[compiler-rt] [sanitizer-common] [Darwin] Provide warning if task_set_exc_guard_behavior errors (PR #165907)

[Andrew Haberlandt via llvm-commits]

https://github.com/ndrewh updated https://github.com/llvm/llvm-project/pull/165907

>From d41ba6149ddff40e4e05d7510b9c57fc2ffa383e Mon Sep 17 00:00:00 2001
From: Andrew Haberlandt <ahaberlandt at apple.com>
Date: Fri, 31 Oct 2025 11:40:22 -0700
Subject: [PATCH 1/2] [sanitizer-common] [Darwin] Provide warning if
 task_set_exc_guard_behavior errors

---
 compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
index b0a29db908639..b3c2ede4f6fb4 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
@@ -960,7 +960,18 @@ static void DisableMmapExcGuardExceptions() {
       RTLD_DEFAULT, "task_set_exc_guard_behavior");
   if (set_behavior == nullptr) return;
   const task_exc_guard_behavior_t task_exc_guard_none = 0;
-  set_behavior(mach_task_self(), task_exc_guard_none);
+  kern_return_t res = set_behavior(mach_task_self(), task_exc_guard_none);
+  if (res != KERN_SUCCESS) {
+    Report(
+        "WARN: task_set_exc_guard_behavior returned %d (%s), "
+        "mmap may fail unexpectedly.\n",
+        res, mach_error_string(res));
+    if (res == KERN_DENIED) {
+      Report(
+          "HINT: Check that task_set_exc_guard_behavior is allowed by "
+          "sandbox.\n");
+    }
+  }
 }
 
 static void VerifyInterceptorsWorking();

>From 76548b0f335feab26da4367d544430a9ae0bc2ae Mon Sep 17 00:00:00 2001
From: Andrew Haberlandt <ahaberlandt at apple.com>
Date: Fri, 31 Oct 2025 23:33:09 -0700
Subject: [PATCH 2/2] Warn when no external symbolizers are found.

---
 .../sanitizer_symbolizer_posix_libcdep.cpp                 | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cpp
index f8d821e125b7a..d005f712d68b9 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cpp
@@ -505,6 +505,13 @@ static void ChooseSymbolizerTools(IntrusiveList<SymbolizerTool> *list,
   }
 
 #  if SANITIZER_APPLE
+  if (list.size() == 0) {
+    Report(
+        "WARN: No external symbolizers found. Symbols will be missing or "
+        "unreliable.\n");
+    Report(
+        "HINT: Is PATH set? Does sandbox allow file-read of /usr/bin/atos?\n");
+  }
   VReport(2, "Using dladdr symbolizer.\n");
   list->push_back(new (*allocator) DlAddrSymbolizer());
 #  endif  // SANITIZER_APPLE