Add indicator that an elf is memory backed.

Modify the unwinder library to indicate that at least one of the stack
frames contains an elf file that is unreadable.

Modify debuggerd to display a note about the unreadable frame and a possible
way to fix it.

Bug: 129769339

Test: New unit tests pass.
Test: Ran an app that crashes and has an unreadable file and verified the
Test: message is displayed. Then setenforce 0 and verify the message is
Test: not displayed.
Change-Id: Ibc4fe1d117e9b5840290454e90914ddc698d3cc2

1 files changed, 20 insertions, 0 deletions

diff --git a/debuggerd/libdebuggerd/utility.cpp b/debuggerd/libdebuggerd/utility.cpp
index 7aebea8fed..9b2779a9e4 100644
--- a/debuggerd/libdebuggerd/utility.cpp
+++ b/debuggerd/libdebuggerd/utility.cpp
@@ -38,6 +38,7 @@
 #include <debuggerd/handler.h>
 #include <log/log.h>
 #include <unwindstack/Memory.h>
+#include <unwindstack/Unwinder.h>
 
 using android::base::unique_fd;
 
@@ -422,3 +423,22 @@ const char* get_sigcode(const siginfo_t* si) {
   // Then give up...
   return "?";
 }
+
+void log_backtrace(log_t* log, unwindstack::Unwinder* unwinder, const char* prefix) {
+  if (unwinder->elf_from_memory_not_file()) {
+    _LOG(log, logtype::BACKTRACE,
+         "%sNOTE: Function names and BuildId information is missing for some frames due\n", prefix);
+    _LOG(log, logtype::BACKTRACE,
+         "%sNOTE: to unreadable libraries. For unwinds of apps, only shared libraries\n", prefix);
+    _LOG(log, logtype::BACKTRACE, "%sNOTE: found under the lib/ directory are readable.\n", prefix);
+#if defined(ROOT_POSSIBLE)
+    _LOG(log, logtype::BACKTRACE,
+         "%sNOTE: On this device, run setenforce 0 to make the libraries readable.\n", prefix);
+#endif
+  }
+
+  unwinder->SetDisplayBuildID(true);
+  for (size_t i = 0; i < unwinder->NumFrames(); i++) {
+    _LOG(log, logtype::BACKTRACE, "%s%s\n", prefix, unwinder->FormatFrame(i).c_str());
+  }
+}