Re: [PATCH v2 3/3] rust: Enable for MIPS

[Gary Guo <gary@garyguo.net>]

On Thu, 05 Sep 2024 14:33:07 +0100
Jiaxun Yang <jiaxun.yang@flygoat.com> wrote:

> Enable rust for linux by implement generate_rust_target.rs
> and select relevant Kconfig options.
> 
> We don't use builtin target as there is no sutiable baremetal
> target for us that can cover all ISA variants supported by kernel.
> 
> Link: https://github.com/Rust-for-Linux/linux/issues/107
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---
> v2:
> 	- Add micromips flags
> 	- Sync issues with upstream
> ---
>  Documentation/rust/arch-support.rst                |  1 +
>  .../translations/zh_CN/rust/arch-support.rst       |  1 +
>  arch/mips/Kconfig                                  |  2 +
>  scripts/generate_rust_target.rs                    | 68 ++++++++++++++++++++++
>  4 files changed, 72 insertions(+)
> 
> diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst
> index 750ff371570a..ab6c0ae5a407 100644
> --- a/Documentation/rust/arch-support.rst
> +++ b/Documentation/rust/arch-support.rst
> @@ -17,6 +17,7 @@ Architecture   Level of support  Constraints
>  =============  ================  ==============================================
>  ``arm64``      Maintained        Little Endian only.
>  ``loongarch``  Maintained        \-
> +``mips``       Maintained        \-
>  ``riscv``      Maintained        ``riscv64`` only.
>  ``um``         Maintained        \-
>  ``x86``        Maintained        ``x86_64`` only.
> diff --git a/Documentation/translations/zh_CN/rust/arch-support.rst b/Documentation/translations/zh_CN/rust/arch-support.rst
> index abd708d48f82..1eaa6c3297ac 100644
> --- a/Documentation/translations/zh_CN/rust/arch-support.rst
> +++ b/Documentation/translations/zh_CN/rust/arch-support.rst
> @@ -21,6 +21,7 @@
>  =============  ================  ==============================================
>  ``arm64``      Maintained        只有小端序
>  ``loongarch``  Maintained        \-
> +``mips``       Maintained        \-
>  ``riscv``      Maintained        只有 ``riscv64``
>  ``um``         Maintained        只有 ``x86_64``
>  ``x86``        Maintained        只有 ``x86_64``
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 43da6d596e2b..a91f0a4fd8e9 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -90,6 +90,8 @@ config MIPS
>  	select HAVE_PERF_USER_STACK_DUMP
>  	select HAVE_REGS_AND_STACK_ACCESS_API
>  	select HAVE_RSEQ
> +	select HAVE_RUST
> +	select HAVE_GENERATE_RUST_TARGET
>  	select HAVE_SPARSE_SYSCALL_NR
>  	select HAVE_STACKPROTECTOR
>  	select HAVE_SYSCALL_TRACEPOINTS
> diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs
> index 863720777313..bbdf8a4dd169 100644
> --- a/scripts/generate_rust_target.rs
> +++ b/scripts/generate_rust_target.rs
> @@ -141,6 +141,13 @@ fn has(&self, option: &str) -> bool {
>          let option = "CONFIG_".to_owned() + option;
>          self.0.contains_key(&option)
>      }
> +
> +    /// Returns the value of the option in the configuration.
> +    /// The argument must be passed without the `CONFIG_` prefix.
> +    fn get(&self, option: &str) -> Option<&String> {
> +        let option = "CONFIG_".to_owned() + option;
> +        self.0.get(&option)

I know you follow the code style above, but this should be

	let option = format!("CONFIG_{option}");

> +    }
>  }
>  
>  fn main() {
> @@ -203,6 +210,67 @@ fn main() {
>          ts.push("target-pointer-width", "32");
>      } else if cfg.has("LOONGARCH") {
>          panic!("loongarch uses the builtin rustc loongarch64-unknown-none-softfloat target");
> +    } else if cfg.has("MIPS") {
> +        let mut features = "+soft-float,+noabicalls".to_string();
> +
> +        if cfg.has("CPU_MICROMIPS") {
> +            features += ",+micromips";
> +        }
> +
> +        if cfg.has("64BIT") {
> +            ts.push("arch", "mips64");
> +            ts.push("abi", "abi64");
> +            cfg.get("TARGET_ISA_REV").map(|isa_rev| {

if let Some(isa_rev) = cfg.get("TARGET_ISA_REV") {
   ...
}

> +                let feature = match isa_rev.as_str() {
> +                    "1" => ",+mips64",
> +                    "2" => ",+mips64r2",
> +                    "5" => ",+mips64r5",
> +                    "6" => ",+mips64r6",
> +                    _ => ",+mips3",
> +                };
> +                features += feature;
> +            });
> +
> +            ts.push("features", features);
> +            if cfg.has("CPU_BIG_ENDIAN") {
> +                ts.push(
> +                    "data-layout",
> +                    "E-m:e-i8:8:32-i16:16:32-i64:64-n32:64-S128",
> +                );
> +                ts.push("llvm-target", "mips64-unknown-linux-gnuabi64");
> +            } else {
> +                ts.push(
> +                    "data-layout",
> +                    "e-m:e-i8:8:32-i16:16:32-i64:64-n32:64-S128",
> +                );
> +                ts.push("llvm-target", "mips64el-unknown-linux-gnuabi64");
> +            }
> +            ts.push("target-pointer-width", "64");
> +        } else {
> +            ts.push("arch", "mips");
> +            cfg.get("TARGET_ISA_REV").map(|isa_rev| {

ditto

> +                let feature = match isa_rev.as_str() {
> +                    "1" => ",+mips32",
> +                    "2" => ",+mips32r2",
> +                    "5" => ",+mips32r5",
> +                    "6" => ",+mips32r6",
> +                    _ => ",+mips2",
> +                };
> +                features += feature;
> +            });
> +
> +            ts.push("features", features);
> +            if cfg.has("CPU_BIG_ENDIAN") {
> +                ts.push("data-layout",
> +                        "E-m:m-p:32:32-i8:8:32-i16:16:32-i64:64-n32-S64");
> +                ts.push("llvm-target", "mips-unknown-linux-gnu");
> +            } else {
> +                ts.push("data-layout",
> +                        "e-m:m-p:32:32-i8:8:32-i16:16:32-i64:64-n32-S64");
> +                ts.push("llvm-target", "mipsel-unknown-linux-gnu");
> +            }
> +            ts.push("target-pointer-width", "32");
> +        }
>      } else {
>          panic!("Unsupported architecture");
>      }
> 

Best,
Gary