diff options
Diffstat (limited to 'third_party/tcmalloc/vendor/src/getpc.h')
| -rw-r--r-- | third_party/tcmalloc/vendor/src/getpc.h | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/third_party/tcmalloc/vendor/src/getpc.h b/third_party/tcmalloc/vendor/src/getpc.h new file mode 100644 index 0000000..9fb2e16 --- /dev/null +++ b/third_party/tcmalloc/vendor/src/getpc.h @@ -0,0 +1,186 @@ +// Copyright (c) 2005, Google Inc. +// All rights reserved. +// +// Redistribution and use in source and binary forms, with or without +// modification, are permitted provided that the following conditions are +// met: +// +// * Redistributions of source code must retain the above copyright +// notice, this list of conditions and the following disclaimer. +// * Redistributions in binary form must reproduce the above +// copyright notice, this list of conditions and the following disclaimer +// in the documentation and/or other materials provided with the +// distribution. +// * Neither the name of Google Inc. nor the names of its +// contributors may be used to endorse or promote products derived from +// this software without specific prior written permission. +// +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +// --- +// Author: Craig Silverstein +// +// This is an internal header file used by profiler.cc. It defines +// the single (inline) function GetPC. GetPC is used in a signal +// handler to figure out the instruction that was being executed when +// the signal-handler was triggered. +// +// To get this, we use the ucontext_t argument to the signal-handler +// callback, which holds the full context of what was going on when +// the signal triggered. How to get from a ucontext_t to a Program +// Counter is OS-dependent. + +#ifndef BASE_GETPC_H_ +#define BASE_GETPC_H_ + +#include "config.h" + +// On many linux systems, we may need _GNU_SOURCE to get access to +// the defined constants that define the register we want to see (eg +// REG_EIP). Note this #define must come first! +#define _GNU_SOURCE 1 +// If #define _GNU_SOURCE causes problems, this might work instead. +// It will cause problems for FreeBSD though!, because it turns off +// the needed __BSD_VISIBLE. +//#define _XOPEN_SOURCE 500 + +#include <string.h> // for memcmp +#if defined(HAVE_SYS_UCONTEXT_H) +#include <sys/ucontext.h> +#elif defined(HAVE_UCONTEXT_H) +#include <ucontext.h> // for ucontext_t (and also mcontext_t) +#elif defined(HAVE_CYGWIN_SIGNAL_H) +#include <cygwin/signal.h> +typedef ucontext ucontext_t; +#endif + + +// Take the example where function Foo() calls function Bar(). For +// many architectures, Bar() is responsible for setting up and tearing +// down its own stack frame. In that case, it's possible for the +// interrupt to happen when execution is in Bar(), but the stack frame +// is not properly set up (either before it's done being set up, or +// after it's been torn down but before Bar() returns). In those +// cases, the stack trace cannot see the caller function anymore. +// +// GetPC can try to identify this situation, on architectures where it +// might occur, and unwind the current function call in that case to +// avoid false edges in the profile graph (that is, edges that appear +// to show a call skipping over a function). To do this, we hard-code +// in the asm instructions we might see when setting up or tearing +// down a stack frame. +// +// This is difficult to get right: the instructions depend on the +// processor, the compiler ABI, and even the optimization level. This +// is a best effort patch -- if we fail to detect such a situation, or +// mess up the PC, nothing happens; the returned PC is not used for +// any further processing. +struct CallUnrollInfo { + // Offset from (e)ip register where this instruction sequence + // should be matched. Interpreted as bytes. Offset 0 is the next + // instruction to execute. Be extra careful with negative offsets in + // architectures of variable instruction length (like x86) - it is + // not that easy as taking an offset to step one instruction back! + int pc_offset; + // The actual instruction bytes. Feel free to make it larger if you + // need a longer sequence. + char ins[16]; + // How many bytes to match from ins array? + int ins_size; + // The offset from the stack pointer (e)sp where to look for the + // call return address. Interpreted as bytes. + int return_sp_offset; +}; + + +// The dereferences needed to get the PC from a struct ucontext were +// determined at configure time, and stored in the macro +// PC_FROM_UCONTEXT in config.h. The only thing we need to do here, +// then, is to do the magic call-unrolling for systems that support it. + +// -- Special case 1: linux x86, for which we have CallUnrollInfo +#if defined(__linux) && defined(__i386) && defined(__GNUC__) +static const CallUnrollInfo callunrollinfo[] = { + // Entry to a function: push %ebp; mov %esp,%ebp + // Top-of-stack contains the caller IP. + { 0, + {0x55, 0x89, 0xe5}, 3, + 0 + }, + // Entry to a function, second instruction: push %ebp; mov %esp,%ebp + // Top-of-stack contains the old frame, caller IP is +4. + { -1, + {0x55, 0x89, 0xe5}, 3, + 4 + }, + // Return from a function: RET. + // Top-of-stack contains the caller IP. + { 0, + {0xc3}, 1, + 0 + } +}; + +inline void* GetPC(const ucontext_t& signal_ucontext) { + // See comment above struct CallUnrollInfo. Only try instruction + // flow matching if both eip and esp looks reasonable. + const int eip = signal_ucontext.uc_mcontext.gregs[REG_EIP]; + const int esp = signal_ucontext.uc_mcontext.gregs[REG_ESP]; + if ((eip & 0xffff0000) != 0 && (~eip & 0xffff0000) != 0 && + (esp & 0xffff0000) != 0) { + char* eip_char = reinterpret_cast<char*>(eip); + for (int i = 0; i < sizeof(callunrollinfo)/sizeof(*callunrollinfo); ++i) { + if (!memcmp(eip_char + callunrollinfo[i].pc_offset, + callunrollinfo[i].ins, callunrollinfo[i].ins_size)) { + // We have a match. + void **retaddr = (void**)(esp + callunrollinfo[i].return_sp_offset); + return *retaddr; + } + } + } + return (void*)eip; +} + +// Special case #2: Windows, which has to do something totally different. +#elif defined(_WIN32) || defined(__CYGWIN__) || defined(__CYGWIN32__) || defined(__MINGW32__) +// If this is ever implemented, probably the way to do it is to have +// profiler.cc use a high-precision timer via timeSetEvent: +// http://msdn2.microsoft.com/en-us/library/ms712713.aspx +// We'd use it in mode TIME_CALLBACK_FUNCTION/TIME_PERIODIC. +// The callback function would be something like prof_handler, but +// alas the arguments are different: no ucontext_t! I don't know +// how we'd get the PC (using StackWalk64?) +// http://msdn2.microsoft.com/en-us/library/ms680650.aspx + +#include "base/logging.h" // for RAW_LOG +#ifndef HAVE_CYGWIN_SIGNAL_H +typedef int ucontext_t; +#endif + +inline void* GetPC(const struct ucontext_t& signal_ucontext) { + RAW_LOG(ERROR, "GetPC is not yet implemented on Windows\n"); + return NULL; +} + +// Normal cases. If this doesn't compile, it's probably because +// PC_FROM_UCONTEXT is the empty string. You need to figure out +// the right value for your system, and add it to the list in +// configure.ac (or set it manually in your config.h). +#else +inline void* GetPC(const ucontext_t& signal_ucontext) { + return (void*)signal_ucontext.PC_FROM_UCONTEXT; // defined in config.h +} + +#endif + +#endif // BASE_GETPC_H_ |