Implemented GetSample like POSIX backtrace()

src/sampler.h

Index: src/sampler.h
diff --git a/src/sampler.h b/src/sampler.h
index c3dce4ed7c2fec7e353cb06d1641f63e82092a84..2b0a62a56dca04eafe9e27f3c07528be4f472f05 100644
--- a/src/sampler.h
+++ b/src/sampler.h
@@ -9,6 +9,149 @@
 #include "src/frames.h"
 #include "src/globals.h"
 
+#if V8_OS_POSIX && !V8_OS_CYGWIN
+
+#define USE_SIGNALS
+
+#include <errno.h>
+#include <pthread.h>
+#include <signal.h>
+#include <sys/time.h>
+
+#if !V8_OS_QNX && !V8_OS_NACL
+#include <sys/syscall.h>  // NOLINT
+#endif
+
+#if V8_OS_MACOSX
+#include <mach/mach.h>
+// OpenBSD doesn't have <ucontext.h>. ucontext_t lives in <signal.h>
+// and is a typedef for struct sigcontext. There is no uc_mcontext.
+#elif(!V8_OS_ANDROID || defined(__BIONIC_HAVE_UCONTEXT_T)) && \
+    !V8_OS_OPENBSD && !V8_OS_NACL
+#include <ucontext.h>
+#endif
+
+#include <unistd.h>
+
+// GLibc on ARM defines mcontext_t has a typedef for 'struct sigcontext'.
+// Old versions of the C library <signal.h> didn't define the type.
+#if V8_OS_ANDROID && !defined(__BIONIC_HAVE_UCONTEXT_T) && \
+    (defined(__arm__) || defined(__aarch64__)) && \
+    !defined(__BIONIC_HAVE_STRUCT_SIGCONTEXT)
+#include <asm/sigcontext.h>  // NOLINT
+#endif
+
+#elif V8_OS_WIN || V8_OS_CYGWIN
+
+#include "src/base/win32-headers.h"
+
+#endif
+
+
+#if V8_OS_ANDROID && !defined(__BIONIC_HAVE_UCONTEXT_T)
+
+// Not all versions of Android's C library provide ucontext_t.
+// Detect this and provide custom but compatible definitions. Note that these
+// follow the GLibc naming convention to access register values from
+// mcontext_t.
+//
+// See http://code.google.com/p/android/issues/detail?id=34784
+
+#if defined(__arm__)
+
+typedef struct sigcontext mcontext_t;
+
+typedef struct ucontext {
+  uint32_t uc_flags;
+  struct ucontext* uc_link;
+  stack_t uc_stack;
+  mcontext_t uc_mcontext;
+  // Other fields are not used by V8, don't define them here.
+} ucontext_t;
+
+#elif defined(__aarch64__)
+
+typedef struct sigcontext mcontext_t;
+
+typedef struct ucontext {
+  uint64_t uc_flags;
+  struct ucontext *uc_link;
+  stack_t uc_stack;
+  mcontext_t uc_mcontext;
+  // Other fields are not used by V8, don't define them here.
+} ucontext_t;
+
+#elif defined(__mips__)
+// MIPS version of sigcontext, for Android bionic.
+typedef struct {
+  uint32_t regmask;
+  uint32_t status;
+  uint64_t pc;
+  uint64_t gregs[32];
+  uint64_t fpregs[32];
+  uint32_t acx;
+  uint32_t fpc_csr;
+  uint32_t fpc_eir;
+  uint32_t used_math;
+  uint32_t dsp;
+  uint64_t mdhi;
+  uint64_t mdlo;
+  uint32_t hi1;
+  uint32_t lo1;
+  uint32_t hi2;
+  uint32_t lo2;
+  uint32_t hi3;
+  uint32_t lo3;
+} mcontext_t;
+
+typedef struct ucontext {
+  uint32_t uc_flags;
+  struct ucontext* uc_link;
+  stack_t uc_stack;
+  mcontext_t uc_mcontext;
+  // Other fields are not used by V8, don't define them here.
+} ucontext_t;
+
+#elif defined(__i386__)
+// x86 version for Android.
+typedef struct {
+  uint32_t gregs[19];
+  void* fpregs;
+  uint32_t oldmask;
+  uint32_t cr2;
+} mcontext_t;
+
+typedef uint32_t kernel_sigset_t[2];  // x86 kernel uses 64-bit signal masks
+typedef struct ucontext {
+  uint32_t uc_flags;
+  struct ucontext* uc_link;
+  stack_t uc_stack;
+  mcontext_t uc_mcontext;
+  // Other fields are not used by V8, don't define them here.
+} ucontext_t;
+enum { REG_EBP = 6, REG_ESP = 7, REG_EIP = 14 };
+
+#elif defined(__x86_64__)
+// x64 version for Android.
+typedef struct {
+  uint64_t gregs[23];
+  void* fpregs;
+  uint64_t __reserved1[8];
+} mcontext_t;
+
+typedef struct ucontext {
+  uint64_t uc_flags;
+  struct ucontext *uc_link;
+  stack_t uc_stack;
+  mcontext_t uc_mcontext;
+  // Other fields are not used by V8, don't define them here.
+} ucontext_t;
+enum { REG_RBP = 10, REG_RSP = 15, REG_RIP = 16 };
+#endif
+
+#endif  // V8_OS_ANDROID && !defined(__BIONIC_HAVE_UCONTEXT_T)
+
+
 namespace v8 {
 namespace internal {
 
@@ -21,13 +164,6 @@ class Isolate;
 // (if used for profiling) the program counter and stack pointer for
 // the thread that created it.
 
-struct RegisterState {
-  RegisterState() : pc(NULL), sp(NULL), fp(NULL) {}
-  Address pc;      // Instruction pointer.
-  Address sp;      // Stack pointer.
-  Address fp;      // Frame pointer.
-};
-
 // TickSample captures the information collected for each sample.
 struct TickSample {
   TickSample()
@@ -37,7 +173,7 @@ struct TickSample {
         frames_count(0),
         has_external_callback(false),
         top_frame_type(StackFrame::NONE) {}
-  void Init(Isolate* isolate, const RegisterState& state);
+  void Init(Isolate* isolate, const v8::RegisterState& state);
   StateTag state;  // The state of the VM.
   Address pc;      // Instruction pointer.
   union {
@@ -67,7 +203,7 @@ class Sampler {
   int interval() const { return interval_; }
 
   // Performs stack sampling.
-  void SampleStack(const RegisterState& regs);
+  void SampleStack(const v8::RegisterState& regs);
 
   // Start and stop sampler.
   void Start();
@@ -85,6 +221,12 @@ class Sampler {
   bool IsActive() const { return base::NoBarrier_Load(&active_); }
 
   void DoSample();
+
+  static int GetSample(Isolate* isolate,
+                       const v8::RegisterState& state,
+                       void** buffer,
+                       unsigned int depth);
+
   // If true next sample must be initiated on the profiler event processor
   // thread right after latest sample is processed.
   void SetHasProcessingThread(bool value) {