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[chromium-blink-merge.git] / third_party / tcmalloc / chromium / src / getpc.h
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1 // Copyright (c) 2005, Google Inc.
2 // All rights reserved.
3 //
4 // Redistribution and use in source and binary forms, with or without
5 // modification, are permitted provided that the following conditions are
6 // met:
7 //
8 // * Redistributions of source code must retain the above copyright
9 // notice, this list of conditions and the following disclaimer.
10 // * Redistributions in binary form must reproduce the above
11 // copyright notice, this list of conditions and the following disclaimer
12 // in the documentation and/or other materials provided with the
13 // distribution.
14 // * Neither the name of Google Inc. nor the names of its
15 // contributors may be used to endorse or promote products derived from
16 // this software without specific prior written permission.
18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 // ---
31 // Author: Craig Silverstein
33 // This is an internal header file used by profiler.cc. It defines
34 // the single (inline) function GetPC. GetPC is used in a signal
35 // handler to figure out the instruction that was being executed when
36 // the signal-handler was triggered.
38 // To get this, we use the ucontext_t argument to the signal-handler
39 // callback, which holds the full context of what was going on when
40 // the signal triggered. How to get from a ucontext_t to a Program
41 // Counter is OS-dependent.
43 #ifndef BASE_GETPC_H_
44 #define BASE_GETPC_H_
46 #include "config.h"
48 // On many linux systems, we may need _GNU_SOURCE to get access to
49 // the defined constants that define the register we want to see (eg
50 // REG_EIP). Note this #define must come first!
51 #define _GNU_SOURCE 1
52 // If #define _GNU_SOURCE causes problems, this might work instead.
53 // It will cause problems for FreeBSD though!, because it turns off
54 // the needed __BSD_VISIBLE.
55 //#define _XOPEN_SOURCE 500
57 #include <string.h> // for memcmp
58 #if defined(HAVE_SYS_UCONTEXT_H)
59 #include <sys/ucontext.h>
60 #elif defined(HAVE_UCONTEXT_H)
61 #include <ucontext.h> // for ucontext_t (and also mcontext_t)
62 #elif defined(HAVE_CYGWIN_SIGNAL_H)
63 #include <cygwin/signal.h>
64 typedef ucontext ucontext_t;
65 #elif defined(__ANDROID__)
66 #include <unwind.h>
67 #endif
70 // Take the example where function Foo() calls function Bar(). For
71 // many architectures, Bar() is responsible for setting up and tearing
72 // down its own stack frame. In that case, it's possible for the
73 // interrupt to happen when execution is in Bar(), but the stack frame
74 // is not properly set up (either before it's done being set up, or
75 // after it's been torn down but before Bar() returns). In those
76 // cases, the stack trace cannot see the caller function anymore.
78 // GetPC can try to identify this situation, on architectures where it
79 // might occur, and unwind the current function call in that case to
80 // avoid false edges in the profile graph (that is, edges that appear
81 // to show a call skipping over a function). To do this, we hard-code
82 // in the asm instructions we might see when setting up or tearing
83 // down a stack frame.
85 // This is difficult to get right: the instructions depend on the
86 // processor, the compiler ABI, and even the optimization level. This
87 // is a best effort patch -- if we fail to detect such a situation, or
88 // mess up the PC, nothing happens; the returned PC is not used for
89 // any further processing.
90 struct CallUnrollInfo {
91 // Offset from (e)ip register where this instruction sequence
92 // should be matched. Interpreted as bytes. Offset 0 is the next
93 // instruction to execute. Be extra careful with negative offsets in
94 // architectures of variable instruction length (like x86) - it is
95 // not that easy as taking an offset to step one instruction back!
96 int pc_offset;
97 // The actual instruction bytes. Feel free to make it larger if you
98 // need a longer sequence.
99 char ins[16];
100 // How many bytes to match from ins array?
101 int ins_size;
102 // The offset from the stack pointer (e)sp where to look for the
103 // call return address. Interpreted as bytes.
104 int return_sp_offset;
108 // The dereferences needed to get the PC from a struct ucontext were
109 // determined at configure time, and stored in the macro
110 // PC_FROM_UCONTEXT in config.h. The only thing we need to do here,
111 // then, is to do the magic call-unrolling for systems that support it.
113 // -- Special case 1: linux x86, for which we have CallUnrollInfo
114 #if defined(__linux) && defined(__i386) && defined(__GNUC__) && \
115 !defined(__ANDROID__)
116 static const CallUnrollInfo callunrollinfo[] = {
117 // Entry to a function: push %ebp; mov %esp,%ebp
118 // Top-of-stack contains the caller IP.
119 { 0,
120 {0x55, 0x89, 0xe5}, 3,
123 // Entry to a function, second instruction: push %ebp; mov %esp,%ebp
124 // Top-of-stack contains the old frame, caller IP is +4.
125 { -1,
126 {0x55, 0x89, 0xe5}, 3,
129 // Return from a function: RET.
130 // Top-of-stack contains the caller IP.
131 { 0,
132 {0xc3}, 1,
137 inline void* GetPC(const ucontext_t& signal_ucontext) {
138 // See comment above struct CallUnrollInfo. Only try instruction
139 // flow matching if both eip and esp looks reasonable.
140 const int eip = signal_ucontext.uc_mcontext.gregs[REG_EIP];
141 const int esp = signal_ucontext.uc_mcontext.gregs[REG_ESP];
142 if ((eip & 0xffff0000) != 0 && (~eip & 0xffff0000) != 0 &&
143 (esp & 0xffff0000) != 0) {
144 char* eip_char = reinterpret_cast<char*>(eip);
145 for (int i = 0; i < sizeof(callunrollinfo)/sizeof(*callunrollinfo); ++i) {
146 if (!memcmp(eip_char + callunrollinfo[i].pc_offset,
147 callunrollinfo[i].ins, callunrollinfo[i].ins_size)) {
148 // We have a match.
149 void **retaddr = (void**)(esp + callunrollinfo[i].return_sp_offset);
150 return *retaddr;
154 return (void*)eip;
157 // Special case #2: Windows, which has to do something totally different.
158 #elif defined(_WIN32) || defined(__CYGWIN__) || defined(__CYGWIN32__) || defined(__MINGW32__)
159 // If this is ever implemented, probably the way to do it is to have
160 // profiler.cc use a high-precision timer via timeSetEvent:
161 // http://msdn2.microsoft.com/en-us/library/ms712713.aspx
162 // We'd use it in mode TIME_CALLBACK_FUNCTION/TIME_PERIODIC.
163 // The callback function would be something like prof_handler, but
164 // alas the arguments are different: no ucontext_t! I don't know
165 // how we'd get the PC (using StackWalk64?)
166 // http://msdn2.microsoft.com/en-us/library/ms680650.aspx
168 #include "base/logging.h" // for RAW_LOG
169 #ifndef HAVE_CYGWIN_SIGNAL_H
170 typedef int ucontext_t;
171 #endif
173 inline void* GetPC(const struct ucontext_t& signal_ucontext) {
174 RAW_LOG(ERROR, "GetPC is not yet implemented on Windows\n");
175 return NULL;
177 #elif defined(__ANDROID__)
178 typedef struct _Unwind_Context ucontext_t;
180 inline void* GetPC(const ucontext_t& signal_ucontext) {
181 // Bionic doesn't export ucontext, see
182 // https://code.google.com/p/android/issues/detail?id=34784.
183 return reinterpret_cast<void*>(_Unwind_GetIP(
184 const_cast<ucontext_t*>(&signal_ucontext)));
187 // Normal cases. If this doesn't compile, it's probably because
188 // PC_FROM_UCONTEXT is the empty string. You need to figure out
189 // the right value for your system, and add it to the list in
190 // configure.ac (or set it manually in your config.h).
191 #else
192 inline void* GetPC(const ucontext_t& signal_ucontext) {
193 return (void*)signal_ucontext.PC_FROM_UCONTEXT; // defined in config.h
196 #endif
198 #endif // BASE_GETPC_H_