Merge pull request #25161 from drodriguez/android-backtraces

[android] Basic support for backtraces.

Author: compnerd

cmake/modules/AddSwift.cmake

@@ -303,6 +303,11 @@ function(_add_variant_c_compile_flags)
                        "-fcoverage-mapping")
   endif()
 
+  if((CFLAGS_ARCH STREQUAL "armv7" OR CFLAGS_ARCH STREQUAL "aarch64") AND
+     (CFLAGS_SDK STREQUAL "LINUX" OR CFLAGS_SDK STREQUAL "ANDROID"))
+     list(APPEND result -funwind-tables)
+  endif()
+
   if("${CFLAGS_SDK}" STREQUAL "ANDROID")
     swift_android_libcxx_include_paths(CFLAGS_CXX_INCLUDES)
     swift_android_include_for_arch("${CFLAGS_ARCH}" "${CFLAGS_ARCH}_INCLUDE")

stdlib/public/runtime/Errors.cpp

@@ -14,7 +14,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if defined(__CYGWIN__) || defined(__ANDROID__) || defined(__HAIKU__)
+#if defined(__CYGWIN__) || defined(__HAIKU__)
 #define SWIFT_SUPPORTS_BACKTRACE_REPORTING 0
 #else
 #define SWIFT_SUPPORTS_BACKTRACE_REPORTING 1
@@ -58,6 +58,10 @@
 #include <android/log.h>
 #endif
 
+#if defined(__ELF__)
+#include <unwind.h>
+#endif
+
 namespace FatalErrorFlags {
 enum: uint32_t {
   ReportBacktrace = 1 << 0
@@ -188,13 +192,46 @@ void swift::dumpStackTraceEntry(unsigned index, void *framePC,
 #endif
 }
 
+#if defined(__ELF__)
+struct UnwindState {
+  void **current;
+  void **end;
+};
+
+static _Unwind_Reason_Code SwiftUnwindFrame(struct _Unwind_Context *context, void *arg) {
+  struct UnwindState *state = static_cast<struct UnwindState *>(arg);
+  if (state->current == state->end) {
+    return _URC_END_OF_STACK;
+  }
+
+  uintptr_t pc;
+#if defined(__arm__)
+  // ARM r15 is PC.  UNW_REG_PC is *not* the same value, and using that will
+  // result in abnormal behaviour.
+  _Unwind_VRS_Get(context, _UVRSC_CORE, 15, _UVRSD_UINT32, &pc);
+  // Clear the ISA bit during the reporting.
+  pc &= ~(uintptr_t)0x1;
+#else
+  pc = _Unwind_GetIP(context);
+#endif
+  if (pc) {
+    *state->current++ = reinterpret_cast<void *>(pc);
+  }
+  return _URC_NO_REASON;
+}
+#endif
+
 LLVM_ATTRIBUTE_NOINLINE
 void swift::printCurrentBacktrace(unsigned framesToSkip) {
 #if SWIFT_SUPPORTS_BACKTRACE_REPORTING
   constexpr unsigned maxSupportedStackDepth = 128;
   void *addrs[maxSupportedStackDepth];
 #if defined(_WIN32)
   int symbolCount = CaptureStackBackTrace(0, maxSupportedStackDepth, addrs, NULL);
+#elif defined(__ELF__)
+  struct UnwindState state = {&addrs[0], &addrs[maxSupportedStackDepth]};
+  _Unwind_Backtrace(SwiftUnwindFrame, &state);
+  int symbolCount = state.current - addrs;
 #else
   int symbolCount = backtrace(addrs, maxSupportedStackDepth);
 #endif