4 files changed, 49 insertions, 7 deletions
diff --git a/debuggerd/libdebuggerd/include/libdebuggerd/types.h b/debuggerd/libdebuggerd/include/libdebuggerd/types.h
index 4f681c260..35c3fd646 100644
--- a/debuggerd/libdebuggerd/include/libdebuggerd/types.h
+++ b/debuggerd/libdebuggerd/include/libdebuggerd/types.h
@@ -41,4 +41,7 @@ struct ProcessInfo {
   uintptr_t fdsan_table_address = 0;
   uintptr_t gwp_asan_state = 0;
   uintptr_t gwp_asan_metadata = 0;
+
+  bool has_fault_address = false;
+  uintptr_t fault_address = 0;
 };
diff --git a/debuggerd/libdebuggerd/include/libdebuggerd/utility.h b/debuggerd/libdebuggerd/include/libdebuggerd/utility.h
index 75bac87d3..7bfcf5d6e 100644
--- a/debuggerd/libdebuggerd/include/libdebuggerd/utility.h
+++ b/debuggerd/libdebuggerd/include/libdebuggerd/utility.h
@@ -93,4 +93,6 @@ void get_signal_sender(char* buf, size_t n, const siginfo_t*);
 const char* get_signame(const siginfo_t*);
 const char* get_sigcode(const siginfo_t*);
 
+uintptr_t get_fault_address(const siginfo_t* siginfo, const ucontext_t* ucontext);
+
 #endif // _DEBUGGERD_UTILITY_H
diff --git a/debuggerd/libdebuggerd/tombstone.cpp b/debuggerd/libdebuggerd/tombstone.cpp
index 87bb8c5ed..e0168d539 100644
--- a/debuggerd/libdebuggerd/tombstone.cpp
+++ b/debuggerd/libdebuggerd/tombstone.cpp
@@ -154,16 +154,16 @@ static void dump_probable_cause(log_t* log, const siginfo_t* si, unwindstack::Ma
 }
 
 static void dump_signal_info(log_t* log, const ThreadInfo& thread_info,
-                             unwindstack::Memory* process_memory) {
+                             const ProcessInfo& process_info, unwindstack::Memory* process_memory) {
   char addr_desc[64];  // ", fault addr 0x1234"
-  if (signal_has_si_addr(thread_info.siginfo)) {
-    void* addr = thread_info.siginfo->si_addr;
+  if (process_info.has_fault_address) {
+    size_t addr = process_info.fault_address;
     if (thread_info.siginfo->si_signo == SIGILL) {
       uint32_t instruction = {};
-      process_memory->Read(reinterpret_cast<uint64_t>(addr), &instruction, sizeof(instruction));
-      snprintf(addr_desc, sizeof(addr_desc), "%p (*pc=%#08x)", addr, instruction);
+      process_memory->Read(addr, &instruction, sizeof(instruction));
+      snprintf(addr_desc, sizeof(addr_desc), "0x%zx (*pc=%#08x)", addr, instruction);
     } else {
-      snprintf(addr_desc, sizeof(addr_desc), "%p", addr);
+      snprintf(addr_desc, sizeof(addr_desc), "0x%zx", addr);
     }
   } else {
     snprintf(addr_desc, sizeof(addr_desc), "--------");
@@ -384,7 +384,7 @@ static bool dump_thread(log_t* log, unwindstack::Unwinder* unwinder, const Threa
   dump_thread_info(log, thread_info);
 
   if (thread_info.siginfo) {
-    dump_signal_info(log, thread_info, unwinder->GetProcessMemory().get());
+    dump_signal_info(log, thread_info, process_info, unwinder->GetProcessMemory().get());
   }
 
   std::unique_ptr<GwpAsanCrashData> gwp_asan_crash_data;
diff --git a/debuggerd/libdebuggerd/utility.cpp b/debuggerd/libdebuggerd/utility.cpp
index 0a1d2a4da..3bf28b6c2 100644
--- a/debuggerd/libdebuggerd/utility.cpp
+++ b/debuggerd/libdebuggerd/utility.cpp
@@ -449,3 +449,40 @@ void log_backtrace(log_t* log, unwindstack::Unwinder* unwinder, const char* pref
     _LOG(log, logtype::BACKTRACE, "%s%s\n", prefix, unwinder->FormatFrame(i).c_str());
   }
 }
+
+#if defined(__aarch64__)
+#define FAR_MAGIC 0x46415201
+
+struct far_context {
+  struct _aarch64_ctx head;
+  __u64 far;
+};
+#endif
+
+uintptr_t get_fault_address(const siginfo_t* siginfo, const ucontext_t* ucontext) {
+  (void)ucontext;
+#if defined(__aarch64__)
+  // This relies on a kernel patch:
+  //   https://patchwork.kernel.org/patch/11435077/
+  // that hasn't been accepted into the kernel yet. TODO(pcc): Update this to
+  // use the official interface once it lands.
+  auto* begin = reinterpret_cast<const char*>(ucontext->uc_mcontext.__reserved);
+  auto* end = begin + sizeof(ucontext->uc_mcontext.__reserved);
+  auto* ptr = begin;
+  while (1) {
+    auto* ctx = reinterpret_cast<const _aarch64_ctx*>(ptr);
+    if (ctx->magic == 0) {
+      break;
+    }
+    if (ctx->magic == FAR_MAGIC) {
+      auto* far_ctx = reinterpret_cast<const far_context*>(ctx);
+      return far_ctx->far;
+    }
+    ptr += ctx->size;
+    if (ctx->size % sizeof(void*) != 0 || ptr < begin || ptr >= end) {
+      break;
+    }
+  }
+#endif
+  return reinterpret_cast<uintptr_t>(siginfo->si_addr);
+}