A set of fixes related to clang, aarch64 and musl pecularities of vmstructs stack unwinder (#199)

* Use heuristic to get frame layout for aarch64

* Improve recovery from Java Anchor Frame

* Add and extend tests for vmstructs based stackwalking

* Adjust for Musl signal trampoline

* Run non-crashy test configs first

* Reduce crashiness and locking of tests

* Use root symbols

* Compensate for GH musl/x64 runner quirks

* Emit 'skip_frames' error frame on java anchor fallback

* Do not try to recover from invalid anchor frames

* Use X-enums for better code clarity

Author: jbachorik

ddprof-lib/src/main/cpp/codeCache.h

@@ -113,7 +113,7 @@ class CodeCache {
 
   void expand();
   void makeImportsPatchable();
-    void saveImport(ImportId id, void** entry);
+  void saveImport(ImportId id, void** entry);
 
 public:
   explicit CodeCache(const char *name, short lib_index = -1,
@@ -177,6 +177,9 @@ class CodeCache {
   }
 
   int count() { return _count; }
+  CodeBlob* blob(int idx) {
+    return &_blobs[idx];
+  }
 };
 
 class CodeCacheArray {

ddprof-lib/src/main/cpp/dwarf.cpp

@@ -89,6 +89,7 @@ FrameDesc FrameDesc::empty_frame = {0, DW_REG_SP | EMPTY_FRAME_SIZE << 8,
 FrameDesc FrameDesc::default_frame = {0, DW_REG_FP | LINKED_FRAME_SIZE << 8,
                                       -LINKED_FRAME_SIZE,
                                       -LINKED_FRAME_SIZE + DW_STACK_SLOT};
+FrameDesc FrameDesc::default_clang_frame = {0, DW_REG_FP | LINKED_FRAME_CLANG_SIZE << 8, -LINKED_FRAME_CLANG_SIZE, -LINKED_FRAME_CLANG_SIZE + DW_STACK_SLOT};
 
 DwarfParser::DwarfParser(const char *name, const char *image_base,
                          const char *eh_frame_hdr) {
@@ -398,12 +399,17 @@ int DwarfParser::parseExpression() {
 
 void DwarfParser::addRecord(u32 loc, u32 cfa_reg, int cfa_off, int fp_off,
                             int pc_off) {
-  // sanity asserts for the values fitting into 16bit
-  assert(cfa_reg <= 0xffffffff);
-  assert(static_cast<u32>(cfa_off) <= 0xffffffff);
+  // Sanity asserts to be able to pack those two values into one u32 vq
+  // Assert that the cfa_reg fits in 8 bits (0 to 255)
+  assert(cfa_reg <= 0xFF);
+
+  // Assert that the cfa_off fits in a 24-bit signed range.
+  // Signed 24-bit integer range: -2^23 (-8,388,608) to 2^23 - 1 (8,388,607)
+  assert(cfa_off >= -8388608 && cfa_off <= 8388607);
 
   // cfa_reg and cfa_off can be encoded to a single 32 bit value, considering the existing and supported systems
-  u32 cfa = static_cast<u16>(cfa_off) << 16 | static_cast<u16>(cfa_reg);
+  u32 cfa = static_cast<u32>(cfa_off) << 8 | static_cast<u32>(cfa_reg & 0xff);
+
   if (_prev == NULL || (_prev->loc == loc && --_count >= 0) ||
       _prev->cfa != cfa || _prev->fp_off != fp_off || _prev->pc_off != pc_off) {
     _prev = addRecordRaw(loc, cfa, fp_off, pc_off);

ddprof-lib/src/main/cpp/dwarf.h

@@ -36,6 +36,7 @@ const int DW_REG_SP = 7;
 const int DW_REG_PC = 16;
 const int EMPTY_FRAME_SIZE = DW_STACK_SLOT;
 const int LINKED_FRAME_SIZE = 2 * DW_STACK_SLOT;
+const int LINKED_FRAME_CLANG_SIZE = LINKED_FRAME_SIZE;
 
 #elif defined(__i386__)
 
@@ -46,6 +47,7 @@ const int DW_REG_SP = 4;
 const int DW_REG_PC = 8;
 const int EMPTY_FRAME_SIZE = DW_STACK_SLOT;
 const int LINKED_FRAME_SIZE = 2 * DW_STACK_SLOT;
+const int LINKED_FRAME_CLANG_SIZE = LINKED_FRAME_SIZE;
 
 #elif defined(__aarch64__)
 
@@ -55,13 +57,9 @@ const int DW_REG_FP = 29;
 const int DW_REG_SP = 31;
 const int DW_REG_PC = 30;
 const int EMPTY_FRAME_SIZE = 0;
-
-// aarch64 function prologue looks like this (if frame pointer is used):
-// stp x29, x30, [sp, -16]!   // Save FP (x29) and LR (x30)
-// mov x29, sp                // Set FP to SP
-// ---
-// LINKED_FRAME_SIZE should be 16
-const int LINKED_FRAME_SIZE = 2 * DW_STACK_SLOT;
+const int LINKED_FRAME_SIZE = 0;
+// clang compiler uses different frame layout than GCC
+const int LINKED_FRAME_CLANG_SIZE = 2 * DW_STACK_SLOT;
 
 #else
 
@@ -72,6 +70,7 @@ const int DW_REG_SP = 1;
 const int DW_REG_PC = 2;
 const int EMPTY_FRAME_SIZE = 0;
 const int LINKED_FRAME_SIZE = 0;
+const int LINKED_FRAME_CLANG_SIZE = LINKED_FRAME_SIZE;
 
 #endif
 
@@ -83,6 +82,7 @@ struct FrameDesc {
 
   static FrameDesc empty_frame;
   static FrameDesc default_frame;
+  static FrameDesc default_clang_frame;
 
   static int comparator(const void *p1, const void *p2) {
     FrameDesc *fd1 = (FrameDesc *)p1;

ddprof-lib/src/main/cpp/profiler.cpp

@@ -252,10 +252,10 @@ CodeBlob *Profiler::findRuntimeStub(const void *address) {
   return _runtime_stubs.findBlobByAddress(address);
 }
 
-bool Profiler::isAddressInCode(const void *pc) {
+bool Profiler::isAddressInCode(const void *pc, bool include_stubs) {
   if (CodeHeap::contains(pc)) {
     return CodeHeap::findNMethod(pc) != NULL &&
-           !(pc >= _call_stub_begin && pc < _call_stub_end);
+           (include_stubs || !(pc >= _call_stub_begin && pc < _call_stub_end));
   } else {
     return _libs->findLibraryByAddress(pc) != NULL;
   }

ddprof-lib/src/main/cpp/profiler.h

@@ -243,7 +243,7 @@ class Profiler {
   const char *getLibraryName(const char *native_symbol);
   const char *findNativeMethod(const void *address);
   CodeBlob *findRuntimeStub(const void *address);
-  bool isAddressInCode(const void *pc);
+  bool isAddressInCode(const void *pc, bool include_stubs = true);
 
   static void segvHandler(int signo, siginfo_t *siginfo, void *ucontext);
   static void busHandler(int signo, siginfo_t *siginfo, void *ucontext);