LinearAlloc.h revision 72e93344b4d1ffc71e9c832ec23de0657e5b04a5 
1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16/*
17 * Simple linear memory allocator.
18 */
19#ifndef _DALVIK_LINEARALLOC
20#define _DALVIK_LINEARALLOC
21
22/*
23 * If this is set, we create additional data structures and make many
24 * additional mprotect() calls.
25 * (this breaks the debugger because the debugBreakpointCount cannot be updated)
26 */
27#define ENFORCE_READ_ONLY   false
28
29/*
30 * Linear allocation state.  We could tuck this into the start of the
31 * allocated region, but that would prevent us from sharing the rest of
32 * that first page.
33 */
34typedef struct LinearAllocHdr {
35    int     curOffset;          /* offset where next data goes */
36    pthread_mutex_t lock;       /* controls updates to this struct */
37
38    char*   mapAddr;            /* start of mmap()ed region */
39    int     mapLength;          /* length of region */
40    int     firstOffset;        /* for chasing through */
41
42    short*  writeRefCount;      /* for ENFORCE_READ_ONLY */
43} LinearAllocHdr;
44
45
46/*
47 * Create a new alloc region.
48 */
49LinearAllocHdr* dvmLinearAllocCreate(Object* classLoader);
50
51/*
52 * Destroy a region.
53 */
54void dvmLinearAllocDestroy(Object* classLoader);
55
56/*
57 * Allocate a chunk of memory.  The memory will be zeroed out.
58 *
59 * For ENFORCE_READ_ONLY, call dvmLinearReadOnly on the result.
60 */
61void* dvmLinearAlloc(Object* classLoader, size_t size);
62
63/*
64 * Reallocate a chunk.  The original storage is not released, but may be
65 * erased to aid debugging.
66 *
67 * For ENFORCE_READ_ONLY, call dvmLinearReadOnly on the result.  Also, the
68 * caller should probably mark the "mem" argument read-only before calling.
69 */
70void* dvmLinearRealloc(Object* classLoader, void* mem, size_t newSize);
71
72/* don't call these directly */
73void dvmLinearSetReadOnly(Object* classLoader, void* mem);
74void dvmLinearSetReadWrite(Object* classLoader, void* mem);
75
76/*
77 * Mark a chunk of memory from Alloc or Realloc as read-only.  This must
78 * be done after all changes to the block of memory have been made.  This
79 * actually operates on a page granularity.
80 */
81INLINE void dvmLinearReadOnly(Object* classLoader, void* mem)
82{
83    if (ENFORCE_READ_ONLY && mem != NULL)
84        dvmLinearSetReadOnly(classLoader, mem);
85}
86
87/*
88 * Make a chunk of memory writable again.
89 */
90INLINE void dvmLinearReadWrite(Object* classLoader, void* mem)
91{
92    if (ENFORCE_READ_ONLY && mem != NULL)
93        dvmLinearSetReadWrite(classLoader, mem);
94}
95
96/*
97 * Free a chunk.  Does not increase available storage, but the freed area
98 * may be erased to aid debugging.
99 */
100void dvmLinearFree(Object* classLoader, void* mem);
101
102/*
103 * Helper function; allocates new storage and copies "str" into it.
104 *
105 * For ENFORCE_READ_ONLY, do *not* call dvmLinearReadOnly on the result.
106 * This is done automatically.
107 */
108char* dvmLinearStrdup(Object* classLoader, const char* str);
109
110/*
111 * Dump the contents of a linear alloc area.
112 */
113void dvmLinearAllocDump(Object* classLoader);
114
115/*
116 * Determine if [start, start+length) is contained in the in-use area of
117 * a single LinearAlloc.  The full set of linear allocators is scanned.
118 */
119bool dvmLinearAllocContains(const void* start, size_t length);
120
121#endif /*_DALVIK_LINEARALLOC*/
122