cpuid.c

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/*
 * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
FILE_SECBOOT ( PERMITTED );

#include <string.h>
#include <errno.h>
#include <ipxe/cpuid.h>

/** @file
 *
 * x86 CPU feature detection
 *
 */

/** Colour for debug messages */
#define colour 0x861d

/**
 * Check whether or not CPUID instruction is supported
 *
 * @ret rc              Return status code
 */
static int cpuid_instruction_supported ( void ) {
        unsigned long original;
        unsigned long inverted;

        /* Check for instruction existence via flag modifiability */
        __asm__ ( "pushf\n\t"
                  "pushf\n\t"
                  "pop %0\n\t"
                  "mov %0,%1\n\t"
                  "xor %2,%1\n\t"
                  "push %1\n\t"
                  "popf\n\t"
                  "pushf\n\t"
                  "pop %1\n\t"
                  "popf\n\t"
                  : "=&r" ( original ), "=&r" ( inverted )
                  : "ir" ( CPUID_FLAG ) );
        if ( ! ( ( original ^ inverted ) & CPUID_FLAG ) ) {
                DBGC ( colour, "CPUID instruction is not supported\n" );
                return -ENOTSUP;
        }

        return 0;
}

/**
 * Check whether or not CPUID function is supported
 *
 * @v function          CPUID function
 * @ret rc              Return status code
 */
int cpuid_supported ( uint32_t function ) {
        uint32_t max_function;
        uint32_t discard_b;
        uint32_t discard_c;
        uint32_t discard_d;
        int rc;

        /* Check that CPUID instruction is available */
        if ( ( rc = cpuid_instruction_supported() ) != 0 )
                return rc;

        /* Find highest supported function number within this family */
        cpuid ( ( function & ( CPUID_EXTENDED | CPUID_HYPERVISOR ) ), 0,
                  &max_function, &discard_b, &discard_c, &discard_d );

        /* Fail if maximum function number is meaningless (e.g. if we
         * are attempting to call an extended function on a CPU which
         * does not support them).
         */
        if ( ( max_function & CPUID_AMD_CHECK_MASK ) !=
             ( function & CPUID_AMD_CHECK_MASK ) ) {
                DBGC ( colour, "CPUID invalid maximum function %#08x\n",
                       max_function );
                return -EINVAL;
        }

        /* Fail if this function is not supported */
        if ( function > max_function ) {
                DBGC ( colour, "CPUID function %#08x not supported\n",
                       function );
                return -ENOTTY;
        }

        return 0;
}

/**
 * Get Intel-defined x86 CPU features
 *
 * @v features          x86 CPU features to fill in
 */
static void x86_intel_features ( struct x86_features *features ) {
        uint32_t discard_a;
        uint32_t discard_b;
        int rc;

        /* Check that features are available via CPUID */
        if ( ( rc = cpuid_supported ( CPUID_FEATURES ) ) != 0 ) {
                DBGC ( features, "CPUID has no Intel-defined features\n" );
                return;
        }

        /* Get features */
        cpuid ( CPUID_FEATURES, 0, &discard_a, &discard_b,
                &features->intel.ecx, &features->intel.edx );
        DBGC ( features, "CPUID Intel features: %%ecx=%08x, %%edx=%08x\n",
               features->intel.ecx, features->intel.edx );

}

/**
 * Get AMD-defined x86 CPU features
 *
 * @v features          x86 CPU features to fill in
 */
static void x86_amd_features ( struct x86_features *features ) {
        uint32_t discard_a;
        uint32_t discard_b;
        int rc;

        /* Check that features are available via CPUID */
        if ( ( rc = cpuid_supported ( CPUID_AMD_FEATURES ) ) != 0 ) {
                DBGC ( features, "CPUID has no AMD-defined features\n" );
                return;
        }

        /* Get features */
        cpuid ( CPUID_AMD_FEATURES, 0, &discard_a, &discard_b,
                &features->amd.ecx, &features->amd.edx );
        DBGC ( features, "CPUID AMD features: %%ecx=%08x, %%edx=%08x\n",
               features->amd.ecx, features->amd.edx );
}

/**
 * Get x86 CPU features
 *
 * @v features          x86 CPU features to fill in
 */
void x86_features ( struct x86_features *features ) {

        /* Clear all features */
        memset ( features, 0, sizeof ( *features ) );

        /* Get Intel-defined features */
        x86_intel_features ( features );

        /* Get AMD-defined features */
        x86_amd_features ( features );
}