Fix minor typos. (#675)

blog/content/second-edition/posts/10-heap-allocation/index.md

@@ -87,7 +87,7 @@ Let's go through an example:
 
 ![The inner function calls `allocate(size_of([u32; 3]))`, writes `z.write([1,2,3]);`, and returns `(z as *mut u32).offset(i)`. The outer function does `deallocate(y, size_of(u32))` on the returned value `y`.](call-stack-heap.svg)
 
-Here the `inner` function uses heap memory instead of static variables for storing `z`. It first allocates a memory block of the required size, which returns a `*mut u8` [raw pointer]. It then uses the [`ptr::write`] method to write the array `[1,2,3]` to it. In the last step, it uses the [`offset`] function to calculate a pointer to the `i`th element and then returns it. (Note that we omitted some required casts and unsafe blocks in this example function for brevity.)
+Here the `inner` function uses heap memory instead of static variables for storing `z`. It first allocates a memory block of the required size, which returns a `*mut u32` [raw pointer]. It then uses the [`ptr::write`] method to write the array `[1,2,3]` to it. In the last step, it uses the [`offset`] function to calculate a pointer to the `i`th element and then returns it. (Note that we omitted some required casts and unsafe blocks in this example function for brevity.)
 
 [raw pointer]: https://doc.rust-lang.org/book/ch19-01-unsafe-rust.html#dereferencing-a-raw-pointer
 [`ptr::write`]: https://doc.rust-lang.org/core/ptr/fn.write.html
@@ -475,7 +475,8 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     println!("Hello World{}", "!");
     blog_os::init();
 
-    let mut mapper = unsafe { memory::init(boot_info.physical_memory_offset) };
+    let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
+    let mut mapper = unsafe { memory::init(phys_mem_offset) };
     let mut frame_allocator = unsafe {
         BootInfoFrameAllocator::init(&boot_info.memory_map)
     };