LibDebug: Parse line number information from DWARF format

DWARF line number information, if generated, is stored  in the
.debug_line section of an object file.

The information is encoded as instructions for a VM that is defined in
the DWARF specification.
By executing these instructions, we can extract the encoded line number
information.

Libraries/LibDebug/DebugInfo.cpp

@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "DebugInfo.h"
+#include <AK/QuickSort.h>
+
+DebugInfo::DebugInfo(NonnullRefPtr<const ELF::Loader> elf)
+    : m_elf(elf)
+{
+    prepare_lines();
+}
+
+void DebugInfo::prepare_lines()
+{
+
+    auto section = m_elf->image().lookup_section(".debug_line");
+    ASSERT(!section.is_undefined());
+
+    auto buffer = ByteBuffer::wrap(reinterpret_cast<const u8*>(section.raw_data()), section.size());
+    BufferStream stream(buffer);
+
+    Vector<LineProgram::LineInfo> all_lines;
+    while (!stream.at_end()) {
+        LineProgram program(stream);
+        all_lines.append(move(program.lines()));
+    }
+
+    for (auto& line_info : all_lines) {
+        String file_path = line_info.file;
+        if (file_path.contains("Toolchain/"))
+            continue;
+        if (file_path.contains("serenity/")) {
+            auto start_index = file_path.index_of("serenity/").value() + String("serenity/").length();
+            file_path = file_path.substring(start_index, file_path.length() - start_index);
+        }
+        m_sorted_lines.append({ line_info.address, file_path, line_info.line });
+    }
+    quick_sort(m_sorted_lines, [](auto& a, auto& b) {
+        return a.address < b.address;
+    });
+}
+
+Optional<DebugInfo::SourcePosition> DebugInfo::get_source_position(u32 target_address) const
+{
+
+    if (m_sorted_lines.is_empty())
+        return {};
+    if (target_address < m_sorted_lines[0].address)
+        return {};
+
+    // TODO: We can do a binray search here
+    for (size_t i = 0; i < m_sorted_lines.size() - 1; ++i) {
+        if (m_sorted_lines[i + 1].address > target_address) {
+            return Optional<SourcePosition>({ m_sorted_lines[i].file, m_sorted_lines[i].line });
+        }
+    }
+    return {};
+}
+
+Optional<u32> DebugInfo::get_instruction_from_source(const String& file, size_t line) const
+{
+    for (const auto& line_entry : m_sorted_lines) {
+        dbg() << line_entry.file;
+        if (line_entry.file == file && line_entry.line == line)
+            return Optional<u32>(line_entry.address);
+    }
+    return {};
+}