zircon/vdso/task.fidl

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
library zx;

@transport("Syscall")
protocol Task {
    // TODO(scottmg): Need something like handle:TASK in this file to mean {job, process, thread}.
    // Or otherwise some way to express multiple options for constraints on inputs in this protocol.

    /// ## Summary
    ///
    /// Suspend the given task. Currently only thread or process handles may be suspended.
    ///
    /// ## Declaration
    ///
    /// ```c
    /// #include <zircon/syscalls.h>
    ///
    /// zx_status_t zx_task_suspend(zx_handle_t handle, zx_handle_t* token);
    /// ```
    ///
    /// ## Description
    ///
    /// `zx_task_suspend()` causes the requested task to suspend
    /// execution. Task suspension is not synchronous and the task might not
    /// be suspended before the call returns. The task will be suspended soon
    /// after `zx_task_suspend()` is invoked, unless it is currently blocked in
    /// the kernel, in which case it will suspend after being unblocked.
    ///
    /// Tasks can be suspended and/or resumed before they are started. If a task is
    /// started while suspended, it will enter suspension before executing any code.
    /// Similarly, starting a new thread on a suspended process will suspend the thread
    /// before it executes any code.
    ///
    /// Invoking [`zx_task_kill()`] on a task that is suspended will successfully kill
    /// the task.
    ///
    /// A task cannot suspend itself or any of its parent tasks because it would never
    /// receive the suspend token and would be unable to resume execution.
    ///
    /// ## RESUMING
    ///
    /// To allow the task to resume, close the suspend token handle. The task will
    /// remain suspended as long as there are any open suspend tokens. Like suspending,
    /// resuming is asynchronous so the thread may not be in a running state when the
    /// [`zx_handle_close()`] call returns, even if no other suspend tokens
    /// are open.
    ///
    /// ## SIGNALS AND EXCEPTIONS
    ///
    /// There are two relevant signals that a thread can assert:
    ///
    /// - **ZX_THREAD_RUNNING**
    /// - **ZX_THREAD_SUSPENDED**
    ///
    /// Neither of these will be asserted until the thread is started via
    /// [`zx_process_start()`] or [`zx_thread_start()`]. When
    /// a thread starts, it will assert **ZX_THREAD_RUNNING** whether it is suspended
    /// or not, but if it is suspended will then switch to **ZX_THREAD_SUSPENDED**
    /// before executing any code.
    ///
    /// The **ZX_EXCP_PROCESS_STARTING** and **ZX_EXCP_THREAD_STARTING** debug
    /// exceptions will also be sent on start whether the task is suspended or not.
    ///
    /// ## Rights
    ///
    /// *handle* must be of type **ZX_OBJ_TYPE_THREAD** or **ZX_OBJ_TYPE_PROCESS** and have **ZX_RIGHT_WRITE**.
    ///
    /// ## Return value
    ///
    /// `zx_task_suspend()` returns **ZX_OK** on success.
    /// In the event of failure, a negative error value is returned.
    ///
    /// ## Errors
    ///
    /// **ZX_ERR_BAD_HANDLE** *handle* is not a valid handle.
    ///
    /// **ZX_ERR_WRONG_TYPE** *handle* is not a thread or process handle.
    ///
    /// **ZX_ERR_INVALID_ARGS**  *token*  was an invalid pointer.
    ///
    /// **ZX_ERR_BAD_STATE**  The task is already dying or dead and cannot be suspended.
    ///
    /// **ZX_ERR_NO_MEMORY**  Failed to allocate memory.
    ///
    /// **ZX_ERR_NOT_SUPPORTED**  The calling thread is attempting to suspend itself or
    ///                           one of its parent tasks.
    ///
    /// ## LIMITATIONS
    ///
    /// Currently only thread and process handles are supported.
    ///
    /// [`zx_handle_close()`]: handle_close.md
    /// [`zx_process_start()`]: process_start.md
    /// [`zx_task_kill()`]: task_kill.md
    /// [`zx_thread_start()`]: thread_start.md
    Suspend(resource struct {
        handle Handle;
    }) -> (resource struct {
        token Handle;
    }) error Status;

    /// This function replaces [task_suspend](task_suspend.md). When all callers are
    /// updated, [`zx_task_suspend()`] will be deleted and this function will be renamed
    /// [`zx_task_suspend()`].
    ///
    /// ## Summary
    ///
    /// Suspend the given task. Currently only thread or process handles may be suspended.
    ///
    /// ## Declaration
    ///
    /// ```c
    /// #include <zircon/syscalls.h>
    ///
    /// zx_status_t zx_task_suspend_token(zx_handle_t handle, zx_handle_t* token);
    /// ```
    ///
    /// ## Description
    ///
    /// `zx_task_suspend_token()` causes the requested task to suspend execution. Task
    /// suspension is not synchronous and the task might not be suspended before the
    /// call returns. The task will be suspended soon after `zx_task_suspend_token()` is
    /// invoked, unless it is currently blocked in the kernel, in which case it will
    /// suspend after being unblocked.
    ///
    /// Invoking [`zx_task_kill()`] on a task that is suspended will successfully kill
    /// the task.
    ///
    /// ## RESUMING
    ///
    /// The allow the task to resume, close the suspend token handle. The task will
    /// remain suspended as long as there are any open suspend tokens. Like suspending,
    /// resuming is asynchronous so the thread may not be in a running state when the
    /// [`zx_handle_close()`] call returns, even if no other suspend tokens
    /// are open.
    ///
    /// ## Rights
    ///
    /// *handle* must be of type **ZX_OBJ_TYPE_THREAD** or **ZX_OBJ_TYPE_PROCESS** and have **ZX_RIGHT_WRITE**.
    ///
    /// ## Return value
    ///
    /// [`zx_task_suspend()`] returns **ZX_OK** on success.
    /// In the event of failure, a negative error value is returned.
    ///
    /// ## Errors
    ///
    /// **ZX_ERR_BAD_HANDLE** *handle* is not a valid handle.
    ///
    /// **ZX_ERR_WRONG_TYPE** *handle* is not a thread handle.
    ///
    /// **ZX_ERR_INVALID_ARGS**  *token*  was an invalid pointer.
    ///
    /// **ZX_ERR_BAD_STATE**  The task is not in a state where suspending is possible.
    ///
    /// ## LIMITATIONS
    ///
    /// Currently only thread handles are supported.
    ///
    /// [`zx_handle_close()`]: handle_close.md
    /// [`zx_task_kill()`]: task_kill.md
    /// [`zx_task_suspend()`]: task_suspend.md
    SuspendToken(resource struct {
        handle Handle;
    }) -> (resource struct {
        token Handle;
    }) error Status;

    /// ## Summary
    ///
    /// Create an exception channel for a given job, process, or thread.
    ///
    /// ## Declaration
    ///
    /// ```c
    /// #include <zircon/syscalls.h>
    ///
    /// zx_status_t zx_task_create_exception_channel(zx_handle_t handle,
    ///                                              uint32_t options,
    ///                                              zx_handle_t* out);
    /// ```
    ///
    /// ## Description
    ///
    /// `zx_task_create_exception_channel()` creates a channel that will receive
    /// exceptions from the thread, process, or job.
    ///
    /// *handle* is the thread, process, or job handle to receive exceptions from.
    ///
    /// *options* can be 0 or **ZX_EXCEPTION_CHANNEL_DEBUGGER** to register for debug
    /// exceptions (process or job only).
    ///
    /// *out* will be filled with the newly created channel endpoint on success. This
    /// channel will be read-only with the following rights:
    ///
    /// * **ZX_RIGHT_TRANSFER**
    /// * **ZX_RIGHT_WAIT**
    /// * **ZX_RIGHT_READ**
    ///
    /// ### Number of Exception Channels
    ///
    /// Each task may have at most one regular exception channel and one debugger
    /// exception channel, except for jobs. A single job may have up to
    /// `ZX_EXCEPTION_CHANNEL_JOB_DEBUGGER_MAX_COUNT` debugger exception channels.
    ///
    /// Attempting to create an exception channel on a task that already has the maximum
    /// number of channels for a given type will result in **ZX_ERR_ALREADY_BOUND**.
    ///
    /// ### Exception Messages
    ///
    /// When an exception occurs, the channel will receive a message containing one
    /// exception handle and one `zx_exception_info_t` data.
    ///
    /// The thread will remain blocked in the exception until the received exception
    /// handle is closed, at which point it will either resume or exception processing
    /// will continue according to the chosen behavior (see **ZX_PROP_EXCEPTION_STATE**
    /// in [`zx_object_get_property()`]).
    ///
    /// ### Unbinding
    ///
    /// Closing the created channel handle will unregister the exception handler. If
    /// an exception message is waiting in the channel at the time it's closed, exception
    /// handling will continue on to the next handler in the search order.
    ///
    /// ## Rights
    ///
    /// *handle* must have **ZX_RIGHT_INSPECT** and have **ZX_RIGHT_DUPLICATE** and have **ZX_RIGHT_TRANSFER** and have **ZX_RIGHT_MANAGE_THREAD**.
    ///
    /// If *handle* is of type **ZX_OBJ_TYPE_JOB** or **ZX_OBJ_TYPE_PROCESS**, it must have **ZX_RIGHT_ENUMERATE**.
    ///
    /// ## Return value
    ///
    /// `zx_task_create_exception_channel()` returns **ZX_OK** on success.
    /// In the event of failure, a negative error value is returned.
    ///
    /// ## Errors
    ///
    /// **ZX_ERR_ACCESS_DENIED** The caller has a job policy in place preventing the
    /// creation of new channels.
    ///
    /// **ZX_ERR_ALREADY_BOUND** The maximum number of exception channels of the given
    /// type are already bound to *handle*.
    ///
    /// **ZX_ERR_BAD_HANDLE** *handle* is not a valid handle.
    ///
    /// **ZX_ERR_BAD_STATE** *handle* is dying or dead.
    ///
    /// **ZX_ERR_INVALID_ARGS** A bad value has been passed in *options*.
    ///
    /// **ZX_ERR_NO_MEMORY**  Failure due to lack of memory.
    /// There is no good way for userspace to handle this (unlikely) error.
    /// In a future build this error will no longer occur.
    ///
    /// **ZX_ERR_WRONG_TYPE**  *handle* is not that of a job, process, or thread.
    ///
    /// ## See also
    ///
    ///  - [exceptions]
    ///  - [`zx_channel_read()`]
    ///
    /// [exceptions]: /docs/concepts/kernel/exceptions.md
    /// [`zx_channel_read()`]: channel_read.md
    /// [`zx_object_get_property()`]: object_get_property.md
    CreateExceptionChannel(resource struct {
        handle Handle;
        options uint32;
    }) -> (resource struct {
        out Handle:CHANNEL;
    }) error Status;

    /// ## Summary
    ///
    /// Kill the provided task (job, process, or thread).
    ///
    /// ## Declaration
    ///
    /// ```c
    /// #include <zircon/syscalls.h>
    ///
    /// zx_status_t zx_task_kill(zx_handle_t handle);
    /// ```
    ///
    /// ## Description
    ///
    /// This asynchronously kills the given process or job and its children recursively,
    /// until the entire task tree rooted at *handle* is dead.
    /// Killing a thread is not supported.
    ///
    /// It is possible to wait for the task to be dead via the **ZX_TASK_TERMINATED**
    /// signal. When the procedure completes, as observed by the signal, the task and
    /// all its children are considered to be in the dead state and most operations
    /// will no longer succeed.
    ///
    /// If *handle* is a job and the syscall is successful, the job can no longer be
    /// used to create new processes.
    ///
    /// When a process or job is killed via this syscall, the `return_code` is
    /// **ZX_TASK_RETCODE_SYSCALL_KILL** as reported by [`zx_object_get_info()`] via
    /// the **ZX_INFO_PROCESS** or **ZX_INFO_JOB** topic.
    ///
    /// Processes and Jobs can also be killed by other agents such as the Job policy with
    /// **ZX_POL_ACTION_KILL** or when the system is running low on memory [OOM](/docs/development/kernel/memory/oom.md).
    ///
    /// ## Rights
    ///
    /// *handle* must have **ZX_RIGHT_DESTROY**.
    ///
    /// ## Return value
    ///
    /// On success, `zx_task_kill()` returns **ZX_OK**. If a process uses
    /// this syscall to kill itself, this syscall does not return.
    ///
    /// ## Errors
    ///
    /// **ZX_ERR_BAD_HANDLE**  *handle* is not a valid handle.
    ///
    /// **ZX_ERR_WRONG_TYPE**  *handle* is not a task handle.
    ///
    /// **ZX_ERR_ACCESS_DENIED**  *handle* does not have the **ZX_RIGHT_DESTROY**
    /// right.
    ///
    /// ## See also
    ///
    ///  - [`zx_job_create()`]
    ///  - [`zx_process_create()`]
    ///
    /// [`zx_job_create()`]: job_create.md
    /// [`zx_object_get_info()`]: object_get_info.md
    /// [`zx_process_create()`]: process_create.md
    Kill(resource struct {
        handle Handle;
    }) -> () error Status;
};