Support x86_64-unknown-uefi

Author: josephlr

.travis.yml

@@ -106,6 +106,7 @@ matrix:
         - rustup target add x86_64-unknown-netbsd
         - rustup target add x86_64-unknown-redox
         - rustup target add x86_64-fortanix-unknown-sgx
+        - cargo install cargo-xbuild # For no_std targets
       script:
         - cargo build --target=x86_64-sun-solaris --all-features
         - cargo build --target=x86_64-unknown-cloudabi --all-features
@@ -114,6 +115,7 @@ matrix:
         - cargo build --target=x86_64-unknown-netbsd --all-features
         - cargo build --target=x86_64-unknown-redox --all-features
         - cargo build --target=x86_64-fortanix-unknown-sgx --all-features
+        - cargo xbuild --target=x86_64-unknown-uefi
         # also test minimum dependency versions are usable
         - cargo generate-lockfile -Z minimal-versions
         - cargo build --target=x86_64-sun-solaris --all-features
@@ -123,6 +125,7 @@ matrix:
         - cargo build --target=x86_64-unknown-netbsd --all-features
         - cargo build --target=x86_64-unknown-redox --all-features
         - cargo build --target=x86_64-fortanix-unknown-sgx --all-features
+        - cargo xbuild --target=x86_64-unknown-uefi
 
     # Trust cross-built/emulated targets. We must repeat all non-default values.
     - rust: stable

Cargo.toml

@@ -39,5 +39,8 @@ stdweb = { version = "0.4.9", optional = true }
 [target.wasm32-wasi.dependencies]
 libc = "0.2.54"
 
+[target.'cfg(any(target_env = "sgx", target_os = "uefi"))'.dependencies]
+lazy_static = { version = "1.3.0", features = ["spin_no_std"] }
+
 [features]
 std = []

src/lib.rs

@@ -190,6 +190,7 @@ mod_use!(cfg(target_os = "redox"), use_file);
 mod_use!(cfg(target_os = "solaris"), solaris_illumos);
 mod_use!(cfg(windows), windows);
 mod_use!(cfg(target_env = "sgx"), rdrand);
+mod_use!(cfg(target_os = "uefi"), rdrand);
 mod_use!(cfg(target_os = "wasi"), wasi);
 
 mod_use!(
@@ -231,6 +232,7 @@ mod_use!(
         target_os = "openbsd",
         target_os = "redox",
         target_os = "solaris",
+        target_os = "uefi",
         target_env = "sgx",
         windows,
         all(

src/rdrand.rs

@@ -9,11 +9,9 @@
 //! Implementation for SGX using RDRAND instruction
 use crate::Error;
 use core::mem;
-use core::arch::x86_64::_rdrand64_step;
+use core::arch::x86_64::{__cpuid, _rdrand64_step};
 use core::num::NonZeroU32;
-
-#[cfg(not(target_feature = "rdrand"))]
-compile_error!("enable rdrand target feature!");
+use lazy_static::lazy_static;
 
 // Recommendation from "Intel® Digital Random Number Generator (DRNG) Software
 // Implementation Guide" - Section 5.2.1 and "Intel® 64 and IA-32 Architectures
@@ -35,7 +33,19 @@ fn rdrand() -> Result<[u8; WORD_SIZE], Error> {
     Err(Error::UNKNOWN)
 }
 
+fn cpuid_check() -> bool {
+    const FEATURE_INFO_LEAF: u32 = 1;
+    const RDRAND_FLAG: u32 = 1 << 30;
+    // SAFETY: All platforms with CPUID support leaf 1
+    unsafe { __cpuid(FEATURE_INFO_LEAF).ecx & RDRAND_FLAG != 0 }
+}
+
 pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
+    lazy_static! { static ref HAS_RDRAND: bool = cpuid_check(); }
+    if cfg!(not(target_feature = "rdrand")) && !*HAS_RDRAND {
+        return Err(Error::UNAVAILABLE);
+    }
+
     // We use chunks_exact_mut instead of chunks_mut as it allows almost all
     // calls to memcpy to be elided by the compiler.
     let mut chunks = dest.chunks_exact_mut(WORD_SIZE);