1// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
2// for details. All rights reserved. Use of this source code is governed by a
3// BSD-style license that can be found in the LICENSE file.
4
5#ifndef RUNTIME_VM_SIGNAL_HANDLER_H_
6#define RUNTIME_VM_SIGNAL_HANDLER_H_
7
8#include "vm/allocation.h"
9#include "vm/globals.h"
10
11#if defined(HOST_OS_LINUX)
12#include <signal.h> // NOLINT
13#include <ucontext.h> // NOLINT
14#elif defined(HOST_OS_ANDROID)
15#include <signal.h> // NOLINT
16#if !defined(__BIONIC_HAVE_UCONTEXT_T)
17#include <asm/sigcontext.h> // NOLINT
18// If ucontext_t is not defined on Android, define it here.
19typedef struct sigcontext mcontext_t;
20typedef struct ucontext {
21 uint32_t uc_flags;
22 struct ucontext* uc_link;
23 stack_t uc_stack;
24 struct sigcontext uc_mcontext;
25 uint32_t uc_sigmask;
26} ucontext_t;
27#endif // !defined(__BIONIC_HAVE_UCONTEXT_T)
28#elif defined(HOST_OS_MACOS)
29#include <signal.h> // NOLINT
30#include <sys/ucontext.h> // NOLINT
31#elif defined(HOST_OS_WINDOWS)
32// Stub out for windows.
33struct siginfo_t;
34struct mcontext_t;
35struct sigset_t {};
36#elif defined(HOST_OS_FUCHSIA)
37#include <signal.h> // NOLINT
38#include <ucontext.h> // NOLINT
39#endif
40
41// Old linux kernels on ARM might require a trampoline to
42// work around incorrect Thumb -> ARM transitions. See SignalHandlerTrampoline
43// below for more details.
44#if defined(HOST_ARCH_ARM) && \
45 (defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)) && \
46 !defined(__thumb__)
47#define USE_SIGNAL_HANDLER_TRAMPOLINE
48#endif
49
50namespace dart {
51
52typedef void (*SignalAction)(int signal, siginfo_t* info, void* context);
53
54class SignalHandler : public AllStatic {
55 public:
56 template <SignalAction action>
57 static void Install() {
58#if defined(USE_SIGNAL_HANDLER_TRAMPOLINE)
59 InstallImpl(SignalHandlerTrampoline<action>);
60#else
61 InstallImpl(action);
62#endif // defined(USE_SIGNAL_HANDLER_TRAMPOLINE)
63 }
64 static void Remove();
65 static uintptr_t GetProgramCounter(const mcontext_t& mcontext);
66 static uintptr_t GetFramePointer(const mcontext_t& mcontext);
67 static uintptr_t GetCStackPointer(const mcontext_t& mcontext);
68 static uintptr_t GetDartStackPointer(const mcontext_t& mcontext);
69 static uintptr_t GetLinkRegister(const mcontext_t& mcontext);
70
71 private:
72 static void InstallImpl(SignalAction action);
73
74#if defined(USE_SIGNAL_HANDLER_TRAMPOLINE)
75 // Work around for a bug in old kernels (only fixed in 3.18 Android kernel):
76 //
77 // Kernel does not clear If-Then execution state bits when entering ARM signal
78 // handler which violates requirements imposed by ARM architecture reference.
79 // Some CPUs look at these bits even while in ARM mode which causes them
80 // to skip some instructions in the prologue of the signal handler.
81 //
82 // To work around the issue we insert enough NOPs in the prologue to ensure
83 // that no actual instructions are skipped and then branch to the actual
84 // signal handler.
85 //
86 // For the kernel patch that fixes the issue see:
87 // http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6ecf830e5029598732e04067e325d946097519cb
88 //
89 // Note: this function is marked "naked" because we must guarantee that
90 // our NOPs occur before any compiler generated prologue.
91 template <SignalAction action>
92 static __attribute__((naked)) void SignalHandlerTrampoline(int signal,
93 siginfo_t* info,
94 void* context_) {
95 // IT (If-Then) instruction makes up to four instructions that follow it
96 // conditional.
97 // Note: clobber all register so that compiler does not attempt to hoist
98 // anything from the next assembly block past this one.
99 asm volatile("nop; nop; nop; nop;"
100 :
101 :
102 : "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", "r8", "r9",
103 "r10", "r11", "r12", "r13", "r14", "memory");
104
105 // Tail-call into the actual signal handler.
106 //
107 // Note: this code is split into a separate inline assembly block because
108 // any code that compiler generates to satisfy register constraints must
109 // be generated after four NOPs.
110 //
111 // Note: there is no portable way to specify that we want to have
112 // signal, info and context_ in r0 - r2 respectively. So we just mark them
113 // as clobbered and hope that compiler does not emit any code that uses
114 // these registers to satisfy action constraint (we tested on clang and
115 // the generated code looks like one would expect).
116 asm volatile("bx %0;" : : "r"(action) : "r0", "r1", "r2", "memory");
117 }
118#endif // defined(USE_SIGNAL_HANDLER_TRAMPOLINE)
119};
120
121#undef USE_SIGNAL_HANDLER_TRAMPOLINE
122
123} // namespace dart
124
125#endif // RUNTIME_VM_SIGNAL_HANDLER_H_
126