1 /*
2 * Copyright (c) 2018, 2025, 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 "code/codeCache.hpp"
26 #include "code/nativeInst.hpp"
27 #include "gc/shared/barrierSetNMethod.hpp"
28 #include "logging/log.hpp"
29 #include "memory/resourceArea.hpp"
30 #include "runtime/javaThread.hpp"
31 #include "runtime/sharedRuntime.hpp"
32 #include "utilities/align.hpp"
33 #include "utilities/debug.hpp"
34 #include "utilities/formatBuffer.hpp"
35 #include "utilities/macros.hpp"
36 #if INCLUDE_JVMCI
37 #include "jvmci/jvmciRuntime.hpp"
38 #endif
39
40 class NativeNMethodCmpBarrier: public NativeInstruction {
41 public:
42 enum Intel_specific_constants {
43 instruction_code = 0x81,
44 instruction_size = 8,
45 imm_offset = 4,
46 instruction_rex_prefix = Assembler::REX | Assembler::REX_B,
47 instruction_modrm = 0x7f // [r15 + offset]
48 };
49
50 address instruction_address() const { return addr_at(0); }
51 address immediate_address() const { return addr_at(imm_offset); }
52
53 jint get_immediate() const { return int_at(imm_offset); }
54 void set_immediate(jint imm) { set_int_at(imm_offset, imm); }
55 bool check_barrier(err_msg& msg) const;
56 void verify() const {
57 #ifdef ASSERT
58 err_msg msg("%s", "");
59 assert(check_barrier(msg), "%s", msg.buffer());
60 #endif
61 }
62 };
63
64 bool NativeNMethodCmpBarrier::check_barrier(err_msg& msg) const {
65 // Only require 4 byte alignment
66 if (((uintptr_t) instruction_address()) & 0x3) {
67 msg.print("Addr: " INTPTR_FORMAT " not properly aligned", p2i(instruction_address()));
68 return false;
69 }
70
71 int prefix = ubyte_at(0);
72 if (prefix != instruction_rex_prefix) {
73 msg.print("Addr: " INTPTR_FORMAT " Code: 0x%x expected 0x%x", p2i(instruction_address()), prefix, instruction_rex_prefix);
74 return false;
75 }
76
77 int inst = ubyte_at(1);
78 if (inst != instruction_code) {
79 msg.print("Addr: " INTPTR_FORMAT " Code: 0x%x expected 0x%x", p2i(instruction_address()), inst, instruction_code);
80 return false;
81 }
82
83 int modrm = ubyte_at(2);
84 if (modrm != instruction_modrm) {
85 msg.print("Addr: " INTPTR_FORMAT " Code: 0x%x expected mod/rm 0x%x", p2i(instruction_address()), modrm, instruction_modrm);
86 return false;
87 }
88 return true;
89 }
90
91 void BarrierSetNMethod::deoptimize(nmethod* nm, address* return_address_ptr) {
92 /*
93 * [ callers frame ]
94 * [ callers return address ] <- callers rsp
95 * [ callers rbp ] <- callers rbp
96 * [ callers frame slots ]
97 * [ return_address ] <- return_address_ptr
98 * [ cookie ] <- used to write the new rsp (callers rsp)
99 * [ stub rbp ]
100 * [ stub stuff ]
101 */
102
103 address* stub_rbp = return_address_ptr - 2;
104 address* callers_rsp = return_address_ptr + nm->frame_size(); /* points to callers return_address now */
105 address* callers_rbp = callers_rsp - 1; // 1 to move to the callers return address, 1 more to move to the rbp
106 address* cookie = return_address_ptr - 1;
107
108 LogTarget(Trace, nmethod, barrier) out;
109 if (out.is_enabled()) {
110 JavaThread* jth = JavaThread::current();
111 ResourceMark mark;
112 log_trace(nmethod, barrier)("deoptimize(nmethod: %p, return_addr: %p, osr: %d, thread: %p(%s), making rsp: %p) -> %p",
113 nm, (address *) return_address_ptr, nm->is_osr_method(), jth,
114 jth->name(), callers_rsp, nm->verified_entry_point());
115 }
116
117 assert(nm->frame_size() >= 3, "invariant");
118 assert(*cookie == (address) -1, "invariant");
119
120 // Preserve caller rbp.
121 *stub_rbp = *callers_rbp;
122
123 // At the cookie address put the callers rsp.
124 *cookie = (address) callers_rsp; // should point to the return address
125
126 // In the slot that used to be the callers rbp we put the address that our stub needs to jump to at the end.
127 // Overwriting the caller rbp should be okay since our stub rbp has the same value.
128 address* jmp_addr_ptr = callers_rbp;
129 *jmp_addr_ptr = SharedRuntime::get_handle_wrong_method_stub();
130 }
131
132 // This is the offset of the entry barrier from where the frame is completed.
133 // If any code changes between the end of the verified entry where the entry
134 // barrier resides, and the completion of the frame, then
135 // NativeNMethodCmpBarrier::verify() will immediately complain when it does
136 // not find the expected native instruction at this offset, which needs updating.
137 // Note that this offset is invariant of PreserveFramePointer.
138 static int entry_barrier_offset(nmethod* nm) {
139 if (nm->is_compiled_by_c2()) {
140 return -14;
141 } else {
142 return -15;
143 }
144 }
145
146 static NativeNMethodCmpBarrier* native_nmethod_barrier(nmethod* nm) {
147 address barrier_address;
148 #if INCLUDE_JVMCI
149 if (nm->is_compiled_by_jvmci()) {
150 barrier_address = nm->code_begin() + nm->jvmci_nmethod_data()->nmethod_entry_patch_offset();
151 } else
152 #endif
153 {
154 barrier_address = nm->code_begin() + nm->frame_complete_offset() + entry_barrier_offset(nm);
155 }
156
157 NativeNMethodCmpBarrier* barrier = reinterpret_cast<NativeNMethodCmpBarrier*>(barrier_address);
158 barrier->verify();
159 return barrier;
160 }
161
162 void BarrierSetNMethod::set_guard_value(nmethod* nm, int value) {
163 if (!supports_entry_barrier(nm)) {
164 return;
165 }
166
167 NativeNMethodCmpBarrier* cmp = native_nmethod_barrier(nm);
168 cmp->set_immediate(value);
169 }
170
171 int BarrierSetNMethod::guard_value(nmethod* nm) {
172 if (!supports_entry_barrier(nm)) {
173 return disarmed_guard_value();
174 }
175
176 NativeNMethodCmpBarrier* cmp = native_nmethod_barrier(nm);
177 return cmp->get_immediate();
178 }
179
180
181 #if INCLUDE_JVMCI
182 bool BarrierSetNMethod::verify_barrier(nmethod* nm, err_msg& msg) {
183 NativeNMethodCmpBarrier* barrier = native_nmethod_barrier(nm);
184 return barrier->check_barrier(msg);
185 }
186 #endif