Merge new upstream LTS 20230802.0

1 files changed, 59 insertions, 23 deletions

diff --git a/absl/debugging/internal/stacktrace_aarch64-inl.inc b/absl/debugging/internal/stacktrace_aarch64-inl.inc
index 71cdaf09..3f087162 100644
--- a/absl/debugging/internal/stacktrace_aarch64-inl.inc
+++ b/absl/debugging/internal/stacktrace_aarch64-inl.inc
@@ -13,6 +13,7 @@
 #include <cassert>
 #include <cstdint>
 #include <iostream>
+#include <limits>
 
 #include "absl/base/attributes.h"
 #include "absl/debugging/internal/address_is_readable.h"
@@ -20,6 +21,10 @@
 #include "absl/debugging/stacktrace.h"
 
 static const size_t kUnknownFrameSize = 0;
+// Stack end to use when we don't know the actual stack end
+// (effectively just the end of address space).
+constexpr uintptr_t kUnknownStackEnd =
+    std::numeric_limits<size_t>::max() - sizeof(void *);
 
 #if defined(__linux__)
 // Returns the address of the VDSO __kernel_rt_sigreturn function, if present.
@@ -79,8 +84,9 @@ static inline size_t ComputeStackFrameSize(const T* low,
 // "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
 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) {
+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) {
   void **new_frame_pointer = reinterpret_cast<void**>(*old_frame_pointer);
   bool check_frame_size = true;
 
@@ -94,16 +100,21 @@ static void **NextStackFrame(void **old_frame_pointer, const void *uc) {
       void **const pre_signal_frame_pointer =
           reinterpret_cast<void **>(ucv->uc_mcontext.regs[29]);
 
+      // The most recent signal always needs special handling to find the frame
+      // pointer, but a nested signal does not.  If pre_signal_frame_pointer is
+      // earlier in the stack than the old_frame_pointer, then use it. If it is
+      // later, then we have already unwound through it and it needs no special
+      // handling.
+      if (pre_signal_frame_pointer >= old_frame_pointer) {
+        new_frame_pointer = pre_signal_frame_pointer;
+      }
       // Check that alleged frame pointer is actually readable. This is to
       // prevent "double fault" in case we hit the first fault due to e.g.
       // stack corruption.
       if (!absl::debugging_internal::AddressIsReadable(
-              pre_signal_frame_pointer))
+              new_frame_pointer))
         return nullptr;
 
-      // Alleged frame pointer is readable, use it for further unwinding.
-      new_frame_pointer = pre_signal_frame_pointer;
-
       // Skip frame size check if we return from a signal. We may be using a
       // an alternate stack for signals.
       check_frame_size = false;
@@ -121,8 +132,26 @@ static void **NextStackFrame(void **old_frame_pointer, const void *uc) {
     const size_t max_size = STRICT_UNWINDING ? 100000 : 1000000;
     const size_t frame_size =
         ComputeStackFrameSize(old_frame_pointer, new_frame_pointer);
-    if (frame_size == kUnknownFrameSize || frame_size > max_size)
-      return nullptr;
+    if (frame_size == kUnknownFrameSize)
+       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.
+    if (frame_size > max_size) {
+       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.
+          return nullptr;
+        }
+      } else {
+        // Stack bounds are unknown, prefer truncated stack to possible crash.
+        return nullptr;
+      }
+    }
   }
 
   return new_frame_pointer;
@@ -138,42 +167,49 @@ static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
 #else
 # error reading stack point not yet supported on this platform.
 #endif
-
   skip_count++;    // Skip the frame for this function.
   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;
+
   // 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
   // is just after the high address of the current frame.  The second word of
-  // a frame contains return adress of to the caller.   To find a pc value
+  // a frame contains return address of to the caller.   To find a pc value
   // associated with the current frame, we need to go down a level in the call
   // chain.  So we remember return the address of the last frame seen.  This
   // does not work for the first stack frame, which belongs to UnwindImp() but
   // we skip the frame for UnwindImp() anyway.
   void* prev_return_address = nullptr;
+  // The nth frame size is the difference between the nth frame pointer and the
+  // the frame pointer below it in the call chain. There is no frame below the
+  // leaf frame, but this function is the leaf anyway, and we skip it.
+  void** prev_frame_pointer = nullptr;
 
-  while (frame_pointer && n < max_depth) {
-    // The absl::GetStackFrames routine is called when we are in some
-    // informational context (the failure signal handler for example).
-    // Use the non-strict unwinding rules to produce a stack trace
-    // that is as complete as possible (even if it contains a few bogus
-    // entries in some rare cases).
-    void **next_frame_pointer =
-        NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(frame_pointer, ucp);
-
+   while (frame_pointer && n < max_depth) {
     if (skip_count > 0) {
       skip_count--;
     } else {
       result[n] = prev_return_address;
       if (IS_STACK_FRAMES) {
         sizes[n] = static_cast<int>(
-            ComputeStackFrameSize(frame_pointer, next_frame_pointer));
+            ComputeStackFrameSize(prev_frame_pointer, frame_pointer));
       }
       n++;
     }
     prev_return_address = frame_pointer[1];
-    frame_pointer = next_frame_pointer;
+    prev_frame_pointer = frame_pointer;
+    // The absl::GetStackFrames routine is called when we are in some
+    // informational context (the failure signal handler for example).
+    // Use the non-strict unwinding rules to produce a stack trace
+    // 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);
   }
+
   if (min_dropped_frames != nullptr) {
     // Implementation detail: we clamp the max of frames we are willing to
     // count, so as not to spend too much time in the loop below.
@@ -185,8 +221,8 @@ static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
       } else {
         num_dropped_frames++;
       }
-      frame_pointer =
-          NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(frame_pointer, ucp);
+      frame_pointer = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(
+          frame_pointer, ucp, stack_low, stack_high);
     }
     *min_dropped_frames = num_dropped_frames;
   }