cpuid.c

/*
 * Copyright Supranational LLC
 * Licensed under the Apache License, Version 2.0, see LICENSE for details.
 * SPDX-License-Identifier: Apache-2.0
 */

#if (defined(__GNUC__) || defined(__clang__) || defined(__SUNPRO_C)) && !defined(_WIN32)
__attribute__((visibility("hidden")))
#endif
int __blst_platform_cap = 0;

#if defined(__x86_64__) || defined(__x86_64) || (defined(_M_X64) && !defined(_M_ARM64EC))

# if defined(__GNUC__) || defined(__clang__) || defined(__SUNPRO_C)
static void __cpuidex(int info[4], int func, int sub)
{
    int eax, ebx, ecx, edx;

    __asm__("cpuid" : "=a"(eax), "=b"(ebx), "=c"(ecx), "=d"(edx)
                    : "a"(func), "c"(sub));

    info[0] = eax;
    info[1] = ebx;
    info[2] = ecx;
    info[3] = edx;
}
# else
#  include <intrin.h>
# endif

# if defined(__GNUC__) || defined(__clang__)
__attribute__((constructor))
# endif
static int __blst_cpuid(void)
{
    int info[4], cap = 0;

    __cpuidex(info, 0, 0);
    if (info[0] > 6) {
        __cpuidex(info, 7, 0);
        cap |= (info[1]>>19) & 1; /* ADX */
        cap |= (info[1]>>28) & 2; /* SHA */
    }

    __blst_platform_cap = cap;

    return 0;
}

# if defined(_MSC_VER) && !defined(__clang__) && !defined(__BLST_DLL_MAIN__)
#  pragma section(".CRT$XCU",read)
__declspec(allocate(".CRT$XCU")) static int (*p)(void) = __blst_cpuid;
# elif defined(__SUNPRO_C)
#  pragma init(__blst_cpuid)
# endif

#elif defined(__aarch64__) || defined(__aarch64) || defined(_M_ARM64) || defined(_M_ARM64EC)

# if defined(__linux__) && (defined(__GNUC__) || defined(__clang__))
extern unsigned long getauxval(unsigned long type) __attribute__ ((weak));

__attribute__((constructor))
static int __blst_cpuid(void)
{
    int cap = 0;

    if (getauxval) {
        unsigned long hwcap_ce = getauxval(16);
        cap = (hwcap_ce>>6) & 1; /* SHA256 */
    }

    __blst_platform_cap = cap;

    return 0;
}
# elif defined(__APPLE__) && (defined(__GNUC__) || defined(__clang__))
__attribute__((constructor))
static int __blst_cpuid()
{
    __blst_platform_cap = 1; /* SHA256 */
    return 0;
}
# elif defined(__FreeBSD__) && __FreeBSD__ >= 12
#  include <sys/auxv.h>
__attribute__((constructor))
static int __blst_cpuid()
{
    unsigned long cap;

    if (elf_aux_info(AT_HWCAP, &cap, sizeof(cap)) == 0)
        __blst_platform_cap = (cap & HWCAP_SHA2) != 0;

    return 0;
}
# elif defined(_WIN64)
int IsProcessorFeaturePresent(int);

#  if defined(__GNUC__) || defined(__clang__)
__attribute__((constructor))
#  endif
static int __blst_cpuid(void)
{
    __blst_platform_cap = IsProcessorFeaturePresent(30); /* AES, SHA1, SHA2 */

    return 0;
}

#  if defined(_MSC_VER) && !defined(__clang__) && !defined(__BLST_DLL_MAIN__)
#   pragma section(".CRT$XCU",read)
__declspec(allocate(".CRT$XCU")) static int (*p)(void) = __blst_cpuid;
#  endif
# endif

#endif

#if defined(_WIN64) && defined(__BLST_DLL_MAIN__)
# define IsProcessorFeaturePresent mask_IsProcessorFeaturePresent
# define WIN32_LEAN_AND_MEAN
# include <windows.h>

BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD dwReason, LPVOID lpvReserved)
{
    if (dwReason == DLL_PROCESS_ATTACH) {
        DisableThreadLibraryCalls(hinstDLL);
        __blst_cpuid();
    }

    return TRUE;

    (void)lpvReserved;
}

# if defined(_MSC_VER)
/*
 * Even though we don't have memcpy/memset anywhere, MSVC compiler
 * generates calls to them as it recognizes corresponding patterns.
 */
#pragma function(memcpy)
void *memcpy(unsigned char *dst, const unsigned char *src, size_t n)
{
    void *ret = dst;

    while(n--)
        *dst++ = *src++;

    return ret;
}

#pragma function(memset)
void *memset(unsigned char *dst, int c, size_t n)
{
    void *ret = dst;

    while(n--)
        *dst++ = (unsigned char)c;

    return ret;
}
# endif
#endif