Merge pull request #320 from rust-embedded/rvrt-asm

`riscv-rt`: organize trap section

Author: romancardenas

riscv-rt/CHANGELOG.md

@@ -18,6 +18,13 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - In multi-hart targets, the hart ID is now validated earlier in the boot process.
 - General purpose registers are no longer zeroed, as this is not strictly necessary.
   This aligns with the `cortex-m-rt` crate.
+- Better organization of the `.trap` section:
+  1. `_trap_vector` (if `v-trap` is enabled).
+  2. `_start_trap` (defaults to `_default_start_trap`).
+  3. `_start_INTERRUPT_trap` routines (if `v-trap` is enabled).
+  4. `_start_DefaultHandler_trap` and `_continue_trap` (if `v-trap` is enabled).
+  5. `_start_trap_rust`.
+  6. Other code in `.trap` section (usually, none)
 
 ### Fixed
 

riscv-rt/link.x.in

@@ -90,9 +90,15 @@ SECTIONS
     /* Put reset handler first in .text section so it ends up as the entry */
     /* point of the program. */
     KEEP(*(.init));
+    
     . = ALIGN(4);
-    *(.trap);
-    *(.trap.rust);
+    KEEP(*(.trap.vector));   /* for _trap_vector (vectored mode only) */
+    KEEP(*(.trap.start));    /* for _start_trap routine */
+    KEEP(*(.trap.start.*));  /* for _start_INTERRUPT_trap routines (vectored mode only) */
+    KEEP(*(.trap.continue)); /* for _continue_trap routine (vectored mode only) */
+    KEEP(*(.trap.rust));     /* for _start_trap_rust Rust function */
+    KEEP(*(.trap .trap.*));  /* Other .trap symbols at the end */
+
     *(.text.abort);
     *(.text .text.*);
 

riscv-rt/macros/src/lib.rs

@@ -1,4 +1,6 @@
 #![deny(warnings)]
+#![allow(unknown_lints)] // reason = "required for next line"
+#![allow(clippy::manual_is_multiple_of)] // reason = "requires MSRV bump"
 
 use proc_macro::TokenStream;
 use proc_macro2::{Span, TokenStream as TokenStream2};
@@ -518,8 +520,8 @@ pub fn default_start_trap(_input: TokenStream) -> TokenStream {
     format!(
         r#"
 core::arch::global_asm!(
-".section .trap, \"ax\"
-.align 4 /* Alignment required for xtvec */
+".section .trap.start, \"ax\"
+.balign 4 /* Alignment required for xtvec */
 .global _default_start_trap
 _default_start_trap:
     addi sp, sp, - {trap_size} * {width}
@@ -557,16 +559,15 @@ pub fn vectored_interrupt_trap(_input: TokenStream) -> TokenStream {
     let instructions = format!(
         r#"
 core::arch::global_asm!(
-".section .trap, \"ax\"
+".section .trap.continue, \"ax\"
 
-.align 4
+.balign 4
 .global _start_DefaultHandler_trap
 _start_DefaultHandler_trap:
     addi sp, sp, -{trap_size} * {width} // allocate space for trap frame
     {store_start}                       // store trap partially (only register a0)
     la a0, DefaultHandler               // load interrupt handler address into a0
 
-.align 4
 .global _continue_interrupt_trap
 _continue_interrupt_trap:
     {store_continue}                   // store trap partially (all registers except a0)
@@ -685,10 +686,11 @@ pub fn exception(args: TokenStream, input: TokenStream) -> TokenStream {
 /// }
 /// ```
 pub fn core_interrupt(args: TokenStream, input: TokenStream) -> TokenStream {
-    let arch = if cfg!(feature = "v-trap") {
-        RiscvArch::try_from_env()
-    } else {
-        None
+    let arch = match () {
+        #[cfg(feature = "v-trap")]
+        () => RiscvArch::try_from_env(),
+        #[cfg(not(feature = "v-trap"))]
+        () => None,
     };
     trap(args, input, RiscvPacItem::CoreInterrupt, arch)
 }
@@ -746,13 +748,14 @@ fn trap(
     let export_name = format!("{int_ident:#}");
 
     let start_trap = match arch {
+        #[cfg(feature = "v-trap")]
         Some(arch) => {
             let trap = start_interrupt_trap(int_ident, arch);
             quote! {
                 #trap
             }
         }
-        None => proc_macro2::TokenStream::new(),
+        _ => proc_macro2::TokenStream::new(),
     };
 
     let pac_trait = pac_item.impl_trait();
@@ -772,6 +775,7 @@ fn trap(
     .into()
 }
 
+#[cfg(feature = "v-trap")]
 fn start_interrupt_trap(ident: &syn::Ident, arch: RiscvArch) -> proc_macro2::TokenStream {
     let interrupt = ident.to_string();
     let width = arch.width();
@@ -780,9 +784,10 @@ fn start_interrupt_trap(ident: &syn::Ident, arch: RiscvArch) -> proc_macro2::Tok
 
     let instructions = format!(
         r#"
+#[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))]
 core::arch::global_asm!(
-    ".section .trap, \"ax\"
-    .align 2
+    ".section .trap.start.{interrupt}, \"ax\"
+    .balign 4
     .global _start_{interrupt}_trap
     _start_{interrupt}_trap:
         addi sp, sp, -{trap_size} * {width} // allocate space for trap frame

riscv/CHANGELOG.md

@@ -14,6 +14,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 
 - Use `cfg(any(target_arch = "riscv32", target_arch = "riscv64"))` instead of `cfg(riscv)`.
+- `riscv::pac_enum(unsafe CoreInterrupt)` now locates the vector table at the `.trap.vector`
+  section instead of `.trap`.
 
 ### Removed
 

riscv/macros/src/lib.rs

@@ -282,7 +282,7 @@ impl PacEnumItem {
             r#"
 #[cfg(all(feature = "v-trap", any(target_arch = "riscv32", target_arch = "riscv64")))]
 core::arch::global_asm!("
-    .section .trap, \"ax\"
+    .section .trap.vector, \"ax\"
     .global _vector_table
     .type _vector_table, @function