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Diffstat (limited to 'wsutil/ws_cpuid.h')
| -rw-r--r-- | wsutil/ws_cpuid.h | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/wsutil/ws_cpuid.h b/wsutil/ws_cpuid.h new file mode 100644 index 00000000..cc17e2a5 --- /dev/null +++ b/wsutil/ws_cpuid.h @@ -0,0 +1,141 @@ +/** @file + * Get the CPU info on x86 processors that support it + * + * Wireshark - Network traffic analyzer + * By Gerald Combs <gerald@wireshark.org> + * Copyright 1998 Gerald Combs + * + * SPDX-License-Identifier: GPL-2.0-or-later + */ + +/* + * Get CPU info on platforms where the x86 cpuid instruction can be used. + * + * Skip 32-bit versions for GCC and Clang, as older IA-32 processors don't + * have cpuid. + * + * Intel has documented the CPUID instruction in the "Intel(r) 64 and IA-32 + * Architectures Developer's Manual" at + * + * https://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-vol-2a-manual.html + * + * The ws_cpuid() routine will return 0 if cpuinfo isn't available, including + * on non-x86 platforms and on 32-bit x86 platforms with GCC and Clang, as + * well as non-MSVC and non-GCC-or-Clang platforms. + * + * The "selector" argument to ws_cpuid() is the "initial EAX value" for the + * instruction. The initial ECX value is 0. + * + * The "CPUInfo" argument points to 4 32-bit values into which the + * resulting values of EAX, EBX, ECX, and EDX are store, in order. + */ + +#include "ws_attributes.h" + +#include <inttypes.h> +#include <stdbool.h> + +#if defined(_MSC_VER) /* MSVC */ + +/* + * XXX - do the same IA-32 (which doesn't have CPUID prior to some versions + * of the 80486 and all versions of the 80586^Woriginal Pentium) vs. + * x86-64 (which always has CPUID) stuff that we do with GCC/Clang? + * + * You will probably not be happy running current versions of Wireshark + * on an 80386 or 80486 machine, and we're dropping support for IA-32 + * on Windows anyway, so the answer is probably "no". + */ +#if defined(_M_IX86) || defined(_M_X64) +static bool +ws_cpuid(uint32_t *CPUInfo, uint32_t selector) +{ + /* https://docs.microsoft.com/en-us/cpp/intrinsics/cpuid-cpuidex */ + + CPUInfo[0] = CPUInfo[1] = CPUInfo[2] = CPUInfo[3] = 0; + __cpuid((int *) CPUInfo, selector); + /* XXX, how to check if it's supported on MSVC? just in case clear all flags above */ + return true; +} +#else /* not x86 */ +static bool +ws_cpuid(uint32_t *CPUInfo _U_, int selector _U_) +{ + /* Not x86, so no cpuid instruction */ + return false; +} +#endif + +#elif defined(__GNUC__) /* GCC/clang */ + +#if defined(__x86_64__) +static inline bool +ws_cpuid(uint32_t *CPUInfo, int selector) +{ + __asm__ __volatile__("cpuid" + : "=a" (CPUInfo[0]), + "=b" (CPUInfo[1]), + "=c" (CPUInfo[2]), + "=d" (CPUInfo[3]) + : "a" (selector), + "c" (0)); + return true; +} +#elif defined(__i386__) +static bool +ws_cpuid(uint32_t *CPUInfo _U_, int selector _U_) +{ + /* + * TODO: need a test if older processors have the cpuid instruction. + * + * The correct way to test for this, according to the Intel64/IA-32 + * documentation from Intel, in section 17.1 "USING THE CPUID + * INSTRUCTION", is to try to change the ID bit (bit 21) in + * EFLAGS. If it can be changed, the machine supports CPUID, + * otherwise it doesn't. + * + * Some 486's, and all subsequent processors, support CPUID. + * + * For those who are curious, the way you distinguish between + * an 80386 and an 80486 is to try to set the flag in EFLAGS + * that causes unaligned accesses to fault - that's bit 18. + * However, if the SMAP bit is set in CR4, that bit controls + * whether explicit supervisor-mode access to user-mode pages + * are allowed, so that should presumably only be done in a + * very controlled environment, such as the system boot process. + * + * So, if you want to find out what type of CPU the system has, + * it's probably best to ask the OS, if it supplies the result + * of any CPU type testing it's done. + */ + return false; +} +#else /* not x86 */ +static bool +ws_cpuid(uint32_t *CPUInfo _U_, int selector _U_) +{ + /* Not x86, so no cpuid instruction */ + return false; +} +#endif + +#else /* Other compilers */ + +static bool +ws_cpuid(uint32_t *CPUInfo _U_, int selector _U_) +{ + return false; +} +#endif + +static int +ws_cpuid_sse42(void) +{ + uint32_t CPUInfo[4]; + + if (!ws_cpuid(CPUInfo, 1)) + return 0; + + /* in ECX bit 20 toggled on */ + return (CPUInfo[2] & (1 << 20)); +} |