memtop_umalloc.c File Reference

External memory allocation. More...

#include <limits.h>
#include <errno.h>
#include <gpxe/uaccess.h>
#include <gpxe/hidemem.h>
#include <gpxe/memmap.h>
#include <gpxe/umalloc.h>

Go to the source code of this file.

Data Structures
struct	external_memory
	An external memory block. More...
Defines
#define	EM_ALIGN   ( 4 * 1024 )
	Alignment of external allocated memory.
#define	UNOWHERE   ( ~UNULL )
	Equivalent of NOWHERE for user pointers.
Functions
	FILE_LICENCE (GPL2_OR_LATER)
static int	init_eheap (void)
	Initialise external heap.
static void	ecollect_free (void)
	Collect free blocks.
static userptr_t	memtop_urealloc (userptr_t ptr, size_t new_size)
	Reallocate external memory.
	PROVIDE_UMALLOC (memtop, urealloc, memtop_urealloc)
Variables
static userptr_t	top = UNULL
	Top of heap.
static userptr_t	bottom = UNULL
	Bottom of heap (current lowest allocated block).

---

Detailed Description

External memory allocation.

Definition in file memtop_umalloc.c.

---

Define Documentation

#define EM_ALIGN   ( 4 * 1024 )

Alignment of external allocated memory.

Definition at line 36 of file memtop_umalloc.c.

Referenced by memtop_urealloc().

#define UNOWHERE   ( ~UNULL )

Equivalent of NOWHERE for user pointers.

Definition at line 39 of file memtop_umalloc.c.

---

Function Documentation

FILE_LICENCE

(

GPL2_OR_LATER

)

static int init_eheap

(

void

)

[static]

Initialise external heap.

Return values:

rc

Return status code

Definition at line 60 of file memtop_umalloc.c.

References bottom, memory_map::count, DBG, memory_region::end, ENOMEM, get_memmap(), phys_to_user(), memory_map::regions, memory_region::start, top, UINT_MAX, and user_to_phys().

Referenced by memtop_urealloc().

                               {
        struct memory_map memmap;
        unsigned long heap_size = 0;
        unsigned int i;

        DBG ( "Allocating external heap\n" );

        get_memmap ( &memmap );
        for ( i = 0 ; i < memmap.count ; i++ ) {
                struct memory_region *region = &memmap.regions[i];
                unsigned long r_start, r_end;
                unsigned long r_size;

                DBG ( "Considering [%llx,%llx)\n", region->start, region->end);

                /* Truncate block to 4GB */
                if ( region->start > UINT_MAX ) {
                        DBG ( "...starts after 4GB\n" );
                        continue;
                }
                r_start = region->start;
                if ( region->end > UINT_MAX ) {
                        DBG ( "...end truncated to 4GB\n" );
                        r_end = 0; /* =4GB, given the wraparound */
                } else {
                        r_end = region->end;
                }

                /* Use largest block */
                r_size = ( r_end - r_start );
                if ( r_size > heap_size ) {
                        DBG ( "...new best block found\n" );
                        top = bottom = phys_to_user ( r_end );
                        heap_size = r_size;
                }
        }

        if ( ! heap_size ) {
                DBG ( "No external heap available\n" );
                return -ENOMEM;
        }

        DBG ( "External heap grows downwards from %lx\n",
              user_to_phys ( top, 0 ) );
        return 0;
}

static void ecollect_free

(

void

)

[static]

Collect free blocks.

Definition at line 111 of file memtop_umalloc.c.

References bottom, copy_from_user(), DBG, external_memory::size, top, external_memory::used, user_to_phys(), and userptr_add().

Referenced by memtop_urealloc().

                                   {
        struct external_memory extmem;

        /* Walk the free list and collect empty blocks */
        while ( bottom != top ) {
                copy_from_user ( &extmem, bottom, -sizeof ( extmem ),
                                 sizeof ( extmem ) );
                if ( extmem.used )
                        break;
                DBG ( "EXTMEM freeing [%lx,%lx)\n", user_to_phys ( bottom, 0 ),
                      user_to_phys ( bottom, extmem.size ) );
                bottom = userptr_add ( bottom,
                                       ( extmem.size + sizeof ( extmem ) ) );
        }
}

static userptr_t memtop_urealloc	(	userptr_t	ptr,
		size_t	new_size
	)			[static]

Reallocate external memory.

Parameters:

	old_ptr	Memory previously allocated by umalloc(), or UNULL
	new_size	Requested size

Return values:

new_ptr

Allocated memory, or UNULL

Calling realloc() with a new size of zero is a valid way to free a memory block.

Definition at line 137 of file memtop_umalloc.c.

References bottom, copy_from_user(), copy_to_user(), DBG, ecollect_free(), EM_ALIGN, hide_umalloc(), init_eheap(), memmove_user(), external_memory::size, top, UNOWHERE, UNULL, external_memory::used, user_to_phys(), and userptr_add().

                                                                    {
        struct external_memory extmem;
        userptr_t new = ptr;
        size_t align;
        int rc;

        /* Initialise external memory allocator if necessary */
        if ( bottom == top ) {
                if ( ( rc = init_eheap() ) != 0 )
                        return UNULL;
        }

        /* Get block properties into extmem */
        if ( ptr && ( ptr != UNOWHERE ) ) {
                /* Determine old size */
                copy_from_user ( &extmem, ptr, -sizeof ( extmem ),
                                 sizeof ( extmem ) );
        } else {
                /* Create a zero-length block */
                ptr = bottom = userptr_add ( bottom, -sizeof ( extmem ) );
                DBG ( "EXTMEM allocating [%lx,%lx)\n",
                      user_to_phys ( ptr, 0 ), user_to_phys ( ptr, 0 ) );
                extmem.size = 0;
        }
        extmem.used = ( new_size > 0 );

        /* Expand/shrink block if possible */
        if ( ptr == bottom ) {
                /* Update block */
                new = userptr_add ( ptr, - ( new_size - extmem.size ) );
                align = ( user_to_phys ( new, 0 ) & ( EM_ALIGN - 1 ) );
                new_size += align;
                new = userptr_add ( new, -align );
                DBG ( "EXTMEM expanding [%lx,%lx) to [%lx,%lx)\n",
                      user_to_phys ( ptr, 0 ),
                      user_to_phys ( ptr, extmem.size ),
                      user_to_phys ( new, 0 ),
                      user_to_phys ( new, new_size ));
                memmove_user ( new, 0, ptr, 0, ( ( extmem.size < new_size ) ?
                                                 extmem.size : new_size ) );
                extmem.size = new_size;
                bottom = new;
        } else {
                /* Cannot expand; can only pretend to shrink */
                if ( new_size > extmem.size ) {
                        /* Refuse to expand */
                        DBG ( "EXTMEM cannot expand [%lx,%lx)\n",
                              user_to_phys ( ptr, 0 ),
                              user_to_phys ( ptr, extmem.size ) );
                        return UNULL;
                }
        }

        /* Write back block properties */
        copy_to_user ( new, -sizeof ( extmem ), &extmem,
                       sizeof ( extmem ) );

        /* Collect any free blocks and update hidden memory region */
        ecollect_free();
        hide_umalloc ( user_to_phys ( bottom, -sizeof ( extmem ) ),
                       user_to_phys ( top, 0 ) );

        return ( new_size ? new : UNOWHERE );
}

PROVIDE_UMALLOC	(	memtop	,
		urealloc	,
		memtop_urealloc
	)

---

Variable Documentation

userptr_t top = UNULL [static]

Top of heap.

Definition at line 50 of file memtop_umalloc.c.

Referenced by ecollect_free(), init_eheap(), and memtop_urealloc().

userptr_t bottom = UNULL [static]

Bottom of heap (current lowest allocated block).

Definition at line 53 of file memtop_umalloc.c.

Referenced by ecollect_free(), init_eheap(), and memtop_urealloc().