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Limine Bare Bones: Difference between revisions
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The Limine boot protocol is firmware and architecture agnostic. The Limine bootloader supports x86-64, IA-32, aarch64, and riscv64.
This article will demonstrate how to write a small Limine-compliant x86-64
It is also very recommended to check out [https://github.com/limine-bootloader/limine-c-template this template project] as it provides example buildable code to go along with this guide.
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For this example, we will create these 2 files to create the basic directory tree of our project:
* src/
* linker.ld
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Obviously, this is just a bare bones example, and one should always refer to the [https://github.com/limine-bootloader/limine/blob/trunk/PROTOCOL.md Limine protocol specification] for more details and information.
===src/
This is the kernel "main".
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#include <limine.h>
// Set the base revision to
// base revision described by the Limine boot protocol specification.
// See specification for further info.
__attribute__((used, section(".requests")))
static volatile LIMINE_BASE_REVISION(
// The Limine requests can be placed anywhere, but it is important that
// the compiler does not optimise them away, so, usually, they should
// be made volatile or equivalent, _and_ they should be accessed at least
// once or marked as used with the "used" attribute as done here.
__attribute__((used, section(".requests")))
static volatile struct limine_framebuffer_request framebuffer_request = {
.id = LIMINE_FRAMEBUFFER_REQUEST,
.revision = 0
};
// Finally, define the start and end markers for the Limine requests.
// These can also be moved anywhere, to any .c file, as seen fit.
__attribute__((used, section(".requests_start_marker")))
static volatile LIMINE_REQUESTS_START_MARKER;
__attribute__((used, section(".requests_end_marker")))
static volatile LIMINE_REQUESTS_END_MARKER;
// GCC and Clang reserve the right to generate calls to the following
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// Note: we assume the framebuffer model is RGB with 32-bit pixels.
for (size_t i = 0; i < 100; i++) {
volatile uint32_t *fb_ptr = framebuffer->address;
fb_ptr[i * (framebuffer->pitch / 4) + i] = 0xffffff;
}
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PHDRS
{
dynamic PT_DYNAMIC FLAGS((1 << 1) | (1 << 2)) ; /* Dynamic PHDR for relocations */
}
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/* that is the beginning of the region. */
. = 0xffffffff80000000;
/* Define a section to contain the Limine requests and assign it to its own PHDR */
.requests : {
*(.requests_start_marker)
*(.requests)
*(.requests_end_marker)
} :requests
/* Move to the next memory page for .text */
. += CONSTANT(MAXPAGESIZE);
.text : {
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