From f025204dfe38805eed795f11f740f53a545f4451 Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Sun, 16 Aug 2020 12:39:06 -0400
Subject: [PATCH] disasm: For ELF inputs, pass an ELFSymbolProvider to
 disassembler

This lets disasm output contain the symbol names of call and jump
destinations:

    8048111:	e8 88 38 01 00       	call   805b99e <__cxa_atexit>
    ...
    8048150:	74 15                	je     8048167 <_start+0x4c>

The latter (the symbol of the current function with an offset) is
arguably more distracting than useful because you usually want to look
at the instruction at the absolute offset in this case, but the former
is very nice to have.

For reasons I do not understand, this cuts the time to run
`disasm /bin/id` in half, from ~1s to ~0.5s.
---
 Userland/disasm.cpp | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Userland/disasm.cpp b/Userland/disasm.cpp
index 9290728514..333400618f 100644
--- a/Userland/disasm.cpp
+++ b/Userland/disasm.cpp
@@ -31,6 +31,7 @@
 #include <LibCore/ArgsParser.h>
 #include <LibELF/Loader.h>
 #include <LibX86/Disassembler.h>
+#include <LibX86/ELFSymbolProvider.h>
 #include <stdio.h>
 #include <string.h>
 
@@ -66,8 +67,13 @@ int main(int argc, char** argv)
     size_t asm_size = file.size();
     size_t file_offset = 0;
     Vector<Symbol>::Iterator current_symbol = symbols.begin();
+    RefPtr<ELF::Loader> elf;
+    OwnPtr<X86::ELFSymbolProvider> symbol_provider; // nullptr for non-ELF disassembly.
     if (asm_size >= 4 && strncmp((const char*)asm_data, "\u007fELF", 4) == 0) {
-        if (auto elf = ELF::Loader::create(asm_data, asm_size)) {
+        NonnullRefPtr<ELF::Loader> elf_loader = ELF::Loader::create(asm_data, asm_size);
+        if (elf_loader->image().is_valid()) {
+            elf = elf_loader;
+            symbol_provider = new X86::ELFSymbolProvider(*elf);
             elf->image().for_each_section_of_type(SHT_PROGBITS, [&](const ELF::Image::Section& section) {
                 // FIXME: Disassemble all SHT_PROGBITS sections, not just .text.
                 if (section.name() != ".text")
@@ -141,7 +147,7 @@ int main(int argc, char** argv)
             is_first_symbol = false;
         }
 
-        out() << String::format("%08x", virtual_offset) << "  " << insn.value().to_string(virtual_offset);
+        out() << String::format("%08x", virtual_offset) << "  " << insn.value().to_string(virtual_offset, symbol_provider);
     }
 
     return 0;