Merge #1191

1191: kernel: make user-kernel boundary in Chip r=alevy a=bradjc



### Pull Request Overview

This pull request adds a new trait type to the `Chip` trait that represents the code that handles switching between kernelspace and userspace. Because this is a hardware feature, it makes sense to include it with the chip so that a user doesn't accidentally choose the wrong arch for a given MCU.

```rust
pub trait Chip {
    type MPU: mpu::MPU;
    type UserspaceKernelBoundary: syscall::UserspaceKernelBoundary;
    type SysTick: systick::SysTick;
    ...
```

This also simplifies main.rs as now setting up processes and the kernel only requires passing in the chip.

### Testing Strategy

This pull request was tested by running a hail kernel.


### TODO or Help Wanted

n/a


### Documentation Updated

- [x] Updated the relevant files in `/docs`, or no updates are required.

### Formatting

- [x] Ran `make formatall`.


Co-authored-by: Brad Campbell <bradjc5@gmail.com>

boards/ek-tm4c1294xl/src/main.rs

@@ -16,7 +16,6 @@ use capsules::virtual_uart::{UartDevice, UartMux};
 use kernel::capabilities;
 use kernel::hil;
 use kernel::hil::Controller;
-use kernel::Chip;
 use kernel::Platform;
 
 #[macro_use]
@@ -255,8 +254,7 @@ pub unsafe fn reset_handler() {
     }
     kernel::procs::load_processes(
         board_kernel,
-        &cortexm4::syscall::SysCall::new(),
-        chip.mpu(),
+        chip,
         &_sapps as *const u8,
         &mut APP_MEMORY,
         &mut PROCESSES,

boards/hail/src/main.rs

@@ -25,7 +25,6 @@ use kernel::hil::entropy::Entropy32;
 use kernel::hil::rng::Rng;
 use kernel::hil::spi::SpiMaster;
 use kernel::hil::Controller;
-use kernel::Chip;
 use kernel::Platform;
 
 /// Support routines for debugging I/O.
@@ -620,8 +619,7 @@ pub unsafe fn reset_handler() {
 
     kernel::procs::load_processes(
         board_kernel,
-        &cortexm4::syscall::SysCall::new(),
-        chip.mpu(),
+        chip,
         &_sapps as *const u8,
         &mut APP_MEMORY,
         &mut PROCESSES,

boards/imix/src/main.rs

@@ -33,7 +33,6 @@ use kernel::hil::radio;
 use kernel::hil::radio::{RadioConfig, RadioData};
 use kernel::hil::spi::SpiMaster;
 use kernel::hil::Controller;
-use kernel::Chip;
 
 use components::adc::AdcComponent;
 use components::alarm::AlarmDriverComponent;
@@ -452,8 +451,7 @@ pub unsafe fn reset_handler() {
     }
     kernel::procs::load_processes(
         board_kernel,
-        &cortexm4::syscall::SysCall::new(),
-        chip.mpu(),
+        chip,
         &_sapps as *const u8,
         &mut APP_MEMORY,
         &mut PROCESSES,

boards/launchxl/src/main.rs

@@ -20,7 +20,6 @@ use kernel::hil;
 use kernel::hil::entropy::Entropy32;
 use kernel::hil::i2c::I2CMaster;
 use kernel::hil::rng::Rng;
-use kernel::Chip;
 
 #[macro_use]
 pub mod io;
@@ -312,8 +311,7 @@ pub unsafe fn reset_handler() {
 
     kernel::procs::load_processes(
         board_kernel,
-        &cortexm4::syscall::SysCall::new(),
-        chip.mpu(),
+        chip,
         &_sapps as *const u8,
         &mut APP_MEMORY,
         &mut PROCESSES,

boards/nordic/nrf51dk/src/main.rs

@@ -412,8 +412,7 @@ pub unsafe fn reset_handler() {
     }
     kernel::procs::load_processes(
         board_kernel,
-        &cortexm0::syscall::SysCall::new(),
-        chip.mpu(),
+        chip,
         &_sapps as *const u8,
         &mut APP_MEMORY,
         &mut PROCESSES,

boards/nordic/nrf52dk_base/src/lib.rs

@@ -23,7 +23,6 @@ use kernel::capabilities;
 use kernel::hil;
 use kernel::hil::entropy::Entropy32;
 use kernel::hil::rng::Rng;
-use kernel::Chip;
 use nrf5x::rtc::Rtc;
 
 /// Pins for SPI for the flash chip MX25R6435F
@@ -438,8 +437,7 @@ pub unsafe fn setup_board(
     }
     kernel::procs::load_processes(
         board_kernel,
-        &cortexm4::syscall::SysCall::new(),
-        chip.mpu(),
+        chip,
         &_sapps as *const u8,
         app_memory,
         process_pointers,

chips/cc26x2/src/chip.rs

@@ -9,13 +9,15 @@ use uart;
 
 pub struct Cc26X2 {
     mpu: cortexm4::mpu::MPU,
+    userspace_kernel_boundary: cortexm4::syscall::SysCall,
     systick: cortexm4::systick::SysTick,
 }
 
 impl Cc26X2 {
     pub unsafe fn new() -> Cc26X2 {
         Cc26X2 {
             mpu: cortexm4::mpu::MPU::new(),
+            userspace_kernel_boundary: cortexm4::syscall::SysCall::new(),
             // The systick clocks with 48MHz by default
             systick: cortexm4::systick::SysTick::new_with_calibration(48 * 1000000),
         }
@@ -24,6 +26,7 @@ impl Cc26X2 {
 
 impl kernel::Chip for Cc26X2 {
     type MPU = cortexm4::mpu::MPU;
+    type UserspaceKernelBoundary = cortexm4::syscall::SysCall;
     type SysTick = cortexm4::systick::SysTick;
 
     fn mpu(&self) -> &Self::MPU {
@@ -33,6 +36,11 @@ impl kernel::Chip for Cc26X2 {
     fn systick(&self) -> &Self::SysTick {
         &self.systick
     }
+
+    fn userspace_kernel_boundary(&self) -> &Self::UserspaceKernelBoundary {
+        &self.userspace_kernel_boundary
+    }
+
     fn service_pending_interrupts(&self) {
         unsafe {
             while let Some(interrupt) = nvic::next_pending() {

chips/nrf51/src/chip.rs

@@ -7,24 +7,33 @@ use nrf5x::peripheral_interrupts;
 use radio;
 use uart;
 
-pub struct NRF51(());
+pub struct NRF51 {
+    userspace_kernel_boundary: cortexm0::syscall::SysCall,
+}
 
 impl NRF51 {
     pub unsafe fn new() -> NRF51 {
-        NRF51(())
+        NRF51 {
+            userspace_kernel_boundary: cortexm0::syscall::SysCall::new(),
+        }
     }
 }
 
 impl kernel::Chip for NRF51 {
     type MPU = ();
+    type UserspaceKernelBoundary = cortexm0::syscall::SysCall;
     type SysTick = ();
 
     fn mpu(&self) -> &Self::MPU {
-        &self.0
+        &()
     }
 
     fn systick(&self) -> &Self::SysTick {
-        &self.0
+        &()
+    }
+
+    fn userspace_kernel_boundary(&self) -> &cortexm0::syscall::SysCall {
+        &self.userspace_kernel_boundary
     }
 
     fn service_pending_interrupts(&self) {

chips/nrf52/src/chip.rs

@@ -13,13 +13,15 @@ use uart;
 
 pub struct NRF52 {
     mpu: cortexm4::mpu::MPU,
+    userspace_kernel_boundary: cortexm4::syscall::SysCall,
     systick: cortexm4::systick::SysTick,
 }
 
 impl NRF52 {
     pub unsafe fn new() -> NRF52 {
         NRF52 {
             mpu: cortexm4::mpu::MPU::new(),
+            userspace_kernel_boundary: cortexm4::syscall::SysCall::new(),
             // The NRF52's systick is uncalibrated, but is clocked from the
             // 64Mhz CPU clock.
             systick: cortexm4::systick::SysTick::new_with_calibration(64000000),
@@ -29,6 +31,7 @@ impl NRF52 {
 
 impl kernel::Chip for NRF52 {
     type MPU = cortexm4::mpu::MPU;
+    type UserspaceKernelBoundary = cortexm4::syscall::SysCall;
     type SysTick = cortexm4::systick::SysTick;
 
     fn mpu(&self) -> &Self::MPU {
@@ -39,6 +42,10 @@ impl kernel::Chip for NRF52 {
         &self.systick
     }
 
+    fn userspace_kernel_boundary(&self) -> &Self::UserspaceKernelBoundary {
+        &self.userspace_kernel_boundary
+    }
+
     fn service_pending_interrupts(&self) {
         unsafe {
             loop {

chips/sam4l/src/chip.rs

@@ -22,8 +22,9 @@ use usart;
 use usbc;
 
 pub struct Sam4l {
-    pub mpu: cortexm4::mpu::MPU,
-    pub systick: cortexm4::systick::SysTick,
+    mpu: cortexm4::mpu::MPU,
+    userspace_kernel_boundary: cortexm4::syscall::SysCall,
+    systick: cortexm4::systick::SysTick,
 }
 
 impl Sam4l {
@@ -62,13 +63,15 @@ impl Sam4l {
 
         Sam4l {
             mpu: cortexm4::mpu::MPU::new(),
+            userspace_kernel_boundary: cortexm4::syscall::SysCall::new(),
             systick: cortexm4::systick::SysTick::new(),
         }
     }
 }
 
 impl Chip for Sam4l {
     type MPU = cortexm4::mpu::MPU;
+    type UserspaceKernelBoundary = cortexm4::syscall::SysCall;
     type SysTick = cortexm4::systick::SysTick;
 
     fn service_pending_interrupts(&self) {
@@ -163,6 +166,10 @@ impl Chip for Sam4l {
         &self.systick
     }
 
+    fn userspace_kernel_boundary(&self) -> &cortexm4::syscall::SysCall {
+        &self.userspace_kernel_boundary
+    }
+
     fn sleep(&self) {
         if pm::deep_sleep_ready() {
             unsafe {

chips/tm4c129x/src/chip.rs

@@ -6,21 +6,24 @@ use kernel::Chip;
 use uart;
 
 pub struct Tm4c129x {
-    pub mpu: cortexm4::mpu::MPU,
-    pub systick: cortexm4::systick::SysTick,
+    mpu: cortexm4::mpu::MPU,
+    userspace_kernel_boundary: cortexm4::syscall::SysCall,
+    systick: cortexm4::systick::SysTick,
 }
 
 impl Tm4c129x {
     pub unsafe fn new() -> Tm4c129x {
         Tm4c129x {
             mpu: cortexm4::mpu::MPU::new(),
+            userspace_kernel_boundary: cortexm4::syscall::SysCall::new(),
             systick: cortexm4::systick::SysTick::new(),
         }
     }
 }
 
 impl Chip for Tm4c129x {
     type MPU = cortexm4::mpu::MPU;
+    type UserspaceKernelBoundary = cortexm4::syscall::SysCall;
     type SysTick = cortexm4::systick::SysTick;
 
     fn service_pending_interrupts(&self) {
@@ -58,6 +61,10 @@ impl Chip for Tm4c129x {
         &self.systick
     }
 
+    fn userspace_kernel_boundary(&self) -> &cortexm4::syscall::SysCall {
+        &self.userspace_kernel_boundary
+    }
+
     fn sleep(&self) {
         /*if pm::deep_sleep_ready() {
             unsafe {

kernel/src/platform/mod.rs

@@ -1,6 +1,7 @@
 //! Interface for chips and boards.
 
 use driver::Driver;
+use syscall;
 
 pub mod mpu;
 crate mod systick;
@@ -17,12 +18,14 @@ pub trait Platform {
 /// Interface for individual MCUs.
 pub trait Chip {
     type MPU: mpu::MPU;
+    type UserspaceKernelBoundary: syscall::UserspaceKernelBoundary;
     type SysTick: systick::SysTick;
 
     fn service_pending_interrupts(&self);
     fn has_pending_interrupts(&self) -> bool;
     fn mpu(&self) -> &Self::MPU;
     fn systick(&self) -> &Self::SysTick;
+    fn userspace_kernel_boundary(&self) -> &Self::UserspaceKernelBoundary;
     fn sleep(&self);
     unsafe fn atomic<F, R>(&self, f: F) -> R
     where