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 "runtime/atomic.hpp"
31 #include "runtime/icache.hpp"
32 #include "runtime/os.hpp"
33 #include "runtime/thread.hpp"
34
35
36 // Implementation of AbstractAssembler
37 //
38 // The AbstractAssembler is generating code into a CodeBuffer. To make code generation faster,
39 // the assembler keeps a copy of the code buffers boundaries & modifies them when
40 // emitting bytes rather than using the code buffers accessor functions all the time.
41 // The code buffer is updated via set_code_end(...) after emitting a whole instruction.
42
43 AbstractAssembler::AbstractAssembler(CodeBuffer* code) {
44 if (code == NULL) return;
45 CodeSection* cs = code->insts();
46 cs->clear_mark(); // new assembler kills old mark
47 if (cs->start() == NULL) {
48 vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "CodeCache: no room for %s", code->name());
49 }
50 _code_section = cs;
51 _oop_recorder= code->oop_recorder();
52 DEBUG_ONLY( _short_branch_delta = 0; )
53 }
54
55 void AbstractAssembler::set_code_section(CodeSection* cs) {
56 assert(cs->outer() == code_section()->outer(), "sanity");
57 assert(cs->is_allocated(), "need to pre-allocate this section");
58 cs->clear_mark(); // new assembly into this section kills old mark
59 _code_section = cs;
60 }
61
62 // Inform CodeBuffer that incoming code and relocation will be for stubs
63 address AbstractAssembler::start_a_stub(int required_space) {
64 CodeBuffer* cb = code();
65 CodeSection* cs = cb->stubs();
66 assert(_code_section == cb->insts(), "not in insts?");
67 if (cs->maybe_expand_to_ensure_remaining(required_space)
68 && cb->blob() == NULL) {
69 return NULL;
70 }
71 set_code_section(cs);
72 return pc();
73 }
74
75 // Inform CodeBuffer that incoming code and relocation will be code
76 // Should not be called if start_a_stub() returned NULL
77 void AbstractAssembler::end_a_stub() {
78 assert(_code_section == code()->stubs(), "not in stubs?");
79 set_code_section(code()->insts());
80 }
81
82 // Inform CodeBuffer that incoming code and relocation will be for stubs
83 address AbstractAssembler::start_a_const(int required_space, int required_align) {
84 CodeBuffer* cb = code();
85 CodeSection* cs = cb->consts();
86 assert(_code_section == cb->insts() || _code_section == cb->stubs(), "not in insts/stubs?");
87 address end = cs->end();
88 int pad = -(intptr_t)end & (required_align-1);
89 if (cs->maybe_expand_to_ensure_remaining(pad + required_space)) {
90 if (cb->blob() == NULL) return NULL;
91 end = cs->end(); // refresh pointer
92 }
93 if (pad > 0) {
94 while (--pad >= 0) { *end++ = 0; }
95 cs->set_end(end);
96 }
97 set_code_section(cs);
98 return end;
99 }
100
101 // Inform CodeBuffer that incoming code and relocation will be code
102 // in section cs (insts or stubs).
103 void AbstractAssembler::end_a_const(CodeSection* cs) {
104 assert(_code_section == code()->consts(), "not in consts?");
105 set_code_section(cs);
106 }
107
108 void AbstractAssembler::flush() {
109 ICache::invalidate_range(addr_at(0), offset());
110 }
111
112 void AbstractAssembler::bind(Label& L) {
113 if (L.is_bound()) {
114 // Assembler can bind a label more than once to the same place.
115 guarantee(L.loc() == locator(), "attempt to redefine label");
116 return;
117 }
118 L.bind_loc(locator());
119 L.patch_instructions((MacroAssembler*)this);
120 }
121
122 void AbstractAssembler::generate_stack_overflow_check(int frame_size_in_bytes) {
123 if (UseStackBanging) {
124 // Each code entry causes one stack bang n pages down the stack where n
125 // is configurable by StackShadowPages. The setting depends on the maximum
126 // depth of VM call stack or native before going back into java code,
127 // since only java code can raise a stack overflow exception using the
128 // stack banging mechanism. The VM and native code does not detect stack
129 // overflow.
130 // The code in JavaCalls::call() checks that there is at least n pages
131 // available, so all entry code needs to do is bang once for the end of
132 // this shadow zone.
133 // The entry code may need to bang additional pages if the framesize
134 // is greater than a page.
135
136 const int page_size = os::vm_page_size();
137 int bang_end = (int)JavaThread::stack_shadow_zone_size();
138
139 // This is how far the previous frame's stack banging extended.
140 const int bang_end_safe = bang_end;
141
142 if (frame_size_in_bytes > page_size) {
143 bang_end += frame_size_in_bytes;
144 }
145
146 int bang_offset = bang_end_safe;
147 while (bang_offset <= bang_end) {
148 // Need at least one stack bang at end of shadow zone.
149 bang_stack_with_offset(bang_offset);
150 bang_offset += page_size;
151 }
152 } // end (UseStackBanging)
153 }
154
155 void Label::add_patch_at(CodeBuffer* cb, int branch_loc, const char* file, int line) {
156 assert(_loc == -1, "Label is unbound");
157 // Don't add patch locations during scratch emit.
158 if (cb->insts()->scratch_emit()) { return; }
159 if (_patch_index < PatchCacheSize) {
160 _patches[_patch_index] = branch_loc;
161 #ifdef ASSERT
162 _lines[_patch_index] = line;
163 _files[_patch_index] = file;
164 #endif
165 } else {
166 if (_patch_overflow == NULL) {
167 _patch_overflow = cb->create_patch_overflow();
168 }
169 _patch_overflow->push(branch_loc);
170 }
171 ++_patch_index;
172 }
173
174 void Label::patch_instructions(MacroAssembler* masm) {
175 assert(is_bound(), "Label is bound");
176 CodeBuffer* cb = masm->code();
177 int target_sect = CodeBuffer::locator_sect(loc());
178 address target = cb->locator_address(loc());
179 while (_patch_index > 0) {
180 --_patch_index;
181 int branch_loc;
182 int line = 0;
183 const char* file = NULL;
184 if (_patch_index >= PatchCacheSize) {
185 branch_loc = _patch_overflow->pop();
186 } else {
187 branch_loc = _patches[_patch_index];
188 #ifdef ASSERT
189 line = _lines[_patch_index];
190 file = _files[_patch_index];
191 #endif
192 }
193 int branch_sect = CodeBuffer::locator_sect(branch_loc);
194 address branch = cb->locator_address(branch_loc);
195 if (branch_sect == CodeBuffer::SECT_CONSTS) {
196 // The thing to patch is a constant word.
197 *(address*)branch = target;
198 continue;
199 }
200
201 #ifdef ASSERT
202 // Cross-section branches only work if the
203 // intermediate section boundaries are frozen.
204 if (target_sect != branch_sect) {
205 for (int n = MIN2(target_sect, branch_sect),
206 nlimit = (target_sect + branch_sect) - n;
207 n < nlimit; n++) {
208 CodeSection* cs = cb->code_section(n);
209 assert(cs->is_frozen(), "cross-section branch needs stable offsets");
210 }
211 }
212 #endif //ASSERT
213
214 // Push the target offset into the branch instruction.
215 masm->pd_patch_instruction(branch, target, file, line);
216 }
217 }
218
219 struct DelayedConstant {
220 typedef void (*value_fn_t)();
221 BasicType type;
222 intptr_t value;
223 value_fn_t value_fn;
224 // This limit of 20 is generous for initial uses.
225 // The limit needs to be large enough to store the field offsets
226 // into classes which do not have statically fixed layouts.
227 // (Initial use is for method handle object offsets.)
228 // Look for uses of "delayed_value" in the source code
229 // and make sure this number is generous enough to handle all of them.
230 enum { DC_LIMIT = 20 };
231 static DelayedConstant delayed_constants[DC_LIMIT];
232 static DelayedConstant* add(BasicType type, value_fn_t value_fn);
233 bool match(BasicType t, value_fn_t cfn) {
234 return type == t && value_fn == cfn;
235 }
236 static void update_all();
237 };
238
239 DelayedConstant DelayedConstant::delayed_constants[DC_LIMIT];
240 // Default C structure initialization rules have the following effect here:
241 // = { { (BasicType)0, (intptr_t)NULL }, ... };
242
243 DelayedConstant* DelayedConstant::add(BasicType type,
244 DelayedConstant::value_fn_t cfn) {
245 for (int i = 0; i < DC_LIMIT; i++) {
246 DelayedConstant* dcon = &delayed_constants[i];
247 if (dcon->match(type, cfn))
248 return dcon;
249 if (dcon->value_fn == NULL) {
250 dcon->value_fn = cfn;
251 dcon->type = type;
252 return dcon;
253 }
254 }
255 // If this assert is hit (in pre-integration testing!) then re-evaluate
256 // the comment on the definition of DC_LIMIT.
257 guarantee(false, "too many delayed constants");
258 return NULL;
259 }
260
261 void DelayedConstant::update_all() {
262 for (int i = 0; i < DC_LIMIT; i++) {
263 DelayedConstant* dcon = &delayed_constants[i];
264 if (dcon->value_fn != NULL && dcon->value == 0) {
265 typedef int (*int_fn_t)();
266 typedef address (*address_fn_t)();
267 switch (dcon->type) {
268 case T_INT: dcon->value = (intptr_t) ((int_fn_t) dcon->value_fn)(); break;
269 case T_ADDRESS: dcon->value = (intptr_t) ((address_fn_t)dcon->value_fn)(); break;
270 default: break;
271 }
272 }
273 }
274 }
275
276 RegisterOrConstant AbstractAssembler::delayed_value(int(*value_fn)(), Register tmp, int offset) {
277 intptr_t val = (intptr_t) (*value_fn)();
278 if (val != 0) return val + offset;
279 return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);
280 }
281 RegisterOrConstant AbstractAssembler::delayed_value(address(*value_fn)(), Register tmp, int offset) {
282 intptr_t val = (intptr_t) (*value_fn)();
283 if (val != 0) return val + offset;
284 return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);
285 }
286 intptr_t* AbstractAssembler::delayed_value_addr(int(*value_fn)()) {
287 DelayedConstant* dcon = DelayedConstant::add(T_INT, (DelayedConstant::value_fn_t) value_fn);
288 return &dcon->value;
289 }
290 intptr_t* AbstractAssembler::delayed_value_addr(address(*value_fn)()) {
291 DelayedConstant* dcon = DelayedConstant::add(T_ADDRESS, (DelayedConstant::value_fn_t) value_fn);
292 return &dcon->value;
293 }
294 void AbstractAssembler::update_delayed_values() {
295 DelayedConstant::update_all();
296 }
297
298 void AbstractAssembler::block_comment(const char* comment) {
299 if (sect() == CodeBuffer::SECT_INSTS) {
300 code_section()->outer()->block_comment(offset(), comment);
301 }
302 }
303
304 const char* AbstractAssembler::code_string(const char* str) {
305 if (sect() == CodeBuffer::SECT_INSTS || sect() == CodeBuffer::SECT_STUBS) {
306 return code_section()->outer()->code_string(str);
307 }
308 return NULL;
309 }
310
311 bool MacroAssembler::uses_implicit_null_check(void* address) {
312 // Exception handler checks the nmethod's implicit null checks table
313 // only when this method returns false.
314 intptr_t cell_header_size = Universe::heap()->cell_header_size();
315 HeapWord* start = (HeapWord*)-cell_header_size;
316 #ifdef _LP64
317 if (UseCompressedOops && Universe::narrow_oop_base() != NULL) {
318 // The first page after heap_base is unmapped and
319 // the 'offset' is equal to [heap_base + offset] for
320 // narrow oop implicit null checks.
321 start += (uintptr_t)Universe::narrow_oop_base();
322 }
323 #endif
324 MemRegion implicit_null_range(start, (os::vm_page_size() + cell_header_size) / HeapWordSize);
325 return implicit_null_range.contains(address);
326 }
327
328 bool MacroAssembler::needs_explicit_null_check(intptr_t offset) {
329 // Check if offset is outside of [-cell_header_size, os::vm_page_size)
330 return offset < -Universe::heap()->cell_header_size() ||
331 offset >= os::vm_page_size();
332 }