Annotation of prex-old/sys/mem/kmem.c, Revision 1.1.1.1.2.1
1.1 nbrk 1: /*-
2: * Copyright (c) 2005-2006, Kohsuke Ohtani
3: * All rights reserved.
4: *
5: * Redistribution and use in source and binary forms, with or without
6: * modification, are permitted provided that the following conditions
7: * are met:
8: * 1. Redistributions of source code must retain the above copyright
9: * notice, this list of conditions and the following disclaimer.
10: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: * 3. Neither the name of the author nor the names of any co-contributors
14: * may be used to endorse or promote products derived from this software
15: * without specific prior written permission.
16: *
17: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20: * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27: * SUCH DAMAGE.
28: */
29:
30: /*
31: * kmem.c - kernel memory allocator
32: */
33:
34: /*
1.1.1.1.2.1! nbrk 35: * This is a memory allocator optimized for the low foot print
! 36: * kernel. It works on top of the underlying page allocator, and
! 37: * manages more smaller memory than page size. It will divide one
! 38: * page into two or more blocks, and each page is linked as a
! 39: * kernel page.
1.1 nbrk 40: *
41: * There are following 3 linked lists to manage used/free blocks.
42: * 1) All pages allocated for the kernel memory are linked.
43: * 2) All blocks divided in the same page are linked.
44: * 3) All free blocks of the same size are linked.
45: *
46: * Currently, it can not handle the memory size exceeding one page.
47: * Instead, a driver can use page_alloc() to allocate larger memory.
48: *
1.1.1.1.2.1! nbrk 49: * The kmem functions are used by not only the kernel core but
! 50: * also by the buggy drivers. If such kernel code illegally
! 51: * writes data in exceeding the allocated area, the system will
! 52: * crash easily. In order to detect the memory over run, each
! 53: * free block has a magic ID.
1.1 nbrk 54: */
55:
56: #include <kernel.h>
57: #include <page.h>
58: #include <sched.h>
59: #include <vm.h>
1.1.1.1.2.1! nbrk 60: #include <kmem.h>
1.1 nbrk 61:
62: /*
63: * Block header
64: *
65: * All free blocks that have same size are linked each other.
66: * In addition, all free blocks within same page are also linked.
67: */
68: struct block_hdr {
69: u_short magic; /* magic number */
70: u_short size; /* size of this block */
71: struct list link; /* link to the free list */
72: struct block_hdr *pg_next; /* next block in same page */
73: };
74:
75: /*
76: * Page header
77: *
1.1.1.1.2.1! nbrk 78: * The page header is placed at the top of each page. This
! 79: * header is used in order to free the page when there are no
! 80: * used block left in the page. If nr_alloc value becomes zero,
! 81: * that page can be removed from kernel page.
1.1 nbrk 82: */
83: struct page_hdr {
84: u_short magic; /* magic number */
85: u_short nallocs; /* number of allocated blocks */
86: struct block_hdr first_blk; /* first block in this page */
87: };
88:
89: #define ALIGN_SIZE 16
90: #define ALIGN_MASK (ALIGN_SIZE - 1)
1.1.1.1.2.1! nbrk 91: #define ALLOC_ALIGN(n) (((vaddr_t)(n) + ALIGN_MASK) & (vaddr_t)~ALIGN_MASK)
1.1 nbrk 92:
93: #define BLOCK_MAGIC 0xdead
94: #define PAGE_MAGIC 0xbeef
95:
96: #define BLKHDR_SIZE (sizeof(struct block_hdr))
97: #define PGHDR_SIZE (sizeof(struct page_hdr))
1.1.1.1.2.1! nbrk 98: #define MAX_ALLOC_SIZE (size_t)(PAGE_SIZE - PGHDR_SIZE)
1.1 nbrk 99:
100: #define MIN_BLOCK_SIZE (BLKHDR_SIZE + 16)
101: #define MAX_BLOCK_SIZE (u_short)(PAGE_SIZE - (PGHDR_SIZE - BLKHDR_SIZE))
102:
103: /* macro to point the page header from specific address */
104: #define PAGE_TOP(n) (struct page_hdr *) \
1.1.1.1.2.1! nbrk 105: ((vaddr_t)(n) & (vaddr_t)~(PAGE_SIZE - 1))
1.1 nbrk 106:
107: /* index of free block list */
1.1.1.1.2.1! nbrk 108: #define BLKIDX(b) ((u_int)((b)->size) >> 4)
1.1 nbrk 109:
110: /* number of free block list */
111: #define NR_BLOCK_LIST (PAGE_SIZE / ALIGN_SIZE)
112:
113: /**
114: * Array of the head block of free block list.
115: *
116: * The index of array is decided by the size of each block.
117: * All block has the size of the multiple of 16.
118: *
119: * ie. free_blocks[0] = list for 16 byte block
120: * free_blocks[1] = list for 32 byte block
121: * free_blocks[2] = list for 48 byte block
122: * .
123: * .
124: * free_blocks[255] = list for 4096 byte block
125: *
126: * Generally, only one list is used to search the free block with
1.1.1.1.2.1! nbrk 127: * a first fit algorithm. Basically, this allocator also uses a
! 128: * first fit method. However it uses multiple lists corresponding
! 129: * to each block size. A search is started from the list of the
! 130: * requested size. So, it is not necessary to search smaller
! 131: * block's list wastefully.
! 132: *
! 133: * Most of kernel memory allocator is using 2^n as block size.
! 134: * But, these implementation will throw away much memory that
! 135: * the block size is not fit. This is not suitable for the
! 136: * embedded system with low foot print.
1.1 nbrk 137: */
138: static struct list free_blocks[NR_BLOCK_LIST];
139:
140: /*
141: * Find the free block for the specified size.
142: * Returns pointer to free block, or NULL on failure.
143: *
144: * First, it searches from the list of same size. If it does not
145: * exists, then it will search the list of larger one.
146: * It will use the block of smallest size that satisfies the
147: * specified size.
148: */
149: static struct block_hdr *
150: block_find(size_t size)
151: {
152: int i;
153: list_t n;
154:
1.1.1.1.2.1! nbrk 155: for (i = (int)((u_int)size >> 4); i < NR_BLOCK_LIST; i++) {
1.1 nbrk 156: if (!list_empty(&free_blocks[i]))
157: break;
158: }
159: if (i >= NR_BLOCK_LIST)
160: return NULL;
161:
162: n = list_first(&free_blocks[i]);
163: return list_entry(n, struct block_hdr, link);
164: }
165:
166: /*
167: * Allocate memory block for kernel
168: *
169: * This function does not fill the allocated block by 0 for performance.
170: * kmem_alloc() returns NULL on failure.
171: */
172: void *
173: kmem_alloc(size_t size)
174: {
1.1.1.1.2.1! nbrk 175: struct block_hdr *blk, *newblk;
1.1 nbrk 176: struct page_hdr *pg;
177: void *p;
178:
179: ASSERT(irq_level == 0);
180:
181: sched_lock(); /* Lock scheduler */
182: /*
183: * First, the free block of enough size is searched
184: * from the page already used. If it does not exist,
185: * new page is allocated for free block.
186: */
187: size = ALLOC_ALIGN(size + BLKHDR_SIZE);
188:
189: ASSERT(size && size <= MAX_ALLOC_SIZE);
190:
191: blk = block_find(size);
192: if (blk) {
193: /* Block found */
194: list_remove(&blk->link); /* Remove from free list */
195: pg = PAGE_TOP(blk); /* Get the page address */
196: } else {
197: /* No block found. Allocate new page */
198: if ((pg = page_alloc(PAGE_SIZE)) == NULL) {
199: sched_unlock();
200: return NULL;
201: }
202: pg = phys_to_virt(pg);
203: pg->nallocs = 0;
204: pg->magic = PAGE_MAGIC;
205:
206: /* Setup first block */
207: blk = &(pg->first_blk);
208: blk->magic = BLOCK_MAGIC;
209: blk->size = MAX_BLOCK_SIZE;
210: blk->pg_next = NULL;
211: }
212: /* Sanity check */
213: if (pg->magic != PAGE_MAGIC || blk->magic != BLOCK_MAGIC)
1.1.1.1.2.1! nbrk 214: panic("kmem_alloc: overrun");
1.1 nbrk 215: /*
216: * If the found block is large enough, split it.
217: */
218: if (blk->size - size >= MIN_BLOCK_SIZE) {
219: /* Make new block */
1.1.1.1.2.1! nbrk 220: newblk = (struct block_hdr *)((char *)blk + size);
! 221: newblk->magic = BLOCK_MAGIC;
! 222: newblk->size = (u_short)(blk->size - size);
! 223: list_insert(&free_blocks[BLKIDX(newblk)], &newblk->link);
1.1 nbrk 224:
225: /* Update page list */
1.1.1.1.2.1! nbrk 226: newblk->pg_next = blk->pg_next;
! 227: blk->pg_next = newblk;
1.1 nbrk 228:
229: blk->size = (u_short)size;
230: }
231: /* Increment allocation count of this page */
232: pg->nallocs++;
1.1.1.1.2.1! nbrk 233: p = (char *)blk + BLKHDR_SIZE;
1.1 nbrk 234: sched_unlock();
235: return p;
236: }
237:
238: /*
239: * Free allocated memory block.
240: *
241: * Some kernel does not release the free page for the kernel memory
242: * because it is needed to allocate immediately later. For example,
243: * it is efficient here if the free page is just linked to the list
244: * of the biggest size. However, consider the case where a driver
245: * requires many small memories temporarily. After these pages are
246: * freed, they can not be reused for an application.
247: */
248: void
249: kmem_free(void *ptr)
250: {
251: struct block_hdr *blk;
252: struct page_hdr *pg;
253:
254: ASSERT(irq_level == 0);
255: ASSERT(ptr);
256:
257: /* Lock scheduler */
258: sched_lock();
259:
260: /* Get the block header */
1.1.1.1.2.1! nbrk 261: blk = (struct block_hdr *)((char *)ptr - BLKHDR_SIZE);
1.1 nbrk 262: if (blk->magic != BLOCK_MAGIC)
1.1.1.1.2.1! nbrk 263: panic("kmem_free: invalid address");
1.1 nbrk 264:
265: /*
1.1.1.1.2.1! nbrk 266: * Return the block to free list. Since kernel code will
! 267: * request fixed size of memory block, we don't merge the
! 268: * blocks to use it as cache.
1.1 nbrk 269: */
270: list_insert(&free_blocks[BLKIDX(blk)], &blk->link);
271:
272: /* Decrement allocation count of this page */
273: pg = PAGE_TOP(blk);
274: if (--pg->nallocs <= 0) {
275: /*
276: * No allocated block in this page.
277: * Remove all blocks and deallocate this page.
278: */
279: for (blk = &(pg->first_blk); blk != NULL; blk = blk->pg_next) {
280: list_remove(&blk->link); /* Remove from free list */
281: }
282: pg->magic = 0;
283: page_free(virt_to_phys(pg), PAGE_SIZE);
284: }
285: sched_unlock();
286: }
287:
288: /*
289: * Map specified virtual address to the kernel address
290: * Returns kernel address on success, or NULL if no mapped memory.
291: */
292: void *
293: kmem_map(void *addr, size_t size)
294: {
295: void *phys;
296:
297: phys = vm_translate(addr, size);
298: if (phys == NULL)
299: return NULL;
300: return phys_to_virt(phys);
301: }
302:
303: void
304: kmem_init(void)
305: {
306: int i;
307:
308: for (i = 0; i < NR_BLOCK_LIST; i++)
309: list_init(&free_blocks[i]);
310: }
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