OSDev.org

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/
|--- arch/
|  |--- amd64/
|  |  |--- boot.S
|  |  |--- syscall.S
|  |  |--- init.c
|  |  \--- [etc...]
|  |--- arm/
|  \--- [etc...]
|--- kernel/
|  |--- mm/
|  |--- mod/
|  |--- fs/
|  \--- [etc...]
\--- [etc...]

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|-- meson-build/
| \-- [build output and meson generated files]
|-- boot.asm
|-- build-iso.make
|-- cross_file.txt
|-- crti.asm
|-- crto.asm
|-- grub.cfg
|-- kernel.cpp
|-- linker.ld
\-- meson.build

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# Specify the project
project('myos', 'c', 'cpp')

# Find where the crtbegin and crtend object files are so we can link to them
find_crtbegin_result = run_command('i686-elf-gcc', ['$CFLAGS', '-print-file-name=crtbegin.o'])
find_crtend_result = run_command('i686-elf-gcc', ['$CFLAGS', '-print-file-name=crtend.o'])
crtbegin_obj = find_crtbegin_result.stdout().strip()
crtend_obj = find_crtend_result.stdout().strip()

# I use nasm for my assembly files, so this is how to use it

# First of all we find nasm
nasm = find_program('nasm')

# We then define a generator that will make object files, if you need different command line
# options to the assembler, then make a new generator
asm_gen = generator(nasm,
    output: '@[email protected]',
    arguments: ['-felf32', '@INPUT@', '-o', '@OUTPUT@'])

# Generators actually take in a array of files to generate
bootstrapobjs = asm_gen.process(['boot.asm'])

# crti and crtn need to be handled by themselves, because the link order is important to them
crtiobj = asm_gen.process(['crti.asm'])
crtnobj = asm_gen.process(['crtn.asm'])

# note, I currently haven't worked out a way to specify the correct link order, i will do a bug report soon
# to try and figure out if there is a way to do this.
# To verify that the constructors actually worked, I edited the ninja build file
# generated by meson to make sure the constructors worked, but since my current kernel
# doesn't use any, I don't need the constructors to work.

linker_file = files('linker.ld')

# Because crtbegin and crtend are already generated object files, we specify them with the
# objects setting, but because of this, they are last on the command line, breaking global constructors
# We use our linker script by depending on it at link time, and specifying our linker args for our kernel
kernel_exe = executable('myos.elf', bootstrapobjs, crtiobj, 'kernel.cpp', crtnobj,
    cpp_args: ['-O2', '-Wall', '-Wextra', '-fno-exceptions', '-fno-rtti', '-nostdlib'],
    link_args: ['-O2', '-lgcc', '-nostdlib', '-T', '../linker.ld'],
    link_depends: 'linker.ld',
    objects: [crtbegin_obj, crtend_obj])

# currently it is easer having a seperate make file just for making the iso image, I am planing
# on finding a better way to do this	

grub_file = files('grub.cfg')
iso_builder = find_program('build-iso.make')
iso_gen = custom_target('build-iso',
    output: ['myos.iso'],
    command: ['make', '-f', iso_builder],
    build_by_default: true,
    depends: [kernel_exe],
    depend_files: 'grub.cfg')

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[binaries]
c = 'i686-elf-gcc'
cpp = 'i686-elf-g++'
ar = 'i686-elf-ar'
strip = 'i686-elf-strip'

[properties]
has_function_printf = false

c_args = ['-ffreestanding']
cpp_args = ['-ffreestanding']
c_link_args = ['-ffreestanding', '-nostdlib', '-lgcc']
cpp_link_args = ['-ffreestanding', '-nostdlib', '-lgcc']

[host_machine]
system = 'myos-kernel'
cpu_family = 'x86'
cpu = 'i686'
endian = 'little'

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CRTBEGIN = $(shell $(CC) $(CFLAGS) -print-file-name=crtbegin.o)
CRTEND   = $(shell $(CC) $(CFLAGS) -print-file-name=crtend.o)
CRTI = $(filter %/crti.S.o, $(OBJECTS))
CRTN = $(filter %/crtn.S.o, $(OBJECTS))
OBJECTS2 = $(filter-out $(CRTI) $(CRTN), $(OBJECTS))

bootloader: $(OBJECTS) $(LDSCRIPT)
	$(LD) $(LDFLAGS) $(CRTI) $(CRTBEGIN) $(OBJECTS2) -lgcc $(CRTEND) $(CRTN) -o $@

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crtbegin = run_command('i686-rainbow-elf-gcc', ['$CFLAGS', '-print-file-name=crtbegin.o']).stdout().strip()
crtend = run_command('i686-rainbow-elf-gcc', ['$CFLAGS', '-print-file-name=crtend.o']).stdout().strip()
libgcc = meson.get_compiler('cpp').find_library('libgcc')

link_deps = [
    libgcc,
]

exe = executable('boot',
    sources: sources,
    include_directories: includes,
    dependencies: link_deps,
    objects: [crtbegin, crtend],     # That's wrong! They end up after all the other objects!
)

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.text : AT(ADDR(.text) - KERNEL_VBASE) {
		*(.text*)

		*(.init_start)
		*(.init)
		*(.init_end)

		*(.fini_start)
		*(.fini)
		*(.fini_end)
	}

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.section .init_start
.global _init
.type _init, @function
_init:
    push %rbp
    movq %rsp, %rbp

.section .fini_start
.global _fini
.type _fini, @function
_fini:
    push %rbp
    movq %rsp, %rbp

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  .ctors          :
  {
    /* gcc uses crtbegin.o to find the start of
       the constructors, so we make sure it is
       first.  Because this is a wildcard, it
       doesn't matter if the user does not
       actually link against crtbegin.o; the
       linker won't look for a file to match a
       wildcard.  The wildcard also means that it
       doesn't matter which directory crtbegin.o
       is in.  */
    KEEP (*crtbegin.o(.ctors))
    KEEP (*crtbegin?.o(.ctors))
    /* We don't want to include the .ctor section from
       the crtend.o file until after the sorted ctors.
       The .ctor section from the crtend file contains the
       end of ctors marker and it must be last */
    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .ctors))
    KEEP (*(SORT(.ctors.*)))
    KEEP (*(.ctors))
  }
  .dtors          :
  {
    KEEP (*crtbegin.o(.dtors))
    KEEP (*crtbegin?.o(.dtors))
    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .dtors))
    KEEP (*(SORT(.dtors.*)))
    KEEP (*(.dtors))
  }

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project('boot',
  ['c', 'cpp'],
  version : '1.0',
  default_options : [
    'cpp_link_args=-T ../../../../src/boot/machine/bios/bios.lds',
...

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link_script = files('machine/bios/bios.lds')

bootloader = executable('bootloader',
    sources: sources,
    include_directories: includes,
    link_depends: link_script,
)

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link_script = 'machine/bios/bios.lds'

bootloader = executable('bootloader',
    sources: sources,
    include_directories: includes,
    link_args: [ '-T' + meson.source_root() / link_script ],
    link_depends: link_script,
)

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extra_flags = []

if (machine == 'efi')
    extra_flags += '-fpic'
    if (arch == 'x86_64')
        extra_flags += '-mno-red-zone'
    endif
endif

add_project_arguments(extra_flags, language: ['c', 'cpp'])

cpp = meson.get_compiler('cpp')
libgcc = cpp.find_library('libgcc')
crtbegin = run_command(cpp, [extra_flags, '-print-file-name=crtbegin.o']).stdout().strip()
crtend = run_command(cpp, [extra_flags, '-print-file-name=crtend.o']).stdout().strip()