riscv-rt: compatibility with RV32E and RV64E

.github/workflows/changelog.yaml

@@ -27,6 +27,8 @@ jobs:
               - 'riscv-rt/**'
             riscv-semihosting:
               - 'riscv-semihosting/**'
+            riscv-target-parser:
+              - 'riscv-target-parser/**'
 
       - name: Check for CHANGELOG.md (riscv)
         if: steps.changes.outputs.riscv == 'true'
@@ -43,7 +45,15 @@ jobs:
           changeLogPath: ./riscv-pac/CHANGELOG.md
           skipLabels: 'skip changelog'
           missingUpdateErrorMessage: 'Please add a changelog entry in the riscv-pac/CHANGELOG.md file.'
-
+
+      - name: Check for CHANGELOG.md (riscv-peripheral)
+        if: steps.changes.outputs.riscv-peripheral == 'true'
+        uses: dangoslen/changelog-enforcer@v3
+        with:
+          changeLogPath: ./riscv-peripheral/CHANGELOG.md
+          skipLabels: 'skip changelog'
+          missingUpdateErrorMessage: 'Please add a changelog entry in the riscv-peripheral/CHANGELOG.md file.'
+
       - name: Check for CHANGELOG.md (riscv-rt)
         if: steps.changes.outputs.riscv-rt == 'true'
         uses: dangoslen/changelog-enforcer@v3
@@ -60,10 +70,10 @@ jobs:
           skipLabels: 'skip changelog'
           missingUpdateErrorMessage: 'Please add a changelog entry in the riscv-semihosting/CHANGELOG.md file.'
 
-      - name: Check for CHANGELOG.md (riscv-peripheral)
-        if: steps.changes.outputs.riscv-peripheral == 'true'
+      - name: Check for CHANGELOG.md (riscv-target-parser)
+        if: steps.changes.outputs.riscv-target-parser == 'true'
         uses: dangoslen/changelog-enforcer@v3
         with:
-          changeLogPath: ./riscv-peripheral/CHANGELOG.md
+          changeLogPath: ./riscv-target-parser/CHANGELOG.md
           skipLabels: 'skip changelog'
-          missingUpdateErrorMessage: 'Please add a changelog entry in the riscv-peripheral/CHANGELOG.md file.'
+          missingUpdateErrorMessage: 'Please add a changelog entry in the riscv-target-parser/CHANGELOG.md file.'

.github/workflows/riscv-rt.yaml

@@ -14,8 +14,10 @@ jobs:
         toolchain: [ stable, nightly, 1.61.0 ]
         target:
           - riscv32i-unknown-none-elf
+          - riscv32im-unknown-none-elf
           - riscv32imc-unknown-none-elf
           - riscv32imac-unknown-none-elf
+          - riscv32imafc-unknown-none-elf
           - riscv64imac-unknown-none-elf
           - riscv64gc-unknown-none-elf
         example:
@@ -25,6 +27,11 @@ jobs:
           # Nightly is only for reference and allowed to fail
           - toolchain: nightly
             experimental: true
+        exclude:
+          - toolchain: 1.61.0
+            target: riscv32im-unknown-none-elf
+          - toolchain: 1.61.0
+            target: riscv32imafc-unknown-none-elf
     runs-on: ubuntu-latest
     continue-on-error: ${{ matrix.experimental || false }}
     steps:

.github/workflows/riscv-target-parser.yaml

@@ -0,0 +1,37 @@
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+  merge_group:
+
+name: Run tests (riscv-target-parser)
+
+jobs:
+  run-tests:
+    strategy:
+      matrix:
+        os: [ macos-latest, ubuntu-latest, windows-latest ]
+        toolchain: [ stable, nightly, 1.61.0 ]
+        include:
+          # Nightly is only for reference and allowed to fail
+          - rust: nightly
+            experimental: true
+    runs-on: ${{ matrix.os }}
+    continue-on-error: ${{ matrix.experimental || false }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Update Rust toolchain
+        run: rustup update ${{ matrix.toolchain }} && rustup default ${{ matrix.toolchain }}
+      - name: Build
+        run: cargo build --package riscv-target-parser
+      - name: Run tests
+        run: cargo test --package riscv-target-parser
+
+  # Job to check that all the builds succeeded
+  tests-check:
+    needs:
+    - run-tests
+    runs-on: ubuntu-latest
+    if: always()
+    steps:
+      - run: jq --exit-status 'all(.result == "success")' <<< '${{ toJson(needs) }}'

Cargo.toml

@@ -6,5 +6,6 @@ members = [
     "riscv-peripheral",
     "riscv-rt",
     "riscv-semihosting",
+    "riscv-target-parser",
     "tests",
 ]

README.md

@@ -7,6 +7,7 @@ This repository contains various crates useful for writing Rust programs on RISC
 * [`riscv-peripheral`]: Interfaces for standard RISC-V peripherals
 * [`riscv-rt`]: Startup code and interrupt handling
 * [`riscv-semihosting`]: Semihosting for RISC-V processors
+* [`riscv-target-parser`]: Utility crate for parsing RISC-V targets in build scripts
 
 This project is developed and maintained by the [RISC-V team][team].
 
@@ -27,5 +28,6 @@ to intervene to uphold that code of conduct.
 [`riscv-peripheral`]: https://crates.io/crates/riscv-peripheral
 [`riscv-rt`]: https://crates.io/crates/riscv-rt
 [`riscv-semihosting`]: https://crates.io/crates/riscv-semihosting
+[`riscv-target-parser`]: https://crates.io/crates/riscv-target-parser
 [team]: https://github.com/rust-embedded/wg#the-risc-v-team
 [CoC]: CODE_OF_CONDUCT.md

riscv-rt/CHANGELOG.md

@@ -9,6 +9,14 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Changed
 
+- Limit rustc cfg flags to `riscvi`, `riscvm`, `riscvf`, and `riscvd`.
+- Temporary use of `RISCV_RT_LLVM_ARCH_PATCH` environment variable to include the
+  temporary patch required for avoid LLVM spurious errors.
+- `riscv-rt` now use the `RISCV_RT_BASE_ISA` environment variable to configure the behavior
+  of `riscv-rt-macros` depending on aspects of the base ISA (e.g., RV32I or RV32E).
+- Use `riscv-target-parser` in build script to identify target-specific configurations.
+- Add documentation to trap frame fields.
+- Avoid using `t3`+ in startup assembly to ensure compatibility with RVE.
 - `link.x.in`: remove references to `eh_frame`.
 - Rename start/end section symbols to align with `cortex-m-rt`:
     - `_stext`: it remains, as linker files can modify it.

riscv-rt/Cargo.toml

@@ -19,10 +19,13 @@ targets = [
     "riscv64imac-unknown-none-elf", "riscv64gc-unknown-none-elf",
 ]
 
+[build-dependencies]
+riscv-target-parser = { path = "../riscv-target-parser", version = "0.1.0" }
+
 [dependencies]
 riscv = { path = "../riscv", version = "0.12.0" }
 riscv-pac = { path = "../riscv-pac", version = "0.2.0" }
-riscv-rt-macros = { path = "macros", version = "0.2.2" }
+riscv-rt-macros = { path = "macros", version = "0.3.0" }
 
 [dev-dependencies]
 panic-halt = "1.0.0"

riscv-rt/build.rs

@@ -1,6 +1,10 @@
 // NOTE: Adapted from cortex-m/build.rs
 
-use std::{collections::HashSet, env, fs, io, path::PathBuf};
+use riscv_target_parser::RiscvTarget;
+use std::{env, fs, io, path::PathBuf};
+
+// List of all possible RISC-V configurations to check for in risv-rt
+const RISCV_CFG: [&str; 4] = ["riscvi", "riscvm", "riscvf", "riscvd"];
 
 fn add_linker_script(arch_width: u32) -> io::Result<()> {
     // Read the file to a string and replace all occurrences of ${ARCH_WIDTH} with the arch width
@@ -17,96 +21,39 @@ fn add_linker_script(arch_width: u32) -> io::Result<()> {
     Ok(())
 }
 
-/// Parse the target RISC-V architecture and returns its bit width and the extension set
-fn parse_target(target: &str, cargo_flags: &str) -> (u32, HashSet<char>) {
-    // isolate bit width and extensions from the rest of the target information
-    let arch = target
-        .trim_start_matches("riscv")
-        .split('-')
-        .next()
-        .unwrap();
-
-    let bits = arch
-        .chars()
-        .take_while(|c| c.is_ascii_digit())
-        .collect::<String>()
-        .parse::<u32>()
-        .unwrap();
-
-    let mut extensions: HashSet<char> = arch.chars().skip_while(|c| c.is_ascii_digit()).collect();
-    // expand the 'g' shorthand extension
-    if extensions.contains(&'g') {
-        extensions.insert('i');
-        extensions.insert('m');
-        extensions.insert('a');
-        extensions.insert('f');
-        extensions.insert('d');
-    }
-
-    let cargo_flags = cargo_flags
-        .split(0x1fu8 as char)
-        .filter(|arg| !arg.is_empty());
-
-    cargo_flags
-        .filter(|k| k.starts_with("target-feature="))
-        .flat_map(|str| {
-            let flags = str.split('=').collect::<Vec<&str>>()[1];
-            flags.split(',')
-        })
-        .for_each(|feature| {
-            let chars = feature.chars().collect::<Vec<char>>();
-            match chars[0] {
-                '+' => {
-                    extensions.insert(chars[1]);
-                }
-                '-' => {
-                    extensions.remove(&chars[1]);
-                }
-                _ => {
-                    panic!("Unsupported target feature operation");
-                }
-            }
-        });
-
-    (bits, extensions)
-}
-
 fn main() {
-    println!("cargo:rustc-check-cfg=cfg(riscv)");
-    println!("cargo:rustc-check-cfg=cfg(riscv32)");
-    println!("cargo:rustc-check-cfg=cfg(riscv64)");
-    for ext in ['i', 'e', 'm', 'a', 'f', 'd', 'g', 'c'] {
-        println!("cargo:rustc-check-cfg=cfg(riscv{})", ext);
+    // Required until target_feature risc-v is stable and in-use (rust 1.75)
+    for ext in RISCV_CFG.iter() {
+        println!("cargo:rustc-check-cfg=cfg({ext})");
     }
 
     let target = env::var("TARGET").unwrap();
     let cargo_flags = env::var("CARGO_ENCODED_RUSTFLAGS").unwrap();
-    let _name = env::var("CARGO_PKG_NAME").unwrap();
 
-    // set configuration flags depending on the target
-    if target.starts_with("riscv") {
-        println!("cargo:rustc-cfg=riscv");
-        // This is required until target_arch & target_feature risc-v work is
-        // stable and in-use (rust 1.75.0)
-        let (bits, extensions) = parse_target(&target, &cargo_flags);
-
-        // generate the linker script and expose the ISA width
-        let arch_width = match bits {
-            32 => {
-                println!("cargo:rustc-cfg=riscv32");
-                4
-            }
-            64 => {
-                println!("cargo:rustc-cfg=riscv64");
-                8
+    if let Ok(target) = RiscvTarget::build(&target, &cargo_flags) {
+        let width = target.width();
+
+        // set environmet variable RISCV_RT_BASE_ISA to the base ISA of the target.
+        println!(
+            "cargo:rustc-env=RISCV_RT_BASE_ISA={}",
+            target.llvm_base_isa()
+        );
+        // set environment variable RISCV_RT_LLVM_ARCH_PATCH to patch LLVM bug.
+        // (this env variable is temporary and will be removed after LLVM being fixed)
+        println!(
+            "cargo:rustc-env=RISCV_RT_LLVM_ARCH_PATCH={}",
+            target.llvm_arch_patch()
+        );
+        // make sure that these env variables are not changed without notice.
+        println!("cargo:rerun-if-env-changed=RISCV_RT_BASE_ISA");
+        println!("cargo:rerun-if-env-changed=RISCV_RT_LLVM_ARCH_PATCH");
+
+        for flag in target.rustc_flags() {
+            // Required until target_feature risc-v is stable and in-use
+            if RISCV_CFG.contains(&flag.as_str()) {
+                println!("cargo:rustc-cfg={flag}");
             }
-            _ => panic!("Unsupported bit width"),
-        };
-        add_linker_script(arch_width).unwrap();
-
-        // expose the ISA extensions
-        for ext in &extensions {
-            println!("cargo:rustc-cfg=riscv{}", ext);
         }
+        add_linker_script(width.into()).unwrap();
     }
 }

riscv-rt/macros/Cargo.toml

@@ -10,7 +10,7 @@ keywords = ["riscv", "runtime", "startup"]
 license = "MIT OR Apache-2.0"
 name = "riscv-rt-macros"
 repository = "https://github.com/rust-embedded/riscv"
-version = "0.2.2"
+version = "0.3.0"
 edition = "2021"
 
 [lib]