1 /*
2 * Copyright 2011, 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 #include "StubLayout.h"
18
19 #include "utils/flush_cpu_cache.h"
20 #include "utils/raw_ostream.h"
21
22 #include <stdint.h>
23 #include <stdlib.h>
24 #include <sys/mman.h>
25
26 #ifdef __arm__
27 #define STUB_SIZE 8 // 8 bytes (2 words)
28 #endif
29
StubLayout()30 StubLayout::StubLayout() : table(NULL), count(0) {
31 }
32
initStubTable(unsigned char * table_,size_t count_)33 void StubLayout::initStubTable(unsigned char *table_, size_t count_) {
34 table = table_;
35 count = count_;
36 }
37
allocateStub(void * addr)38 void *StubLayout::allocateStub(void *addr) {
39 #ifdef __arm__
40 if (count == 0) {
41 // No free stub slot is available
42 return NULL;
43 }
44
45 // Initialize the stub
46 unsigned char *stub = table;
47 setStubAddress(stub, addr);
48
49 // Increase the free stub slot pointer
50 table += STUB_SIZE;
51 count--;
52
53 return stub;
54
55 #else
56 return NULL;
57 #endif
58 }
59
setStubAddress(void * stub_,void * addr)60 void StubLayout::setStubAddress(void *stub_, void *addr) {
61 #ifdef __arm__
62 uint8_t *stub = (uint8_t *)stub_;
63 stub[0] = 0x04; // ldr pc, [pc, #-4]
64 stub[1] = 0xf0; // ldr pc, [pc, #-4]
65 stub[2] = 0x1f; // ldr pc, [pc, #-4]
66 stub[3] = 0xe5; // ldr pc, [pc, #-4]
67
68 void **target = (void **)(stub + 4);
69 *target = addr;
70 #endif
71 }
72
calcStubTableSize(size_t count) const73 size_t StubLayout::calcStubTableSize(size_t count) const {
74 #ifdef __arm__
75 return count * STUB_SIZE;
76 #else
77 return 0;
78 #endif
79 }
80