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Merge pull request #535 from jannic/link_section
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Add link_section = ".HardFault.user" to _HardFault
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adamgreig authored Sep 10, 2024
2 parents febacfd + 94bd9c8 commit 57ce011
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Showing 3 changed files with 37 additions and 1 deletion.
1 change: 1 addition & 0 deletions cortex-m-rt/ci/script.sh
Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@ main() {
divergent-default-handler
divergent-exception
entry-static
hard-fault-trampoline
main
minimal
override-exception
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31 changes: 31 additions & 0 deletions cortex-m-rt/examples/hard-fault-trampoline.rs
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@@ -0,0 +1,31 @@
//! This is not an example; this is a linker test that ensures
//! that the jump from HardFault to _HardFault doesn't exceed
//! the 2kB limit of the branch instruction.

#![deny(warnings)]
#![no_main]
#![no_std]

extern crate cortex_m_rt;
extern crate panic_halt;

use core::arch::asm;
use cortex_m_rt::{entry, exception, ExceptionFrame};

// This defines both `HardFault` and `_HardFault`. Both should have
// link_section attributes placing them at the end of the .text section,
// close to each other. If one of them is missing that attribute, they
// will end up separated by `foo`, which will make the linker fail.
#[exception(trampoline = true)]
unsafe fn HardFault(_ef: &ExceptionFrame) -> ! {
loop {}
}

#[entry]
fn foo() -> ! {
unsafe {
// 2kB of NOP instructions to make the function artificially larger
asm!(".fill 1024,2,0xbf00",);
}
loop {}
}
6 changes: 5 additions & 1 deletion cortex-m-rt/macros/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -368,6 +368,10 @@ pub fn exception(args: TokenStream, input: TokenStream) -> TokenStream {
#(#attrs)*
#[doc(hidden)]
#[export_name = "_HardFault"]
// Only emit link_section when building for embedded targets,
// because some hosted platforms (used to check the build)
// cannot handle the long link section names.
#[cfg_attr(target_os = "none", link_section = ".HardFault.user")]
unsafe extern "C" fn #tramp_ident(frame: &::cortex_m_rt::ExceptionFrame) {
#ident(frame)
}
Expand All @@ -379,7 +383,7 @@ pub fn exception(args: TokenStream, input: TokenStream) -> TokenStream {
// Depending on the stack mode in EXC_RETURN, fetches stack from either MSP or PSP.
core::arch::global_asm!(
".cfi_sections .debug_frame
.section .HardFault.user, \"ax\"
.section .HardFaultTrampoline, \"ax\"
.global HardFault
.type HardFault,%function
.thumb_func
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