Interface for memory-like address space accessible via IPC. More...

#include <mmio_space>

Inheritance diagram for L4Re::Mmio_space:

Collaboration diagram for L4Re::Mmio_space:

Public Types
enum	Access_width { Wd_8bit = 0 , Wd_16bit = 1 , Wd_32bit = 2 , Wd_64bit = 3 }
	Actual size of the value to read or write. More...

typedef l4_uint64_t	Addr
	Device address.

Public Member Functions
long	mmio_read (Addr addr, char width, l4_uint64_t *value)
	Read a value from the given address.

long	mmio_write (Addr addr, char width, l4_uint64_t value)
	Write a value to the given address.

Public Member Functions inherited from L4::Kobject
l4_msgtag_t	dec_refcnt (l4_mword_t diff, l4_utcb_t *utcb=l4_utcb())
	Decrement the in kernel reference counter for the object.

Additional Inherited Members
Protected Types inherited from L4::Kobject_t< Mmio_space, L4::Kobject, L4RE_PROTO_MMIO_SPACE >
typedef Mmio_space	Class
	The target interface type (inheriting from Kobject_t)

typedef Typeid::Iface< PROTO, Mmio_space >	__Iface
	The interface description for the derived class.

typedef Typeid::Merge_list< Typeid::Iface_list< __Iface >, typename Base::__Iface_list >	__Iface_list
	The list of all RPC interfaces provided directly or through inheritance.

Protected Member Functions inherited from L4::Kobject_t< Mmio_space, L4::Kobject, L4RE_PROTO_MMIO_SPACE >
L4::Cap< Class >	c () const noexcept
	Get the capability to ourselves.

Protected Member Functions inherited from L4::Kobject
l4_cap_idx_t	cap () const noexcept
	Return capability selector.

Static Protected Member Functions inherited from L4::Kobject_t< Mmio_space, L4::Kobject, L4RE_PROTO_MMIO_SPACE >
static void	__check_protocols__ () noexcept
	Helper to check for protocol conflicts.

Detailed Description

Interface for memory-like address space accessible via IPC.

This interface defines methods for indirect access to MMIO regions.

Memory mapped IO (MMIO) is used by device drivers to control hardware devices. Access to MMIO regions is assigned to user-level device drivers via mappings of memory pages.

However, there are hardware platforms where MMIO regions for different devices share the same memory page. With respect to security and safety, it is often not allowed to map a memory page to multiple device drivers because the driver of one device could then influence operation of another device, which violates security boundaries.

A solution to that problem is to implement a third (trusted) component that gets exclusive access to the shared memory page, and that drivers can access via IPC with the Mmio_space protocol. This proxy-component can then enforce an access policy.

Include File: #include <l4/re/mmio_space>

mmio_space
Interface definition to emit MMIO-like accesses via IPC.

Definition at line 46 of file mmio_space.

Member Enumeration Documentation

◆ Access_width

enum L4Re::Mmio_space::Access_width

Actual size of the value to read or write.

Enumerator
Wd_8bit	Value is a byte.
Wd_16bit	Value is a 2-byte word.
Wd_32bit	Value is a 4-byte word.
Wd_64bit	Value is a 8-byte word.

Definition at line 50 of file mmio_space.

Member Function Documentation

◆ mmio_read()

long L4Re::Mmio_space::mmio_read	(	Addr	addr,
		char	width,
		l4_uint64_t *	value
	)

Read a value from the given address.

Parameters

	addr	Device virtual address to read from. The address must be aligned relative to the access width.
	width	Access width of value to be read, see Access_width.
[out]	value	Return value. If width is smaller than 64 bit,the upper bits are guaranteed to be 0.

Return values

L4_EOK	Success.
-L4_EPERM	Insufficient read rights.
-L4_EINVAL	Address does not exist or cannot be accessed with the given width.

◆ mmio_write()

long L4Re::Mmio_space::mmio_write	(	Addr	addr,
		char	width,
		l4_uint64_t	value
	)

Write a value to the given address.

Parameters

addr	Device virtual address to write to. The address must be aligned relative to the access width.
width	Access width of value to write, see Access_width.
value	Value to write. If width is smaller than 64 bit, the upper bits are ignored.

Return values

L4_EOK	Success.
-L4_EPERM	Insufficient write rights.
-L4_EINVAL	Address does not exist or cannot be accessed with the given width.

The documentation for this struct was generated from the following file:

l4/re/mmio_space

Public Types