Struct memory::MappedPages

source ·
pub struct MappedPages { /* private fields */ }
Expand description

Represents a contiguous range of virtual memory pages that are currently mapped. A MappedPages object can only have a single range of contiguous pages, not multiple disjoint ranges. This does not guarantee that its pages are mapped to frames that are contiguous in physical memory.

This object also represents ownership of those pages; if this object falls out of scope, it will be dropped, and the pages will be unmapped and then also de-allocated. Thus, it ensures memory safety by guaranteeing that this object must be held in order to access data stored in these mapped pages, much like a guard type.

Implementations

Returns an empty MappedPages object that performs no allocation or mapping actions. Can be used as a placeholder, but will not permit any real usage.

Returns the flags that describe this MappedPages page table permissions.

Merges the given MappedPages object mp into this MappedPages object (self).

For example, if you have the following MappedPages objects:

  • this mapping, with a page range including one page at 0x2000
  • mp, with a page range including two pages at 0x3000 and 0x4000 Then this MappedPages object will be updated to cover three pages from [0x2000:0x4000] inclusive.

In addition, the MappedPages objects must have the same flags and page table root frame (i.e., they must have all been mapped using the same set of page tables).

If an error occurs, such as the mappings not being contiguous or having different flags, then a tuple including an error message and the original mp will be returned, which prevents the mp from being dropped.

Note

No remapping actions or page reallocations will occur on either a failure or a success.

Splits this MappedPages into two separate MappedPages objects:

  • [beginning : at_page - 1]
  • [at_page : end]

This function follows the behavior of core::slice::split_at(), thus, either one of the returned MappedPages objects may be empty.

  • If at_page == self.pages.start, the first returned MappedPages object will be empty.
  • If at_page == self.pages.end + 1, the second returned MappedPages object will be empty.

Returns an Err containing this MappedPages (self) if at_page is not within its bounds.

Note

No remapping actions or page reallocations will occur on either a failure or a success.

Creates a deep copy of this MappedPages memory region, by duplicating not only the virtual memory mapping but also the underlying physical memory frames.

The caller can optionally specify new flags for the duplicated mapping, otherwise, the same flags as the existing MappedPages will be used. This is useful for when you want to modify contents in the new pages, since it avoids extra remap() operations.

Returns a new MappedPages object with the same in-memory contents as this object, but at a completely new memory region.

Change the permissions (new_flags) of this MappedPages’s page table entries.

Note that attempting to change certain “reserved” flags will have no effect. For example, arbitrarily setting the EXCLUSIVE bit would cause unsafety, so it cannot be changed.

Consumes and unmaps this MappedPages object without auto-deallocating its AllocatedPages and AllocatedFrames, allowing the caller to continue using them directly, e.g., reusing them for a future mapping. This removes the need to attempt to to reallocate those same pages or frames on a separate code path.

Note that only the first contiguous range of AllocatedFrames will be returned, if any were unmapped. All other non-contiguous ranges will be auto-dropped and deallocated. This is due to how frame deallocation works.

Reinterprets this MappedPages’s underlying memory region as a struct of the given type T, i.e., overlays a struct on top of this mapped memory region.

Requirements

The type T must implement the FromBytes trait, which is similar to the requirements of a “plain old data” type, in that it cannot contain Rust references (& or &mut). This makes sense because there is no valid way to reinterpret a region of untyped memory as a Rust reference. In addition, if we did permit that, a Rust reference created from unchecked memory contents could never be valid, safe, or sound, as it could allow random memory access (just like with an arbitrary pointer dereference) that could break isolation.

To satisfy this condition, you can use #[derive(FromBytes)] on your struct type T, which will only compile correctly if the struct can be validly constructed from “untyped” memory, i.e., an array of bytes.

Arguments
  • byte_offset: the offset (in number of bytes) from the beginning of the memory region at which the struct is located (where it should start). This offset must be properly aligned with respect to the alignment requirements of type T, otherwise an error will be returned.

Returns a reference to the new struct (&T) that is formed from the underlying memory region, with a lifetime dependent upon the lifetime of this MappedPages object. This ensures safety by guaranteeing that the returned struct reference cannot be used after this MappedPages object is dropped and unmapped.

Same as MappedPages::as_type(), but returns a mutable reference to the type T.

Thus, it also checks that the underlying mapping is writable.

Reinterprets this MappedPages’s underlying memory region as &[T], a length-element slice of type T.

It has similar requirements and behavior as MappedPages::as_type().

Arguments
  • byte_offset: the offset (in number of bytes) into the memory region at which the slice should start. This offset must be properly aligned with respect to the alignment requirements of type T, otherwise an error will be returned.
  • length: the length of the slice, i.e., the number of elements of type T in the slice. Thus, the slice’s address bounds will span the range from byte_offset (inclusive) to byte_offset + (size_of::<T>() * length) (exclusive).

Returns a reference to the new slice that is formed from the underlying memory region, with a lifetime dependent upon the lifetime of this MappedPages object. This ensures safety by guaranteeing that the returned slice cannot be used after this MappedPages object is dropped and unmapped.

Same as MappedPages::as_slice(), but returns a mutable slice.

Thus, it checks that the underlying mapping is writable.

A convenience function for BorrowedMappedPages::from().

A convenience function for BorrowedMappedPages::from_mut().

A convenience function for BorrowedSliceMappedPages::from().

A convenience function for BorrowedSliceMappedPages::from_mut().

Methods from Deref<Target = PageRange>

Returns the VirtualAddress of the starting Page in this PageRange.

Returns the number of Pages covered by this iterator.

Use this instead of Iterator::count() method. This is instant, because it doesn’t need to iterate over each entry, unlike normal iterators.

Returns the size of this range in number of bytes.

Returns true if this PageRange contains the given VirtualAddress.

Returns the offset of the given VirtualAddress within this PageRange, i.e., addr - self.start_address().

If the given addr is not covered by this range of Pages, this returns None.

Examples

If the range covers addresses 0x2000 to 0x4000, then offset_of_address(0x3500) would return Some(0x1500).

Returns the VirtualAddress at the given offset into this PageRangewithin this PageRange, i.e., addr - self.start_address().

If the given offset is not within this range of Pages, this returns None.

Examples

If the range covers addresses 0x2000 to 0x4000, then address_at_offset(0x1500) would return Some(0x3500).

Returns a new separate PageRange that is extended to include the given Page.

Returns an inclusive PageRange representing the Pages that overlap across this PageRange and the given other PageRange.

If there is no overlap between the two ranges, None is returned.

Methods from Deref<Target = RangeInclusive<Page>>

Returns the lower bound of the range (inclusive).

When using an inclusive range for iteration, the values of start() and end() are unspecified after the iteration ended. To determine whether the inclusive range is empty, use the is_empty() method instead of comparing start() > end().

Note: the value returned by this method is unspecified after the range has been iterated to exhaustion.

Examples
assert_eq!((3..=5).start(), &3);

Returns the upper bound of the range (inclusive).

When using an inclusive range for iteration, the values of start() and end() are unspecified after the iteration ended. To determine whether the inclusive range is empty, use the is_empty() method instead of comparing start() > end().

Note: the value returned by this method is unspecified after the range has been iterated to exhaustion.

Examples
assert_eq!((3..=5).end(), &5);

Returns true if item is contained in the range.

Examples
assert!(!(3..=5).contains(&2));
assert!( (3..=5).contains(&3));
assert!( (3..=5).contains(&4));
assert!( (3..=5).contains(&5));
assert!(!(3..=5).contains(&6));

assert!( (3..=3).contains(&3));
assert!(!(3..=2).contains(&3));

assert!( (0.0..=1.0).contains(&1.0));
assert!(!(0.0..=1.0).contains(&f32::NAN));
assert!(!(0.0..=f32::NAN).contains(&0.0));
assert!(!(f32::NAN..=1.0).contains(&1.0));

This method always returns false after iteration has finished:

let mut r = 3..=5;
assert!(r.contains(&3) && r.contains(&5));
for _ in r.by_ref() {}
// Precise field values are unspecified here
assert!(!r.contains(&3) && !r.contains(&5));

Returns true if the range contains no items.

Examples
assert!(!(3..=5).is_empty());
assert!(!(3..=3).is_empty());
assert!( (3..=2).is_empty());

The range is empty if either side is incomparable:

assert!(!(3.0..=5.0).is_empty());
assert!( (3.0..=f32::NAN).is_empty());
assert!( (f32::NAN..=5.0).is_empty());

This method returns true after iteration has finished:

let mut r = 3..=5;
for _ in r.by_ref() {}
// Precise field values are unspecified here
assert!(r.is_empty());

Trait Implementations

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