int15.c

Go to the documentation of this file.

/*
 * Copyright (C) 2006 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 );

#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <realmode.h>
#include <bios.h>
#include <memsizes.h>
#include <ipxe/io.h>
#include <ipxe/memmap.h>

/**
 * @file
 *
 * Memory mapping
 *
 */

/** Magic value for INT 15,e820 calls */
#define SMAP ( 0x534d4150 )

/** An INT 15,e820 memory map entry */
struct e820_entry {
        /** Start of region */
        uint64_t start;
        /** Length of region */
        uint64_t len;
        /** Type of region */
        uint32_t type;
        /** Extended attributes (optional) */
        uint32_t attrs;
} __attribute__ (( packed ));

#define E820_TYPE_RAM           1 /**< Normal memory */
#define E820_TYPE_RESERVED      2 /**< Reserved and unavailable */
#define E820_TYPE_ACPI          3 /**< ACPI reclaim memory */
#define E820_TYPE_NVS           4 /**< ACPI NVS memory */

#define E820_ATTR_ENABLED       0x00000001UL
#define E820_ATTR_NONVOLATILE   0x00000002UL
#define E820_ATTR_UNKNOWN       0xfffffffcUL

#define E820_MIN_SIZE           20

/** Buffer for INT 15,e820 calls */
static struct e820_entry __bss16 ( e820buf );
#define e820buf __use_data16 ( e820buf )

/** We are running during POST; inhibit INT 15,e820 and INT 15,e801 */
uint8_t __bss16 ( memmap_post );
#define memmap_post __use_data16 ( memmap_post )

/**
 * Get size of extended memory via INT 15,e801
 *
 * @ret extmem          Extended memory size, in kB, or 0
 */
static unsigned int extmemsize_e801 ( void ) {
        uint16_t extmem_1m_to_16m_k, extmem_16m_plus_64k;
        uint16_t confmem_1m_to_16m_k, confmem_16m_plus_64k;
        unsigned int flags;
        unsigned int extmem;

        /* Inhibit INT 15,e801 during POST */
        if ( memmap_post ) {
                DBG ( "INT 15,e801 not available during POST\n" );
                return 0;
        }

        __asm__ __volatile__ ( REAL_CODE ( "stc\n\t"
                                           "int $0x15\n\t"
                                           "pushfw\n\t"
                                           "popw %w0\n\t" )
                               : "=R" ( flags ),
                                 "=a" ( extmem_1m_to_16m_k ),
                                 "=b" ( extmem_16m_plus_64k ),
                                 "=c" ( confmem_1m_to_16m_k ),
                                 "=d" ( confmem_16m_plus_64k )
                               : "a" ( 0xe801 ) );

        if ( flags & CF ) {
                DBG ( "INT 15,e801 failed with CF set\n" );
                return 0;
        }

        if ( ! ( extmem_1m_to_16m_k | extmem_16m_plus_64k ) ) {
                DBG ( "INT 15,e801 extmem=0, using confmem\n" );
                extmem_1m_to_16m_k = confmem_1m_to_16m_k;
                extmem_16m_plus_64k = confmem_16m_plus_64k;
        }

        extmem = ( extmem_1m_to_16m_k + ( extmem_16m_plus_64k * 64 ) );
        DBG ( "INT 15,e801 extended memory size %d+64*%d=%d kB "
              "[100000,%llx)\n", extmem_1m_to_16m_k, extmem_16m_plus_64k,
              extmem, ( 0x100000 + ( ( ( uint64_t ) extmem ) * 1024 ) ) );

        /* Sanity check.  Some BIOSes report the entire 4GB address
         * space as available, which cannot be correct (since that
         * would leave no address space available for 32-bit PCI
         * BARs).
         */
        if ( extmem == ( 0x400000 - 0x400 ) ) {
                DBG ( "INT 15,e801 reported whole 4GB; assuming insane\n" );
                return 0;
        }

        return extmem;
}

/**
 * Get size of extended memory via INT 15,88
 *
 * @ret extmem          Extended memory size, in kB
 */
static unsigned int extmemsize_88 ( void ) {
        uint16_t extmem;

        /* Ignore CF; it is not reliable for this call */
        __asm__ __volatile__ ( REAL_CODE ( "int $0x15" )
                               : "=a" ( extmem ) : "a" ( 0x8800 ) );

        DBG ( "INT 15,88 extended memory size %d kB [100000, %x)\n",
              extmem, ( 0x100000 + ( extmem * 1024 ) ) );
        return extmem;
}

/**
 * Get size of extended memory
 *
 * @ret extmem          Extended memory size, in kB
 *
 * Note that this is only an approximation; for an accurate picture,
 * use the E820 memory map obtained via memmap_describe();
 */
unsigned int extmemsize ( void ) {
        unsigned int extmem_e801;
        unsigned int extmem_88;

        /* Try INT 15,e801 first, then fall back to INT 15,88 */
        extmem_88 = extmemsize_88();
        extmem_e801 = extmemsize_e801();
        return ( extmem_e801 ? extmem_e801 : extmem_88 );
}

/**
 * Get e820 memory map
 *
 * @v region            Memory region of interest to be updated
 * @ret rc              Return status code
 */
static int meme820 ( struct memmap_region *region ) {
        unsigned int count = 0;
        uint64_t start = 0;
        uint64_t len = 0;
        uint32_t next = 0;
        uint32_t smap;
        uint32_t size;
        unsigned int flags;
        unsigned int discard_D;

        /* Inhibit INT 15,e820 during POST */
        if ( memmap_post ) {
                DBG ( "INT 15,e820 not available during POST\n" );
                return -ENOTTY;
        }

        /* Clear the E820 buffer.  Do this once before starting,
         * rather than on each call; some BIOSes rely on the contents
         * being preserved between calls.
         */
        memset ( &e820buf, 0, sizeof ( e820buf ) );

        do {
                /* Some BIOSes corrupt %esi for fun. Guard against
                 * this by telling gcc that all non-output registers
                 * may be corrupted.
                 */
                __asm__ __volatile__ ( REAL_CODE ( "pushl %%ebp\n\t"
                                                   "stc\n\t"
                                                   "int $0x15\n\t"
                                                   "pushfw\n\t"
                                                   "popw %%dx\n\t"
                                                   "popl %%ebp\n\t" )
                                       : "=a" ( smap ), "=b" ( next ),
                                         "=c" ( size ), "=d" ( flags ),
                                         "=D" ( discard_D )
                                       : "a" ( 0xe820 ), "b" ( next ),
                                         "D" ( __from_data16 ( &e820buf ) ),
                                         "c" ( sizeof ( e820buf ) ),
                                         "d" ( SMAP )
                                       : "esi", "memory" );

                if ( smap != SMAP ) {
                        DBG ( "INT 15,e820 failed SMAP signature check\n" );
                        return -ENOTSUP;
                }

                if ( size < E820_MIN_SIZE ) {
                        DBG ( "INT 15,e820 returned only %d bytes\n", size );
                        return -EINVAL;
                }

                if ( flags & CF ) {
                        DBG ( "INT 15,e820 terminated on CF set\n" );
                        break;
                }

                DBG ( "INT 15,e820 region [%llx,%llx) type %d",
                      e820buf.start, ( e820buf.start + e820buf.len ),
                      ( int ) e820buf.type );
                if ( size > offsetof ( typeof ( e820buf ), attrs ) ) {
                        DBG ( " (%s", ( ( e820buf.attrs & E820_ATTR_ENABLED )
                                        ? "enabled" : "disabled" ) );
                        if ( e820buf.attrs & E820_ATTR_NONVOLATILE )
                                DBG ( ", non-volatile" );
                        if ( e820buf.attrs & E820_ATTR_UNKNOWN )
                                DBG ( ", other [%08x]", e820buf.attrs );
                        DBG ( ")" );
                }
                DBG ( "\n" );

                /* Discard non-RAM regions */
                if ( e820buf.type != E820_TYPE_RAM )
                        continue;

                /* Check extended attributes, if present */
                if ( size > offsetof ( typeof ( e820buf ), attrs ) ) {
                        if ( ! ( e820buf.attrs & E820_ATTR_ENABLED ) )
                                continue;
                        if ( e820buf.attrs & E820_ATTR_NONVOLATILE )
                                continue;
                }

                /* Check for adjacent regions and merge them */
                if ( e820buf.start == ( start + len ) ) {
                        len += e820buf.len;
                } else {
                        start = e820buf.start;
                        len = e820buf.len;
                }

                /* Sanity check: first region (base memory) should
                 * start at address zero.
                 */
                if ( ( count == 0 ) && ( start != 0 ) ) {
                        DBG ( "INT 15,e820 region 0 starts at %llx (expected "
                              "0); assuming insane\n", start );
                        return -EINVAL;
                }

                /* Sanity check: second region (extended memory)
                 * should start at address 0x100000.
                 */
                if ( ( count == 1 ) && ( start != 0x100000 ) ) {
                        DBG ( "INT 15,e820 region 1 starts at %llx (expected "
                              "100000); assuming insane\n", start );
                        return -EINVAL;
                }

                /* Update region of interest */
                memmap_update ( region, start, len, MEMMAP_FL_MEMORY, "e820" );
                count++;

        } while ( next != 0 );

        /* Sanity checks.  Some BIOSes report complete garbage via INT
         * 15,e820 (especially at POST time), despite passing the
         * signature checks.  We currently check for a base memory
         * region (starting at 0) and at least one high memory region
         * (starting at 0x100000).
         */
        if ( count < 2 ) {
                DBG ( "INT 15,e820 returned only %d regions; assuming "
                      "insane\n", count );
                return -EINVAL;
        }

        return 0;
}

/**
 * Describe memory region from system memory map
 *
 * @v min               Minimum address
 * @v hide              Hide in-use regions from the memory map
 * @v region            Region descriptor to fill in
 */
static void int15_describe ( uint64_t min, int hide,
                             struct memmap_region *region ) {
        unsigned int basemem;
        unsigned int extmem;
        uint64_t inaccessible;
        int rc;

        /* Initialise region */
        memmap_init ( min, region );

        /* Mark addresses above 4GB as inaccessible: we have no way to
         * access them either in a 32-bit build or in a 64-bit build
         * (since the 64-bit build identity-maps only the 32-bit
         * address space).
         */
        inaccessible = ( 1ULL << 32 );
        memmap_update ( region, inaccessible, -inaccessible,
                        MEMMAP_FL_INACCESSIBLE, NULL );

        /* Enable/disable INT 15 interception as applicable */
        int15_intercept ( hide );

        /* Try INT 15,e820 first, falling back to constructing a map
         * from basemem and extmem sizes
         */
        if ( ( rc = meme820 ( region ) ) == 0 ) {
                DBG ( "Obtained system memory map via INT 15,e820\n" );
        } else {
                basemem = basememsize();
                DBG ( "FBMS base memory size %d kB [0,%x)\n",
                      basemem, ( basemem * 1024 ) );
                extmem = extmemsize();
                memmap_update ( region, 0, ( basemem * 1024 ),
                                MEMMAP_FL_MEMORY, "basemem" );
                memmap_update ( region, 0x100000, ( extmem * 1024 ),
                                MEMMAP_FL_MEMORY, "extmem" );
        }

        /* Restore INT 15 interception */
        int15_intercept ( 1 );
}

PROVIDE_MEMMAP ( int15, memmap_describe, int15_describe );