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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)
[![Build status (FreeBSD)](https://api.cirrus-ci.com/github/tailix/libkernaux.svg?task=main_freebsd)](https://cirrus-ci.com/github/tailix/libkernaux)
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)
* [Configuration](#configuration)
* [Non-default options](#non-default-options)
* [Default options](#default-options)
* [Tips](#tips)
* [Installation](#installation)
* [Development](#development)
* [Cross](#cross)
* [Architectures](#architectures)
* [Portability](#portability)
API
---
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
* Architecture-specific code (*work in progress*)
* [Declarations](/include/kernaux/arch/)
* [Functions](/include/kernaux/asm/)
* [Assertions](/include/kernaux/assert.h) (*stable since* **0.1.0**, *non-breaking since* **0.2.0**)
* [Assert: simple](/examples/assert_simple.c)
* [Assert: guards](/examples/assert_guards.c)
* [Panic: simple](/examples/panic_simple.c)
* [Panic: guards](/examples/panic_guards.c)
* Stack trace *(planned)*
* Device drivers (for debugging only)
* [Serial console](/include/kernaux/console.h) (*work in progress*)
* [Framebuffer](/include/kernaux/framebuffer.h) (*planned*)
* USB (*planned*)
* Algorithms
* [Simple command line parser](/include/kernaux/cmdline.h) (*stable 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*)
* [Master Boot Record](/include/kernaux/mbr.h) (*work in progress*)
* [Multiboot 2 (GRUB 2)](/include/kernaux/multiboot2.h) (*work in progress*)
* Stivale 2 (Limine) (*planned*)
* Utilities
* [Measurement units utils](/include/kernaux/units.h) (*work in progress*)
* [To human](/examples/units_human.c)
* Usual functions
* [libc replacement](/include/kernaux/libc.h) (*stable since* **0.1.0**)
* [itoa/ftoa replacement](/include/kernaux/ntoa.h) (*stable since* **0.1.0**)
* [printf replacement](/include/kernaux/printf.h) (*stable since* **0.1.0**)
* Code from [https://github.com/mpaland/printf](https://github.com/mpaland/printf). Thank you!
* [printf](/examples/printf.c)
* [vprintf](/examples/printf_va.c)
* [snprintf](/examples/snprintf.c)
* [vsnprintf](/examples/snprintf_va.c)
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
#### Packages
* `--with-libc` - provides the replacement for some standard C functions. Useful
in freestanding environment, where no libc is present. You can also separately
include or exclude components:
* `--with[out]-libc-atoi`
* `--with[out]-libc-isdigit`
* `--with[out]-libc-isspace`
* `--with[out]-libc-memset`
* `--with[out]-libc-strcpy`
* `--with[out]-libc-strlen`
* `--with[out]-libc-strnlen`
### Default options
#### Features
* `--enable-bloat`, disable with `--disable-bloat`
* `--enable-float`, disable with `--disable-float`
#### Packages
All packages all included by default. To exclude all packages except those
explicitly included, use `--without-all`.
* `--with[out]-ntoa`
* `--with[out]-printf`
Tips
----
### Installation
```
./autogen.sh
./configure CFLAGS='-fPIC'
make
sudo make install
```
This is just a usual library. You can use most of it's APIs in hosted
environment.
### Development
```
./autogen.sh
./configure --enable-tests CFLAGS='-fPIC'
make
```
You can test with `make check`.
### Cross
Create configuration script with `./autogen.sh`.
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' \
--with-libc \
AR="$(which i386-elf-ar)" \
CC="$(which i386-elf-gcc)" \
RANLIB="$(which i386-elf-ranlib)" \
CFLAGS='-ffreestanding -nostdlib -fno-builtin -fno-stack-protector'
```
You can see the following messages. It's
[a bug](https://savannah.gnu.org/support/index.php?110393) in **autoconf**, just
ignore it.
```
checking for _Bool... no
checking stdarg.h usability... no
checking stdarg.h presence... yes
configure: WARNING: stdarg.h: present but cannot be compiled
configure: WARNING: stdarg.h: check for missing prerequisite headers?
configure: WARNING: stdarg.h: see the Autoconf documentation
configure: WARNING: stdarg.h: section "Present But Cannot Be Compiled"
configure: WARNING: stdarg.h: proceeding with the compiler's result
configure: WARNING: ## ---------------------------------------------------------- ##
configure: WARNING: ## Report this to https://github.com/tailix/libkernaux/issues ##
configure: WARNING: ## ---------------------------------------------------------- ##
checking for stdarg.h... no
checking stddef.h usability... no
checking stddef.h presence... yes
configure: WARNING: stddef.h: present but cannot be compiled
configure: WARNING: stddef.h: check for missing prerequisite headers?
configure: WARNING: stddef.h: see the Autoconf documentation
configure: WARNING: stddef.h: section "Present But Cannot Be Compiled"
configure: WARNING: stddef.h: proceeding with the compiler's result
configure: WARNING: ## ---------------------------------------------------------- ##
configure: WARNING: ## Report this to https://github.com/tailix/libkernaux/issues ##
configure: WARNING: ## ---------------------------------------------------------- ##
checking for stddef.h... no
```
To install into specific directory use full path: `DESTDIR="$(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
```
Architectures
-------------
Architectures should be properly identified. We use the following scheme, but it
may change in future:
* `x86`
* `i386`
* `x86_64`
* `riscv`
* `riscv64`
* `arm` - we need more info, now similar to [Debian](https://www.debian.org/ports/arm/)
* `armel`
* `armhf`
* `arm64`
Portability
-----------
Except GNU/Linux, the library is periodically successfully built (starting with
`./autogen.sh`) and tested with **autoconf**, **automake**, **binutils** and
**gcc**/**clang** (depending on what is present) on the following operating
systems:
* FreeBSD 13.0
* Minix 3.3.0
* NetBSD 9.2
* OpenBSD 7.0
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