libkernaux

Auxiliary library for kernel development.

Table of contents

• Overview
• Table of contents
• API
• Tips
  • Installation
  • Development
  • Cross
• Portability
• Discussion
• Summary
  • Pure code size
  • Used header files

API

• Runtime environment
  • Assertions
    • Example
  • Architecture-specific helpers
• Device drivers (for debugging only)
  • Serial console
  • Framebuffer (planned)
• Algorithms
  • Simple command line parser
    • Example
  • Page Frame Allocator
    • Example
• Data formats
  • Multiboot 2 (GRUB 2) information parser
  • ELF utils (work in progress)
• Utilities
  • Measurement units utils (work in progress)
    • To human
• Usual functions
  • libc replacement
    • memset
    • strcpy
    • strlen
  • itoa replacement (work in progress)
  • printf replacement (work in progress)
    • printf
    • printf_va

Tips

Installation

./autogen.sh
./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
./configure --enable-assert --enable-null-guard
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 in $PATH to make without it in $PATH:

./configure \
  --host='i386-elf' \
  --enable-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 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
• Thread on r/osdev

Summary

This information is updated from time to time.

Pure code size

cloc --vcs=git include/ src/

-------------------------------------------------------------------------------
Language                     files          blank        comment           code
-------------------------------------------------------------------------------
C                               12            236             19           1548
C/C++ Header                    14            179             64            597
Assembly                         2              7              6             28
make                             1              0              0             13
-------------------------------------------------------------------------------
SUM:                            29            422             89           2186
-------------------------------------------------------------------------------

Used header files

git grep '#include <' -- include/ src/ | grep -v '#include <kernaux' | awk '{ print $2; }' | sort | uniq

• stdarg.h
• stdbool.h
• stddef.h