.
Configuration
-------------
Because this library has no external dependencies, we use **autoconf** features
to control behavior of the library, and packages to choose it's components.
Configuration options also follow the [semantic versioning](https://semver.org)
scheme and are split into stable and work-in-progress ones. Here we cover only
stable options.
### Non-default options
#### Features
* `--enable-tests` - enable usual tests and examples
* `--enable-tests-all` - enable all tests
* `--enable-tests-python` - enable tests that require Python 3 with YAML and
Jinja2
#### Packages
* `--with-drivers` - device drivers
* `--with-libc` - provides the replacement for some standard C functions.
Useful in freestanding environment, where no libc is present.
### Default options
#### Features
* `--(enable|disable)-debug` - debugging
* `--(enable|disable)-float` - floating-point arithmetic
* `--(enable|disable)-werror` - fail on warning (`CFLAGS+='-Werror'`)
#### Packages
All packages are included by default. To exclude all packages except those
explicitly included, use `--without-all`.
* `--with[out]-arch-all` - all architectures
* `--with[out]-arch-i386` - architecture i386
* `--with[out]-arch-riscv64` - architecture riscv64
* `--with[out]-arch-x86-64` - architecture x86-64
* `--with[out]-asm` - kernel assembler helpers
* `--with[out]-cmdline` - command line parser
* `--with[out]-free-list` - free list memory allocator
* `--with[out]-memmap` - memory map
* `--with[out]-ntoa` - itoa/ftoa
* `--with[out]-printf` - printf
Tips
----
### Installation
```
./autogen.sh # if present
./configure
make
sudo make install
```
This is just a usual library. You can use most of it's APIs in hosted
environment.
### Development
```
./autogen.sh # if present
./configure --enable-tests # or --enable-tests-all, but see prerequisites
make
```
You can test with `make check`.
### Cross
Create configuration script with `./autogen.sh` (if present).
Let's assume that your target triplet is `i386-elf`. Configure with
[cross-compiler](https://wiki.osdev.org/GCC_Cross-Compiler) in `$PATH` to make
without it in `$PATH`:
```
./configure \
--host='i386-elf' \
--enable-freestanding \
--with-drivers \
--with-libc \
AR="$(which i386-elf-ar)" \
CC="$(which i386-elf-gcc)" \
RANLIB="$(which i386-elf-ranlib)"
```
You can see the following messages. It's
[a bug](https://savannah.gnu.org/support/index.php?110393) in **autoconf**, just
ignore it.
```
checking for _Bool... no
checking stdarg.h usability... no
checking stdarg.h presence... yes
configure: WARNING: stdarg.h: present but cannot be compiled
configure: WARNING: stdarg.h: check for missing prerequisite headers?
configure: WARNING: stdarg.h: see the Autoconf documentation
configure: WARNING: stdarg.h: section "Present But Cannot Be Compiled"
configure: WARNING: stdarg.h: proceeding with the compiler's result
configure: WARNING: ## ---------------------------------------------------------- ##
configure: WARNING: ## Report this to https://github.com/tailix/libkernaux/issues ##
configure: WARNING: ## ---------------------------------------------------------- ##
checking for stdarg.h... no
checking stddef.h usability... no
checking stddef.h presence... yes
configure: WARNING: stddef.h: present but cannot be compiled
configure: WARNING: stddef.h: check for missing prerequisite headers?
configure: WARNING: stddef.h: see the Autoconf documentation
configure: WARNING: stddef.h: section "Present But Cannot Be Compiled"
configure: WARNING: stddef.h: proceeding with the compiler's result
configure: WARNING: ## ---------------------------------------------------------- ##
configure: WARNING: ## Report this to https://github.com/tailix/libkernaux/issues ##
configure: WARNING: ## ---------------------------------------------------------- ##
checking for stddef.h... no
```
To install into specific directory use full path: `DESTDIR="$(pwd)/dest" make
install` instead of `DESTDIR=dest make install`.
Check if compilation targets i386: `objdump -d src/asm/i386.o`. It should output
something like this:
```
src/asm/i386.o: file format elf32-i386
Disassembly of section .text:
00000000 <kernaux_asm_i386_read_cr0>:
0: 0f 20 c0 mov %cr0,%eax
3: c3 ret
00000004 <kernaux_asm_i386_read_cr4>:
4: 0f 20 e0 mov %cr4,%eax
7: c3 ret
00000008 <kernaux_asm_i386_write_cr0>:
8: 8b 44 24 04 mov 0x4(%esp),%eax
c: 0f 22 c0 mov %eax,%cr0
f: c3 ret
00000010 <kernaux_asm_i386_write_cr3>:
10: 8b 44 24 04 mov 0x4(%esp),%eax
14: 0f 22 d8 mov %eax,%cr3
17: c3 ret
00000018 <kernaux_asm_i386_write_cr4>:
18: 8b 44 24 04 mov 0x4(%esp),%eax
1c: 0f 22 e0 mov %eax,%cr4
1f: c3 ret
```
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