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multiboot2: foundation for mutable reference to tags #171

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2 changes: 1 addition & 1 deletion multiboot2/src/boot_loader_name.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,7 @@ impl BootLoaderNameTag {
///
/// ```rust,no_run
/// # use multiboot2::{BootInformation, BootInformationHeader};
/// # let ptr = 0xdeadbeef as *const BootInformationHeader;
/// # let ptr = 0xdeadbeef as *mut BootInformationHeader;
/// # let boot_info = unsafe { BootInformation::load(ptr).unwrap() };
/// if let Some(tag) = boot_info.boot_loader_name_tag() {
/// assert_eq!(Ok("GRUB 2.02~beta3-5"), tag.name());
Expand Down
2 changes: 1 addition & 1 deletion multiboot2/src/builder/information.rs
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Expand Up @@ -448,7 +448,7 @@ mod tests {
let mb2i_data = create_builder().build();

// Step 2/2: Test the built MBI
let mb2i = unsafe { BootInformation::load(mb2i_data.as_ptr().cast()) }
let mb2i = unsafe { BootInformation::load(mb2i_data.as_ptr().cast_mut().cast()) }
.expect("generated information should be readable");

assert_eq!(mb2i.basic_memory_info_tag().unwrap().memory_lower(), 640);
Expand Down
2 changes: 1 addition & 1 deletion multiboot2/src/command_line.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -48,7 +48,7 @@ impl CommandLineTag {
///
/// ```rust,no_run
/// # use multiboot2::{BootInformation, BootInformationHeader};
/// # let ptr = 0xdeadbeef as *const BootInformationHeader;
/// # let ptr = 0xdeadbeef as *mut BootInformationHeader;
/// # let boot_info = unsafe { BootInformation::load(ptr).unwrap() };
/// if let Some(tag) = boot_info.command_line_tag() {
/// let command_line = tag.cmdline();
Expand Down
92 changes: 58 additions & 34 deletions multiboot2/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@
//!
//! fn kernel_entry(mb_magic: u32, mbi_ptr: u32) {
//! if mb_magic == multiboot2::MAGIC {
//! let boot_info = unsafe { BootInformation::load(mbi_ptr as *const BootInformationHeader).unwrap() };
//! let boot_info = unsafe { BootInformation::load(mbi_ptr as *mut BootInformationHeader).unwrap() };
//! let _cmd = boot_info.command_line_tag();
//! } else { /* Panic or use multiboot1 flow. */ }
//! }
Expand Down Expand Up @@ -91,7 +91,9 @@ pub use vbe_info::{
};

use core::fmt;
use core::marker::PhantomData;
use core::mem::size_of;
use core::ptr::NonNull;
use derive_more::Display;
// Must be public so that custom tags can be DSTs.
#[cfg(feature = "builder")]
Expand Down Expand Up @@ -177,8 +179,16 @@ impl BootInformationInner {
}

/// A Multiboot 2 Boot Information (MBI) accessor.
///
/// This type acts like it owns the memory of the MBI. It allows reading all
/// kind of tags. Furthermore, it gives you mutable access to a certain degree
/// to some tags, in case you want to modify them. The latter is most likely
/// only relevant in niche cases.
#[repr(transparent)]
pub struct BootInformation<'a>(&'a BootInformationInner);
pub struct BootInformation<'a> {
ptr: NonNull<BootInformationInner>,
_phantom: PhantomData<&'a mut BootInformationInner>,
}

impl<'a> BootInformation<'a> {
/// Loads the [`BootInformation`] from a pointer. The pointer must be valid
Expand All @@ -191,7 +201,7 @@ impl<'a> BootInformation<'a> {
///
/// fn kernel_entry(mb_magic: u32, mbi_ptr: u32) {
/// if mb_magic == multiboot2::MAGIC {
/// let boot_info = unsafe { BootInformation::load(mbi_ptr as *const BootInformationHeader).unwrap() };
/// let boot_info = unsafe { BootInformation::load(mbi_ptr as *mut BootInformationHeader).unwrap() };
/// let _cmd = boot_info.command_line_tag();
/// } else { /* Panic or use multiboot1 flow. */ }
/// }
Expand All @@ -204,7 +214,7 @@ impl<'a> BootInformation<'a> {
/// boot environments, such as UEFI.
/// * The memory at `ptr` must not be modified after calling `load` or the
/// program may observe unsynchronized mutation.
pub unsafe fn load(ptr: *const BootInformationHeader) -> Result<Self, MbiLoadError> {
pub unsafe fn load(ptr: *mut BootInformationHeader) -> Result<Self, MbiLoadError> {
// null or not aligned
if ptr.is_null() || ptr.align_offset(8) != 0 {
return Err(MbiLoadError::IllegalAddress);
Expand All @@ -220,24 +230,36 @@ impl<'a> BootInformation<'a> {

let slice_size = mbi.total_size as usize - size_of::<BootInformationHeader>();
// mbi: reference to full mbi
let mbi = ptr_meta::from_raw_parts::<BootInformationInner>(ptr.cast(), slice_size);
let mbi = &*mbi;
let mbi_ptr = ptr_meta::from_raw_parts_mut::<BootInformationInner>(ptr.cast(), slice_size);
let mbi_ref = &*mbi_ptr;

if !mbi.has_valid_end_tag() {
if !mbi_ref.has_valid_end_tag() {
return Err(MbiLoadError::NoEndTag);
}

Ok(Self(mbi))
Ok(Self {
// Safety: checked earlier that this is not null
ptr: NonNull::new_unchecked(mbi_ptr),
_phantom: PhantomData,
})
}

/// Get the start address of the boot info.
pub fn start_address(&self) -> usize {
self.as_ptr() as usize
fn inner(&self) -> &BootInformationInner {
unsafe { self.ptr.as_ref() }
}

fn inner_mut(&mut self) -> &mut BootInformationInner {
unsafe { self.ptr.as_mut() }
}

/// Get the start address of the boot info as pointer.
pub fn as_ptr(&self) -> *const () {
core::ptr::addr_of!(*self.0).cast()
pub fn as_ptr(&self) -> *const BootInformationHeader {
self.ptr.as_ptr().cast()
}

/// Get the start address of the boot info.
pub fn start_address(&self) -> usize {
self.as_ptr() as usize
}

/// Get the end address of the boot info.
Expand All @@ -246,7 +268,7 @@ impl<'a> BootInformation<'a> {
///
/// ```rust,no_run
/// # use multiboot2::{BootInformation, BootInformationHeader};
/// # let ptr = 0xdeadbeef as *const BootInformationHeader;
/// # let ptr = 0xdeadbeef as *mut BootInformationHeader;
/// # let boot_info = unsafe { BootInformation::load(ptr).unwrap() };
/// let end_addr = boot_info.start_address() + boot_info.total_size();
/// ```
Expand All @@ -256,7 +278,7 @@ impl<'a> BootInformation<'a> {

/// Get the total size of the boot info struct.
pub fn total_size(&self) -> usize {
self.0.header.total_size as usize
self.inner().header.total_size as usize
}

// ######################################################
Expand Down Expand Up @@ -332,7 +354,7 @@ impl<'a> BootInformation<'a> {
///
/// ```rust,no_run
/// # use multiboot2::{BootInformation, BootInformationHeader};
/// # let ptr = 0xdeadbeef as *const BootInformationHeader;
/// # let ptr = 0xdeadbeef as *mut BootInformationHeader;
/// # let boot_info = unsafe { BootInformation::load(ptr).unwrap() };
/// if let Some(sections) = boot_info.elf_sections() {
/// let mut total = 0;
Expand Down Expand Up @@ -448,7 +470,7 @@ impl<'a> BootInformation<'a> {
/// Tag::get_dst_str_slice(&self.name)
/// }
/// }
/// let mbi_ptr = 0xdeadbeef as *const BootInformationHeader;
/// let mbi_ptr = 0xdeadbeef as *mut BootInformationHeader;
/// let mbi = unsafe { BootInformation::load(mbi_ptr).unwrap() };
///
/// let tag = mbi
Expand All @@ -464,7 +486,7 @@ impl<'a> BootInformation<'a> {

/// Returns an iterator over all tags.
fn tags(&self) -> TagIter {
TagIter::new(&self.0.tags)
TagIter::new(&self.inner().tags)
}
}

Expand All @@ -481,8 +503,10 @@ impl fmt::Debug for BootInformation<'_> {

let mut debug = f.debug_struct("Multiboot2BootInformation");
debug
.field("start_address", &self.start_address())
.field("end_address", &self.end_address())
.field("start_address", &self.as_ptr())
.field("end_address", unsafe {
&self.as_ptr().cast::<u8>().add(self.total_size())
})
.field("total_size", &self.total_size())
// now tags in alphabetical order
.field("basic_memory_info", &(self.basic_memory_info_tag()))
Expand Down Expand Up @@ -540,7 +564,7 @@ mod tests {
]);
let ptr = bytes.0.as_ptr();
let addr = ptr as usize;
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();
assert_eq!(addr, bi.start_address());
assert_eq!(addr + bytes.0.len(), bi.end_address());
Expand All @@ -565,7 +589,7 @@ mod tests {
]);
let ptr = bytes.0.as_ptr();
let addr = ptr as usize;
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();
assert_eq!(addr, bi.start_address());
assert_eq!(addr + bytes.0.len(), bi.end_address());
Expand All @@ -590,7 +614,7 @@ mod tests {
]);
let ptr = bytes.0.as_ptr();
let addr = ptr as usize;
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();
assert_eq!(addr, bi.start_address());
assert_eq!(addr + bytes.0.len(), bi.end_address());
Expand Down Expand Up @@ -619,7 +643,7 @@ mod tests {
]);
let ptr = bytes.0.as_ptr();
let addr = ptr as usize;
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();
assert_eq!(addr, bi.start_address());
assert_eq!(addr + bytes.0.len(), bi.end_address());
Expand Down Expand Up @@ -663,7 +687,7 @@ mod tests {
]);
let ptr = bytes.0.as_ptr();
let addr = ptr as usize;
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();
assert_eq!(addr, bi.start_address());
assert_eq!(addr + bytes.0.len(), bi.end_address());
Expand Down Expand Up @@ -724,7 +748,7 @@ mod tests {
]);
let ptr = bytes.0.as_ptr();
let addr = ptr as usize;
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();
assert_eq!(addr, bi.start_address());
assert_eq!(addr + bytes.0.len(), bi.end_address());
Expand Down Expand Up @@ -842,7 +866,7 @@ mod tests {

let ptr = bytes.0.as_ptr();
let addr = ptr as usize;
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();
assert_eq!(addr, bi.start_address());
assert_eq!(addr + bytes.0.len(), bi.end_address());
Expand Down Expand Up @@ -1202,7 +1226,7 @@ mod tests {
}
let ptr = bytes.0.as_ptr();
let addr = ptr as usize;
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();
test_grub2_boot_info(&bi, addr, string_addr, &bytes.0, &string_bytes.0);

Expand Down Expand Up @@ -1409,7 +1433,7 @@ mod tests {
}
let ptr = bytes.0.as_ptr();
let addr = ptr as usize;
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();
assert_eq!(addr, bi.start_address());
assert_eq!(addr + bytes.0.len(), bi.end_address());
Expand Down Expand Up @@ -1453,7 +1477,7 @@ mod tests {
]);
let ptr = bytes.0.as_ptr();
let addr = ptr as usize;
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();
assert_eq!(addr, bi.start_address());
assert_eq!(addr + bytes.0.len(), bi.end_address());
Expand Down Expand Up @@ -1489,7 +1513,7 @@ mod tests {
0, 0, 0, 0, // end tag type.
8, 0, 0, 0, // end tag size.
]);
let bi = unsafe { BootInformation::load(bytes2.0.as_ptr().cast()) };
let bi = unsafe { BootInformation::load(bytes2.0.as_ptr().cast_mut().cast()) };
let bi = bi.unwrap();
let efi_mmap = bi.efi_memory_map_tag();
assert!(efi_mmap.is_none());
Expand Down Expand Up @@ -1559,7 +1583,7 @@ mod tests {
]);
let ptr = bytes.0.as_ptr();
let addr = ptr as usize;
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();
assert_eq!(addr, bi.start_address());
assert_eq!(addr + bytes.0.len(), bi.end_address());
Expand Down Expand Up @@ -1637,7 +1661,7 @@ mod tests {
]);
let ptr = bytes.0.as_ptr();
let addr = ptr as usize;
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();
assert_eq!(addr, bi.start_address());
assert_eq!(addr + bytes.0.len(), bi.end_address());
Expand Down Expand Up @@ -1689,7 +1713,7 @@ mod tests {
]);

let ptr = bytes.0.as_ptr();
let bi = unsafe { BootInformation::load(ptr.cast()) };
let bi = unsafe { BootInformation::load(ptr.cast_mut().cast()) };
let bi = bi.unwrap();

let _tag = bi.get_tag::<CommandLineTag>().unwrap();
Expand Down