Kernel+Profiler: Improve profiling subsystem

This turns the perfcore format into more a log than it was before,
which lets us properly log process, thread and region
creation/destruction. This also makes it unnecessary to dump the
process' regions every time it is scheduled like we did before.

Incidentally this also fixes 'profile -c' because we previously ended
up incorrectly dumping the parent's region map into the profile data.

Log-based mmap support enables profiling shared libraries which
are loaded at runtime, e.g. via dlopen().

This enables profiling both the parent and child process for
programs which use execve(). Previously we'd discard the profiling
data for the old process.

The Profiler tool has been updated to not treat thread IDs as
process IDs anymore. This enables support for processes with more
than one thread. Also, there's a new widget to filter which
process should be displayed.

Userland/DevTools/Profiler/Process.cpp

@@ -0,0 +1,119 @@
+/*
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "Process.h"
+
+Thread* Process::find_thread(pid_t tid, u64 timestamp)
+{
+    auto it = threads.find(tid);
+    if (it == threads.end())
+        return nullptr;
+    for (auto& thread : it->value) {
+        if (thread.start_valid < timestamp && (thread.end_valid == 0 || thread.end_valid > timestamp))
+            return &thread;
+    }
+    return nullptr;
+}
+
+void Process::handle_thread_create(pid_t tid, u64 timestamp)
+{
+    auto it = threads.find(tid);
+    if (it == threads.end()) {
+        threads.set(tid, {});
+        it = threads.find(tid);
+    }
+
+    auto thread = Thread { tid, timestamp, 0 };
+    it->value.append(move(thread));
+}
+
+void Process::handle_thread_exit(pid_t tid, u64 timestamp)
+{
+    auto* thread = find_thread(tid, timestamp);
+    if (!thread)
+        return;
+    thread->end_valid = timestamp;
+}
+
+HashMap<String, OwnPtr<MappedObject>> g_mapped_object_cache;
+
+static MappedObject* get_or_create_mapped_object(const String& path)
+{
+    if (auto it = g_mapped_object_cache.find(path); it != g_mapped_object_cache.end())
+        return it->value.ptr();
+
+    auto file_or_error = MappedFile::map(path);
+    if (file_or_error.is_error()) {
+        g_mapped_object_cache.set(path, {});
+        return nullptr;
+    }
+    auto elf = ELF::Image(file_or_error.value()->bytes());
+    if (!elf.is_valid()) {
+        g_mapped_object_cache.set(path, {});
+        return nullptr;
+    }
+    auto new_mapped_object = adopt_own(*new MappedObject {
+        .file = file_or_error.release_value(),
+        .elf = elf,
+    });
+    auto* ptr = new_mapped_object.ptr();
+    g_mapped_object_cache.set(path, move(new_mapped_object));
+    return ptr;
+}
+
+void LibraryMetadata::handle_mmap(FlatPtr base, size_t size, const String& name)
+{
+    String path;
+    if (name.contains("Loader.so"))
+        path = "Loader.so";
+    else if (!name.contains(":"))
+        return;
+    else
+        path = name.substring(0, name.view().find_first_of(":").value());
+
+    String full_path;
+    if (name.contains(".so"))
+        full_path = String::formatted("/usr/lib/{}", path);
+    else
+        full_path = path;
+
+    auto* mapped_object = get_or_create_mapped_object(full_path);
+    if (!mapped_object) {
+        full_path = String::formatted("/usr/local/lib/{}", path);
+        mapped_object = get_or_create_mapped_object(full_path);
+        if (!mapped_object)
+            return;
+    }
+
+    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 String::formatted("?? <{:p}>", ptr);
+
+    return object->elf.symbolicate(ptr - base + text_base, offset);
+}
+
+const LibraryMetadata::Library* LibraryMetadata::library_containing(FlatPtr ptr) const
+{
+    for (auto& it : m_libraries) {
+        if (!it.value)
+            continue;
+        auto& library = *it.value;
+        if (ptr >= library.base && ptr < (library.base + library.size))
+            return &library;
+    }
+    return nullptr;
+}