libkernaux

Auxiliary library for kernel development.

Table of contents

• Overview
• Table of contents
• API
• Tips
• Portability
• Discussion

API

• Simple command line parser (work in progress)
• Multiboot 2 (GRUB 2) information parser
• Serial console
• Page Frame Allocator (work in progress)
• ELF utils (planned)
• Architecture-specific helpers
• printf replacement (work in progress)
• stdlib replacement:
  • memset
  • strlen
  • strncpy
  • itoa (work in progress)

Tips

Create configuration script with ./autogen.sh.

Configure with cross-compiler in $PATH to make without it in $PATH:

./configure \
  --host=x86-elf \
  AR="$(which x86-elf-ar)" \
  CC="$(which x86-elf-gcc)" \
  RANLIB="$(which x86-elf-ranlib)" \
  CFLAGS='-ffreestanding -nostdlib -fno-builtin -fno-stack-protector'

When configuring with cross-compiler 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/kernelmq/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/kernelmq/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 x86: objdump -d src/arch/x86.o. It should output something like this:

src/arch/x86.o:     file format elf32-i386


Disassembly of section .text:

00000000 <kernaux_arch_x86_hang>:
   0:   fa                    cli
   1:   f4                    hlt
   2:   eb fc                 jmp    0 <kernaux_arch_x86_hang>

00000004 <kernaux_arch_x86_read_cr0>:
   4:   0f 20 c0              mov    %cr0,%eax
   7:   c3                    ret

00000008 <kernaux_arch_x86_read_cr4>:
   8:   0f 20 e0              mov    %cr4,%eax
   b:   c3                    ret

0000000c <kernaux_arch_x86_write_cr0>:
   c:   8b 44 24 04           mov    0x4(%esp),%eax
  10:   0f 22 c0              mov    %eax,%cr0
  13:   c3                    ret

00000014 <kernaux_arch_x86_write_cr3>:
  14:   8b 44 24 04           mov    0x4(%esp),%eax
  18:   0f 22 d8              mov    %eax,%cr3
  1b:   c3                    ret

0000001c <kernaux_arch_x86_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) with autoconf, automake, binutils and gcc/clang (depending on what is present) on the following operating systems:

• FreeBSD 12.2
• OpenBSD 6.8
• Minix 3.3.0
• NetBSD 9.1

Discussion

• Topic on OSDev.org forum
• Thread on r/osdev