forked from osmocom/wireshark
139 lines
4.0 KiB
C
139 lines
4.0 KiB
C
/** @file
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* Get the CPU info on x86 processors that support it
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*
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* Wireshark - Network traffic analyzer
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* By Gerald Combs <gerald@wireshark.org>
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* Copyright 1998 Gerald Combs
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*
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* SPDX-License-Identifier: GPL-2.0-or-later
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*/
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/*
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* Get CPU info on platforms where the x86 cpuid instruction can be used.
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*
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* Skip 32-bit versions for GCC and Clang, as older IA-32 processors don't
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* have cpuid.
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*
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* Intel has documented the CPUID instruction in the "Intel(r) 64 and IA-32
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* Architectures Developer's Manual" at
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*
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* https://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-vol-2a-manual.html
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*
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* The ws_cpuid() routine will return 0 if cpuinfo isn't available, including
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* on non-x86 platforms and on 32-bit x86 platforms with GCC and Clang, as
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* well as non-MSVC and non-GCC-or-Clang platforms.
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*
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* The "selector" argument to ws_cpuid() is the "initial EAX value" for the
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* instruction. The initial ECX value is 0.
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*
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* The "CPUInfo" argument points to 4 32-bit values into which the
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* resulting values of EAX, EBX, ECX, and EDX are store, in order.
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*/
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#include "ws_attributes.h"
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#if defined(_MSC_VER) /* MSVC */
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/*
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* XXX - do the same IA-32 (which doesn't have CPUID prior to some versions
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* of the 80486 and all versions of the 80586^Woriginal Pentium) vs.
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* x86-64 (which always has CPUID) stuff that we do with GCC/Clang?
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*
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* You will probably not be happy running current versions of Wireshark
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* on an 80386 or 80486 machine, and we're dropping support for IA-32
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* on Windows anyway, so the answer is probably "no".
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*/
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#if defined(_M_IX86) || defined(_M_X64)
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static gboolean
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ws_cpuid(guint32 *CPUInfo, guint32 selector)
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{
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/* https://docs.microsoft.com/en-us/cpp/intrinsics/cpuid-cpuidex */
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CPUInfo[0] = CPUInfo[1] = CPUInfo[2] = CPUInfo[3] = 0;
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__cpuid((int *) CPUInfo, selector);
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/* XXX, how to check if it's supported on MSVC? just in case clear all flags above */
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return TRUE;
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}
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#else /* not x86 */
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static gboolean
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ws_cpuid(guint32 *CPUInfo _U_, int selector _U_)
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{
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/* Not x86, so no cpuid instruction */
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return FALSE;
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}
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#endif
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#elif defined(__GNUC__) /* GCC/clang */
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#if defined(__x86_64__)
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static inline gboolean
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ws_cpuid(guint32 *CPUInfo, int selector)
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{
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__asm__ __volatile__("cpuid"
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: "=a" (CPUInfo[0]),
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"=b" (CPUInfo[1]),
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"=c" (CPUInfo[2]),
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"=d" (CPUInfo[3])
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: "a" (selector),
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"c" (0));
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return TRUE;
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}
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#elif defined(__i386__)
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static gboolean
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ws_cpuid(guint32 *CPUInfo _U_, int selector _U_)
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{
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/*
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* TODO: need a test if older processors have the cpuid instruction.
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*
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* The correct way to test for this, according to the Intel64/IA-32
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* documentation from Intel, in section 17.1 "USING THE CPUID
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* INSTRUCTION", is to try to change the ID bit (bit 21) in
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* EFLAGS. If it can be changed, the machine supports CPUID,
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* otherwise it doesn't.
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*
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* Some 486's, and all subsequent processors, support CPUID.
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*
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* For those who are curious, the way you distinguish between
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* an 80386 and an 80486 is to try to set the flag in EFLAGS
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* that causes unaligned accesses to fault - that's bit 18.
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* However, if the SMAP bit is set in CR4, that bit controls
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* whether explicit supervisor-mode access to user-mode pages
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* are allowed, so that should presumably only be done in a
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* very controlled environment, such as the system boot process.
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*
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* So, if you want to find out what type of CPU the system has,
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* it's probably best to ask the OS, if it supplies the result
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* of any CPU type testing it's done.
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*/
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return FALSE;
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}
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#else /* not x86 */
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static gboolean
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ws_cpuid(guint32 *CPUInfo _U_, int selector _U_)
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{
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/* Not x86, so no cpuid instruction */
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return FALSE;
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}
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#endif
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#else /* Other compilers */
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static gboolean
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ws_cpuid(guint32 *CPUInfo _U_, int selector _U_)
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{
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return FALSE;
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}
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#endif
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static int
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ws_cpuid_sse42(void)
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{
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guint32 CPUInfo[4];
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if (!ws_cpuid(CPUInfo, 1))
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return 0;
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/* in ECX bit 20 toggled on */
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return (CPUInfo[2] & (1 << 20));
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}
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