Start work on x86_64 boot

notes.md

@@ -19,7 +19,7 @@ Loader must provide modinfo to kernel, a TLV structure
 * `MODINFOMD_EFI_FB`: Some structure describing UEFI framebuffer
 * `MODINFOMD_KEYBUF`: `struct keybuf` object with cached keys, don't really need it
 * `MODINFOMD_FW_HANDLE`: physical address of RuntimeServices system table
-* `MODINFOMD_MODULEP`: Base physical address of modinfo, probably
+* `MODINFOMD_MODULEP`: Base physical address of TLV structure, only seems to matter for x86\_64 Xen
 * `MODINFOMD_KERNEND`: Last physical address of kernel, should be free after
 * `MODINFOMD_HOWTO`: u32 with a bunch of bitflags that start with `RB_` in `sys/sys/reboot.h`
 * `MODINFOMD_ELFHDR`: copy of the elf header

src/abi.rs

@@ -1,7 +1,10 @@
 extern crate alloc;
-use alloc::string::String;
 use alloc::vec::Vec;
-use uefi::proto::console::gop::{GraphicsOutput, PixelFormat};
+use alloc::{collections::BTreeMap, string::String};
+use uefi::{
+    proto::console::gop::{GraphicsOutput, PixelFormat},
+    table::boot::PAGE_SIZE,
+};
 
 fn align_slice(unaligned: &mut [u8], alignment: usize) -> &mut [u8] {
     let base_addr = &unaligned[0] as *const u8 as usize;
@@ -17,17 +20,29 @@ pub trait Serialize {
     /// Calculate output size of object, from base address to final byte written
     fn size(&self) -> usize;
 
+    /// Conservative estimate of size to allocate
+    fn alloc_size(&self) -> usize {
+        self.size() + Self::alignment() - 1
+    }
+
     /// Serliaze data into a buffer. Buffer must be aligned at alignment and size of size().
     fn serialize_raw(&self, out: &mut [u8]);
 
-    /// Serialize to an unaligned buffer, returning the end address
+    /// Serialize to an unaligned buffer, returning the pointer to the base and the end address as
+    /// a slice
     #[must_use]
-    fn serialize_unaligned<'a>(&self, out: &'a mut [u8]) -> &'a mut [u8] {
+    fn serialize_unaligned_base<'a>(&self, out: &'a mut [u8]) -> (*const u8, &'a mut [u8]) {
         let aligned = align_slice(out, Self::alignment());
         let size = self.size();
         self.serialize_raw(&mut aligned[..size]);
 
-        &mut aligned[size..]
+        (aligned.as_ptr(), &mut aligned[size..])
+    }
+
+    /// Serialize to an unaligned buffer, returning the end address as a slice
+    #[must_use]
+    fn serialize_unaligned<'a>(&self, out: &'a mut [u8]) -> &'a mut [u8] {
+        self.serialize_unaligned_base(out).1
     }
 }
 
@@ -99,6 +114,7 @@ impl Serialize for EFIFramebufferParams {
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[repr(u32)]
+#[allow(dead_code)]
 /// Tag in the module info TLV
 pub enum ModuleInfoType {
     /// Module name (MODINFO_NAME)
@@ -123,6 +139,12 @@ pub enum ModuleInfoType {
     EndSymbols = 0x8004,
     /// Base virtual address of `PT_DYNAMIC` segment (MODINFOMD_DYNAMIC)
     Dynamic = 0x8005,
+    /// Loader environment variables (MODINFOMD_ENVP)
+    Environment = 0x8006,
+    /// Boot bitflags starting with `RB_` (MODINFOMD_HOWTO)
+    Howto = 0x8007,
+    /// Free virtual address after staging buffer (MODINFOMD_KERNEND)
+    FreeAddress = 0x8008,
     /// Section header table (MODINFOMD_SHDR)
     SectionHeader = 0x8009,
     /// Base virtual address of constructors (MODINFOMD_CTORS_ADDR)
@@ -200,7 +222,7 @@ impl core::fmt::Debug for ModuleInfoValue {
             Self::String(arg0) => f.debug_tuple("String").field(arg0).finish(),
             Self::Pointer(arg0) => f.debug_tuple("Pointer").field(arg0).finish(),
             Self::Size(arg0) => f.debug_tuple("Size").field(arg0).finish(),
-            Self::Buffer(_) => write!(f, "Buffer(elided)"),
+            Self::Buffer(arg0) => write!(f, "Buffer(len={})", arg0.len()),
         }
     }
 }
@@ -228,3 +250,34 @@ impl Serialize for ModuleInfoItem {
         self.value.serialize_raw(&mut out[8..]);
     }
 }
+
+#[derive(Debug, Clone)]
+pub struct Environment(pub BTreeMap<String, String>);
+
+impl Serialize for Environment {
+    fn alignment() -> usize {
+        // FreeBSD aligns to pages, might not matter though
+        PAGE_SIZE
+    }
+
+    fn size(&self) -> usize {
+        self.0
+            .iter()
+            .map(|(k, v)| k.len() + v.len() + 2)
+            .sum::<usize>()
+            + 1
+    }
+
+    fn serialize_raw(&self, mut out: &mut [u8]) {
+        // Format is `key1=value1\0key2=value2\0\0`
+        for (key, value) in self.0.iter() {
+            let entry_len = key.len() + 1 + value.len();
+            out[..key.len()].copy_from_slice(key.as_bytes());
+            out[key.len()] = b'=';
+            out[key.len() + 1..entry_len].copy_from_slice(value.as_bytes());
+            out[entry_len] = 0;
+            out = &mut out[entry_len + 1..];
+        }
+        out[out.len() - 1] = 0;
+    }
+}

src/boot.rs

@@ -0,0 +1,77 @@
+#[cfg(target_arch = "x86_64")]
+pub use x86_64::boot_kernel;
+
+#[cfg(target_arch = "x86_64")]
+mod x86_64 {
+    use core::{arch::global_asm, ptr::null, slice};
+
+    
+    use uefi::table::{Boot, SystemTable};
+
+    use crate::{object::Kernel, staging::allocate_code};
+
+    global_asm!(
+        r#"
+    .text
+    .globl trampoline_code
+trampoline_code:
+    cli
+    mov rsp,rdi
+    push rcx
+    sal rdx, #32
+    push rdx
+    push r8
+    mov cr3,rsi
+    ret
+
+trampoline_end:
+    .data
+    .globl trampoline_size
+trampoline_size:
+    .long trampoline_end-trampoline_code
+"#
+    );
+
+    // use sysv64 because i don't want to pop from the stack
+    extern "sysv64" {
+        static trampoline_size: u32;
+
+        fn trampoline_code(
+            stack: *const u8,
+            pagetable: *const u8,
+            modinfo_base: *const u8,
+            free_ptr: *const u8,
+            entry: *const u8,
+        );
+    }
+
+    type TrampolineFunction =
+        extern "sysv64" fn(*const u8, *const u8, *const u8, *const u8, *const u8);
+
+    pub fn boot_kernel(
+        system_table: SystemTable<Boot>,
+        kernel: Kernel,
+        kernel_base: *const u8,
+        modinfo_base: *const u8,
+        free_ptr: *const u8,
+    ) {
+        let trampoline_code_size = unsafe { trampoline_size } as usize;
+        let misc_buf = allocate_code(system_table.boot_services(), trampoline_code_size + 64);
+
+        let (stack_buf, trampoline_buf) = misc_buf.split_at_mut(64);
+        trampoline_buf[..trampoline_code_size].copy_from_slice(unsafe {
+            slice::from_raw_parts(trampoline_code as *const u8, trampoline_code_size)
+        });
+
+        unsafe {
+            let trampoline_func: TrampolineFunction = core::mem::transmute(trampoline_buf.as_ptr());
+            trampoline_func(
+                stack_buf.as_ptr(),
+                null(),
+                modinfo_base,
+                free_ptr,
+                kernel.entry_addr(kernel_base),
+            );
+        }
+    }
+}

src/main.rs

@@ -2,10 +2,14 @@
 #![no_std]
 
 mod abi;
+mod boot;
 mod object;
 mod staging;
 
-use abi::{ModuleInfoItem, Serialize};
+extern crate alloc;
+
+use abi::{Environment, ModuleInfoItem, ModuleInfoType, ModuleInfoValue, Serialize};
+use alloc::{collections::btree_map::BTreeMap, string::ToString};
 use log::info;
 use object::{Kernel, Module};
 use uefi::{fs::FileSystem, prelude::*};
@@ -16,42 +20,61 @@ fn main(image_handle: Handle, mut system_table: SystemTable<Boot>) -> Status {
 
     info!("Starting freeloader");
 
-    let mut esp = FileSystem::new(
-        system_table
-            .boot_services()
-            .get_image_file_system(image_handle)
-            .expect("Failed to get ESP handle"),
-    );
-
-    let kernel_data = esp
-        .read(cstr16!("efi\\freebsd\\kernel"))
-        .expect("Failed to read kernel");
+    let kernel_data = {
+        let mut esp = FileSystem::new(
+            system_table
+                .boot_services()
+                .get_image_file_system(image_handle)
+                .expect("Failed to get ESP handle"),
+        );
 
+        esp.read(cstr16!("efi\\freebsd\\kernel"))
+            .expect("Failed to read kernel")
+    };
     info!("Read kernel");
 
     let kernel = Kernel::from_elf_bytes(&kernel_data);
-    let kernel_metadata = kernel.metadata();
+    let mut kernel_metadata = kernel.metadata();
     info!("Kernel metadata is {:x?}", kernel_metadata);
 
-    let metadata_size: usize = kernel_metadata
-        .iter()
-        .map(|item| item.size().next_multiple_of(ModuleInfoItem::alignment()))
-        .sum();
+    let environment = Environment(BTreeMap::from([(
+        "kernel".to_string(),
+        "kernel".to_string(),
+    )]));
 
     // Allocate an extra 16KiB for items we have to add to metadata
-    let alloc_size = kernel.size() + Kernel::alignment() + metadata_size + 16 * 1024;
+    let metadata_size: usize = kernel_metadata
+        .iter()
+        .map(|item| item.alloc_size())
+        .sum::<usize>()
+        + 16 * 1024;
 
-    let staging = staging::allocate_staging(system_table.boot_services(), alloc_size);
+    let alloc_size = kernel.alloc_size() + environment.alloc_size() + metadata_size;
+    let staging = staging::allocate_code(system_table.boot_services(), alloc_size);
 
-    {
-        let mut next = staging;
-        next = kernel.serialize_unaligned(next);
-        for item in kernel_metadata.iter() {
-            next = item.serialize_unaligned(next);
-        }
+    let (environ_base, next) = environment.serialize_unaligned_base(staging);
+
+    let (kernel_base, mut next) = kernel.serialize_unaligned_base(next);
+
+    kernel_metadata.push(abi::ModuleInfoItem {
+        tag: ModuleInfoType::Environment,
+        value: ModuleInfoValue::Pointer(environ_base),
+    });
+
+    let modinfo_base = next.as_ptr();
+
+    let free_ptr = unsafe { next.as_ptr().byte_add(metadata_size) };
+    kernel_metadata.push(ModuleInfoItem {
+        tag: ModuleInfoType::FreeAddress,
+        value: ModuleInfoValue::Pointer(free_ptr),
+    });
+
+    for item in kernel_metadata.iter() {
+        next = item.serialize_unaligned(next);
     }
 
-    loop {
-        system_table.boot_services().stall(10_000_000);
-    }
+    boot::boot_kernel(system_table, kernel, kernel_base, modinfo_base, free_ptr);
+
+    // boot_kernel shouldn't return
+    Status::ABORTED
 }

src/object.rs

@@ -62,8 +62,8 @@ impl<'a> Kernel<'a> {
         }
     }
 
-    pub fn entry_addr(&self, load_addr: usize) -> usize {
-        self.parsed.header.e_entry as usize - self.min_loadaddr + load_addr
+    pub fn entry_addr(&self, serialize_addr: *const u8) -> *const u8 {
+        unsafe { serialize_addr.byte_add(self.parsed.header.e_entry as usize - self.min_loadaddr) }
     }
 
     fn find_symbol_headers(parsed: &Elf) -> Option<(SectionHeader, SectionHeader)> {

src/staging.rs

@@ -1,7 +1,7 @@
 use log::info;
 use uefi::table::boot::{AllocateType, BootServices, MemoryType, PAGE_SIZE};
 
-pub fn allocate_staging(boot_services: &BootServices, size: usize) -> &'static mut [u8] {
+pub fn allocate_code(boot_services: &BootServices, size: usize) -> &'static mut [u8] {
     let allocation_type = if cfg!(target_arch = "x86_64") {
         // Must be under 4GiB because we need to pass a 32-bit pointer
         AllocateType::MaxAddress(4 * 1024 * 1024 * 1024)