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/** @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));
}
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