memmap.c File Reference

Memory mapping. More...

#include <stdint.h>
#include <errno.h>
#include <realmode.h>
#include <bios.h>
#include <memsizes.h>
#include <gpxe/memmap.h>

Go to the source code of this file.

Data Structures
struct	e820_entry
	An INT 15,e820 memory map entry. More...
Defines
#define	SMAP   ( 0x534d4150 )
	Magic value for INT 15,e820 calls.
#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
#define	e820buf   __use_data16 ( e820buf )
Functions
	FILE_LICENCE (GPL2_OR_LATER)
static struct e820_entry	__bss16 (e820buf)
	Buffer for INT 15,e820 calls.
static unsigned int	extmemsize_e801 (void)
	Get size of extended memory via INT 15,e801.
static unsigned int	extmemsize_88 (void)
	Get size of extended memory via INT 15,88.
unsigned int	extmemsize (void)
	Get size of extended memory.
static int	meme820 (struct memory_map *memmap)
	Get e820 memory map.
void	get_memmap (struct memory_map *memmap)
	Get memory map.
Variables
struct e820_entry	packed
	An INT 15,e820 memory map entry.

---

Detailed Description

Memory mapping.

Definition in file memmap.c.

---

Define Documentation

#define SMAP   ( 0x534d4150 )

Magic value for INT 15,e820 calls.

Definition at line 36 of file memmap.c.

Referenced by meme820().

#define E820_TYPE_RAM   1

Normal memory.

Definition at line 50 of file memmap.c.

#define E820_TYPE_RESERVED   2

Reserved and unavailable.

Definition at line 51 of file memmap.c.

#define E820_TYPE_ACPI   3

ACPI reclaim memory.

Definition at line 52 of file memmap.c.

#define E820_TYPE_NVS   4

ACPI NVS memory.

Definition at line 53 of file memmap.c.

#define E820_ATTR_ENABLED   0x00000001UL

Definition at line 55 of file memmap.c.

Referenced by meme820().

#define E820_ATTR_NONVOLATILE   0x00000002UL

Definition at line 56 of file memmap.c.

Referenced by meme820().

#define E820_ATTR_UNKNOWN   0xfffffffcUL

Definition at line 57 of file memmap.c.

Referenced by meme820().

#define E820_MIN_SIZE   20

Definition at line 59 of file memmap.c.

Referenced by meme820().

#define e820buf   __use_data16 ( e820buf )

Definition at line 63 of file memmap.c.

Referenced by meme820().

---

Function Documentation

FILE_LICENCE

(

GPL2_OR_LATER

)

static struct e820_entry __bss16

(

e820buf

)

[static, read]

Buffer for INT 15,e820 calls.

static unsigned int extmemsize_e801

(

void

)

[static]

Get size of extended memory via INT 15,e801.

Return values:

extmem

Extended memory size, in kB, or 0

Definition at line 70 of file memmap.c.

References __asm__(), CF, DBG, and REAL_CODE.

Referenced by extmemsize().

                                             {
        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;

        __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;
}

static unsigned int extmemsize_88

(

void

)

[static]

Get size of extended memory via INT 15,88.

Return values:

extmem

Extended memory size, in kB

Definition at line 121 of file memmap.c.

References __asm__(), DBG, and REAL_CODE.

Referenced by extmemsize().

                                           {
        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;
}

unsigned int extmemsize

(

void

)

Get size of extended memory.

Return values:

extmem

Extended memory size, in kB

Note that this is only an approximation; for an accurate picture, use the E820 memory map obtained via get_memmap();

Definition at line 141 of file memmap.c.

References extmemsize_88(), and extmemsize_e801().

Referenced by get_memmap(), and nbi_process_segments().

                                 {
        unsigned int extmem;

        /* Try INT 15,e801 first, then fall back to INT 15,88 */
        extmem = extmemsize_e801();
        if ( ! extmem )
                extmem = extmemsize_88();
        return extmem;
}

static int meme820

(

struct memory_map *

memmap

)

[static]

Get e820 memory map.

Parameters:

memmap

Memory map to fill in

Return values:

rc

Return status code

Definition at line 157 of file memmap.c.

References __asm__(), __from_data16, CF, memory_map::count, DBG, E820_ATTR_ENABLED, E820_ATTR_NONVOLATILE, E820_ATTR_UNKNOWN, E820_MIN_SIZE, E820_TYPE_RAM, e820buf, EINVAL, memory_region::end, ENOTSUP, memset(), offsetof, REAL_CODE, memory_map::regions, size, SMAP, and memory_region::start.

Referenced by get_memmap().

                                                 {
        struct memory_region *region = memmap->regions;
        uint32_t next = 0;
        uint32_t smap;
        size_t size;
        unsigned int flags;
        unsigned int discard_D;

        /* 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 %zd bytes\n", size );
                        return -EINVAL;
                }

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

                /* If first region is not RAM, assume map is invalid */
                if ( ( memmap->count == 0 ) &&
                     ( e820buf.type != E820_TYPE_RAM ) ) {
                       DBG ( "INT 15,e820 failed, first entry not RAM\n" );
                       return -EINVAL;
                }

                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;
                }

                region->start = e820buf.start;
                region->end = e820buf.start + e820buf.len;
                region++;
                memmap->count++;

                if ( memmap->count >= ( sizeof ( memmap->regions ) /
                                        sizeof ( memmap->regions[0] ) ) ) {
                        DBG ( "INT 15,e820 too many regions returned\n" );
                        /* Not a fatal error; what we've got so far at
                         * least represents valid regions of memory,
                         * even if we couldn't get them all.
                         */
                        break;
                }
        } 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 ( memmap->count < 2 ) {
                DBG ( "INT 15,e820 returned only %d regions; assuming "
                      "insane\n", memmap->count );
                return -EINVAL;
        }
        if ( memmap->regions[0].start != 0 ) {
                DBG ( "INT 15,e820 region 0 starts at %llx (expected 0); "
                      "assuming insane\n", memmap->regions[0].start );
                return -EINVAL;
        }
        if ( memmap->regions[1].start != 0x100000 ) {
                DBG ( "INT 15,e820 region 1 starts at %llx (expected 100000); "
                      "assuming insane\n", memmap->regions[0].start );
                return -EINVAL;
        }

        return 0;
}

void get_memmap

(

struct memory_map *

memmap

)

Get memory map.

Parameters:

memmap

Memory map to fill in

Definition at line 285 of file memmap.c.

References basememsize(), memory_map::count, DBG, memory_region::end, extmemsize(), meme820(), memset(), memory_map::regions, and memory_region::start.

Referenced by com32_exec(), hide_etherboot(), init_eheap(), int13_boot(), multiboot_build_memmap(), phys_ram_within_limit(), prep_segment(), relocate(), and umalloc_test().

                                              {
        unsigned int basemem, extmem;
        int rc;

        DBG ( "Fetching system memory map\n" );

        /* Clear memory map */
        memset ( memmap, 0, sizeof ( *memmap ) );

        /* Get base and extended memory sizes */
        basemem = basememsize();
        DBG ( "FBMS base memory size %d kB [0,%x)\n",
              basemem, ( basemem * 1024 ) );
        extmem = extmemsize();
        
        /* Try INT 15,e820 first */
        if ( ( rc = meme820 ( memmap ) ) == 0 ) {
                DBG ( "Obtained system memory map via INT 15,e820\n" );
                return;
        }

        /* Fall back to constructing a map from basemem and extmem sizes */
        DBG ( "INT 15,e820 failed; constructing map\n" );
        memmap->regions[0].end = ( basemem * 1024 );
        memmap->regions[1].start = 0x100000;
        memmap->regions[1].end = 0x100000 + ( extmem * 1024 );
        memmap->count = 2;
}

---

Variable Documentation

struct e820_entry packed

An INT 15,e820 memory map entry.