| #[cfg(feature = "cc")] |
| use cc::Build; |
| use std::env::var; |
| use std::io::Write; |
| |
| /// The directory for out-of-line ("outline") libraries. |
| const OUTLINE_PATH: &str = "src/backend/linux_raw/arch/outline"; |
| |
| fn main() { |
| // Don't rerun this on changes other than build.rs, as we only depend on |
| // the rustc version. |
| println!("cargo:rerun-if-changed=build.rs"); |
| |
| use_feature_or_nothing("rustc_attrs"); |
| |
| // Features only used in no-std configurations. |
| #[cfg(not(feature = "std"))] |
| { |
| use_feature_or_nothing("const_raw_ptr_deref"); |
| use_feature_or_nothing("core_ffi_c"); |
| use_feature_or_nothing("core_c_str"); |
| use_feature_or_nothing("alloc_c_string"); |
| } |
| |
| // Gather target information. |
| let arch = var("CARGO_CFG_TARGET_ARCH").unwrap(); |
| let asm_name = format!("{}/{}.s", OUTLINE_PATH, arch); |
| let asm_name_present = std::fs::metadata(&asm_name).is_ok(); |
| let os_name = var("CARGO_CFG_TARGET_OS").unwrap(); |
| let pointer_width = var("CARGO_CFG_TARGET_POINTER_WIDTH").unwrap(); |
| let endian = var("CARGO_CFG_TARGET_ENDIAN").unwrap(); |
| |
| // Check for special target variants. |
| let is_x32 = arch == "x86_64" && pointer_width == "32"; |
| let is_arm64_ilp32 = arch == "aarch64" && pointer_width == "32"; |
| let is_powerpc64be = arch == "powerpc64" && endian == "big"; |
| let is_mipseb = arch == "mips" && endian == "big"; |
| let is_mips64eb = arch == "mips64" && endian == "big"; |
| let is_unsupported_abi = is_x32 || is_arm64_ilp32 || is_powerpc64be || is_mipseb || is_mips64eb; |
| |
| // Check for `--features=use-libc`. This allows crate users to enable the |
| // libc backend. |
| let feature_use_libc = var("CARGO_FEATURE_USE_LIBC").is_ok(); |
| |
| // Check for `--features=rustc-dep-of-std`. This is used when rustix is |
| // being used to build std, in which case `can_compile` doesn't work |
| // because `core` isn't available yet, but also, we can assume we have a |
| // recent compiler. |
| let feature_rustc_dep_of_std = var("CARGO_FEATURE_RUSTC_DEP_OF_STD").is_ok(); |
| |
| // Check for `RUSTFLAGS=--cfg=rustix_use_libc`. This allows end users to |
| // enable the libc backend even if rustix is depended on transitively. |
| let cfg_use_libc = var("CARGO_CFG_RUSTIX_USE_LIBC").is_ok(); |
| |
| // Check for eg. `RUSTFLAGS=--cfg=rustix_use_experimental_asm`. This is a |
| // rustc flag rather than a cargo feature flag because it's experimental |
| // and not something we want accidentally enabled via `--all-features`. |
| let rustix_use_experimental_asm = var("CARGO_CFG_RUSTIX_USE_EXPERIMENTAL_ASM").is_ok(); |
| |
| // Miri doesn't support inline asm, and has builtin support for recognizing |
| // libc FFI calls, so if we're running under miri, use the libc backend. |
| let miri = var("CARGO_CFG_MIRI").is_ok(); |
| |
| // If the libc backend is requested, or if we're not on a platform for |
| // which we have linux_raw support, use the libc backend. |
| // |
| // For now Android uses the libc backend; in theory it could use the |
| // linux_raw backend, but to do that we'll need to figure out how to |
| // install the toolchain for it. |
| if feature_use_libc |
| || cfg_use_libc |
| || os_name != "linux" |
| || !asm_name_present |
| || is_unsupported_abi |
| || miri |
| { |
| // Use the libc backend. |
| use_feature("libc"); |
| } else { |
| // Use the linux_raw backend. |
| use_feature("linux_raw"); |
| use_feature_or_nothing("core_intrinsics"); |
| |
| // Use inline asm if we have it, or outline asm otherwise. On PowerPC |
| // and MIPS, Rust's inline asm is considered experimental, so only use |
| // it if `--cfg=rustix_use_experimental_asm` is given. |
| if (feature_rustc_dep_of_std || can_compile("use std::arch::asm;")) |
| && (arch != "x86" || has_feature("naked_functions")) |
| && ((arch != "powerpc64" && arch != "mips" && arch != "mips64") |
| || rustix_use_experimental_asm) |
| { |
| use_feature("asm"); |
| if arch == "x86" { |
| use_feature("naked_functions"); |
| } |
| if rustix_use_experimental_asm { |
| use_feature("asm_experimental_arch"); |
| } |
| } else { |
| link_in_librustix_outline(&arch, &asm_name); |
| } |
| } |
| |
| // Detect whether the compiler requires us to use thumb mode on ARM. |
| if arch == "arm" && use_thumb_mode() { |
| use_feature("thumb_mode"); |
| } |
| |
| println!("cargo:rerun-if-env-changed=CARGO_CFG_RUSTIX_USE_EXPERIMENTAL_ASM"); |
| println!("cargo:rerun-if-env-changed=CARGO_CFG_RUSTIX_USE_LIBC"); |
| |
| // Rerun this script if any of our features or configuration flags change, |
| // or if the toolchain we used for feature detection changes. |
| println!("cargo:rerun-if-env-changed=CARGO_FEATURE_USE_LIBC"); |
| println!("cargo:rerun-if-env-changed=CARGO_FEATURE_RUSTC_DEP_OF_STD"); |
| println!("cargo:rerun-if-env-changed=CARGO_CFG_MIRI"); |
| println!("cargo:rerun-if-env-changed=CARGO_ENCODED_RUSTFLAGS"); |
| println!("cargo:rerun-if-env-changed=RUSTC"); |
| println!("cargo:rerun-if-env-changed=TARGET"); |
| println!("cargo:rerun-if-env-changed=RUSTC_WRAPPER"); |
| println!("cargo:rerun-if-env-changed=PROFILE"); |
| } |
| |
| /// Link in the desired version of librustix_outline_{arch}.a, containing the |
| /// outline assembly code for making syscalls. |
| fn link_in_librustix_outline(arch: &str, asm_name: &str) { |
| let name = format!("rustix_outline_{}", arch); |
| let profile = var("PROFILE").unwrap(); |
| let to = format!("{}/{}/lib{}.a", OUTLINE_PATH, profile, name); |
| println!("cargo:rerun-if-changed={}", to); |
| |
| // If "cc" is not enabled, use a pre-built library. |
| #[cfg(not(feature = "cc"))] |
| { |
| let _ = asm_name; |
| println!("cargo:rustc-link-search={}/{}", OUTLINE_PATH, profile); |
| println!("cargo:rustc-link-lib=static={}", name); |
| } |
| |
| // If "cc" is enabled, build the library from source, update the pre-built |
| // version, and assert that the pre-built version is checked in. |
| #[cfg(feature = "cc")] |
| { |
| let out_dir = var("OUT_DIR").unwrap(); |
| Build::new().file(&asm_name).compile(&name); |
| println!("cargo:rerun-if-changed={}", asm_name); |
| if std::fs::metadata(".git").is_ok() { |
| let from = format!("{}/lib{}.a", out_dir, name); |
| let prev_metadata = std::fs::metadata(&to); |
| std::fs::copy(&from, &to).unwrap(); |
| assert!( |
| prev_metadata.is_ok(), |
| "{} didn't previously exist; please inspect the new file and `git add` it", |
| to |
| ); |
| assert!( |
| std::process::Command::new("git") |
| .arg("diff") |
| .arg("--quiet") |
| .arg(&to) |
| .status() |
| .unwrap() |
| .success(), |
| "{} changed; please inspect the change and `git commit` it", |
| to |
| ); |
| } |
| } |
| } |
| |
| fn use_thumb_mode() -> bool { |
| // In thumb mode, r7 is reserved. |
| !can_compile("pub unsafe fn f() { core::arch::asm!(\"udf #16\", in(\"r7\") 0); }") |
| } |
| |
| fn use_feature_or_nothing(feature: &str) { |
| if has_feature(feature) { |
| use_feature(feature); |
| } |
| } |
| |
| fn use_feature(feature: &str) { |
| println!("cargo:rustc-cfg={}", feature); |
| } |
| |
| /// Test whether the rustc at `var("RUSTC")` supports the given feature. |
| fn has_feature(feature: &str) -> bool { |
| can_compile(&format!( |
| "#![allow(stable_features)]\n#![feature({})]", |
| feature |
| )) |
| } |
| |
| /// Test whether the rustc at `var("RUSTC")` can compile the given code. |
| fn can_compile<T: AsRef<str>>(test: T) -> bool { |
| use std::process::Stdio; |
| |
| let out_dir = var("OUT_DIR").unwrap(); |
| let rustc = var("RUSTC").unwrap(); |
| let target = var("TARGET").unwrap(); |
| |
| let mut cmd = if let Ok(wrapper) = var("RUSTC_WRAPPER") { |
| let mut cmd = std::process::Command::new(wrapper); |
| // The wrapper's first argument is supposed to be the path to rustc. |
| cmd.arg(rustc); |
| cmd |
| } else { |
| std::process::Command::new(rustc) |
| }; |
| |
| cmd.arg("--crate-type=rlib") // Don't require `main`. |
| .arg("--emit=metadata") // Do as little as possible but still parse. |
| .arg("--target") |
| .arg(target) |
| .arg("--out-dir") |
| .arg(out_dir); // Put the output somewhere inconsequential. |
| |
| // If Cargo wants to set RUSTFLAGS, use that. |
| if let Ok(rustflags) = var("CARGO_ENCODED_RUSTFLAGS") { |
| if !rustflags.is_empty() { |
| for arg in rustflags.split('\x1f') { |
| cmd.arg(arg); |
| } |
| } |
| } |
| |
| let mut child = cmd |
| .arg("-") // Read from stdin. |
| .stdin(Stdio::piped()) // Stdin is a pipe. |
| .stderr(Stdio::null()) // Errors from feature detection aren't interesting and can be confusing. |
| .spawn() |
| .unwrap(); |
| |
| writeln!(child.stdin.take().unwrap(), "{}", test.as_ref()).unwrap(); |
| |
| child.wait().unwrap().success() |
| } |
