aboutsummaryrefslogtreecommitdiffstats
path: root/gpxe/src/arch/i386/interface/pcbios/memtop_umalloc.c
blob: 744d8e3053964d031441189a3530573040649adf (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
/*
 * Copyright (C) 2007 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/**
 * @file
 *
 * External memory allocation
 *
 */

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

/** Alignment of external allocated memory */
#define EM_ALIGN ( 4 * 1024 )

/** Equivalent of NOWHERE for user pointers */
#define UNOWHERE ( ~UNULL )

/** An external memory block */
struct external_memory {
	/** Size of this memory block (excluding this header) */
	size_t size;
	/** Block is currently in use */
	int used;
};

/** Top of heap */
static userptr_t top = UNULL;

/** Bottom of heap (current lowest allocated block) */
static userptr_t bottom = UNULL;

/**
 * Initialise external heap
 *
 * @ret rc		Return status code
 */
static int init_eheap ( void ) {
	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;
}

/**
 * Collect free blocks
 *
 */
static void ecollect_free ( void ) {
	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 ) ) );
	}
}

/**
 * Reallocate external memory
 *
 * @v old_ptr		Memory previously allocated by umalloc(), or UNULL
 * @v new_size		Requested size
 * @ret new_ptr		Allocated memory, or UNULL
 *
 * Calling realloc() with a new size of zero is a valid way to free a
 * memory block.
 */
static userptr_t memtop_urealloc ( userptr_t ptr, size_t new_size ) {
	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 );