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 * Target-specific optimization and run-time hints
18 */
19
20
21 #include "Dalvik.h"
22 #include "libdex/DexClass.h"
23
24 #include <stdlib.h>
25 #include <stddef.h>
26 #include <sys/stat.h>
27
28
29 /*
30 * The class loader will associate with each method a 32-bit info word
31 * (jniArgInfo) to support JNI calls. The high order 4 bits of this word
32 * are the same for all targets, while the lower 28 are used for hints to
33 * allow accelerated JNI bridge transfers.
34 *
35 * jniArgInfo (32-bit int) layout:
36 *
37 * SRRRHHHH HHHHHHHH HHHHHHHH HHHHHHHH
38 *
39 * S - if set, ignore the hints and do things the hard way (scan signature)
40 * R - return-type enumeration
41 * H - target-specific hints (see below for details)
42 *
43 * This function produces x86-specific hints for the standard 32-bit 386 ABI.
44 * Note that the JNI requirements are very close to the 386 runtime model. In
45 * particular, natural datatype alignments do not apply to passed arguments.
46 * All arguments have 32-bit alignment. As a result, we don't have to worry
47 * about padding - just total size. The only tricky bit is that floating point
48 * return values come back on the FP stack.
49 *
50 *
51 * 386 ABI JNI hint format
52 *
53 * ZZZZ ZZZZZZZZ AAAAAAAA AAAAAAAA
54 *
55 * Z - reserved, must be 0
56 * A - size of variable argument block in 32-bit words (note - does not
57 * include JNIEnv or clazz)
58 *
59 * For the 386 ABI, valid hints should always be generated.
60 */
dvmPlatformInvokeHints(const DexProto * proto)61 u4 dvmPlatformInvokeHints( const DexProto* proto)
62 {
63 const char* sig = dexProtoGetShorty(proto);
64 unsigned int jniHints, wordCount;
65 char sigByte;
66
67 wordCount = 0;
68 while (true) {
69 sigByte = *(sig++);
70
71 if (sigByte == '\0')
72 break;
73
74 wordCount++;
75
76 if (sigByte == 'D' || sigByte == 'J') {
77 wordCount++;
78 }
79 }
80
81 if (wordCount > 0xFFFF) {
82 /* Invalid - Dex file limitation */
83 jniHints = DALVIK_JNI_NO_ARG_INFO;
84 } else {
85 jniHints = wordCount;
86 }
87
88 return jniHints;
89 }
90