Initial support for emitting unwinding information in perf jitdump.

src/perf-jit.cc

Index: src/perf-jit.cc
diff --git a/src/perf-jit.cc b/src/perf-jit.cc
index 6f3551468abb48088e752014512889845533ab41..b72b21c9e39f95d6d064f8bafd5049c7cb3dc24d 100644
--- a/src/perf-jit.cc
+++ b/src/perf-jit.cc
@@ -29,6 +29,7 @@
 
 #include "src/assembler.h"
 #include "src/objects-inl.h"
+#include "src/unwinding-info.h"
 
 #if V8_OS_LINUX
 #include <fcntl.h>
@@ -56,7 +57,13 @@ struct PerfJitHeader {
 };
 
 struct PerfJitBase {
-  enum PerfJitEvent { kLoad = 0, kMove = 1, kDebugInfo = 2, kClose = 3 };
+  enum PerfJitEvent {
+    kLoad = 0,
+    kMove = 1,
+    kDebugInfo = 2,
+    kClose = 3,
+    kUnwindingInfo = 4
+  };
 
   uint32_t event_;
   uint32_t size_;
@@ -85,6 +92,13 @@ struct PerfJitCodeDebugInfo : PerfJitBase {
   // Followed by entry_count_ instances of PerfJitDebugEntry.
 };
 
+struct PerfJitCodeUnwindingInfo : PerfJitBase {
+  uint64_t unwinding_size_;
+  uint64_t eh_frame_hdr_size_;
+  uint64_t mapped_size_;
+  // Followed by size_ - sizeof(PerfJitCodeUnwindingInfo) bytes of data.
+};
+
 const char PerfJitLogger::kFilenameFormatString[] = "./jit-%d.dump";
 
 // Extra padding for the PID in the filename
@@ -204,6 +218,9 @@ void PerfJitLogger::LogRecordedBuffer(AbstractCode* abstract_code,
   uint32_t code_size = code->is_crankshafted() ? code->safepoint_table_offset()
                                                : code->instruction_size();
 
+  // Unwinding info comes right after debug info.
+  if (FLAG_perf_prof) LogWriteUnwindingInfo(code);
+
   static const char string_terminator[] = "\0";
 
   PerfJitCodeLoad code_load;
@@ -303,6 +320,48 @@ void PerfJitLogger::LogWriteDebugInfo(Code* code, SharedFunctionInfo* shared) {
   LogWriteBytes(padding_bytes, padding);
 }
 
+void PerfJitLogger::LogWriteUnwindingInfo(Code* code) {
+  EhFrameHdr eh_frame_hdr(code);
+
+  PerfJitCodeUnwindingInfo unwinding_info_header;
+  unwinding_info_header.event_ = PerfJitCodeLoad::kUnwindingInfo;
+  unwinding_info_header.time_stamp_ = GetTimestamp();
+  unwinding_info_header.eh_frame_hdr_size_ = EhFrameHdr::kRecordSize;
+
+  int unwinding_info_size;

[rmcilroy, 2016/06/21 13:47:44]

nit - just use the field rather than having an extra local.

[Stefano Sanfilippo, 2016/06/23 15:23:44]

Done.

+  if (code->has_unwinding_info()) {
+    unwinding_info_size = code->unwinding_info_size();
+    unwinding_info_header.mapped_size_ = unwinding_info_size;
+  } else {
+    unwinding_info_size = EhFrameHdr::kRecordSize;
+    unwinding_info_header.mapped_size_ = 0;
+  }
+  unwinding_info_header.unwinding_size_ = unwinding_info_size;
+
+  int content_size = sizeof(unwinding_info_header) + unwinding_info_size;
+  int padding_size = ((content_size + 7) & (~7)) - content_size;

[rmcilroy, 2016/06/21 13:47:44]

Don't use literals for '7'. Can you use RoundUp here instead?

[Stefano Sanfilippo, 2016/06/23 15:23:44]

Done.

+  unwinding_info_header.size_ = content_size + padding_size;
+
+  LogWriteBytes(reinterpret_cast<const char*>(&unwinding_info_header),
+                sizeof(unwinding_info_header));
+
+  if (code->has_unwinding_info()) {
+    PatchProcedureBoundariesInEhFrame(code);

[rmcilroy, 2016/06/21 13:47:44]

You don't have any code which actually writes to the unwinding_info here. It's
impossible for me to tell what this is doing given I don't know how the
unwinding info is structured yet. Could you remove this function (and anything
relating to reading from unwind_info) from this CL and move it to one where it
actually does something (and can be tested). Let's just make this CL about
writing the dummy header and having the plumbing to pass unwind_info on code
objects.

[Stefano Sanfilippo, 2016/06/23 15:23:44]

Agreed. Done.

+
+    // The last EhFrameHdr::kRecordSize bytes were a placeholder for the header.
+    // Discard them and write the actual eh_frame_hdr (below).
+    DCHECK_GE(code->unwinding_info_size(), EhFrameHdr::kRecordSize);
+    LogWriteBytes(reinterpret_cast<const char*>(code->unwinding_info_start()),
+                  code->unwinding_info_size() - EhFrameHdr::kRecordSize);
+  }
+
+  LogWriteBytes(reinterpret_cast<const char*>(&eh_frame_hdr),
+                EhFrameHdr::kRecordSize);
+
+  char padding_bytes[] = "\0\0\0\0\0\0\0\0";
+  LogWriteBytes(padding_bytes, padding_size);
+}
+
 void PerfJitLogger::CodeMoveEvent(AbstractCode* from, Address to) {
   // Code relocation not supported.
   UNREACHABLE();