From 373a595c567cb467aa1f1c627dcfb4fac94dbf86 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Wed, 3 Mar 2021 22:59:45 +0100
Subject: [PATCH] Profiler: Symbolicate addresses in non-PIE ELF objects

This is a little bit messy, but basically if an ELF object is non-PIE,
we have to account for the executable mapping being at a hard-coded
offset and subtract that when doing symbolication.

There's probably a nicer way to solve this, I just hacked this together
so we can see "cc1plus" and friends in profiles. :^)
---
 Userland/DevTools/Profiler/Profile.cpp | 23 +++++++++++++++++------
 Userland/DevTools/Profiler/Profile.h   |  3 +++
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/Userland/DevTools/Profiler/Profile.cpp b/Userland/DevTools/Profiler/Profile.cpp
index 1f61b1c3e36..b59b6d1a6fd 100644
--- a/Userland/DevTools/Profiler/Profile.cpp
+++ b/Userland/DevTools/Profiler/Profile.cpp
@@ -316,11 +316,7 @@ Result<NonnullOwnPtr<Profile>, String> Profile::load_from_perfcore_file(const St
                     library_metadata = it->library_metadata.ptr();
                 if (auto* library = library_metadata ? library_metadata->library_containing(ptr) : nullptr) {
                     object_name = library->name;
-                    if (library->object) {
-                        symbol = library->object->elf.symbolicate(ptr - library->base, &offset);
-                    } else {
-                        symbol = "??";
-                    }
+                    symbol = library->symbolicate(ptr, &offset);
                 } else {
                     symbol = "??";
                 }
@@ -455,10 +451,25 @@ LibraryMetadata::LibraryMetadata(JsonArray regions)
         if (!mapped_object)
             continue;
 
-        m_libraries.set(name, adopt_own(*new Library { base, size, name, mapped_object }));
+        FlatPtr text_base {};
+        mapped_object->elf.for_each_program_header([&](const ELF::Image::ProgramHeader& ph) {
+            if (ph.is_executable())
+                text_base = ph.vaddr().get();
+            return IterationDecision::Continue;
+        });
+
+        m_libraries.set(name, adopt_own(*new Library { base, size, name, text_base, mapped_object }));
     }
 }
 
+String LibraryMetadata::Library::symbolicate(FlatPtr ptr, u32* offset) const
+{
+    if (!object)
+        return "??"sv;
+
+    return object->elf.symbolicate(ptr - base + text_base, offset);
+}
+
 const LibraryMetadata::Library* LibraryMetadata::library_containing(FlatPtr ptr) const
 {
     for (auto& it : m_libraries) {
diff --git a/Userland/DevTools/Profiler/Profile.h b/Userland/DevTools/Profiler/Profile.h
index 63728410379..8a76073487c 100644
--- a/Userland/DevTools/Profiler/Profile.h
+++ b/Userland/DevTools/Profiler/Profile.h
@@ -59,7 +59,10 @@ public:
         FlatPtr base;
         size_t size;
         String name;
+        FlatPtr text_base;
         MappedObject* object { nullptr };
+
+        String symbolicate(FlatPtr, u32* offset) const;
     };
 
     const Library* library_containing(FlatPtr) const;