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Set linker script from build.rs file
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This has two advantages:

1. It adds a `cargo:rerun-if-changed` command to ensure we rebuild
   crates if the linker script changes.
2. The path to the linker script does not depend on the directory that
   Cargo is executed from, so `cargo build` can be done from anywhere.

Signed-off-by: James Wainwright <[email protected]>
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jwnrt committed Jan 16, 2024
1 parent f4ef5ce commit b9ccd89
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Showing 8 changed files with 48 additions and 3 deletions.
3 changes: 0 additions & 3 deletions sw/rust/.cargo/config.toml
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Expand Up @@ -7,9 +7,6 @@ target = "riscv32imc-unknown-none-elf"

[target.riscv32imc-unknown-none-elf]
runner = "../../util/load_demo_system.sh run"
rustflags = [
"-C", "link-arg=-T../common/link.ld",
]

[unstable]
build-std = ["core"]
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1 change: 1 addition & 0 deletions sw/rust/Cargo.toml
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Expand Up @@ -12,6 +12,7 @@ members = [
"demo/lcd_hal",
"demo/pwm_hal",
]
resolver = "2"

[profile.release]
debug = true
42 changes: 42 additions & 0 deletions sw/rust/build.rs
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@@ -0,0 +1,42 @@
// Copyright lowRISC contributors.
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0

//! This Cargo build script locates and uses the `link.ld` linker script.
//!
//! This build script can be used by a crate from its Cargo.toml:
//!
//! ```toml
//! [package]
//! ...
//! build = "../path/to/build.rs"
//! ```
//!
//! Build scripts are run with their working directory as the root of the
//! crate being built. We must find the path to the Cargo workspace in order
//! to get the correct path to the `link.ld` script.
use std::path::PathBuf;
use std::process::Command;

fn main() {
// Ask Cargo for the path of the workspace.
let workspace_path = Command::new(env!("CARGO"))
.arg("locate-project")
.arg("--workspace")
.arg("--message-format=plain")
.output()
.expect("failed to locate project using cargo")
.stdout;
let workspace_path = std::str::from_utf8(&workspace_path).expect("path to workspace not UTF-8");
let workspace_path = PathBuf::from(workspace_path);
let workspace_path = workspace_path.parent().expect("failed to get parent");

// Find the path of the linker script relative to the workspace.
let linker_script_path = workspace_path.join("../common/link.ld");
let linker_script_path = linker_script_path.display();

// Use the linker script and rebuild crates if it changes.
println!("cargo:rerun-if-changed={linker_script_path}");
println!("cargo:rustc-link-arg=-T{linker_script_path}");
}
1 change: 1 addition & 0 deletions sw/rust/demo/hello_world/Cargo.toml
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Expand Up @@ -6,6 +6,7 @@
name = "hello_world"
version = "0.1.0"
edition = "2021"
build = "../../build.rs"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

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1 change: 1 addition & 0 deletions sw/rust/demo/lcd_hal/Cargo.toml
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Expand Up @@ -6,6 +6,7 @@
name = "lcd_hal"
version = "0.1.0"
edition = "2021"
build = "../../build.rs"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

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1 change: 1 addition & 0 deletions sw/rust/demo/led/Cargo.toml
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Expand Up @@ -6,6 +6,7 @@
name = "led"
version = "0.1.0"
edition = "2021"
build = "../../build.rs"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

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1 change: 1 addition & 0 deletions sw/rust/demo/led_hal/Cargo.toml
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Expand Up @@ -6,6 +6,7 @@
name = "led_hal"
version = "0.1.0"
edition = "2021"
build = "../../build.rs"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

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1 change: 1 addition & 0 deletions sw/rust/demo/pwm_hal/Cargo.toml
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Expand Up @@ -6,6 +6,7 @@
name = "pwm_hal"
version = "0.1.0"
edition = "2021"
build = "../../build.rs"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

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