Properly handle signal stacks and frame-size calculations

We can determine the signal stack, so use that information to
make better decisions about when to calculate the frame size
and when not to. This fixes a several tests where the memory
layout had the signal stack and main stack in position that
confused some of the greater-than/less-than comparisons.

Also cleanup certain types to avoid more casting than necessary.

PiperOrigin-RevId: 580221819
Change-Id: I0365b03e7893741603dc66e6d36a069d0b7f5404

1 files changed, 38 insertions, 17 deletions

diff --git a/absl/debugging/internal/stacktrace_aarch64-inl.inc b/absl/debugging/internal/stacktrace_aarch64-inl.inc
index c46a91db..fba0ba49 100644
--- a/absl/debugging/internal/stacktrace_aarch64-inl.inc
+++ b/absl/debugging/internal/stacktrace_aarch64-inl.inc
@@ -4,6 +4,7 @@
 // Generate stack tracer for aarch64
 
 #if defined(__linux__)
+#include <signal.h>
 #include <sys/mman.h>
 #include <ucontext.h>
 #include <unistd.h>
@@ -70,7 +71,7 @@ static const unsigned char* GetKernelRtSigreturnAddress() {
 // Compute the size of a stack frame in [low..high).  We assume that
 // low < high.  Return size of kUnknownFrameSize.
 template<typename T>
-static inline size_t ComputeStackFrameSize(const T* low,
+static size_t ComputeStackFrameSize(const T* low,
                                            const T* high) {
   const char* low_char_ptr = reinterpret_cast<const char *>(low);
   const char* high_char_ptr = reinterpret_cast<const char *>(high);
@@ -78,6 +79,20 @@ static inline size_t ComputeStackFrameSize(const T* low,
                     : kUnknownFrameSize;
 }
 
+// Saves stack info that is expensive to calculate to avoid recalculating per frame.
+struct StackInfo {
+  uintptr_t stack_low;
+  uintptr_t stack_high;
+  uintptr_t sig_stack_low;
+  uintptr_t sig_stack_high;
+};
+
+static bool InsideSignalStack(void** ptr, const StackInfo* stack_info) {
+  uintptr_t comparable_ptr = reinterpret_cast<uintptr_t>(ptr);
+  return (comparable_ptr >= stack_info->sig_stack_low &&
+          comparable_ptr < stack_info->sig_stack_high);
+}
+
 // Given a pointer to a stack frame, locate and return the calling
 // stackframe, or return null if no stackframe can be found. Perform sanity
 // checks (the strictness of which is controlled by the boolean parameter
@@ -86,9 +101,8 @@ template<bool STRICT_UNWINDING, bool WITH_CONTEXT>
 ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS  // May read random elements from stack.
 ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY  // May read random elements from stack.
 static void **NextStackFrame(void **old_frame_pointer, const void *uc,
-                             size_t stack_low, size_t stack_high) {
+                             const StackInfo *stack_info) {
   void **new_frame_pointer = reinterpret_cast<void**>(*old_frame_pointer);
-  bool check_frame_size = true;
 
 #if defined(__linux__)
   if (WITH_CONTEXT && uc != nullptr) {
@@ -114,10 +128,6 @@ static void **NextStackFrame(void **old_frame_pointer, const void *uc,
       if (!absl::debugging_internal::AddressIsReadable(
               new_frame_pointer))
         return nullptr;
-
-      // Skip frame size check if we return from a signal. We may be using a
-      // an alternate stack for signals.
-      check_frame_size = false;
     }
   }
 #endif
@@ -126,9 +136,11 @@ static void **NextStackFrame(void **old_frame_pointer, const void *uc,
   if ((reinterpret_cast<uintptr_t>(new_frame_pointer) & 7) != 0)
     return nullptr;
 
-  // Check frame size.  In strict mode, we assume frames to be under
-  // 100,000 bytes.  In non-strict mode, we relax the limit to 1MB.
-  if (check_frame_size) {
+  // Only check the size if both frames are in the same stack.
+  if (InsideSignalStack(new_frame_pointer, stack_info) ==
+      InsideSignalStack(old_frame_pointer, stack_info)) {
+    // Check frame size.  In strict mode, we assume frames to be under
+    // 100,000 bytes.  In non-strict mode, we relax the limit to 1MB.
     const size_t max_size = STRICT_UNWINDING ? 100000 : 1000000;
     const size_t frame_size =
         ComputeStackFrameSize(old_frame_pointer, new_frame_pointer);
@@ -136,15 +148,21 @@ static void **NextStackFrame(void **old_frame_pointer, const void *uc,
        return nullptr;
     // A very large frame may mean corrupt memory or an erroneous frame
     // pointer. But also maybe just a plain-old large frame.  Assume that if the
-    // frame is within the known stack, then it is valid.
+    // frame is within a known stack, then it is valid.
     if (frame_size > max_size) {
-       if (stack_high < kUnknownStackEnd &&
+      size_t stack_low = stack_info->stack_low;
+      size_t stack_high = stack_info->stack_high;
+      if (InsideSignalStack(new_frame_pointer, stack_info)) {
+        stack_low = stack_info->sig_stack_low;
+        stack_high = stack_info->sig_stack_high;
+      }
+      if (stack_high < kUnknownStackEnd &&
           static_cast<size_t>(getpagesize()) < stack_low) {
         const uintptr_t new_fp_u =
             reinterpret_cast<uintptr_t>(new_frame_pointer);
         // Stack bounds are known.
         if (!(stack_low < new_fp_u && new_fp_u <= stack_high)) {
-          // new_frame_pointer is not within the known stack.
+          // new_frame_pointer is not within a known stack.
           return nullptr;
         }
       } else {
@@ -174,8 +192,11 @@ static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
   int n = 0;
 
   // Assume that the first page is not stack.
-  size_t stack_low = static_cast<size_t>(getpagesize());
-  size_t stack_high = kUnknownStackEnd;
+  StackInfo stack_info;
+  stack_info.stack_low = getpagesize();
+  stack_info.stack_high = kUnknownStackEnd;
+  stack_info.sig_stack_low = stack_info.stack_low;
+  stack_info.sig_stack_high = kUnknownStackEnd;
 
   // The frame pointer points to low address of a frame.  The first 64-bit
   // word of a frame points to the next frame up the call chain, which normally
@@ -210,7 +231,7 @@ static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
     // that is as complete as possible (even if it contains a few bogus
     // entries in some rare cases).
     frame_pointer = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(
-        frame_pointer, ucp, stack_low, stack_high);
+        frame_pointer, ucp, &stack_info);
   }
 
   if (min_dropped_frames != nullptr) {
@@ -225,7 +246,7 @@ static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
         num_dropped_frames++;
       }
       frame_pointer = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(
-          frame_pointer, ucp, stack_low, stack_high);
+          frame_pointer, ucp, &stack_info);
     }
     *min_dropped_frames = num_dropped_frames;
   }