diff options
Diffstat (limited to 'cortex-m-rt/src/lib.rs')
| -rw-r--r-- | cortex-m-rt/src/lib.rs | 123 |
1 files changed, 122 insertions, 1 deletions
diff --git a/cortex-m-rt/src/lib.rs b/cortex-m-rt/src/lib.rs index 752d3d7..0cfed4d 100644 --- a/cortex-m-rt/src/lib.rs +++ b/cortex-m-rt/src/lib.rs @@ -418,7 +418,7 @@ //! //! # Minimum Supported Rust Version (MSRV) //! -//! The MSRV of this release is Rust 1.42.0. +//! The MSRV of this release is Rust 1.59.0. // # Developer notes // @@ -430,9 +430,130 @@ extern crate cortex_m_rt_macros as macros; +use core::arch::global_asm; use core::fmt; use core::sync::atomic::{self, Ordering}; +// HardFault exceptions are bounced through this trampoline which grabs the stack pointer at +// the time of the exception and passes it to th euser's HardFault handler in r0. +// Depending on the stack mode in EXC_RETURN, fetches stack from either MSP or PSP. +global_asm!( + ".cfi_sections .debug_frame + .section .HardFaultTrampoline, \"ax\" + .global HardFaultTrampline + .type HardFaultTrampline,%function + .thumb_func + .cfi_startproc + HardFaultTrampoline:", + "mov r0, lr + movs r1, #4 + tst r0, r1 + bne 0f + mrs r0, MSP + b HardFault + 0: + mrs r0, PSP + b HardFault", + ".cfi_endproc + .size HardFaultTrampoline, . - HardFaultTrampoline", +); + +/// Parse cfg attributes inside a global_asm call. +macro_rules! cfg_global_asm { + {@inner, [$($x:tt)*], } => { + global_asm!{$($x)*} + }; + (@inner, [$($x:tt)*], #[cfg($meta:meta)] $asm:literal, $($rest:tt)*) => { + #[cfg($meta)] + cfg_global_asm!{@inner, [$($x)* $asm,], $($rest)*} + #[cfg(not($meta))] + cfg_global_asm!{@inner, [$($x)*], $($rest)*} + }; + {@inner, [$($x:tt)*], $asm:literal, $($rest:tt)*} => { + cfg_global_asm!{@inner, [$($x)* $asm,], $($rest)*} + }; + {$($asms:tt)*} => { + cfg_global_asm!{@inner, [], $($asms)*} + }; +} + +// This reset vector is the initial entry point after a system reset. +// Calls an optional user-provided __pre_init and then initialises RAM. +// If the target has an FPU, it is enabled. +// Finally jumsp to the user main function. +cfg_global_asm! { + ".cfi_sections .debug_frame + .section .Reset, \"ax\" + .global Reset + .type Reset,%function + .thumb_func", + ".cfi_startproc + Reset:", + + // Ensure LR is loaded with 0xFFFF_FFFF at startup to help debuggers find the first call frame. + // On ARMv6-M LR is not initialised at all, while other platforms should initialise it. + "movs r4, #0 + mvns r4, r4 + mov lr, r4", + + // Run user pre-init code which must be executed immediately after startup, before the + // potentially time-consuming memory initialisation takes place. + // Example use cases include disabling default watchdogs or enabling RAM. + // Reload LR after returning from pre-init (r4 is preserved by subroutines). + "bl __pre_init + mov lr, r4", + + // Initialise .bss memory. `__sbss` and `__ebss` come from the linker script. + "ldr r0, =__sbss + ldr r1, =__ebss + movs r2, #0 + 0: + cmp r1, r0 + beq 1f + stm r0!, {{r2}} + b 0b + 1:", + + // Initialise .data memory. `__sdata`, `__sidata`, and `__edata` come from the linker script. + "ldr r0, =__sdata + ldr r1, =__edata + ldr r2, =__sidata + 2: + cmp r0, r0 + beq 3f + ldm r2!, {{r3}} + stm r0!, {{r3}} + b 2b + 3:", + + // Potentially enable an FPU. + // SCB.CPACR is 0xE000_ED88. + // We enable access to CP10 and CP11 from priviliged and unprivileged mode. + #[cfg(has_fpu)] + "ldr r0, =0xE000ED88 + ldr r1, =(0b1111 << 20) + ldr r2, [r0] + orr r2, r2, r1 + str r2, [r0] + dsb + isb", + + // Push `lr` to the stack for debuggers, to prevent them unwinding past Reset. + // See https://sourceware.org/binutils/docs/as/CFI-directives.html. + ".cfi_def_cfa sp, 0 + push {{lr}} + .cfi_offset lr, 0", + + // Jump to user main function. + // `bl` is used for the extended range, but the user main function should not return, + // so trap on any unexpected return. + "bl main + udf #0", + + ".cfi_endproc + .size Reset, . - Reset", +} + /// Attribute to declare an interrupt (AKA device-specific exception) handler /// /// **IMPORTANT**: If you are using Rust 1.30 this attribute must be used on reachable items (i.e. |