Building this crate

Having rustup and CHERIoT-enabled LLVM installed locally should suffice. Note: your local build of LLVM should have enabled both the riscv32cheriot-unknown-cheriotrtos target and the host target, because the rustc fork calls some LLVM API that are different from upstream (in particular, for memcpy and memmove -- see more here).

1. Clone the rustc fork with the CHERIoT target added:

$ git clone https://github.com/xdoardo/rust --branch=cheriot-on-1.88.0

2. Generate the bootstrap.toml file. Note: needs the $CHERIOT_SYSROOT_DIR env variable to be set and pointing to the llvm-project/build directory of your local LLVM build.

$ cd rust && ./gen_bootstrap.sh

3. Build the compiler and needed libraries:

$ ./x build compiler core panic_abort --target=riscv32cheriot-unknown-cheriotrtos

4. Link the toolchain with rustup:

$ rustup toolchain link 'cheriot' build/host/stage1

5. Build this crate!

$ cd rust-cheriot-basic && cargo +cheriot build --release  --target=riscv32cheriot-unknown-cheriotrtos

What should work

The goal of this example is that of producing a working rustc compiler that can compile simple programs to CHERIoT. We expect this crate to be compiled to an .s library with the symbols for the defined functions.

You should then be able to link the generated .s library with an RTOS program that uses these functions. The test I ran looks like this:

extern "C" int                zero();
extern "C" int                add(int a, int b);
extern "C" long long unsigned div(long long unsigned a, long long unsigned b);

#include "cheri.hh"
#define TEST_NAME "RUST"
#include "tests.hh"

int test_rust()
{
	int zero_from_rust = zero();
	debug_log("Got zero from rust: {}", zero_from_rust);

	int add_from_rust = add(4, 2);
	debug_log("Got add from rust: {}", add_from_rust);

	long long unsigned div_from_rust = div(4, 2);
	debug_log("Got div from rust: {}", div_from_rust);

	return 0;
}

I got xmake to build it successfully by changing

batchcmds:vrunv(target:tool("ld"), table.join({"--script=" .. linkerscript, "--compartment", "--gc-sections", "--relax", "-o", target:targetfile()}, target:objectfiles()), opt)

to

batchcmds:vrunv(target:tool("ld"), table.join({"--script=" .. linkerscript, "-L<path_to_rust_cheriot_basic_dir>", "-lrust_cheriot_basic", "--compartment", "--gc-sections", "--relax", "-o", target:targetfile()}, target:objectfiles()), opt)

in cheriot-rtos/sdk/xmake.lua, and adding the relevant test(...) settings in cheriot-rtos/tests/xmake.lua.