1 /*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17
18 #include "fault_handler.h"
19 #include <sys/ucontext.h>
20 #include "art_method-inl.h"
21 #include "base/macros.h"
22 #include "globals.h"
23 #include "base/logging.h"
24 #include "base/hex_dump.h"
25 #include "registers_mips64.h"
26 #include "thread.h"
27 #include "thread-inl.h"
28
29 extern "C" void art_quick_throw_stack_overflow();
30 extern "C" void art_quick_throw_null_pointer_exception();
31
32 //
33 // Mips64 specific fault handler functions.
34 //
35
36 namespace art {
37
HandleNestedSignal(int sig ATTRIBUTE_UNUSED,siginfo_t * info ATTRIBUTE_UNUSED,void * context ATTRIBUTE_UNUSED)38 void FaultManager::HandleNestedSignal(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED,
39 void* context ATTRIBUTE_UNUSED) {
40 }
41
GetMethodAndReturnPcAndSp(siginfo_t * siginfo,void * context,ArtMethod ** out_method,uintptr_t * out_return_pc,uintptr_t * out_sp)42 void FaultManager::GetMethodAndReturnPcAndSp(siginfo_t* siginfo, void* context,
43 ArtMethod** out_method,
44 uintptr_t* out_return_pc, uintptr_t* out_sp) {
45 struct ucontext* uc = reinterpret_cast<struct ucontext*>(context);
46 struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
47 *out_sp = static_cast<uintptr_t>(sc->sc_regs[29]); // SP register
48 VLOG(signals) << "sp: " << *out_sp;
49 if (*out_sp == 0) {
50 return;
51 }
52
53 // In the case of a stack overflow, the stack is not valid and we can't
54 // get the method from the top of the stack. However it's in r0.
55 uintptr_t* fault_addr = reinterpret_cast<uintptr_t*>(siginfo->si_addr); // BVA addr
56 uintptr_t* overflow_addr = reinterpret_cast<uintptr_t*>(
57 reinterpret_cast<uint8_t*>(*out_sp) - GetStackOverflowReservedBytes(kMips64));
58 if (overflow_addr == fault_addr) {
59 *out_method = reinterpret_cast<ArtMethod*>(sc->sc_regs[4]); // A0 register
60 } else {
61 // The method is at the top of the stack.
62 *out_method = *reinterpret_cast<ArtMethod**>(*out_sp);
63 }
64
65 // Work out the return PC. This will be the address of the instruction
66 // following the faulting ldr/str instruction.
67
68 VLOG(signals) << "pc: " << std::hex
69 << static_cast<void*>(reinterpret_cast<uint8_t*>(sc->sc_pc));
70
71 *out_return_pc = sc->sc_pc + 4;
72 }
73
Action(int sig ATTRIBUTE_UNUSED,siginfo_t * info ATTRIBUTE_UNUSED,void * context)74 bool NullPointerHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED,
75 void* context) {
76 // The code that looks for the catch location needs to know the value of the
77 // PC at the point of call. For Null checks we insert a GC map that is immediately after
78 // the load/store instruction that might cause the fault.
79
80 struct ucontext *uc = reinterpret_cast<struct ucontext*>(context);
81 struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
82
83 sc->sc_regs[31] = sc->sc_pc + 4; // RA needs to point to gc map location
84 sc->sc_pc = reinterpret_cast<uintptr_t>(art_quick_throw_null_pointer_exception);
85 sc->sc_regs[25] = sc->sc_pc; // make sure T9 points to the function
86 VLOG(signals) << "Generating null pointer exception";
87 return true;
88 }
89
Action(int sig ATTRIBUTE_UNUSED,siginfo_t * info ATTRIBUTE_UNUSED,void * context ATTRIBUTE_UNUSED)90 bool SuspensionHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED,
91 void* context ATTRIBUTE_UNUSED) {
92 return false;
93 }
94
95 // Stack overflow fault handler.
96 //
97 // This checks that the fault address is equal to the current stack pointer
98 // minus the overflow region size (16K typically). The instruction that
99 // generates this signal is:
100 //
101 // lw zero, -16384(sp)
102 //
103 // It will fault if sp is inside the protected region on the stack.
104 //
105 // If we determine this is a stack overflow we need to move the stack pointer
106 // to the overflow region below the protected region.
107
Action(int sig ATTRIBUTE_UNUSED,siginfo_t * info,void * context)108 bool StackOverflowHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info, void* context) {
109 struct ucontext* uc = reinterpret_cast<struct ucontext*>(context);
110 struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
111 VLOG(signals) << "stack overflow handler with sp at " << std::hex << &uc;
112 VLOG(signals) << "sigcontext: " << std::hex << sc;
113
114 uintptr_t sp = sc->sc_regs[29]; // SP register
115 VLOG(signals) << "sp: " << std::hex << sp;
116
117 uintptr_t fault_addr = reinterpret_cast<uintptr_t>(info->si_addr); // BVA addr
118 VLOG(signals) << "fault_addr: " << std::hex << fault_addr;
119 VLOG(signals) << "checking for stack overflow, sp: " << std::hex << sp <<
120 ", fault_addr: " << fault_addr;
121
122 uintptr_t overflow_addr = sp - GetStackOverflowReservedBytes(kMips64);
123
124 // Check that the fault address is the value expected for a stack overflow.
125 if (fault_addr != overflow_addr) {
126 VLOG(signals) << "Not a stack overflow";
127 return false;
128 }
129
130 VLOG(signals) << "Stack overflow found";
131
132 // Now arrange for the signal handler to return to art_quick_throw_stack_overflow_from.
133 // The value of RA must be the same as it was when we entered the code that
134 // caused this fault. This will be inserted into a callee save frame by
135 // the function to which this handler returns (art_quick_throw_stack_overflow).
136 sc->sc_pc = reinterpret_cast<uintptr_t>(art_quick_throw_stack_overflow);
137 sc->sc_regs[25] = sc->sc_pc; // make sure T9 points to the function
138
139 // The kernel will now return to the address in sc->arm_pc.
140 return true;
141 }
142 } // namespace art
143