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/barrierSetNMethod.hpp"
29 #include "logging/log.hpp"
30 #include "memory/resourceArea.hpp"
31 #include "runtime/javaThread.hpp"
32 #include "runtime/sharedRuntime.hpp"
33 #include "utilities/align.hpp"
34 #include "utilities/debug.hpp"
35 #include "utilities/macros.hpp"
36
37 class NativeNMethodCmpBarrier: public NativeInstruction {
38 public:
39 #ifdef _LP64
40 enum Intel_specific_constants {
41 instruction_code = 0x81,
42 instruction_size = 8,
43 imm_offset = 4,
44 instruction_rex_prefix = Assembler::REX | Assembler::REX_B,
45 instruction_modrm = 0x7f // [r15 + offset]
46 };
47 #else
48 enum Intel_specific_constants {
49 instruction_code = 0x81,
50 instruction_size = 7,
51 imm_offset = 2,
52 instruction_modrm = 0x3f // [rdi]
53 };
54 #endif
55
56 address instruction_address() const { return addr_at(0); }
57 address immediate_address() const { return addr_at(imm_offset); }
58
59 jint get_immediate() const { return int_at(imm_offset); }
60 void set_immediate(jint imm) { set_int_at(imm_offset, imm); }
61 void verify() const;
62 };
63
64 #ifdef _LP64
65 void NativeNMethodCmpBarrier::verify() const {
66 if (((uintptr_t) instruction_address()) & 0x3) {
67 fatal("Not properly aligned");
68 }
69
70 int prefix = ubyte_at(0);
71 if (prefix != instruction_rex_prefix) {
72 tty->print_cr("Addr: " INTPTR_FORMAT " Prefix: 0x%x", p2i(instruction_address()),
73 prefix);
74 fatal("not a cmp barrier");
75 }
76
77 int inst = ubyte_at(1);
78 if (inst != instruction_code) {
79 tty->print_cr("Addr: " INTPTR_FORMAT " Code: 0x%x", p2i(instruction_address()),
80 inst);
81 fatal("not a cmp barrier");
82 }
83
84 int modrm = ubyte_at(2);
85 if (modrm != instruction_modrm) {
86 tty->print_cr("Addr: " INTPTR_FORMAT " mod/rm: 0x%x", p2i(instruction_address()),
87 modrm);
88 fatal("not a cmp barrier");
89 }
90 }
91 #else
92 void NativeNMethodCmpBarrier::verify() const {
93 if (((uintptr_t) instruction_address()) & 0x3) {
94 fatal("Not properly aligned");
95 }
96
97 int inst = ubyte_at(0);
98 if (inst != instruction_code) {
99 tty->print_cr("Addr: " INTPTR_FORMAT " Code: 0x%x", p2i(instruction_address()),
100 inst);
101 fatal("not a cmp barrier");
102 }
103
104 int modrm = ubyte_at(1);
105 if (modrm != instruction_modrm) {
106 tty->print_cr("Addr: " INTPTR_FORMAT " mod/rm: 0x%x", p2i(instruction_address()),
107 modrm);
108 fatal("not a cmp barrier");
109 }
110 }
111 #endif // _LP64
112
113 void BarrierSetNMethod::deoptimize(nmethod* nm, address* return_address_ptr) {
114 /*
115 * [ callers frame ]
116 * [ callers return address ] <- callers rsp
117 * [ callers rbp ] <- callers rbp
118 * [ callers frame slots ]
119 * [ return_address ] <- return_address_ptr
120 * [ cookie ] <- used to write the new rsp (callers rsp)
121 * [ stub rbp ]
122 * [ stub stuff ]
123 */
124
125 address* stub_rbp = return_address_ptr - 2;
126 address* callers_rsp = return_address_ptr + nm->frame_size(); /* points to callers return_address now */
127 address* callers_rbp = callers_rsp - 1; // 1 to move to the callers return address, 1 more to move to the rbp
128 address* cookie = return_address_ptr - 1;
129
130 LogTarget(Trace, nmethod, barrier) out;
131 if (out.is_enabled()) {
132 JavaThread* jth = JavaThread::current();
133 ResourceMark mark;
134 log_trace(nmethod, barrier)("deoptimize(nmethod: %p, return_addr: %p, osr: %d, thread: %p(%s), making rsp: %p) -> %p",
135 nm, (address *) return_address_ptr, nm->is_osr_method(), jth,
136 jth->name(), callers_rsp, nm->verified_entry_point());
137 }
138
139 assert(nm->frame_size() >= 3, "invariant");
140 assert(*cookie == (address) -1, "invariant");
141
142 // Preserve caller rbp.
143 *stub_rbp = *callers_rbp;
144
145 // At the cookie address put the callers rsp.
146 *cookie = (address) callers_rsp; // should point to the return address
147
148 // In the slot that used to be the callers rbp we put the address that our stub needs to jump to at the end.
149 // Overwriting the caller rbp should be okay since our stub rbp has the same value.
150 address* jmp_addr_ptr = callers_rbp;
151 *jmp_addr_ptr = SharedRuntime::get_handle_wrong_method_stub();
152 }
153
154 // This is the offset of the entry barrier from where the frame is completed.
155 // If any code changes between the end of the verified entry where the entry
156 // barrier resides, and the completion of the frame, then
157 // NativeNMethodCmpBarrier::verify() will immediately complain when it does
158 // not find the expected native instruction at this offset, which needs updating.
159 // Note that this offset is invariant of PreserveFramePointer.
160 static const int entry_barrier_offset(nmethod* nm) {
161 #ifdef _LP64
162 if (nm->is_compiled_by_c2()) {
163 return -14;
164 } else {
165 return -15;
166 }
167 #else
168 return -18;
169 #endif
170 }
171
172 static NativeNMethodCmpBarrier* native_nmethod_barrier(nmethod* nm) {
173 address barrier_address = nm->code_begin() + nm->frame_complete_offset() + entry_barrier_offset(nm);
174 NativeNMethodCmpBarrier* barrier = reinterpret_cast<NativeNMethodCmpBarrier*>(barrier_address);
175 debug_only(barrier->verify());
176 return barrier;
177 }
178
179 void BarrierSetNMethod::set_guard_value(nmethod* nm, int value) {
180 if (!supports_entry_barrier(nm)) {
181 return;
182 }
183
184 NativeNMethodCmpBarrier* cmp = native_nmethod_barrier(nm);
185 cmp->set_immediate(value);
186 }
187
188 int BarrierSetNMethod::guard_value(nmethod* nm) {
189 if (!supports_entry_barrier(nm)) {
190 return disarmed_guard_value();
191 }
192
193 NativeNMethodCmpBarrier* cmp = native_nmethod_barrier(nm);
194 return cmp->get_immediate();
195 }