1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186

//! The Supervisor module.
//!
//! Supervisor is an abstraction for the `SVC` assembly instruction, which means
//! **S**uper**V**isor **C**all, and the `SV_CALL` exception.
//!
//! # Usage
//!
//! ```
//! # #![feature(const_fn_fn_ptr_basics)]
//! # #![feature(naked_functions)]
//! # fn main() {}
//! use drone_cortexm::{sv, sv::Supervisor, thr};
//!
//! sv::pool! {
//!     /// Pool of services.
//!     pool => SERVICES;
//!
//!     /// Supervisor type.
//!     supervisor => pub Sv;
//!
//!     // Attached services.
//!     services => {
//!         // SwitchContextService;
//!         // SwitchBackService;
//!     }
//! }
//!
//! thr::nvic! {
//!     thread => pub Thr {};
//!     local => pub ThrLocal {};
//!     index => pub Thrs;
//!     vtable => pub Vtable;
//!     init => pub ThrsInit;
//!     supervisor => Sv;
//!     threads => {
//!         exceptions => {
//!             // Define an external function handler for the SV_CALL exception.
//!             naked(Sv::handler) sv_call;
//!         };
//!     };
//! }
//!
//! #[no_mangle]
//! pub static VTABLE: Vtable = Vtable::new(reset);
//!
//! unsafe extern "C" fn reset() -> ! {
//!     loop {}
//! }
//! ```
//!
//! # Predefined Services
//!
//! If [`SwitchContextService`] and [`SwitchBackService`] are defined for the
//! supervisor, [`Switch::switch_context`] and [`Switch::switch_back`] functions
//! become available to switch the program stack.
//!
//! ```no_run
//! # #![feature(const_fn_fn_ptr_basics)]
//! # #![feature(naked_functions)]
//! # #![feature(new_uninit)]
//! use drone_cortexm::sv::{Switch, SwitchBackService, SwitchContextService};
//!
//! use drone_cortexm::sv;
//!
//! sv::pool! {
//!     /// Pool of services.
//!     pool => SERVICES;
//!
//!     /// The supervisor type.
//!     supervisor => pub Sv;
//!
//!     // Attached services.
//!     services => {
//!         SwitchContextService;
//!         SwitchBackService;
//!     }
//! }
//!
//! # fn main() {
//! unsafe {
//!     // Allocate the stack.
//!     let stack = Box::<[u8]>::new_uninit_slice(0x800).assume_init();
//!     // `stack_ptr` will store the current stack pointer.
//!     let mut stack_ptr = stack.as_ptr();
//!     let mut data = Box::<u32>::new(0);
//!     let mut data_ptr = &mut *data as *mut u32;
//!     Sv::switch_context(data_ptr, &mut stack_ptr);
//!     // -------------------
//!     // Using the new stack.
//!     // -------------------
//!     Sv::switch_back(&mut data_ptr);
//! }
//! # }
//! ```

#![cfg_attr(feature = "std", allow(unreachable_code, unused_variables))]

mod switch;

pub use self::switch::{Switch, SwitchBackService, SwitchContextService};

/// Defines the supervisor type.
///
/// See [the module level documentation](self) for details.
#[doc(inline)]
pub use drone_cortexm_macros::sv_pool as pool;

use core::mem::size_of;

/// Generic supervisor.
pub trait Supervisor: Sized + 'static {
    /// `SV_CALL` exception handler for the supervisor.
    ///
    /// # Safety
    ///
    /// This function should be called only by NVIC as part of the vector table.
    unsafe extern "C" fn handler();
}

/// A supervisor call.
pub trait SvCall<T: SvService>: Supervisor {
    /// Calls the supervisor service `service`. Translates to `SVC num`
    /// instruction, where `num` corresponds to the service `T`.
    ///
    /// # Safety
    ///
    /// Safety is implementation defined.
    unsafe fn call(service: &mut T);
}

/// Generic supervisor service.
pub trait SvService: Sized + Send + 'static {
    /// Called when `SVC num` instruction was invoked and `num` corresponds to
    /// the service.
    ///
    /// # Safety
    ///
    /// This function should not be called directly.
    unsafe extern "C" fn handler(&mut self);
}

/// Calls `SVC num` instruction.
///
/// # Safety
///
/// This function should not be called directly.
#[inline(always)]
pub unsafe fn sv_call<T: SvService, const NUM: u8>(service: &mut T) {
    #[cfg(feature = "std")]
    return unimplemented!();
    #[cfg(not(feature = "std"))]
    unsafe {
        if size_of::<T>() == 0 {
            asm!(
                "svc {}",
                const NUM,
                options(nomem, preserves_flags),
            );
        } else {
            asm!(
                "svc {}",
                const NUM,
                in("r12") service,
                options(nomem, preserves_flags),
            );
        }
    }
}

/// This function is called by [`Sv::handler`] for the supervisor service
/// `T`. Parameter `T` is based on the number `num` in the `SVC num`
/// instruction.
///
/// # Safety
///
/// This function should not be called directly.
pub unsafe extern "C" fn service_handler<T: SvService>(mut frame: *mut *mut u8) {
    if size_of::<T>() == 0 {
        unsafe { T::handler(&mut *frame.cast::<T>()) };
    } else {
        unsafe {
            frame = frame.add(4); // Stacked R12
            T::handler(&mut *(*frame).cast::<T>());
        }
    }
}