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.
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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/atomic.hpp"
33#include "runtime/icache.hpp"
34#include "runtime/os.hpp"
35#include "runtime/thread.hpp"
36
37
38// Implementation of AbstractAssembler
39//
40// The AbstractAssembler is generating code into a CodeBuffer. To make code generation faster,
41// the assembler keeps a copy of the code buffers boundaries & modifies them when
42// emitting bytes rather than using the code buffers accessor functions all the time.
43// The code buffer is updated via set_code_end(...) after emitting a whole instruction.
44
45AbstractAssembler::AbstractAssembler(CodeBuffer* code) {
46 if (code == NULL) return;
47 CodeSection* cs = code->insts();
48 cs->clear_mark(); // new assembler kills old mark
49 if (cs->start() == NULL) {
50 vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "CodeCache: no room for %s", code->name());
51 }
52 _code_section = cs;
53 _oop_recorder= code->oop_recorder();
54 DEBUG_ONLY( _short_branch_delta = 0; )
55}
56
57void AbstractAssembler::set_code_section(CodeSection* cs) {
58 assert(cs->outer() == code_section()->outer(), "sanity");
59 assert(cs->is_allocated(), "need to pre-allocate this section");
60 cs->clear_mark(); // new assembly into this section kills old mark
61 _code_section = cs;
62}
63
64// Inform CodeBuffer that incoming code and relocation will be for stubs
65address AbstractAssembler::start_a_stub(int required_space) {
66 CodeBuffer* cb = code();
67 CodeSection* cs = cb->stubs();
68 assert(_code_section == cb->insts(), "not in insts?");
69 if (cs->maybe_expand_to_ensure_remaining(required_space)
70 && cb->blob() == NULL) {
71 return NULL;
72 }
73 set_code_section(cs);
74 return pc();
75}
76
77// Inform CodeBuffer that incoming code and relocation will be code
78// Should not be called if start_a_stub() returned NULL
79void AbstractAssembler::end_a_stub() {
80 assert(_code_section == code()->stubs(), "not in stubs?");
81 set_code_section(code()->insts());
82}
83
84// Inform CodeBuffer that incoming code and relocation will be for stubs
85address AbstractAssembler::start_a_const(int required_space, int required_align) {
86 CodeBuffer* cb = code();
87 CodeSection* cs = cb->consts();
88 assert(_code_section == cb->insts() || _code_section == cb->stubs(), "not in insts/stubs?");
89 address end = cs->end();
90 int pad = -(intptr_t)end & (required_align-1);
91 if (cs->maybe_expand_to_ensure_remaining(pad + required_space)) {
92 if (cb->blob() == NULL) return NULL;
93 end = cs->end(); // refresh pointer
94 }
95 if (pad > 0) {
96 while (--pad >= 0) { *end++ = 0; }
97 cs->set_end(end);
98 }
99 set_code_section(cs);
100 return end;
101}
102
103// Inform CodeBuffer that incoming code and relocation will be code
104// in section cs (insts or stubs).
105void AbstractAssembler::end_a_const(CodeSection* cs) {
106 assert(_code_section == code()->consts(), "not in consts?");
107 set_code_section(cs);
108}
109
110void AbstractAssembler::flush() {
111 ICache::invalidate_range(addr_at(0), offset());
112}
113
114void AbstractAssembler::bind(Label& L) {
115 if (L.is_bound()) {
116 // Assembler can bind a label more than once to the same place.
117 guarantee(L.loc() == locator(), "attempt to redefine label");
118 return;
119 }
120 L.bind_loc(locator());
121 L.patch_instructions((MacroAssembler*)this);
122}
123
124void AbstractAssembler::generate_stack_overflow_check(int frame_size_in_bytes) {
125 if (UseStackBanging) {
126 // Each code entry causes one stack bang n pages down the stack where n
127 // is configurable by StackShadowPages. The setting depends on the maximum
128 // depth of VM call stack or native before going back into java code,
129 // since only java code can raise a stack overflow exception using the
130 // stack banging mechanism. The VM and native code does not detect stack
131 // overflow.
132 // The code in JavaCalls::call() checks that there is at least n pages
133 // available, so all entry code needs to do is bang once for the end of
134 // this shadow zone.
135 // The entry code may need to bang additional pages if the framesize
136 // is greater than a page.
137
138 const int page_size = os::vm_page_size();
139 int bang_end = (int)JavaThread::stack_shadow_zone_size();
140
141 // This is how far the previous frame's stack banging extended.
142 const int bang_end_safe = bang_end;
143
144 if (frame_size_in_bytes > page_size) {
145 bang_end += frame_size_in_bytes;
146 }
147
148 int bang_offset = bang_end_safe;
149 while (bang_offset <= bang_end) {
150 // Need at least one stack bang at end of shadow zone.
151 bang_stack_with_offset(bang_offset);
152 bang_offset += page_size;
153 }
154 } // end (UseStackBanging)
155}
156
157void Label::add_patch_at(CodeBuffer* cb, int branch_loc, const char* file, int line) {
158 assert(_loc == -1, "Label is unbound");
159 // Don't add patch locations during scratch emit.
160 if (cb->insts()->scratch_emit()) { return; }
161 if (_patch_index < PatchCacheSize) {
162 _patches[_patch_index] = branch_loc;
163#ifdef ASSERT
164 _lines[_patch_index] = line;
165 _files[_patch_index] = file;
166#endif
167 } else {
168 if (_patch_overflow == NULL) {
169 _patch_overflow = cb->create_patch_overflow();
170 }
171 _patch_overflow->push(branch_loc);
172 }
173 ++_patch_index;
174}
175
176void Label::patch_instructions(MacroAssembler* masm) {
177 assert(is_bound(), "Label is bound");
178 CodeBuffer* cb = masm->code();
179 int target_sect = CodeBuffer::locator_sect(loc());
180 address target = cb->locator_address(loc());
181 while (_patch_index > 0) {
182 --_patch_index;
183 int branch_loc;
184 int line = 0;
185 const char* file = NULL;
186 if (_patch_index >= PatchCacheSize) {
187 branch_loc = _patch_overflow->pop();
188 } else {
189 branch_loc = _patches[_patch_index];
190#ifdef ASSERT
191 line = _lines[_patch_index];
192 file = _files[_patch_index];
193#endif
194 }
195 int branch_sect = CodeBuffer::locator_sect(branch_loc);
196 address branch = cb->locator_address(branch_loc);
197 if (branch_sect == CodeBuffer::SECT_CONSTS) {
198 // The thing to patch is a constant word.
199 *(address*)branch = target;
200 continue;
201 }
202
203#ifdef ASSERT
204 // Cross-section branches only work if the
205 // intermediate section boundaries are frozen.
206 if (target_sect != branch_sect) {
207 for (int n = MIN2(target_sect, branch_sect),
208 nlimit = (target_sect + branch_sect) - n;
209 n < nlimit; n++) {
210 CodeSection* cs = cb->code_section(n);
211 assert(cs->is_frozen(), "cross-section branch needs stable offsets");
212 }
213 }
214#endif //ASSERT
215
216 // Push the target offset into the branch instruction.
217 masm->pd_patch_instruction(branch, target, file, line);
218 }
219}
220
221struct DelayedConstant {
222 typedef void (*value_fn_t)();
223 BasicType type;
224 intptr_t value;
225 value_fn_t value_fn;
226 // This limit of 20 is generous for initial uses.
227 // The limit needs to be large enough to store the field offsets
228 // into classes which do not have statically fixed layouts.
229 // (Initial use is for method handle object offsets.)
230 // Look for uses of "delayed_value" in the source code
231 // and make sure this number is generous enough to handle all of them.
232 enum { DC_LIMIT = 20 };
233 static DelayedConstant delayed_constants[DC_LIMIT];
234 static DelayedConstant* add(BasicType type, value_fn_t value_fn);
235 bool match(BasicType t, value_fn_t cfn) {
236 return type == t && value_fn == cfn;
237 }
238 static void update_all();
239};
240
241DelayedConstant DelayedConstant::delayed_constants[DC_LIMIT];
242// Default C structure initialization rules have the following effect here:
243// = { { (BasicType)0, (intptr_t)NULL }, ... };
244
245DelayedConstant* DelayedConstant::add(BasicType type,
246 DelayedConstant::value_fn_t cfn) {
247 for (int i = 0; i < DC_LIMIT; i++) {
248 DelayedConstant* dcon = &delayed_constants[i];
249 if (dcon->match(type, cfn))
250 return dcon;
251 if (dcon->value_fn == NULL) {
252 dcon->value_fn = cfn;
253 dcon->type = type;
254 return dcon;
255 }
256 }
257 // If this assert is hit (in pre-integration testing!) then re-evaluate
258 // the comment on the definition of DC_LIMIT.
259 guarantee(false, "too many delayed constants");
260 return NULL;
261}
262
263void DelayedConstant::update_all() {
264 for (int i = 0; i < DC_LIMIT; i++) {
265 DelayedConstant* dcon = &delayed_constants[i];
266 if (dcon->value_fn != NULL && dcon->value == 0) {
267 typedef int (*int_fn_t)();
268 typedef address (*address_fn_t)();
269 switch (dcon->type) {
270 case T_INT: dcon->value = (intptr_t) ((int_fn_t) dcon->value_fn)(); break;
271 case T_ADDRESS: dcon->value = (intptr_t) ((address_fn_t)dcon->value_fn)(); break;
272 default: break;
273 }
274 }
275 }
276}
277
278RegisterOrConstant AbstractAssembler::delayed_value(int(*value_fn)(), Register tmp, int offset) {
279 intptr_t val = (intptr_t) (*value_fn)();
280 if (val != 0) return val + offset;
281 return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);
282}
283RegisterOrConstant AbstractAssembler::delayed_value(address(*value_fn)(), Register tmp, int offset) {
284 intptr_t val = (intptr_t) (*value_fn)();
285 if (val != 0) return val + offset;
286 return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);
287}
288intptr_t* AbstractAssembler::delayed_value_addr(int(*value_fn)()) {
289 DelayedConstant* dcon = DelayedConstant::add(T_INT, (DelayedConstant::value_fn_t) value_fn);
290 return &dcon->value;
291}
292intptr_t* AbstractAssembler::delayed_value_addr(address(*value_fn)()) {
293 DelayedConstant* dcon = DelayedConstant::add(T_ADDRESS, (DelayedConstant::value_fn_t) value_fn);
294 return &dcon->value;
295}
296void AbstractAssembler::update_delayed_values() {
297 DelayedConstant::update_all();
298}
299
300void AbstractAssembler::block_comment(const char* comment) {
301 if (sect() == CodeBuffer::SECT_INSTS) {
302 code_section()->outer()->block_comment(offset(), comment);
303 }
304}
305
306const char* AbstractAssembler::code_string(const char* str) {
307 if (sect() == CodeBuffer::SECT_INSTS || sect() == CodeBuffer::SECT_STUBS) {
308 return code_section()->outer()->code_string(str);
309 }
310 return NULL;
311}
312
313bool MacroAssembler::uses_implicit_null_check(void* address) {
314 // Exception handler checks the nmethod's implicit null checks table
315 // only when this method returns false.
316 intptr_t int_address = reinterpret_cast<intptr_t>(address);
317 intptr_t cell_header_size = Universe::heap()->cell_header_size();
318 size_t region_size = os::vm_page_size() + cell_header_size;
319#ifdef _LP64
320 if (UseCompressedOops && CompressedOops::base() != NULL) {
321 // A SEGV can legitimately happen in C2 code at address
322 // (heap_base + offset) if Matcher::narrow_oop_use_complex_address
323 // is configured to allow narrow oops field loads to be implicitly
324 // null checked
325 intptr_t start = ((intptr_t)CompressedOops::base()) - cell_header_size;
326 intptr_t end = start + region_size;
327 if (int_address >= start && int_address < end) {
328 return true;
329 }
330 }
331#endif
332 intptr_t start = -cell_header_size;
333 intptr_t end = start + region_size;
334 return int_address >= start && int_address < end;
335}
336
337bool MacroAssembler::needs_explicit_null_check(intptr_t offset) {
338 // The offset -1 is used (hardcoded) in a number of places in C1 and MacroAssembler
339 // to indicate an unknown offset. For example, TemplateTable::pop_and_check_object(Register r)
340 // calls MacroAssembler::null_check(Register reg, int offset = -1) which gets here
341 // with -1. Another example is GraphBuilder::access_field(...) which uses -1 as placeholder
342 // for offsets to be patched in later. The -1 there means the offset is not yet known
343 // and may lie outside of the zero-trapping page, and thus we need to ensure we're forcing
344 // an explicit null check for -1, even if it may otherwise be in the range
345 // [-cell_header_size, os::vm_page_size).
346 // TODO: Find and replace all relevant uses of -1 with a reasonably named constant.
347 if (offset == -1) return true;
348
349 // Check if offset is outside of [-cell_header_size, os::vm_page_size)
350 return offset < -Universe::heap()->cell_header_size() ||
351 offset >= os::vm_page_size();
352}
353