kernel/ipc.rs
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// Licensed under the Apache License, Version 2.0 or the MIT License.
// SPDX-License-Identifier: Apache-2.0 OR MIT
// Copyright Tock Contributors 2022.
//! Inter-process communication mechanism for Tock.
//!
//! This is a special syscall driver that allows userspace applications to
//! share memory.
use crate::capabilities::MemoryAllocationCapability;
use crate::grant::{AllowRoCount, AllowRwCount, Grant, UpcallCount};
use crate::kernel::Kernel;
use crate::process;
use crate::process::ProcessId;
use crate::processbuffer::ReadableProcessBuffer;
use crate::syscall_driver::{CommandReturn, SyscallDriver};
use crate::ErrorCode;
/// Syscall number
pub const DRIVER_NUM: usize = 0x10000;
/// Ids for read-only allow buffers
mod ro_allow {
pub(super) const SEARCH: usize = 0;
/// The number of allow buffers the kernel stores for this grant.
pub(super) const COUNT: u8 = 1;
}
/// Enum to mark which type of upcall is scheduled for the IPC mechanism.
#[derive(Copy, Clone, Debug)]
pub enum IPCUpcallType {
/// Indicates that the upcall is for the service upcall handler this
/// process has setup.
Service,
/// Indicates that the upcall is from a different service app and will
/// call one of the client upcalls setup by this process.
Client,
}
/// State that is stored in each process's grant region to support IPC.
#[derive(Default)]
struct IPCData;
/// The IPC mechanism struct.
pub struct IPC<const NUM_PROCS: u8> {
/// The grant regions for each process that holds the per-process IPC data.
data: Grant<
IPCData,
UpcallCount<NUM_PROCS>,
AllowRoCount<{ ro_allow::COUNT }>,
AllowRwCount<NUM_PROCS>,
>,
}
impl<const NUM_PROCS: u8> IPC<NUM_PROCS> {
pub fn new(
kernel: &'static Kernel,
driver_num: usize,
capability: &dyn MemoryAllocationCapability,
) -> Self {
Self {
data: kernel.create_grant(driver_num, capability),
}
}
/// Schedule an IPC upcall for a process. This is called by the main
/// scheduler loop if an IPC task was queued for the process.
pub(crate) unsafe fn schedule_upcall(
&self,
schedule_on: ProcessId,
called_from: ProcessId,
cb_type: IPCUpcallType,
) -> Result<(), process::Error> {
let schedule_on_id = schedule_on.index().ok_or(process::Error::NoSuchApp)?;
let called_from_id = called_from.index().ok_or(process::Error::NoSuchApp)?;
// Verify that IPC is not trying to share with the same app. If so, this
// will cause a double grant enter if we don't return now.
if schedule_on_id == called_from_id {
return Err(process::Error::AlreadyInUse);
}
self.data.enter(schedule_on, |_, schedule_on_data| {
self.data.enter(called_from, |_, called_from_data| {
// If the other app shared a buffer with us, make
// sure we have access to that slice and then call
// the upcall. If no slice was shared then just
// call the upcall.
let (len, ptr) = match called_from_data.get_readwrite_processbuffer(schedule_on_id)
{
Ok(slice) => {
// Ensure receiving app has MPU access to sending app's buffer
self.data
.kernel
.process_map_or(None, schedule_on, |process| {
process.add_mpu_region(slice.ptr(), slice.len(), slice.len())
});
(slice.len(), slice.ptr() as usize)
}
Err(_) => (0, 0),
};
let to_schedule: usize = match cb_type {
IPCUpcallType::Service => schedule_on_id,
IPCUpcallType::Client => called_from_id,
};
let _ = schedule_on_data.schedule_upcall(to_schedule, (called_from_id, len, ptr));
})
})?
}
}
impl<const NUM_PROCS: u8> SyscallDriver for IPC<NUM_PROCS> {
/// command is how notify() is implemented.
/// Notifying an IPC service is done by setting client_or_svc to 0,
/// and notifying an IPC client is done by setting client_or_svc to 1.
/// In either case, the target_id is the same number as provided in a notify
/// upcall or as returned by allow.
///
/// Returns INVAL if the other process doesn't exist.
/// Initiates a service discovery or notifies a client or service.
///
/// ### `command_num`
///
/// - `0`: Driver existence check, always returns Ok(())
/// - `1`: Perform discovery on the package name passed to `allow_readonly`. Returns the
/// service descriptor if the service is found, otherwise returns an error.
/// - `2`: Notify a service previously discovered to have the service descriptor in
/// `target_id`. Returns an error if `target_id` refers to an invalid service or the
/// notify fails to enqueue.
/// - `3`: Notify a client with descriptor `target_id`, typically in response to a previous
/// notify from the client. Returns an error if `target_id` refers to an invalid client
/// or the notify fails to enqueue.
fn command(
&self,
command_number: usize,
target_id: usize,
_: usize,
processid: ProcessId,
) -> CommandReturn {
match command_number {
0 => CommandReturn::success(),
1 =>
/* Discover */
{
self.data
.enter(processid, |_, kernel_data| {
kernel_data
.get_readonly_processbuffer(ro_allow::SEARCH)
.and_then(|search| {
search.enter(|slice| {
self.data
.kernel
.process_until(|p| {
let s = p.get_process_name().as_bytes();
// are slices equal?
if s.len() == slice.len()
&& s.iter()
.zip(slice.iter())
.all(|(c1, c2)| *c1 == c2.get())
{
// Return the index of the process which is used for
// subscribe number
p.processid()
.index()
.map(|i| CommandReturn::success_u32(i as u32))
} else {
None
}
})
.unwrap_or(CommandReturn::failure(ErrorCode::NODEVICE))
})
})
.unwrap_or(CommandReturn::failure(ErrorCode::INVAL))
})
.unwrap_or(CommandReturn::failure(ErrorCode::NOMEM))
}
2 =>
/* Service notify */
{
let cb_type = IPCUpcallType::Service;
let other_process =
self.data
.kernel
.process_until(|p| match p.processid().index() {
Some(i) if i == target_id => Some(p.processid()),
_ => None,
});
other_process.map_or(CommandReturn::failure(ErrorCode::INVAL), |otherapp| {
self.data.kernel.process_map_or(
CommandReturn::failure(ErrorCode::INVAL),
otherapp,
|target| {
let ret = target.enqueue_task(process::Task::IPC((processid, cb_type)));
match ret {
Ok(()) => CommandReturn::success(),
Err(e) => {
// `enqueue_task` does not provide information on whether the
// recipient has set a non-null callback. It only reports
// general failures, such as insufficient memory in the pending
// tasks queue
CommandReturn::failure(e)
}
}
},
)
})
}
3 =>
/* Client notify */
{
let cb_type = IPCUpcallType::Client;
let other_process =
self.data
.kernel
.process_until(|p| match p.processid().index() {
Some(i) if i == target_id => Some(p.processid()),
_ => None,
});
other_process.map_or(CommandReturn::failure(ErrorCode::INVAL), |otherapp| {
self.data.kernel.process_map_or(
CommandReturn::failure(ErrorCode::INVAL),
otherapp,
|target| {
let ret = target.enqueue_task(process::Task::IPC((processid, cb_type)));
match ret {
Ok(()) => CommandReturn::success(),
Err(e) => {
// `enqueue_task` does not provide information on whether the
// recipient has set a non-null callback. It only reports
// general failures, such as insufficient memory in the pending
// tasks queue
CommandReturn::failure(e)
}
}
},
)
})
}
_ => CommandReturn::failure(ErrorCode::NOSUPPORT),
}
}
fn allocate_grant(&self, processid: ProcessId) -> Result<(), crate::process::Error> {
self.data.enter(processid, |_, _| {})
}
}