Move SYS_GETRANDOM stuff from C to Rust.

crypto/crypto.c

@@ -12,10 +12,6 @@
  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
 
-#if defined(__linux__)
-#define _GNU_SOURCE
-#endif
-
 #include <GFp/cpu.h>
 #include "internal.h"
 
@@ -46,29 +42,3 @@ HIDDEN uint32_t GFp_ia32cap_P[4] = {0};
 HIDDEN uint32_t GFp_armcap_P = 0;
 
 #endif
-
-#if defined(__linux__)
-
-// The getrandom syscall was added in Linux 3.17. For some important platforms,
-// we also support building against older kernels' headers. For other
-// platforms, the newer kernel's headers are required. */
-#if !defined(SYS_getrandom)
-#if defined(OPENSSL_AARCH64)
-#define SYS_getrandom 278
-#elif defined(OPENSSL_ARM)
-#define SYS_getrandom 384
-#elif defined(OPENSSL_X86)
-#define SYS_getrandom 355
-#elif defined(OPENSSL_X86_64)
-#define SYS_getrandom 318
-#else
-#include <sys/syscall.h>
-#if !defined(SYS_getrandom)
-#error "Error: Kernel headers are too old; SYS_getrandom not defined."
-#endif
-#endif
-
-#endif
-
-const long GFp_SYS_GETRANDOM = SYS_getrandom;
-#endif

src/rand.rs

@@ -127,15 +127,24 @@ mod sysrand_chunk {
     use crate::error;
     use libc::{self, size_t};
 
-    extern "C" {
-        static GFp_SYS_GETRANDOM: libc::c_long;
-    }
-
     #[inline]
     pub fn chunk(dest: &mut [u8]) -> Result<usize, error::Unspecified> {
+        // See `SYS_getrandom` in #include <sys/syscall.h>.
+
+        #[cfg(target_arch = "aarch64")]
+        const SYS_GETRANDOM: libc::c_long = 278;
+
+        #[cfg(target_arch = "arm")]
+        const SYS_GETRANDOM: libc::c_long = 384;
+
+        #[cfg(target_arch = "x86")]
+        const SYS_GETRANDOM: libc::c_long = 355;
+
+        #[cfg(target_arch = "x86_64")]
+        const SYS_GETRANDOM: libc::c_long = 318;
+
         let chunk_len: size_t = dest.len();
-        let flags: libc::c_uint = 0;
-        let r = unsafe { libc::syscall(GFp_SYS_GETRANDOM, dest.as_mut_ptr(), chunk_len, flags) };
+        let r = unsafe { libc::syscall(SYS_GETRANDOM, dest.as_mut_ptr(), chunk_len, 0) };
         if r < 0 {
             if unsafe { *libc::__errno_location() } == libc::EINTR {
                 // If an interrupt occurs while getrandom() is blocking to wait