[clang] [compiler-rt] [XRay] Add support for instrumentation of DSOs on x86_64 (PR #90959)

[Jan Patrick Lehr via cfe-commits]

================
@@ -111,6 +156,71 @@ void __xray_init() XRAY_NEVER_INSTRUMENT {
 #endif
 }
 
+// Default visibility is hidden, so we have to explicitly make it visible to
+// DSO.
+SANITIZER_INTERFACE_ATTRIBUTE int32_t __xray_register_dso(
+    const XRaySledEntry *SledsBegin, const XRaySledEntry *SledsEnd,
+    const XRayFunctionSledIndex *FnIndexBegin,
+    const XRayFunctionSledIndex *FnIndexEnd,
+    XRayTrampolines Trampolines) XRAY_NEVER_INSTRUMENT {
+  // Make sure XRay has been initialized in the main executable.
+  __xray_init();
+
+  if (__xray_num_objects() == 0) {
+    if (Verbosity())
+      Report("No XRay instrumentation map in main executable. Not initializing "
+             "XRay for DSO.\n");
+    return -1;
+  }
+
+  // Register sleds in global map.
+  int ObjId = __xray_register_sleds(SledsBegin, SledsEnd, FnIndexBegin,
+                                     FnIndexEnd, true, Trampolines);
+
+#ifndef XRAY_NO_PREINIT
+  if (ObjId >= 0 && flags()->patch_premain)
+    __xray_patch_object(ObjId);
+#endif
+
+  return ObjId;
+}
+
+SANITIZER_INTERFACE_ATTRIBUTE bool
+__xray_deregister_dso(int32_t ObjId) XRAY_NEVER_INSTRUMENT {
+  // Make sure XRay has been initialized in the main executable.
+  __xray_init();
+
+  if (ObjId <= 0 || ObjId >= __xray_num_objects()) {
+    if (Verbosity())
+      Report("Can't deregister object with ID %d: ID is invalid.\n", ObjId);
+    return false;
+  }
+
+  {
+    SpinMutexLock Guard(&XRayInstrMapMutex);
+    auto &Entry = XRayInstrMaps[ObjId];
+    if (!Entry.FromDSO) {
+      if (Verbosity())
+        Report("Can't deregister object with ID %d: object does not correspond "
+               "to a shared library.\n",
+               ObjId);
+      return false;
+    }
+    if (!Entry.Loaded) {
+      if (Verbosity())
+        Report("Can't deregister object with ID %d: object is not loaded.\n",
+               ObjId);
+    }
+    // This is all we have to do here.
----------------
jplehr wrote:

I don't think this comment is helpful. Maybe better: explain why.

https://github.com/llvm/llvm-project/pull/90959