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libkernaux/README.md

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libkernaux
==========
Auxiliary library for kernel development.
Table of contents
-----------------
* [Overview](#libkernaux)
* [Table of contents](#table-of-contents)
* [API](#api)
* [Tips](#tips)
* [Compilation](#compilation)
* [Cross-compilation](#cross-compilation)
* [Portability](#portability)
* [Discussion](#discussion)
API
---
* [Measurement units utils](/include/kernaux/units.h) *(work in progress)*
* [Simple command line parser](/include/kernaux/cmdline.h)
* [Multiboot 2 (GRUB 2) information parser](/include/kernaux/multiboot2.h)
* [Serial console](/include/kernaux/console.h)
* [Page Frame Allocator](/include/kernaux/pfa.h) *(work in progress)*
* [ELF utils](/include/kernaux/elf.h) *(work in progress)*
* [Architecture-specific helpers](/include/kernaux/arch/)
* [printf replacement](/include/kernaux/printf.h) *(work in progress)*
* [stdlib replacement](/include/kernaux/stdlib.h):
* `memset`
* `strlen`
* `strncpy`
* `itoa` *(work in progress)*
Tips
----
### Compilation
```
./autogen.sh
./configure
make
sudo make install
```
You can test with `make check`.
This is just a usual library. You can use most of it's APIs in hosted
environment.
### Cross-compilation
Create configuration script with `./autogen.sh`.
Configure with [cross-compiler](https://wiki.osdev.org/GCC_Cross-Compiler) in
`$PATH` to make without it in `$PATH`:
```
./configure \
--host='i386-elftailix' \
AR="$(which i386-elftailix-ar)" \
CC="$(which i386-elftailix-gcc)" \
RANLIB="$(which i386-elftailix-ranlib)" \
CFLAGS='-ffreestanding -nostdlib -fno-builtin -fno-stack-protector'
```
You can see the following messages. It's
[a bug](https://savannah.gnu.org/support/index.php?110393) in **autoconf**, just
ignore it.
```
checking for _Bool... no
checking stdarg.h usability... no
checking stdarg.h presence... yes
configure: WARNING: stdarg.h: present but cannot be compiled
configure: WARNING: stdarg.h: check for missing prerequisite headers?
configure: WARNING: stdarg.h: see the Autoconf documentation
configure: WARNING: stdarg.h: section "Present But Cannot Be Compiled"
configure: WARNING: stdarg.h: proceeding with the compiler's result
configure: WARNING: ## ---------------------------------------------------------- ##
configure: WARNING: ## Report this to https://github.com/tailix/libkernaux/issues ##
configure: WARNING: ## ---------------------------------------------------------- ##
checking for stdarg.h... no
checking stddef.h usability... no
checking stddef.h presence... yes
configure: WARNING: stddef.h: present but cannot be compiled
configure: WARNING: stddef.h: check for missing prerequisite headers?
configure: WARNING: stddef.h: see the Autoconf documentation
configure: WARNING: stddef.h: section "Present But Cannot Be Compiled"
configure: WARNING: stddef.h: proceeding with the compiler's result
configure: WARNING: ## ---------------------------------------------------------- ##
configure: WARNING: ## Report this to https://github.com/tailix/libkernaux/issues ##
configure: WARNING: ## ---------------------------------------------------------- ##
checking for stddef.h... no
```
To install into specific directory use full path:
`DESTDIR="$(pwd)/dest" make install` instead of `DESTDIR=dest make install`.
When configured with cross-compiler, library can't be build and installed with
just `make && sudo make install`. Instead use the following commands:
* `make libkernaux.a`
* `sudo make install-exec`
* `sudo make install-data`
Check if compilation targets i386: `objdump -d src/arch/i386.o`. It should
output something like this:
```
src/arch/i386.o: file format elf32-i386
Disassembly of section .text:
00000000 <kernaux_arch_i386_hang>:
0: fa cli
1: f4 hlt
2: eb fc jmp 0 <kernaux_arch_i386_hang>
00000004 <kernaux_arch_i386_read_cr0>:
4: 0f 20 c0 mov %cr0,%eax
7: c3 ret
00000008 <kernaux_arch_i386_read_cr4>:
8: 0f 20 e0 mov %cr4,%eax
b: c3 ret
0000000c <kernaux_arch_i386_write_cr0>:
c: 8b 44 24 04 mov 0x4(%esp),%eax
10: 0f 22 c0 mov %eax,%cr0
13: c3 ret
00000014 <kernaux_arch_i386_write_cr3>:
14: 8b 44 24 04 mov 0x4(%esp),%eax
18: 0f 22 d8 mov %eax,%cr3
1b: c3 ret
0000001c <kernaux_arch_i386_write_cr4>:
1c: 8b 44 24 04 mov 0x4(%esp),%eax
20: 0f 22 e0 mov %eax,%cr4
23: c3 ret
```
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
Discussion
----------
* [Topic on OSDev.org forum](https://forum.osdev.org/viewtopic.php?f=1&t=37958)
* [Thread on r/osdev](https://www.reddit.com/r/osdev/comments/k3ueeu/libkernaux_auxiliary_library_for_kernel/)