Error compiling AESNI in Mbed-TLS with clang on Windows

[sergio-nsk]

Summary

clang does not have MSVS intrinsics, the pre-processor condition below does not cover this case if clang runs in MSVC compatibility mode

mbedtls/library/aesni.h

Lines 42 to 46 in 1ec6906

	#if defined(_MSC_VER)
	/* Visual Studio supports AESNI intrinsics since VS 2008 SP1. We only support
	* VS 2013 and up for other reasons anyway, so no need to check the version. */
	#define MBEDTLS_AESNI_HAVE_INTRINSICS
	#endif

It should be

#if defined(_MSC_VER) && !defined(__clang__)
/* Visual Studio supports AESNI intrinsics since VS 2008 SP1. We only support
 * VS 2013 and up for other reasons anyway, so no need to check the version. */
#define MBEDTLS_AESNI_HAVE_INTRINSICS
#endif

System information

Mbed TLS version 2.28.5, 3.5.0
Operating system and version: Windows 10/11
Default configuration.
Compiler: LLVM clang, clang-cl

Expected behavior

Built without errors.

Actual behavior

Got many errors

/mbedtls/library/aesni.c:62:17: error: passing 'unsigned int[4]' to parameter of type 'int *' converts between pointers to integer types with different sign [-Werror,-Wpointer-sign]
        __cpuid(info, 1);
                ^~~~
C:\PROGRA~1\LLVM\lib\clang\16\include\intrin.h:60:17: note: passing argument to parameter here
void __cpuid(int[4], int);
                ^
/mbedtls/library/aesni.c:102:21: error: call to undeclared function '_mm_aesdec_si128'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
            state = _mm_aesdec_si128(state, *rk);
                    ^
/mbedtls/library/aesni.c:102:21: note: did you mean '_mm_and_si128'?
C:\PROGRA~1\LLVM\lib\clang\16\include\emmintrin.h:2611:46: note: '_mm_and_si128' declared here
static __inline__ __m128i __DEFAULT_FN_ATTRS _mm_and_si128(__m128i __a,
                                             ^
<...>

Additional infromation

Fixing PRs will be offered soon.

[gilles-peskine-arm]

This is different, but closely related to #8332, and at first glance I think #8339 should fix this. Can you please check if #8339 works for you?

[sergio-nsk]

@gilles-peskine-arm Yes, it looks very similarly. I tried to search existing issues with my errors and could not find them. #8339 will not work for me, because clang does not define the macro __GNUC__ and <cpuid.h> does not exist on Windows.

There is the task Consider removing AESNI assembly #8231, maybe it's more correct that #8339 does not update aesni.c for MinGW but disables easni.c like I want to do it in easni.h.

[lpy4105]

#8339 will not work for me, because clang does not define the macro __GNUC__ and <cpuid.h> does not exist on Windows.

I believe it would fix the issue arround __cpuid, but we do have issue of AESNI implementation selection for clang in MSVC compatible mode.

[pengsel]

Is there any way to solve this compilation problem without modifying the code?