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{{FirstPerson}}
{{You}}
{{BeginnersWarning}}
{{Rating|1}}{{Template:Kernel designs}}
{{Kernel designs}}
 
In thisThis tutorial we continuecontinues from [[Bare Bones]] and createcreates a minimal template
operating system in the [[Stan Dard]] style suitable for further modification or as inspiration for your
as inspiration for your initial operating system version. The [[Bare Bones]] tutorial only gives you the
tutorial only gives you the absolutely minimal code to demonstrate how to correctly cross-compile a kernel,
correctly cross-compile a kernel, however this is unsuitable as an example operating system. Additionally, this
operating system. Additionally, this tutorial implements neccesary ABI features needed to satisfy the ABI and
needed to satisfy the ABI and compiler contracts to prevent possible mysterious errors.
errors.
 
This tutorial also serves as the initial template tutorial on how to
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== Building a Cross-Compiler ==
:''{{Main article: [[|GCC Cross-Compiler]], [[|Why do I need a Cross Compiler?]]}}
 
You ''must'' use a [[GCC Cross-Compiler]] in this tutorial as in the
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<tt>sysroot/boot</tt> directory.
 
We already use system roots already now because it will make it smoother to add a user-space when you get that far. This scheme is very convenient when you later [[Cross-Porting_Software|Port Third-Party Software by Cross-Compiling It]].
 
The <tt>-elf</tt> targets have no user-space and are incapable of having one. We configured the compiler with system root support, so it will look in <tt>${SYSROOT}/usr/lib</tt> as expected. We prevented the compiler from searching for a standard library using the --without-headers option when building <tt>i686-elf-gcc</tt>, so it will ''not'' look in <tt>${SYSROOT}/usr/include</tt>. (Once you add a user-space and a libc, you will configure your custom cross-gcc with <tt>--with-sysroot</tt> and it will look in <tt>${SYSROOT}/usr/include</tt>. As a temporary work-around until you get that far, we fix it by passing <tt>-isystem=/usr/include</tt>).
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provide the compiler a copy of your headers before you actually compile your
system. You will [[Hosted_GCC_Cross-Compiler#Sysroot_Headers|need to provide the
standard library headers]] when you in the future build a [[Hosted GCC Cross-Compiler]] in the
future that is capable of an user-space.
 
Note how your cross-compiler comes with a number of fully freestanding headers
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are used, while a default is used if the user has no opinion. The makefiles also
make sure that particular options are always in CFLAGS. This is done by having
two phases in the makefiles: one that setsets a default value and one that adds
mandatory options the project makefile requires:
 
<sourcesyntaxhighlight lang="make">
# Default CFLAGS:
CFLAGS?=-O2 -g
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# Add mandatory options to CFLAGS:
CFLAGS:=$(CFLAGS) -Wall -Wextra
</syntaxhighlight>
</source>
 
== Architecture Directories ==
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--->
 
You can easily download the source code using [[Git]] from the [https://gitlab.com/sortie/meaty-skeleton Meaty Skeleton Git repository]. This is preferable to doing a manual error-prone copy, as you may make a mistake or whitespace getsmay get garbled due to bugs in our syntax highlighting. To clone the git repository, do:
 
<sourcesyntaxhighlight lang="bash">
git clone https://gitlab.com/sortie/meaty-skeleton.git
</syntaxhighlight>
</source>
 
Check for differences between the git revision used in this article and what you cloned (empty output means there is no difference):
<sourcesyntaxhighlight lang="bash">
git diff 084d1624bedaa9f9e395f055c6bd99299bd97f58..master
</syntaxhighlight>
</source>
 
Operating systems development is about being an expert. Take the time to read the code carefully through and understand it. Please seek further information and help if you don't understand aspects of it. This code is minimal and almost everything is done deliberately, often to pre-emptively solve future problems.
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==== kernel/include/kernel/tty.h ====
 
<sourcesyntaxhighlight lang="c">
#ifndef _KERNEL_TTY_H
#define _KERNEL_TTY_H
Line 249 ⟶ 252:
 
#endif
</syntaxhighlight>
</source>
 
==== kernel/Makefile ====
 
<sourcesyntaxhighlight lang="make">
DEFAULT_HOST!=../default-host.sh
HOST?=DEFAULT_HOST
Line 337 ⟶ 340:
 
-include $(OBJS:.o=.d)
</syntaxhighlight>
</source>
 
==== kernel/kernel/kernel.c ====
 
<sourcesyntaxhighlight lang="c">
#include <stdio.h>
 
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printf("Hello, kernel World!\n");
}
</syntaxhighlight>
</source>
 
==== kernel/arch/i386/tty.c ====
 
<sourcesyntaxhighlight lang="c">
#include <stdbool.h>
#include <stddef.h>
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const size_t index = y * VGA_WIDTH + x;
terminal_buffer[index] = vga_entry(c, color);
}
 
void terminal_scroll(int line) {
int loop;
char c;
 
for(loop = line * (VGA_WIDTH * 2) + 0xB8000; loop < VGA_WIDTH * 2; loop++) {
c = *loop;
*(loop - (VGA_WIDTH * 2)) = c;
}
}
 
void terminal_delete_last_line() {
int x, *ptr;
 
for(x = 0; x < VGA_WIDTH * 2; x++) {
ptr = 0xB8000 + (VGA_WIDTH * 2) * (VGA_HEIGHT - 1) + x;
*ptr = 0;
}
}
 
void terminal_putchar(char c) {
int line;
unsigned char uc = c;
 
terminal_putentryat(uc, terminal_color, terminal_column, terminal_row);
if (++terminal_column == VGA_WIDTH) {
terminal_column = 0;
if (++terminal_row == VGA_HEIGHT)
{
terminal_row = 0;
for(line = 1; line <= VGA_HEIGHT - 1; line++)
{
terminal_scroll(line);
}
terminal_delete_last_line();
terminal_row = VGA_HEIGHT - 1;
}
}
}
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terminal_write(data, strlen(data));
}
</syntaxhighlight>
</source>
 
==== kernel/arch/i386/crtn.S ====
Line 431 ⟶ 462:
==== kernel/arch/i386/vga.h ====
 
<sourcesyntaxhighlight lang="c">
#ifndef ARCH_I386_VGA_H
#define ARCH_I386_VGA_H
Line 465 ⟶ 496:
 
#endif
</syntaxhighlight>
</source>
 
==== kernel/arch/i386/make.config ====
 
<sourcesyntaxhighlight lang="make">
KERNEL_ARCH_CFLAGS=
KERNEL_ARCH_CPPFLAGS=
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$(ARCHDIR)/boot.o \
$(ARCHDIR)/tty.o \
</syntaxhighlight>
</source>
 
==== kernel/arch/i386/crti.S ====
Line 604 ⟶ 635:
==== libc/include/string.h ====
 
<sourcesyntaxhighlight lang="c">
#ifndef _STRING_H
#define _STRING_H 1
Line 627 ⟶ 658:
 
#endif
</syntaxhighlight>
</source>
 
==== libc/include/stdio.h ====
 
<sourcesyntaxhighlight lang="c">
#ifndef _STDIO_H
#define _STDIO_H 1
Line 652 ⟶ 683:
 
#endif
</syntaxhighlight>
</source>
 
==== libc/include/sys/cdefs.h ====
 
<sourcesyntaxhighlight lang="c">
#ifndef _SYS_CDEFS_H
#define _SYS_CDEFS_H 1
Line 663 ⟶ 694:
 
#endif
</syntaxhighlight>
</source>
 
==== libc/include/stdlib.h ====
 
<sourcesyntaxhighlight lang="c">
#ifndef _STDLIB_H
#define _STDLIB_H 1
Line 685 ⟶ 716:
 
#endif
</syntaxhighlight>
</source>
 
==== libc/Makefile ====
 
<sourcesyntaxhighlight lang="make">
DEFAULT_HOST!=../default-host.sh
HOST?=DEFAULT_HOST
Line 783 ⟶ 814:
-include $(OBJS:.o=.d)
-include $(LIBK_OBJS:.o=.d)
</syntaxhighlight>
</source>
 
==== libc/stdlib/abort.c ====
 
<sourcesyntaxhighlight lang="c">
#include <stdio.h>
#include <stdlib.h>
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// TODO: Add proper kernel panic.
printf("kernel: panic: abort()\n");
asm volatile("hlt");
#else
// TODO: Abnormally terminate the process as if by SIGABRT.
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__builtin_unreachable();
}
</syntaxhighlight>
</source>
 
==== libc/string/memmove.c ====
 
<sourcesyntaxhighlight lang="c">
#include <string.h>
 
Line 822 ⟶ 854:
return dstptr;
}
</syntaxhighlight>
</source>
 
==== libc/string/strlen.c ====
 
<sourcesyntaxhighlight lang="c">
#include <string.h>
 
Line 835 ⟶ 867:
return len;
}
</syntaxhighlight>
</source>
 
==== libc/string/memcmp.c ====
 
<sourcesyntaxhighlight lang="c">
#include <string.h>
 
Line 853 ⟶ 885:
return 0;
}
</syntaxhighlight>
</source>
 
==== libc/string/memset.c ====
 
<sourcesyntaxhighlight lang="c">
#include <string.h>
 
Line 866 ⟶ 898:
return bufptr;
}
</syntaxhighlight>
</source>
 
==== libc/string/memcpy.c ====
 
<sourcesyntaxhighlight lang="c">
#include <string.h>
 
Line 880 ⟶ 912:
return dstptr;
}
</syntaxhighlight>
</source>
 
==== libc/stdio/puts.c ====
 
<sourcesyntaxhighlight lang="c">
#include <stdio.h>
 
Line 890 ⟶ 922:
return printf("%s\n", string);
}
</syntaxhighlight>
</source>
 
==== libc/stdio/putchar.c ====
 
<sourcesyntaxhighlight lang="c">
#include <stdio.h>
 
Line 910 ⟶ 942:
return ic;
}
</syntaxhighlight>
</source>
 
==== libc/stdio/printf.c ====
 
<sourcesyntaxhighlight lang="c">
#include <limits.h>
#include <stdbool.h>
Line 995 ⟶ 1,027:
return written;
}
</syntaxhighlight>
</source>
 
==== libc/arch/i386/make.config ====
 
<sourcesyntaxhighlight lang="make">
ARCH_CFLAGS=
ARCH_CPPFLAGS=
Line 1,008 ⟶ 1,040:
 
ARCH_HOSTEDOBJS=\
</syntaxhighlight>
</source>
 
==== libc/.gitignore ====
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==== build.sh ====
 
<sourcesyntaxhighlight lang="bash">
#!/bin/sh
set -e
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(cd $PROJECT && DESTDIR="$SYSROOT" $MAKE install)
done
</syntaxhighlight>
</source>
 
You should make this executable script executable by running:
<sourcesyntaxhighlight lang="bash">
chmod +x build.sh
</syntaxhighlight>
</source>
 
==== clean.sh ====
 
<sourcesyntaxhighlight lang="bash">
#!/bin/sh
set -e
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rm -rf isodir
rm -rf myos.iso
</syntaxhighlight>
</source>
 
You should make this executable script executable by running:
<sourcesyntaxhighlight lang="bash">
chmod +x clean.sh
</syntaxhighlight>
</source>
 
==== config.sh ====
 
<sourcesyntaxhighlight lang="bash">
SYSTEM_HEADER_PROJECTS="libc kernel"
PROJECTS="libc kernel"
Line 1,091 ⟶ 1,123:
export CC="$CC -isystem=$INCLUDEDIR"
fi
</syntaxhighlight>
</source>
 
==== default-host.sh ====
 
<sourcesyntaxhighlight lang="bash">
#!/bin/sh
echo i686-elf
</syntaxhighlight>
</source>
 
You should make this executable script executable by running:
<sourcesyntaxhighlight lang="bash">
chmod +x default-host.sh
</syntaxhighlight>
</source>
 
==== headers.sh ====
 
<sourcesyntaxhighlight lang="bash">
#!/bin/sh
set -e
Line 1,117 ⟶ 1,149:
(cd $PROJECT && DESTDIR="$SYSROOT" $MAKE install-headers)
done
</syntaxhighlight>
</source>
 
You should make this executable script executable by running:
<sourcesyntaxhighlight lang="bash">
chmod +x headers.sh
</syntaxhighlight>
</source>
 
==== iso.sh ====
 
<sourcesyntaxhighlight lang="bash">
#!/bin/sh
set -e
Line 1,142 ⟶ 1,174:
EOF
grub-mkrescue -o myos.iso isodir
</syntaxhighlight>
</source>
 
You should make this executable script executable by running:
<sourcesyntaxhighlight lang="bash">
chmod +x iso.sh
</syntaxhighlight>
</source>
 
==== qemu.sh ====
 
<sourcesyntaxhighlight lang="bash">
#!/bin/sh
set -e
Line 1,157 ⟶ 1,189:
 
qemu-system-$(./target-triplet-to-arch.sh $HOST) -cdrom myos.iso
</syntaxhighlight>
</source>
 
You should make this executable script executable by running:
<sourcesyntaxhighlight lang="bash">
chmod +x qemu.sh
</syntaxhighlight>
</source>
 
==== target-triplet-to-arch.sh ====
 
<sourcesyntaxhighlight lang="bash">
#!/bin/sh
if echo "$1" | grep -Eq 'i[[:digit:]]86-'; then
Line 1,173 ⟶ 1,205:
echo "$1" | grep -Eo '^[[:alnum:]_]*'
fi
</syntaxhighlight>
</source>
 
You should make this executable script executable by running:
<sourcesyntaxhighlight lang="bash">
chmod +x target-triplet-to-arch.sh
</syntaxhighlight>
</source>
 
==== .gitignore ====
Line 1,197 ⟶ 1,229:
the source tree by invoking:
 
<sourcesyntaxhighlight lang="bash">
./clean.sh
</syntaxhighlight>
</source>
 
You can install all the system headers into the system root without relying on
Line 1,205 ⟶ 1,237:
[[Hosted GCC Cross-Compiler]], by invoking:
 
<sourcesyntaxhighlight lang="bash">
./headers.sh
</syntaxhighlight>
</source>
 
You can build a bootable cdrom image of the operating system by invoking:
 
<sourcesyntaxhighlight lang="bash">
./iso.sh
</syntaxhighlight>
</source>
 
It's probably a good idea to create a quick ''build-and-then-launch'' short-cut
like used in this example to run the system in your favorite emulator quickly:
 
<sourcesyntaxhighlight lang="bash">
./qemu.sh
</syntaxhighlight>
</source>
 
== Troubleshooting ==
 
If you receive odd errors during the build, you may have made a mistake during manual copying, perhaps missed a file, forgottenforgot to make a file executable, or bugs in the highlighting software we use cause unintended whitespace to appear. Perform a git repository clone as described above, and use that code instead, or compare the two directory trees with the <tt>diff(1)</tt> diff command line utility. If you made personal changes to the code, those may be at fault.
 
== Moving Forward ==
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* [[topic:36584|A link error found & fixed]]
 
[[Category:Bare bones tutorialsTutorials]]
[[Category:C]]
Retrieved from "https://osdev.wiki/wiki/Special:MobileDiff/16991...27412"