From bf71132cd0809da3664715c6f29598ade0838761 Mon Sep 17 00:00:00 2001
From: Artemis Tosini <me@artem.ist>
Date: Mon, 29 Jul 2024 22:54:36 +0000
Subject: [PATCH] A bit more ABI work

---
 src/abi.rs | 80 +++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 55 insertions(+), 25 deletions(-)

diff --git a/src/abi.rs b/src/abi.rs
index a370d43..d1904fd 100644
--- a/src/abi.rs
+++ b/src/abi.rs
@@ -17,8 +17,8 @@ impl EFIFramebufferParams {
     pub fn from_graphics_output(graphics_output: &mut GraphicsOutput) -> Option<Self> {
         let mode = graphics_output.current_mode_info();
         let (mask_red, mask_green, mask_blue, mask_reserved) = match mode.pixel_format() {
-            PixelFormat::Rgb => (0x0000_00ff, 0x0000_ff00, 0x00ff_0000, 0xff00_000),
-            PixelFormat::Bgr => (0x00ff_0000, 0x0000_ff00, 0x0000_00ff, 0xff00_000),
+            PixelFormat::Rgb => (0x0000_00ff, 0x0000_ff00, 0x00ff_0000, 0xff00_0000),
+            PixelFormat::Bgr => (0x00ff_0000, 0x0000_ff00, 0x0000_00ff, 0xff00_0000),
             PixelFormat::Bitmask => {
                 let bitmask = mode.pixel_bitmask()?;
                 (bitmask.red, bitmask.green, bitmask.blue, bitmask.reserved)
@@ -45,34 +45,64 @@ impl EFIFramebufferParams {
     }
 }
 
-#[cfg_attr(target_pointer_width = "64", repr(C, align(8)))]
-#[cfg_attr(target_pointer_width = "32", repr(C, align(4)))]
-pub struct ModuleDirectoryElem<T> {
-    ident: ModInfo,
-    size: u32,
-    data: T,
+/// Single TLV in the metadata buffer.
+/// In the FreeBSD kernel would be placed in `preload_metadata`
+pub enum PreloadDirectoryElem<'a> {
+    /// Module name (MOD_NAME)
+    Name(&'a str),
+    /// Module type (MOD_TYPE)
+    Type(&'a str),
+    /// Module parameters (MOD_ARGS)
+    Args(&'a str),
+    // TODO: figure out how to make this pointer safer
+    /// Module address (MOD_ADDR)
+    LoadAddress(*const u8),
+    /// Module size (MOD_SIZE)
+    Size(usize),
+    /// Type-speicfic metadata (MOD_METADATA)
+    Metadata(FileMetadataType, &'a [u8]),
+    End,
 }
 
+impl<'a> PreloadDirectoryElem<'a> {
+    fn copy_str(data: &str, output: &mut [u8]) -> Option<u32> {
+        output[..data.len()].copy_from_slice(data.as_bytes());
+        output[data.len()] = 0;
+        data.len().checked_add(1)?.try_into().ok()
+    }
 
-#[repr(C)]
-pub struct FileMetadataElem<T> {
-    size: usize,
-    typ: FileMetadataType,
-    addr: *const T,
-    next: Option<*const FileMetadataElem<T>>,
-    data: T,
-}
-
-#[repr(u32)]
-pub enum ModInfo {
-    End = 0,
-    Name = 1,
-    Type = 2,
-    Addr = 3,
-    Size = 4,
-    Args = 6,
+    pub fn copy_to_output<'b>(&'a self, output: &'b mut [u8]) -> Option<&'b mut [u8]> {
+        let usize_size = core::mem::size_of::<usize>();
+
+        let (tag, length) = match self {
+            Self::Name(name) => (1u32, Self::copy_str(name, &mut output[8..])?),
+            Self::Type(typ) => (2u32, Self::copy_str(typ, &mut output[8..])?),
+            Self::Args(args) => (6u32, Self::copy_str(args, &mut output[8..])?),
+            Self::LoadAddress(addr) => {
+                output[8..(8 + usize_size)].copy_from_slice(&(*addr as usize).to_ne_bytes());
+                (3u32, usize_size as u32)
+            }
+            Self::Size(size) => {
+                output[8..(8 + usize_size)].copy_from_slice(&size.to_ne_bytes());
+                (4u32, usize_size as u32)
+            }
+            Self::Metadata(typ, metadata) => {
+                output[8..(8 + metadata.len())].copy_from_slice(metadata);
+                (0x8000 | (*typ as u32), metadata.len() as u32)
+            }
+            Self::End => (0u32, 0u32),
+        };
+
+        output[..4].copy_from_slice(&tag.to_ne_bytes());
+        output[4..8].copy_from_slice(&length.to_ne_bytes());
+
+        let aligned_length = ((length as usize + usize_size - 1) / usize_size) * usize_size;
+
+        Some(&mut output[(aligned_length + 8)..])
+    }
 }
 
+#[derive(Debug, Copy, Clone)]
 #[repr(u16)]
 pub enum FileMetadataType {
     AoutExecHeader = 1,