diff options
Diffstat (limited to 'cortex-m-rt/src/lib.rs')
| -rw-r--r-- | cortex-m-rt/src/lib.rs | 92 |
1 files changed, 13 insertions, 79 deletions
diff --git a/cortex-m-rt/src/lib.rs b/cortex-m-rt/src/lib.rs index ab4bc3f..e5e290d 100644 --- a/cortex-m-rt/src/lib.rs +++ b/cortex-m-rt/src/lib.rs @@ -192,11 +192,9 @@ //! //! One will always find the following (unmangled) symbols in `cortex-m-rt` applications: //! -//! - `Reset`. This is the reset handler. The microcontroller will executed this function upon +//! - `Reset`. This is the reset handler. The microcontroller will execute this function upon //! booting. This function will call the user program entry point (cf. [`#[entry]`][attr-entry]) -//! using the `main` symbol so you may also find that symbol in your program; if you do, `main` -//! will contain your application code. Some other times `main` gets inlined into `Reset` so you -//! won't find it. +//! using the `main` symbol so you will also find that symbol in your program. //! //! - `DefaultHandler`. This is the default handler. If not overridden using `#[exception] fn //! DefaultHandler(..` this will be an infinite loop. @@ -212,8 +210,8 @@ //! the initial value of the stack pointer; this is where the stack will be located -- the stack //! grows downwards towards smaller addresses. //! -//! - `__RESET_VECTOR`. This is the reset vector, a pointer into the `Reset` handler. This vector is -//! located in the `.vector_table` section after `__STACK_START`. +//! - `__RESET_VECTOR`. This is the reset vector, a pointer to the `Reset` function. This vector +//! is located in the `.vector_table` section after `__STACK_START`. //! //! - `__EXCEPTIONS`. This is the core exceptions portion of the vector table; it's an array of 14 //! exception vectors, which includes exceptions like `HardFault` and `SysTick`. This array is @@ -226,19 +224,11 @@ //! //! - `__pre_init`. This is a function to be run before RAM is initialized. It defaults to an empty //! function. The function called can be changed by applying the [`#[pre_init]`][attr-pre_init] -//! attribute to a function. The empty function is not optimized out by default, but if an empty -//! function is passed to [`#[pre_init]`][attr-pre_init] the function call will be optimized out. +//! attribute to a function. //! //! If you override any exception handler you'll find it as an unmangled symbol, e.g. `SysTick` or //! `SVCall`, in the output of `objdump`, //! -//! If you are targeting the `thumbv7em-none-eabihf` target you'll also see a `ResetTrampoline` -//! symbol in the output. To avoid the compiler placing FPU instructions before the FPU has been -//! enabled (cf. `vpush`) `Reset` calls the function `ResetTrampoline` which is marked as -//! `#[inline(never)]` and `ResetTrampoline` calls `main`. The compiler is free to inline `main` -//! into `ResetTrampoline` but it can't inline `ResetTrampoline` into `Reset` -- the FPU is enabled -//! in `Reset`. -//! //! # Advanced usage //! //! ## Setting the program entry point @@ -248,9 +238,9 @@ //! guarantees. //! //! The `Reset` handler will call a symbol named `main` (unmangled) *after* initializing `.bss` and -//! `.data`, and enabling the FPU (if the target is `thumbv7em-none-eabihf`). A function with the -//! `entry` attribute will be set to have the export name "`main`"; in addition, its mutable -//! statics are turned into safe mutable references (see [`#[entry]`][attr-entry] for details). +//! `.data`, and enabling the FPU (if the target has an FPU). A function with the `entry` attribute +//! will be set to have the export name "`main`"; in addition, its mutable statics are turned into +//! safe mutable references (see [`#[entry]`][attr-entry] for details). //! //! The unmangled `main` symbol must have signature `extern "C" fn() -> !` or its invocation from //! `Reset` will result in undefined behavior. @@ -411,7 +401,7 @@ //! *(.ccmram .ccmram.*); //! . = ALIGN(4); //! } > CCMRAM -//! } INSERT AFTER .bss; +//! } //! ``` //! //! You can then use something like this to place a variable into this specific section of memory: @@ -438,7 +428,6 @@ #![no_std] extern crate cortex_m_rt_macros as macros; -extern crate r0; use core::fmt; use core::sync::atomic::{self, Ordering}; @@ -701,8 +690,8 @@ pub use macros::exception; /// /// # Safety /// -/// The function will be called before static variables are initialized. Any access of static -/// variables will result in undefined behavior. +/// The function will be called before memory is initialized, as soon as possible after reset. Any +/// access of memory, including any static variables, will result in undefined behavior. /// /// **Warning**: Due to [rvalue static promotion][rfc1414] static variables may be accessed whenever /// taking a reference to a constant. This means that even trivial expressions such as `&1` in the @@ -919,66 +908,12 @@ pub fn heap_start() -> *mut u32 { unsafe { &mut __sheap } } -/* Entry point */ +// Entry point is Reset. #[doc(hidden)] #[link_section = ".vector_table.reset_vector"] #[no_mangle] -#[cfg(not(armv6m))] pub static __RESET_VECTOR: unsafe extern "C" fn() -> ! = Reset; -#[doc(hidden)] -#[link_section = ".vector_table.reset_vector"] -#[no_mangle] -#[cfg(armv6m)] -pub static __RESET_VECTOR: unsafe extern "C" fn() -> ! = PreResetTrampoline; - -#[doc(hidden)] -#[link_section = ".Reset"] -#[no_mangle] -pub unsafe extern "C" fn Reset() -> ! { - extern "C" { - - // These symbols come from `link.x` - static mut __sbss: u32; - static mut __ebss: u32; - - static mut __sdata: u32; - static mut __edata: u32; - static __sidata: u32; - } - - extern "Rust" { - // This symbol will be provided by the user via `#[pre_init]` - fn __pre_init(); - } - - __pre_init(); - - // Initialize RAM - r0::zero_bss(&mut __sbss, &mut __ebss); - r0::init_data(&mut __sdata, &mut __edata, &__sidata); - - #[allow(clippy::match_single_binding)] - match () { - #[cfg(not(has_fpu))] - () => { - extern "C" { - // This symbol will be provided by the user via `#[entry]` - fn main() -> !; - } - main() - } - #[cfg(has_fpu)] - () => { - extern "C" { - fn FpuTrampoline() -> !; - } - - FpuTrampoline() - } - } -} - #[allow(unused_variables)] #[doc(hidden)] #[link_section = ".HardFault.default"] @@ -1038,8 +973,7 @@ pub enum Exception { pub use self::Exception as exception; extern "C" { - #[cfg(armv6m)] - fn PreResetTrampoline() -> !; + fn Reset() -> !; fn NonMaskableInt(); |