Merge pull request #1516 from ltratt/dladdr_can_fail

`dladdr` can fail for sensible reasons so make sure we deal with it.

ykaddr/src/addr.rs

@@ -86,22 +86,25 @@ pub fn dladdr(vaddr: usize) -> Option<DLInfo> {
 /// and the byte offset.
 #[cached]
 pub fn vaddr_to_obj_and_off(vaddr: usize) -> Option<(PathBuf, u64)> {
-    // Find the object file from which the virtual address was loaded.
-    let info = dladdr(vaddr).unwrap();
-    let containing_obj = PathBuf::from(info.dli_fname.unwrap().to_str().unwrap());
-
-    // Find the corresponding byte offset of the virtual address in the object.
-    for obj in PHDR_OBJECT_CACHE.iter() {
-        let obj_name = obj.name();
-        let obj_name: &Path = if unsafe { *obj_name.as_ptr() } == 0 {
-            SELF_BIN_PATH.as_path()
-        } else {
-            Path::new(obj_name.to_str().unwrap())
-        };
-        if obj_name != containing_obj {
-            continue;
+    // Find the object file from which the virtual address was loaded. This may fail for several
+    // reasons e.g. if we traced into code generated by another JIT (e.g. PCRE's JIT), `dladdr`
+    // won't be able to tell us what's going on.
+    if let Some(info) = dladdr(vaddr) {
+        let containing_obj = PathBuf::from(info.dli_fname.unwrap().to_str().unwrap());
+
+        // Find the corresponding byte offset of the virtual address in the object.
+        for obj in PHDR_OBJECT_CACHE.iter() {
+            let obj_name = obj.name();
+            let obj_name: &Path = if unsafe { *obj_name.as_ptr() } == 0 {
+                SELF_BIN_PATH.as_path()
+            } else {
+                Path::new(obj_name.to_str().unwrap())
+            };
+            if obj_name != containing_obj {
+                continue;
+            }
+            return Some((containing_obj, u64::try_from(vaddr).unwrap() - obj.addr()));
         }
-        return Some((containing_obj, u64::try_from(vaddr).unwrap() - obj.addr()));
     }
     None
 }