draw to framebuffer

kernel/.cargo/config.toml

@@ -3,6 +3,7 @@ codegen-backend = "llvm"
 
 [unstable]
 json-target-spec = true # lets us specify a custom target specification file
+build-std-features = ["compiler-builtins-mem"]
 build-std = ["core", "compiler_builtins"]
 
 [build]

kernel/build.rs

@@ -0,0 +1,6 @@
+fn main() {
+    println!("cargo::rerun-if-changed=build.rs");
+
+    println!("cargo::rustc-link-arg-bin=kernel=-Tkernel.lds");
+    println!("cargo::rerun-if-changed=kernel.lds");
+}

kernel/kernel.lds

@@ -0,0 +1,43 @@
+OUTPUT_FORMAT(elf64-x86-64)
+ENTRY(_start)
+
+PHDRS {
+    limine_requests PT_LOAD;
+    text PT_LOAD;
+    rodata PT_LOAD;
+    data PT_LOAD;
+}
+
+SECTIONS {
+    . = 0xffffffff80000000;
+    .limine_requests : {
+        KEEP(*(.limine_requests_start))
+        KEEP(*(.limine_requests))
+        KEEP(*(.limine_requests_end))
+    } :limine_requests
+
+    . = ALIGN(CONSTANT(MAXPAGESIZE));
+    .text : {
+        *(.text .text.*)
+    } :text
+
+    . = ALIGN(CONSTANT(MAXPAGESIZE));
+    .rodata : {
+        *(.rodata .rodata.*)
+    } :rodata
+
+    . = ALIGN(CONSTANT(MAXPAGESIZE));
+    .data : {
+        *(.data .data.*)
+    } :data
+
+    .bss : {
+        *(.bss .bss.*)
+        *(COMMON)
+    } :data
+
+    /DISCARD/ : {
+        *(.eh_frame*)
+        *(.note .note.*)
+    }
+}

kernel/src/lib.rs

@@ -1,5 +1,7 @@
 #![no_std]
+#![feature(const_trait_impl, const_default)]
 
+pub mod limine;
 pub mod x86_64;
 
 /// # Safety

kernel/src/limine.rs

@@ -0,0 +1,164 @@
+use core::{cell::UnsafeCell, ptr::NonNull};
+
+#[repr(C)]
+pub struct BaseRevision(UnsafeCell<[u64; 3]>);
+
+unsafe impl Send for BaseRevision {}
+unsafe impl Sync for BaseRevision {}
+
+impl BaseRevision {
+    pub const fn from_revision(revision: u64) -> Self {
+        Self(UnsafeCell::new([
+            0xf9562b2d5c95a6c8,
+            0x6a7b384944536bdc,
+            revision,
+        ]))
+    }
+    pub fn is_supported(&self) -> bool {
+        unsafe { self.0.get().cast::<u64>().add(2).read_volatile() == 0 }
+    }
+    pub fn base_revision(&self) -> u64 {
+        unsafe { self.0.get().cast::<u64>().add(2).read_volatile() }
+    }
+}
+
+#[repr(transparent)]
+pub struct RequestsStartMarker([u64; 4]);
+pub const REQUESTS_START_MARKER: RequestsStartMarker = RequestsStartMarker([
+    0xf6b8f4b39de7d1ae,
+    0xfab91a6940fcb9cf,
+    0x785c6ed015d3e316,
+    0x181e920a7852b9d9,
+]);
+
+#[repr(transparent)]
+pub struct RequestsEndMarker([u64; 2]);
+pub const REQUESTS_END_MARKER: RequestsEndMarker =
+    RequestsEndMarker([0xadc0e0531bb10d03, 0x9572709f31764c62]);
+
+#[repr(C)]
+pub struct Request<T, U = ()> {
+    magic: [u64; 2],
+    id: [u64; 2],
+    revision: u64,
+    response: UnsafeCell<Option<NonNull<Response<T>>>>,
+    request: U,
+}
+
+unsafe impl<T, U> Send for Request<T, U> {}
+unsafe impl<T, U> Sync for Request<T, U> {}
+
+#[repr(C)]
+pub struct Response<T> {
+    revision: u64,
+    response: T,
+}
+
+impl<T, U> Request<T, U> {
+    pub const MAGIC: [u64; 2] = [0xc7b1dd30df4c8b88, 0x0a82e883a194f07b];
+
+    pub const fn new_raw(id: [u64; 2], revision: u64, request: U) -> Self {
+        Self {
+            magic: Self::MAGIC,
+            id,
+            revision,
+            response: UnsafeCell::new(None),
+            request,
+        }
+    }
+
+    pub fn response(&self) -> Option<&Response<T>> {
+        unsafe {
+            self.response
+                .get()
+                .cast::<Option<NonNull<Response<T>>>>()
+                .read_volatile()
+        }
+        .map(|ptr| unsafe { ptr.as_ref() })
+    }
+}
+
+#[repr(C)]
+pub struct Framebuffer {
+    pub addr: *mut u8,
+    pub width: u64,
+    pub height: u64,
+    pub pitch: u64,
+    pub bpp: u16,
+    pub memory_model: u8,
+    pub red_mask_size: u8,
+    pub red_mask_shift: u8,
+    pub green_mask_size: u8,
+    pub green_mask_shift: u8,
+    pub blue_mask_size: u8,
+    pub blue_mask_shift: u8,
+    pub reserved: [u8; 7],
+    pub edid_size: u64,
+    pub edid: *mut u8,
+}
+
+pub struct Color(pub [u8; 3]);
+
+impl Framebuffer {
+    pub fn draw_pixel(&self, x: u64, y: u64, color: Color) {
+        assert!(self.bpp <= 64);
+        let bytes_per_pixel = self.bpp.div_ceil(8) as usize;
+
+        let [r, g, b] = color.0;
+
+        let mask_color = |c: u8, bits: u8, shift: u8| {
+            let mask = (1 << bits) - 1;
+            (c as u64 & mask) << shift
+        };
+
+        let mut pixel = 0u64;
+        pixel |= mask_color(r, self.red_mask_size, self.red_mask_shift);
+        pixel |= mask_color(g, self.green_mask_size, self.green_mask_shift);
+        pixel |= mask_color(b, self.blue_mask_size, self.blue_mask_shift);
+
+        let pixel = pixel.to_le_bytes();
+
+        let dst = unsafe {
+            self.addr
+                .add((y * self.pitch + x * bytes_per_pixel as u64) as usize)
+        };
+        unsafe { super::volatile_copy(pixel.as_ptr(), dst, bytes_per_pixel) }
+    }
+}
+
+#[repr(C)]
+pub struct FramebufferResponse {
+    count: u64,
+    framebuffers: *const *const Framebuffer,
+}
+
+pub type FramebufferRequest = Request<FramebufferResponse>;
+
+const impl Default for FramebufferRequest {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl FramebufferRequest {
+    pub const ID: [u64; 2] = [0x9d5827dcd881dd75, 0xa3148604f6fab11b];
+
+    pub const fn new() -> Self {
+        Self::new_raw(Self::ID, 0, ())
+    }
+
+    pub fn framebuffers<'limine>(&self) -> &'limine [&'limine Framebuffer] {
+        // SAFETY: limine responses are guaranteed to be valid for the lifetime of the memory mapping.
+        self.response()
+            .map(|response| unsafe {
+                core::slice::from_raw_parts(
+                    response
+                        .response
+                        .framebuffers
+                        .cast::<&'limine Framebuffer>(),
+                    response.response.count as usize,
+                )
+            })
+            .unwrap_or(&[])
+    }
+}

kernel/src/main.rs

@@ -8,5 +8,48 @@ fn panic(_info: &core::panic::PanicInfo) -> ! {
 
 #[unsafe(no_mangle)]
 fn _start() -> ! {
+    assert!(limine_requests::LIMINE_BASE_REVISION.is_supported());
+
+    let fb = limine_requests::FRAMEBUFFER_REQUEST
+        .framebuffers()
+        .first()
+        .expect("No framebuffer found");
+
+    for y in 0..fb.height {
+        for x in 0..fb.width {
+            let mut bits = ((x * 255 / fb.width) as u32) << 8;
+            bits ^= (y * 255 / fb.height) as u32;
+
+            fb.draw_pixel(
+                x,
+                y,
+                kernel::limine::Color(*bits.to_le_bytes().first_chunk().unwrap()),
+            );
+        }
+    }
+
     kernel::x86_64::halt_loop()
 }
+
+mod limine_requests {
+    use kernel::limine::{
+        BaseRevision, FramebufferRequest, REQUESTS_END_MARKER, REQUESTS_START_MARKER,
+        RequestsEndMarker, RequestsStartMarker,
+    };
+
+    #[unsafe(link_section = ".limine_requests_start")]
+    #[unsafe(no_mangle)]
+    static LIMINE_REQUESTS_START: RequestsStartMarker = REQUESTS_START_MARKER;
+
+    #[unsafe(link_section = ".limine_requests")]
+    #[unsafe(no_mangle)]
+    pub static LIMINE_BASE_REVISION: BaseRevision = BaseRevision::from_revision(6);
+
+    #[unsafe(link_section = ".limine_requests")]
+    #[unsafe(no_mangle)]
+    pub static FRAMEBUFFER_REQUEST: FramebufferRequest = FramebufferRequest::new();
+
+    #[unsafe(link_section = ".limine_requests_end")]
+    #[unsafe(no_mangle)]
+    static LIMINE_REQUESTS_END: RequestsEndMarker = REQUESTS_END_MARKER;
+}

kernel/x86_64-unknown-kernel.json

@@ -1,28 +1,29 @@
 {
-  "arch": "x86_64",
-  "code-model": "kernel",
-  "cpu": "x86-64",
-  "crt-objects-fallback": "false",
-  "data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
-  "disable-redzone": true,
-  "target-endian": "little",
-  "features": "-mmx,-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2,+soft-float",
-  "linker": "mold",
-  "linker-flavor": "gnu",
-  "llvm-target": "x86_64-unknown-none-elf",
-  "max-atomic-width": 64,
-  "panic-strategy": "abort",
-  "plt-by-default": false,
-  "position-independent-executables": true,
-  "relro-level": "full",
-  "rustc-abi": "softfloat",
-  "stack-probes": {
-    "kind": "inline"
-  },
-  "static-position-independent-executables": true,
-  "supported-sanitizers": [
-    "kcfi",
-    "kernel-address"
-  ],
-  "target-pointer-width": 64
+    "arch": "x86_64",
+    "code-model": "kernel",
+    "cpu": "x86-64",
+    "crt-objects-fallback": "false",
+    "data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
+    "disable-redzone": true,
+    "target-endian": "little",
+    "features": "-mmx,-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2,+soft-float",
+    "linker": "rust-lld",
+    "linker-flavor": "ld.lld",
+    "llvm-target": "x86_64-unknown-none-elf",
+    "max-atomic-width": 64,
+    "panic-strategy": "abort",
+    "plt-by-default": false,
+    "os": "none",
+    "executables": true,
+    "relro-level": "full",
+    "rustc-abi": "softfloat",
+    "stack-probes": {
+        "kind": "inline"
+    },
+    "supported-sanitizers": [
+        "kcfi",
+        "kernel-address"
+    ],
+    "target-pointer-width": 64,
+    "target-c-int-width": 32
 }