build: ensure memcpy is optimzed in SGX

Author: Taowyoo

mbedtls-sys/build/build.rs

@@ -63,7 +63,12 @@ impl BuildConfig {
                 if FEATURES.have_platform_component("time", "custom") {
                     writeln!(f, "long long mbedtls_time(long long*);")?;
                 }
-                f.write_all(config::SUFFIX.as_bytes())
+                f.write_all(config::SUFFIX.as_bytes())?;
+
+                if features::env_have_target_cfg("env", "sgx") {
+                    f.write_all(config::INLINE_MEMCPY_SUFFIX.as_bytes())?;
+                }
+                Ok(())
             })
             .expect("config.h I/O error");
     }
@@ -105,6 +110,11 @@ impl BuildConfig {
             cflags.push("-D_FORTIFY_SOURCE=0".into());
             cflags.push("-fno-stack-protector".into());
         }
+        if features::env_have_target_cfg("env", "sgx") {
+            // In SGX, define memcpy to another string, so could ensure the inline functions added above in config.h
+            // always take effect. This is necessary because source file may include `string.h` before include `config.h`.
+            cflags.push("-Dmemcpy=not_memcpy_".into());
+        }
 
         BuildConfig {
             config_h,

mbedtls-sys/build/config.rs

@@ -444,3 +444,17 @@ pub const SUFFIX: &'static str = r#"
 #include "mbedtls/target_config.h"
 #endif
 "#;
+
+pub const INLINE_MEMCPY_SUFFIX: &'static str = r#"
+// In SGX, use following macro to ensure all calls to memcpy is calling __builtin_memcpy
+// so that ensure compiler can optimize it
+#define memcpy not_memcpy_
+#include <string.h>
+#undef memcpy
+#ifndef MEMCPY_WRAPPER_
+#define MEMCPY_WRAPPER_
+static inline void memcpy(void *dst, const void *src, size_t n) {
+    __builtin_memcpy(dst, src, n);
+}
+#endif
+"#;

mbedtls-sys/build/features.rs

@@ -91,7 +91,7 @@ impl Features {
     }
 }
 
-fn env_have_target_cfg(var: &'static str, value: &'static str) -> bool {
+pub(super) fn env_have_target_cfg(var: &'static str, value: &'static str) -> bool {
     let env = format!("CARGO_CFG_TARGET_{}", var).to_uppercase().replace("-", "_");
     env::var_os(env).map_or(false, |s| s == value)
 }