1 /*
2 * Copyright (c) 2018, 2022, 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 "code/codeCache.hpp"
27 #include "code/nativeInst.hpp"
28 #include "gc/shared/barrierSet.hpp"
29 #include "gc/shared/barrierSetAssembler.hpp"
30 #include "gc/shared/barrierSetNMethod.hpp"
31 #include "logging/log.hpp"
32 #include "memory/resourceArea.hpp"
33 #include "runtime/frame.inline.hpp"
34 #include "runtime/javaThread.hpp"
35 #include "runtime/sharedRuntime.hpp"
36 #include "runtime/registerMap.hpp"
37 #include "utilities/align.hpp"
38 #include "utilities/debug.hpp"
39
40 static int slow_path_size(nmethod* nm) {
41 // The slow path code is out of line with C2
42 return nm->is_compiled_by_c2() ? 0 : 6;
43 }
44
45 // This is the offset of the entry barrier from where the frame is completed.
46 // If any code changes between the end of the verified entry where the entry
47 // barrier resides, and the completion of the frame, then
48 // NativeNMethodCmpBarrier::verify() will immediately complain when it does
49 // not find the expected native instruction at this offset, which needs updating.
50 // Note that this offset is invariant of PreserveFramePointer.
51 static int entry_barrier_offset(nmethod* nm) {
52 BarrierSetAssembler* bs_asm = BarrierSet::barrier_set()->barrier_set_assembler();
53 switch (bs_asm->nmethod_patching_type()) {
54 case NMethodPatchingType::stw_instruction_and_data_patch:
55 return -4 * (4 + slow_path_size(nm));
56 case NMethodPatchingType::conc_instruction_and_data_patch:
57 return -4 * (10 + slow_path_size(nm));
58 case NMethodPatchingType::conc_data_patch:
59 return -4 * (5 + slow_path_size(nm));
60 }
61 ShouldNotReachHere();
62 return 0;
63 }
64
65 class NativeNMethodBarrier: public NativeInstruction {
66 address instruction_address() const { return addr_at(0); }
67
68 int local_guard_offset(nmethod* nm) {
69 // It's the last instruction
70 return (-entry_barrier_offset(nm)) - 4;
71 }
72
73 int *guard_addr(nmethod* nm) {
74 if (nm->is_compiled_by_c2()) {
75 // With c2 compiled code, the guard is out-of-line in a stub
76 // We find it using the RelocIterator.
77 RelocIterator iter(nm);
78 while (iter.next()) {
79 if (iter.type() == relocInfo::entry_guard_type) {
80 entry_guard_Relocation* const reloc = iter.entry_guard_reloc();
81 return reinterpret_cast<int*>(reloc->addr());
82 }
83 }
84 ShouldNotReachHere();
85 }
86 return reinterpret_cast<int*>(instruction_address() + local_guard_offset(nm));
87 }
88
89 public:
90 int get_value(nmethod* nm) {
91 return Atomic::load_acquire(guard_addr(nm));
92 }
93
94 void set_value(nmethod* nm, int value) {
95 Atomic::release_store(guard_addr(nm), value);
96 }
97
98 void verify() const;
99 };
100
101 // Store the instruction bitmask, bits and name for checking the barrier.
102 struct CheckInsn {
103 uint32_t mask;
104 uint32_t bits;
105 const char *name;
106 };
107
108 // The first instruction of the nmethod entry barrier is an ldr (literal)
109 // instruction. Verify that it's really there, so the offsets are not skewed.
110 void NativeNMethodBarrier::verify() const {
111 uint32_t* addr = (uint32_t*) instruction_address();
112 uint32_t inst = *addr;
113 if ((inst & 0xff000000) != 0x18000000) {
114 tty->print_cr("Addr: " INTPTR_FORMAT " Code: 0x%x", (intptr_t)addr, inst);
115 fatal("not an ldr (literal) instruction.");
116 }
117 }
118
119
120 /* We're called from an nmethod when we need to deoptimize it. We do
121 this by throwing away the nmethod's frame and jumping to the
122 ic_miss stub. This looks like there has been an IC miss at the
123 entry of the nmethod, so we resolve the call, which will fall back
124 to the interpreter if the nmethod has been unloaded. */
125 void BarrierSetNMethod::deoptimize(nmethod* nm, address* return_address_ptr) {
126
127 typedef struct {
128 intptr_t *sp; intptr_t *fp; address lr; address pc;
129 } frame_pointers_t;
130
131 frame_pointers_t *new_frame = (frame_pointers_t *)(return_address_ptr - 5);
132
133 JavaThread *thread = JavaThread::current();
134 RegisterMap reg_map(thread,
135 RegisterMap::UpdateMap::skip,
136 RegisterMap::ProcessFrames::include,
137 RegisterMap::WalkContinuation::skip);
138 frame frame = thread->last_frame();
139
140 assert(frame.is_compiled_frame() || frame.is_native_frame(), "must be");
141 assert(frame.cb() == nm, "must be");
142 frame = frame.sender(®_map);
143
144 LogTarget(Trace, nmethod, barrier) out;
145 if (out.is_enabled()) {
146 ResourceMark mark;
147 log_trace(nmethod, barrier)("deoptimize(nmethod: %s(%p), return_addr: %p, osr: %d, thread: %p(%s), making rsp: %p) -> %p",
148 nm->method()->name_and_sig_as_C_string(),
149 nm, *(address *) return_address_ptr, nm->is_osr_method(), thread,
150 thread->name(), frame.sp(), nm->verified_entry_point());
151 }
152
153 new_frame->sp = frame.sp();
154 new_frame->fp = frame.fp();
155 new_frame->lr = frame.pc();
156 new_frame->pc = SharedRuntime::get_handle_wrong_method_stub();
157 }
158
159 static NativeNMethodBarrier* native_nmethod_barrier(nmethod* nm) {
160 address barrier_address = nm->code_begin() + nm->frame_complete_offset() + entry_barrier_offset(nm);
161 NativeNMethodBarrier* barrier = reinterpret_cast<NativeNMethodBarrier*>(barrier_address);
162 debug_only(barrier->verify());
163 return barrier;
164 }
165
166 void BarrierSetNMethod::set_guard_value(nmethod* nm, int value) {
167 if (!supports_entry_barrier(nm)) {
168 return;
169 }
170
171 if (value == disarmed_guard_value()) {
172 // The patching epoch is incremented before the nmethod is disarmed. Disarming
173 // is performed with a release store. In the nmethod entry barrier, the values
174 // are read in the opposite order, such that the load of the nmethod guard
175 // acquires the patching epoch. This way, the guard is guaranteed to block
176 // entries to the nmethod, until it has safely published the requirement for
177 // further fencing by mutators, before they are allowed to enter.
178 BarrierSetAssembler* bs_asm = BarrierSet::barrier_set()->barrier_set_assembler();
179 bs_asm->increment_patching_epoch();
180 }
181
182 NativeNMethodBarrier* barrier = native_nmethod_barrier(nm);
183 barrier->set_value(nm, value);
184 }
185
186 int BarrierSetNMethod::guard_value(nmethod* nm) {
187 if (!supports_entry_barrier(nm)) {
188 return disarmed_guard_value();
189 }
190
191 NativeNMethodBarrier* barrier = native_nmethod_barrier(nm);
192 return barrier->get_value(nm);
193 }