load kernel

nel_os_bootloader/src/main.rs

@@ -4,11 +4,11 @@
 extern crate alloc;
 
 use alloc::{boxed::Box, vec};
-use core::arch::asm;
-use goblin::elf;
+use core::{arch::asm, slice};
+use goblin::elf::{self, Elf};
 use uefi::{
     allocator::Allocator,
-    boot::{MemoryType, ScopedProtocol},
+    boot::{AllocateType, MemoryType, ScopedProtocol},
     mem::memory_map::MemoryMap,
     prelude::*,
     println,
@@ -56,6 +56,48 @@ fn read_kernel(name: &CStr16) -> Box<[u8]> {
     buf.into_boxed_slice()
 }
 
+fn load_elf(bin: Box<[u8]>) -> u64 {
+    let elf = elf::Elf::parse(&bin).expect("Failed to parse elf");
+    let mut dest_start = u64::MAX;
+    let mut dest_end = 0u64;
+
+    elf.program_headers
+        .iter()
+        .filter(|header| header.p_type == elf::program_header::PT_LOAD)
+        .for_each(|header| {
+            dest_start = dest_start.min(header.p_vaddr);
+            dest_end = dest_end.max(header.p_vaddr + header.p_memsz);
+        });
+
+    uefi::boot::allocate_pages(
+        AllocateType::Address(dest_start),
+        MemoryType::LOADER_DATA,
+        dest_end
+            .checked_sub(dest_start)
+            .and_then(|size| size.checked_add(4095))
+            .map(|size| size / 4096)
+            .unwrap_or(0) as usize,
+    )
+    .expect("Failed to allocate pages");
+
+    elf.program_headers
+        .iter()
+        .filter(|header| header.p_type == elf::program_header::PT_LOAD)
+        .for_each(|header| {
+            let dest = unsafe {
+                slice::from_raw_parts_mut(header.p_vaddr as *mut u8, header.p_memsz as usize)
+            };
+
+            let file_size = header.p_filesz as usize;
+            let offset = header.p_offset as usize;
+
+            dest[..file_size].copy_from_slice(&bin[offset..offset + file_size]);
+            dest[file_size..].fill(0);
+        });
+
+    elf.entry
+}
+
 #[entry]
 fn main() -> Status {
     uefi::helpers::init().unwrap();
@@ -78,13 +120,17 @@ fn main() -> Status {
 
     let kernel = read_kernel(cstr16!("nel_os_kernel.elf"));
 
-    let elf = elf::Elf::parse(&kernel).expect("Failed to parse kernel");
+    let entry_point = load_elf(kernel);
 
-    println!("Entry point: {}", elf.entry);
+    println!("Entry point: {:#x}", entry_point);
+
+    let entry: extern "sysv64" fn() = unsafe { core::mem::transmute(entry_point) };
 
     unsafe {
         let _ = uefi::boot::exit_boot_services(Some(MemoryType::LOADER_DATA));
     }
 
+    entry();
+
     hlt_loop();
 }

nel_os_kernel/x86_64-nel_os.json

@@ -15,5 +15,13 @@
     "features": "-mmx,-sse,+soft-float",
     "rustc-abi": "x86-softfloat",
 	"code-model": "kernel",
-	"max-atomic-width": 64
+	"max-atomic-width": 64,
+	"position-independent-executables": false,
+	"post-link-args": {
+		"ld.lld": [
+			"--entry=asm_main",
+			"--image-base=0x100000",
+			"--static"
+		]
+	}
 }