LibDebug: Add ProcessInspector base class

ProcessInspector is an abstract base class for an object that can
inspect the address space of a process.

Concrete sub classes need to implement methods for peeking & poking
memory and walking the loaded libraries.

It is currently only implemented by DebugSession.

Userland/Libraries/LibDebug/ProcessInspector.cpp

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2021, Itamar S. <itamar8910@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "ProcessInspector.h"
+#include "DebugInfo.h"
+
+namespace Debug {
+
+const LoadedLibrary* ProcessInspector::library_at(FlatPtr address) const
+{
+    const LoadedLibrary* result = nullptr;
+    for_each_loaded_library([&result, address](const auto& lib) {
+        if (address >= lib.base_address && address < lib.base_address + lib.debug_info->elf().size()) {
+            result = &lib;
+            return IterationDecision::Break;
+        }
+        return IterationDecision::Continue;
+    });
+    return result;
+}
+
+Optional<ProcessInspector::SymbolicationResult> ProcessInspector::symbolicate(FlatPtr address) const
+{
+    auto* lib = library_at(address);
+    if (!lib)
+        return {};
+    // FIXME: ELF::Image symlicate() API should return String::empty() if symbol is not found (It currently returns ??)
+    auto symbol = lib->debug_info->elf().symbolicate(address - lib->base_address);
+    return { { lib->name, symbol } };
+}
+
+Optional<DebugInfo::SourcePositionAndAddress> ProcessInspector::get_address_from_source_position(String const& file, size_t line) const
+{
+    Optional<DebugInfo::SourcePositionAndAddress> result;
+    for_each_loaded_library([file, line, &result](auto& lib) {
+        // The loader contains its own definitions for LibC symbols, so we don't want to include it in the search.
+        if (lib.name == "Loader.so")
+            return IterationDecision::Continue;
+
+        auto source_position_and_address = lib.debug_info->get_address_from_source_position(file, line);
+        if (!source_position_and_address.has_value())
+            return IterationDecision::Continue;
+
+        result = source_position_and_address;
+        result.value().address += lib.base_address;
+        return IterationDecision::Break;
+    });
+    return result;
+}
+
+Optional<DebugInfo::SourcePosition> ProcessInspector::get_source_position(FlatPtr address) const
+{
+    auto* lib = library_at(address);
+    if (!lib)
+        return {};
+    return lib->debug_info->get_source_position(address - lib->base_address);
+}
+
+}