1 /*
2 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "asm/codeBuffer.hpp"
27 #include "asm/macroAssembler.hpp"
28 #include "asm/macroAssembler.inline.hpp"
29 #include "gc/shared/collectedHeap.hpp"
30 #include "memory/universe.hpp"
31 #include "oops/compressedOops.hpp"
32 #include "runtime/icache.hpp"
33 #include "runtime/os.hpp"
34 #include "runtime/thread.hpp"
35
36
37 // Implementation of AbstractAssembler
38 //
39 // The AbstractAssembler is generating code into a CodeBuffer. To make code generation faster,
40 // the assembler keeps a copy of the code buffers boundaries & modifies them when
41 // emitting bytes rather than using the code buffers accessor functions all the time.
42 // The code buffer is updated via set_code_end(...) after emitting a whole instruction.
43
44 AbstractAssembler::AbstractAssembler(CodeBuffer* code) {
45 if (code == NULL) return;
46 CodeSection* cs = code->insts();
47 cs->clear_mark(); // new assembler kills old mark
48 if (cs->start() == NULL) {
49 vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "CodeCache: no room for %s", code->name());
50 }
51 _code_section = cs;
52 _oop_recorder= code->oop_recorder();
53 DEBUG_ONLY( _short_branch_delta = 0; )
54 }
55
56 void AbstractAssembler::set_code_section(CodeSection* cs) {
57 assert(cs->outer() == code_section()->outer(), "sanity");
58 assert(cs->is_allocated(), "need to pre-allocate this section");
59 cs->clear_mark(); // new assembly into this section kills old mark
60 _code_section = cs;
61 }
62
63 // Inform CodeBuffer that incoming code and relocation will be for stubs
64 address AbstractAssembler::start_a_stub(int required_space) {
65 CodeBuffer* cb = code();
66 CodeSection* cs = cb->stubs();
67 assert(_code_section == cb->insts(), "not in insts?");
68 if (cs->maybe_expand_to_ensure_remaining(required_space)
69 && cb->blob() == NULL) {
70 return NULL;
71 }
72 set_code_section(cs);
73 return pc();
74 }
75
76 // Inform CodeBuffer that incoming code and relocation will be code
77 // Should not be called if start_a_stub() returned NULL
78 void AbstractAssembler::end_a_stub() {
79 assert(_code_section == code()->stubs(), "not in stubs?");
80 set_code_section(code()->insts());
81 }
82
83 // Inform CodeBuffer that incoming code and relocation will be for stubs
84 address AbstractAssembler::start_a_const(int required_space, int required_align) {
85 CodeBuffer* cb = code();
86 CodeSection* cs = cb->consts();
87 assert(_code_section == cb->insts() || _code_section == cb->stubs(), "not in insts/stubs?");
88 address end = cs->end();
89 int pad = -(intptr_t)end & (required_align-1);
90 if (cs->maybe_expand_to_ensure_remaining(pad + required_space)) {
91 if (cb->blob() == NULL) return NULL;
92 end = cs->end(); // refresh pointer
93 }
94 if (pad > 0) {
95 while (--pad >= 0) { *end++ = 0; }
96 cs->set_end(end);
97 }
98 set_code_section(cs);
99 return end;
100 }
101
102 // Inform CodeBuffer that incoming code and relocation will be code
103 // in section cs (insts or stubs).
104 void AbstractAssembler::end_a_const(CodeSection* cs) {
105 assert(_code_section == code()->consts(), "not in consts?");
106 set_code_section(cs);
107 }
108
109 void AbstractAssembler::flush() {
110 ICache::invalidate_range(addr_at(0), offset());
111 }
112
113 void AbstractAssembler::bind(Label& L) {
114 if (L.is_bound()) {
115 // Assembler can bind a label more than once to the same place.
116 guarantee(L.loc() == locator(), "attempt to redefine label");
117 return;
118 }
119 L.bind_loc(locator());
120 L.patch_instructions((MacroAssembler*)this);
121 }
122
123 void AbstractAssembler::generate_stack_overflow_check(int frame_size_in_bytes) {
124 if (UseStackBanging) {
125 // Each code entry causes one stack bang n pages down the stack where n
126 // is configurable by StackShadowPages. The setting depends on the maximum
127 // depth of VM call stack or native before going back into java code,
128 // since only java code can raise a stack overflow exception using the
129 // stack banging mechanism. The VM and native code does not detect stack
130 // overflow.
131 // The code in JavaCalls::call() checks that there is at least n pages
132 // available, so all entry code needs to do is bang once for the end of
133 // this shadow zone.
134 // The entry code may need to bang additional pages if the framesize
135 // is greater than a page.
136
137 const int page_size = os::vm_page_size();
138 int bang_end = (int)JavaThread::stack_shadow_zone_size();
139
140 // This is how far the previous frame's stack banging extended.
141 const int bang_end_safe = bang_end;
142
143 if (frame_size_in_bytes > page_size) {
144 bang_end += frame_size_in_bytes;
145 }
146
147 int bang_offset = bang_end_safe;
148 while (bang_offset <= bang_end) {
149 // Need at least one stack bang at end of shadow zone.
150 bang_stack_with_offset(bang_offset);
151 bang_offset += page_size;
152 }
153 } // end (UseStackBanging)
154 }
155
156 void Label::add_patch_at(CodeBuffer* cb, int branch_loc, const char* file, int line) {
157 assert(_loc == -1, "Label is unbound");
158 // Don't add patch locations during scratch emit.
159 if (cb->insts()->scratch_emit()) { return; }
160 if (_patch_index < PatchCacheSize) {
161 _patches[_patch_index] = branch_loc;
162 #ifdef ASSERT
163 _lines[_patch_index] = line;
164 _files[_patch_index] = file;
165 #endif
166 } else {
167 if (_patch_overflow == NULL) {
168 _patch_overflow = cb->create_patch_overflow();
169 }
170 _patch_overflow->push(branch_loc);
171 }
172 ++_patch_index;
173 }
174
175 void Label::patch_instructions(MacroAssembler* masm) {
176 assert(is_bound(), "Label is bound");
177 CodeBuffer* cb = masm->code();
178 int target_sect = CodeBuffer::locator_sect(loc());
179 address target = cb->locator_address(loc());
180 while (_patch_index > 0) {
181 --_patch_index;
182 int branch_loc;
183 int line = 0;
184 const char* file = NULL;
185 if (_patch_index >= PatchCacheSize) {
186 branch_loc = _patch_overflow->pop();
187 } else {
188 branch_loc = _patches[_patch_index];
189 #ifdef ASSERT
190 line = _lines[_patch_index];
191 file = _files[_patch_index];
192 #endif
193 }
194 int branch_sect = CodeBuffer::locator_sect(branch_loc);
195 address branch = cb->locator_address(branch_loc);
196 if (branch_sect == CodeBuffer::SECT_CONSTS) {
197 // The thing to patch is a constant word.
198 *(address*)branch = target;
199 continue;
200 }
201
202 #ifdef ASSERT
203 // Cross-section branches only work if the
204 // intermediate section boundaries are frozen.
205 if (target_sect != branch_sect) {
206 for (int n = MIN2(target_sect, branch_sect),
207 nlimit = (target_sect + branch_sect) - n;
208 n < nlimit; n++) {
209 CodeSection* cs = cb->code_section(n);
210 assert(cs->is_frozen(), "cross-section branch needs stable offsets");
211 }
212 }
213 #endif //ASSERT
214
215 // Push the target offset into the branch instruction.
216 masm->pd_patch_instruction(branch, target, file, line);
217 }
218 }
219
220 void AbstractAssembler::block_comment(const char* comment) {
221 if (sect() == CodeBuffer::SECT_INSTS) {
222 code_section()->outer()->block_comment(offset(), comment);
223 }
224 }
225
226 const char* AbstractAssembler::code_string(const char* str) {
227 if (sect() == CodeBuffer::SECT_INSTS || sect() == CodeBuffer::SECT_STUBS) {
228 return code_section()->outer()->code_string(str);
229 }
230 return NULL;
231 }
232
233 bool MacroAssembler::uses_implicit_null_check(void* address) {
234 // Exception handler checks the nmethod's implicit null checks table
235 // only when this method returns false.
236 uintptr_t addr = reinterpret_cast<uintptr_t>(address);
237 uintptr_t page_size = (uintptr_t)os::vm_page_size();
238 #ifdef _LP64
239 if (UseCompressedOops && CompressedOops::base() != NULL) {
240 // A SEGV can legitimately happen in C2 code at address
241 // (heap_base + offset) if Matcher::narrow_oop_use_complex_address
242 // is configured to allow narrow oops field loads to be implicitly
243 // null checked
244 uintptr_t start = (uintptr_t)CompressedOops::base();
245 uintptr_t end = start + page_size;
246 if (addr >= start && addr < end) {
247 return true;
248 }
249 }
250 #endif
251 return addr < page_size;
252 }
253
254 bool MacroAssembler::needs_explicit_null_check(intptr_t offset) {
255 // The offset -1 is used (hardcoded) in a number of places in C1 and MacroAssembler
256 // to indicate an unknown offset. For example, TemplateTable::pop_and_check_object(Register r)
257 // calls MacroAssembler::null_check(Register reg, int offset = -1) which gets here
258 // with -1. Another example is GraphBuilder::access_field(...) which uses -1 as placeholder
259 // for offsets to be patched in later. The -1 there means the offset is not yet known
260 // and may lie outside of the zero-trapping page, and thus we need to ensure we're forcing
261 // an explicit null check for -1.
262
263 // Check if offset is outside of [0, os::vm_page_size()]
264 return offset < 0 || offset >= os::vm_page_size();
265 }