1 files changed, 141 insertions, 0 deletions
diff --git a/wsutil/ws_cpuid.h b/wsutil/ws_cpuid.h
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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));
+}