From bd3965a41d725a3165a4aa83a739401be8f1e186 Mon Sep 17 00:00:00 2001
From: Ollrogge <nils-ollrogge@outlook.de>
Date: Sun, 7 Jan 2024 20:10:39 +0100
Subject: [PATCH] LibELF: Correctly determine symbol amount for DT_GNU_HASH
 table

---
 Userland/Libraries/LibELF/DynamicObject.cpp | 37 ++++++++++++++++++---
 Userland/Utilities/readelf.cpp              |  1 -
 2 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/Userland/Libraries/LibELF/DynamicObject.cpp b/Userland/Libraries/LibELF/DynamicObject.cpp
index f68e65144f493d..efa7ef683ede9d 100644
--- a/Userland/Libraries/LibELF/DynamicObject.cpp
+++ b/Userland/Libraries/LibELF/DynamicObject.cpp
@@ -216,10 +216,39 @@ void DynamicObject::parse()
         m_size_of_relocation_table -= m_size_of_plt_relocation_entry_list;
     }
 
-    auto hash_section_address = hash_section().address().as_ptr();
-    // TODO: consider base address - it might not be zero
-    auto num_hash_chains = ((u32*)hash_section_address)[1];
-    m_symbol_count = num_hash_chains;
+    u32 const* hash_table_begin = reinterpret_cast<u32 const*>(hash_section().address().as_ptr());
+
+    if (m_hash_type == HashType::SYSV) {
+        u32 n_chain = hash_table_begin[1];
+        m_symbol_count = n_chain;
+        return;
+    }
+
+    // Determine amount of symbols by finding the chain with the highest
+    // starting index and walking this chain until the end to find the
+    // maximum index = amount of symbols.
+    using BloomWord = FlatPtr;
+    size_t const num_buckets = hash_table_begin[0];
+    size_t const num_omitted_symbols = hash_table_begin[1];
+    u32 const num_maskwords = hash_table_begin[2];
+    BloomWord const* bloom_words = reinterpret_cast<BloomWord const*>(&hash_table_begin[4]);
+    u32 const* const buckets = reinterpret_cast<u32 const*>(&bloom_words[num_maskwords]);
+    u32 const* const chains = &buckets[num_buckets];
+
+    size_t highest_chain_idx = 0;
+    for (size_t i = 0; i < num_buckets; i++) {
+        if (buckets[i] > highest_chain_idx) {
+            highest_chain_idx = buckets[i];
+        }
+    }
+
+    size_t amount_symbols = highest_chain_idx;
+    u32 const* last_chain = &chains[highest_chain_idx - num_omitted_symbols];
+    while ((*(last_chain++) & 1) == 0) {
+        amount_symbols++;
+    }
+
+    m_symbol_count = amount_symbols + 1;
 }
 
 DynamicObject::Relocation DynamicObject::RelocationSection::relocation(unsigned index) const
diff --git a/Userland/Utilities/readelf.cpp b/Userland/Utilities/readelf.cpp
index 29e5822023110a..74cf1bccc7d021 100644
--- a/Userland/Utilities/readelf.cpp
+++ b/Userland/Utilities/readelf.cpp
@@ -565,7 +565,6 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
             });
 
             if (object->symbol_count()) {
-                // FIXME: Add support for init/fini/start/main sections
                 outln("   Num: Value{}      Size{}       Type     Bind     Name", addr_padding, addr_padding);
                 object->for_each_symbol([](const ELF::DynamicObject::Symbol& sym) {
                     out("  {:>4}: ", sym.index());