C interface of the Task kernel object, see L4::Task for the C++ interface. More...

Collaboration diagram for Task:

Enumerations
enum	l4_unmap_flags_t { L4_FP_ALL_SPACES , L4_FP_DELETE_OBJ , L4_FP_OTHER_SPACES }
	Flags for the unmap operation. More...

Functions
l4_msgtag_t	l4_task_vgicc_map (l4_cap_idx_t task, l4_fpage_t vgicc_fpage) L4_NOTHROW
	Map the GIC virtual CPU interface page to the task in case Fiasco detected a GIC version 2.

l4_msgtag_t	l4_task_map (l4_cap_idx_t dst_task, l4_cap_idx_t src_task, l4_fpage_t snd_fpage, l4_umword_t snd_base) L4_NOTHROW
	Map resources available in the source task to a destination task.

l4_msgtag_t	l4_task_unmap (l4_cap_idx_t task, l4_fpage_t fpage, l4_umword_t map_mask) L4_NOTHROW
	Revoke rights from the task.

l4_msgtag_t	l4_task_unmap_batch (l4_cap_idx_t task, l4_fpage_t const *fpages, unsigned num_fpages, l4_umword_t map_mask) L4_NOTHROW
	Revoke rights from a task.

l4_msgtag_t	l4_task_delete_obj (l4_cap_idx_t task, l4_cap_idx_t obj) L4_NOTHROW
	Release capability and delete object.

l4_msgtag_t	l4_task_release_cap (l4_cap_idx_t task, l4_cap_idx_t cap) L4_NOTHROW
	Release object capability.

l4_msgtag_t	l4_task_cap_valid (l4_cap_idx_t task, l4_cap_idx_t cap) L4_NOTHROW
	Check whether a capability is present (refers to an object).

l4_msgtag_t	l4_task_cap_equal (l4_cap_idx_t task, l4_cap_idx_t cap_a, l4_cap_idx_t cap_b) L4_NOTHROW
	Test whether two capabilities point to the same object with the same rights.

l4_msgtag_t	l4_task_add_ku_mem (l4_cap_idx_t task, l4_fpage_t *ku_mem) L4_NOTHROW
	Add kernel-user memory.

Detailed Description

C interface of the Task kernel object, see L4::Task for the C++ interface.

A task represents a combination of the address spaces provided by the L4Re micro kernel. A task consists of at least a memory address space and an object address space. On IA32 there is also an IO-port address space.

Task objects are created using the Factory interface.

Include File: #include <l4/sys/task.h>

Enumeration Type Documentation

◆ l4_unmap_flags_t

enum l4_unmap_flags_t

Flags for the unmap operation.

See also: L4::Task::unmap() and l4_task_unmap()

Enumerator

L4_FP_ALL_SPACES

Flag to tell the unmap operation to revoke permissions from all child mappings including the mapping in the invoked task.

Note: Object capabilities are not hierarchical – they have no children. The result of the map operation on an object capability is a copy of that capability in the object space of the destination task. An unmap operation on object capabilities is a no-op if this flag is not specified.

See also: L4::Task::unmap() l4_task_unmap()

L4_FP_DELETE_OBJ

Flag that indicates that an unmap operation on object capabilities shall try to delete the corresponding objects immediately.

This flag implies the L4_FP_ALL_SPACES flag. The concept of deletion is only applicable to kernel objects. Therefore, for memory and I/O port capabilities, this flag has the same effect as L4_FP_ALL_SPACES alone.

See also: L4::Task::unmap() l4_task_unmap()

L4_FP_OTHER_SPACES

Counterpart to L4_FP_ALL_SPACES; revoke permissions from child mappings only.

See also: L4::Task::unmap() l4_task_unmap()

Definition at line 184 of file consts.h.

Function Documentation

◆ l4_task_add_ku_mem()

l4_msgtag_t l4_task_add_ku_mem	(	l4_cap_idx_t	task,
		l4_fpage_t *	ku_mem
	)

inline

Add kernel-user memory.

Parameters

	task	Capability selector of the task to add the memory to.
[in,out]	ku_mem	Flexpage describing the virtual area the memory goes to. On systems without MMU, the flexpage is adjusted to reflect the acually allocated physical address.

Returns: Syscall return tag

Kernel-user memory (ku_mem) is memory that is shared between the kernel and user-space. It is needed for the UTCB area of threads (see l4_thread_control_bind()) and for (extended) vCPU state. Note that existing kernel-user memory cannot be unmapped or mapped somewhere else.

Note: The amount of kernel-user memory that can be allocated at once is limited by the used kernel implementation. The minimum allocatable amount is one page (L4_PAGESIZE). A portable implementation should not depend on allocations greater than 16KiB to succeed.; This function is only guaranteed to work on L4::Task objects. It might or might not work on L4::Vm objects or on L4Re::Dma_space objects but there is no practical use for adding kernel-user memory to L4::Vm objects or to L4Re::Dma_space objects.

Definition at line 468 of file task.h.

References l4_utcb().

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◆ l4_task_cap_equal()

l4_msgtag_t l4_task_cap_equal	(	l4_cap_idx_t	task,
		l4_cap_idx_t	cap_a,
		l4_cap_idx_t	cap_b
	)

inline

Test whether two capabilities point to the same object with the same rights.

Parameters

task	Capability selector of the destination task to do the lookup in
cap_a	Capability selector to compare
cap_b	Capability selector to compare

Returns: label contains 1 if equal, 0 if not equal

Definition at line 461 of file task.h.

References l4_utcb().

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◆ l4_task_cap_valid()

l4_msgtag_t l4_task_cap_valid	(	l4_cap_idx_t	task,
		l4_cap_idx_t	cap
	)

inline

Check whether a capability is present (refers to an object).

Parameters

task	Task to check the capability in.
cap	Valid capability to check for presence.

Return values

l4_msgtag_t::label() > 0	Capability is present (refers to an object).
l4_msgtag_t::label() == 0	No capability present (void object).

A capability is considered present when it refers to an existing kernel object.

Precondition: cap must be a valid capability index (i.e. not L4_INVALID_CAP or the like).

Definition at line 455 of file task.h.

References l4_utcb().

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◆ l4_task_delete_obj()

l4_msgtag_t l4_task_delete_obj	(	l4_cap_idx_t	task,
		l4_cap_idx_t	obj
	)

inline

Release capability and delete object.

Parameters

task	Capability selector of destination task.
obj	Capability index of the object to delete.

Returns: Syscall return tag

If obj has the delete permission, initiates the deletion of the object. This implies that all capabilities for that object are gone afterwards. However, kernel-internally, objects are not destroyed until all other kernel objects holding a reference to it drop the reference. Hence, quota used by that object might not be freed immediately.

If obj does not have the delete permission, no error will be reported and only the capability obj is removed. (Note that, depending on the object’s reference counter, this might still imply initiation of deletion.)

This operation is equivalent to l4_task_unmap() with L4_FP_DELETE_OBJ flag.

Definition at line 434 of file task.h.

References l4_utcb().

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◆ l4_task_map()

l4_msgtag_t l4_task_map	(	l4_cap_idx_t	dst_task,
		l4_cap_idx_t	src_task,
		l4_fpage_t	snd_fpage,
		l4_umword_t	snd_base
	)

inline

Map resources available in the source task to a destination task.

Parameters

dst_task	Capability selector of the destination task.
src_task	Capability selector of the source task.
snd_fpage	Send flexpage that describes an area in the address space or object space of the source task.
snd_base	Send base that describes an offset in the receive window of the destination task. The lower bits contain additional map control flags (see l4_fpage_cacheability_opt_t for memory mappings, L4_obj_fpage_ctl for object mappings, and L4_MAP_ITEM_GRANT; also see l4_map_control() and l4_map_obj_control()).

Returns: Syscall return tag. The function l4_error() shall be used to test if the map operation was successful.

Return values

L4_EOK	Operation successful (but see notes below).
-L4_EPERM	No L4_CAP_FPAGE_W right on `dst_task`.
-L4_EINVAL	Invalid source task capability.
-L4_IPC_SEMAPFAILED	The map operation failed due to limited quota.

This method allows for asynchronous transfer of capabilities, memory mappings, and IO-port mappings (on IA32) from one task to another. The receive window is the whole address space of dst_task. By specifying proper rights in snd_fpage and snd_base, it is possible to remove rights during transfer.

Note: If the send flex page is of type L4_FPAGE_OBJ, the L4_CAP_FPAGE_S right is removed from the transferred capability unless both the source and destination task capabilities possess the L4_CAP_FPAGE_S right themselves.; Even with l4_error() returning L4_EOK there might be cases where not all pages of the send flexpage were mapped respectively granted to the destination task, for instance, if the corresponding mapping in the destination task does already exist.

For more information on spaces and mappings, see Spaces and Mappings. The flexpage API is described in more detail at Flex pages.

Note: For peculiarities when using grant, see L4_MAP_ITEM_GRANT.

Definition at line 404 of file task.h.

References l4_utcb().

Referenced by L4::Cap_base::copy(), and L4::Cap_base::move().

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◆ l4_task_release_cap()

l4_msgtag_t l4_task_release_cap	(	l4_cap_idx_t	task,
		l4_cap_idx_t	cap
	)

inline

Release object capability.

Parameters

task	Capability selector of destination task
cap	Capability selector of object to release

Returns: Syscall return tag

This operation unmaps the capability from the specified task.

Note: If the reference counter of the kernel object referenced by cap goes down to zero, deletion of the object is initiated. Objects are not destroyed until all other kernel objects holding a reference to it drop the reference.

Definition at line 449 of file task.h.

References l4_utcb().

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◆ l4_task_unmap()

l4_msgtag_t l4_task_unmap	(	l4_cap_idx_t	task,
		l4_fpage_t	fpage,
		l4_umword_t	map_mask
	)

inline

Revoke rights from the task.

Parameters

task	Capability selector of destination task
fpage	Flexpage that describes an area in one capability space of the destination task
map_mask	Unmap mask, see l4_unmap_flags_t

Returns: Syscall return tag

This method allows to revoke rights from the destination task. For a flex page describing IO ports or memory, it also revokes rights from all the tasks that got the rights delegated from the destination task (i.e., this operation does a recursive rights revocation). If the set of rights is empty after the revocation, the capability is unmapped. It is guaranteed that the rights revocation is completed before this function returns.

Note: If the reference counter of a kernel object referenced in fpage goes down to zero (as a result of deleting capabilities), the deletion of the object is initiated. Objects are not destroyed until all other kernel objects holding a reference to it drop the reference.

Examples: examples/sys/utcb-ipc/main.c.

Definition at line 411 of file task.h.

References l4_utcb().

Referenced by L4Re::Util::Cap_alloc_base::free(), L4Re::Util::Counting_cap_alloc< COUNTERTYPE, Dbg >::free(), and L4Re::Util::Counting_cap_alloc< COUNTERTYPE, Dbg >::release().

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◆ l4_task_unmap_batch()

l4_msgtag_t l4_task_unmap_batch	(	l4_cap_idx_t	task,
		l4_fpage_t const *	fpages,
		unsigned	num_fpages,
		l4_umword_t	map_mask
	)

inline

Revoke rights from a task.

Parameters

task	Capability selector of destination task
fpages	An array of flexpages. Each item describes an area in one capability space of the destination task.
num_fpages	The size of the fpages array in elements (number of fpages sent).
map_mask	Unmap mask, see l4_unmap_flags_t

Returns: Syscall return tag

Revoke rights specified in an array of flexpages, see l4_task_unmap for details.

Precondition: The caller needs to take care that num_fpages is not bigger than L4_UTCB_GENERIC_DATA_SIZE - 2.

Definition at line 418 of file task.h.

References l4_utcb().

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◆ l4_task_vgicc_map()

l4_msgtag_t l4_task_vgicc_map	(	l4_cap_idx_t	task,
		l4_fpage_t	vgicc_fpage
	)

inline

Map the GIC virtual CPU interface page to the task in case Fiasco detected a GIC version 2.

Parameters

task	Capability selector of destination task
vgicc_fpage	Flexpage that describes an area in the address space of the destination task to map the vGICC page to

Returns: Syscall return tag

Definition at line 57 of file __task-arm.h.

References l4_utcb().

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Enumerations

Functions

Detailed Description

Enumeration Type Documentation

◆ l4_unmap_flags_t

Function Documentation

◆ l4_task_add_ku_mem()

◆ l4_task_cap_equal()

◆ l4_task_cap_valid()

◆ l4_task_delete_obj()

◆ l4_task_map()

◆ l4_task_release_cap()

◆ l4_task_unmap()

◆ l4_task_unmap_batch()

◆ l4_task_vgicc_map()