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LibELF: Avoid calculating symbol hashes when we don't need them

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This commit is contained in:
Gunnar Beutner 2021-04-22 09:16:17 +02:00 committed by Andreas Kling
parent 39d34fb1f1
commit f74b8a2d1f
Notes: sideshowbarker 2024-07-18 19:10:14 +09:00 
Author: https://github.com/gunnarbeutner
Commit: https://github.com/SerenityOS/serenity/commit/f74b8a2d1f6
Pull-request: https://github.com/SerenityOS/serenity/pull/6546
Reviewed-by: https://github.com/awesomekling
4 changed files with 44 additions and 15 deletions
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7
Userland/Libraries/LibELF/DynamicLinker.cpp
View File

@ -45,15 +45,14 @@ bool g_allowed_to_check_environment_variables { false };
bool g_do_breakpoint_trap_before_entry { false };
}
Optional<DynamicObject::SymbolLookupResult> DynamicLinker::lookup_global_symbol(const StringView& symbol)
Optional<DynamicObject::SymbolLookupResult> DynamicLinker::lookup_global_symbol(const StringView& name)
{
Optional<DynamicObject::SymbolLookupResult> weak_result;
auto gnu_hash = compute_gnu_hash(symbol);
auto sysv_hash = compute_sysv_hash(symbol);
auto symbol = DynamicObject::HashSymbol { name };
for (auto& lib : g_global_objects) {
auto res = lib->lookup_symbol(symbol, gnu_hash, sysv_hash);
auto res = lib->lookup_symbol(symbol);
if (!res.has_value())
continue;
if (res.value().bind == STB_GLOBAL)

2
Userland/Libraries/LibELF/DynamicLoader.cpp
View File

@ -125,7 +125,7 @@ bool DynamicLoader::validate()
void* DynamicLoader::symbol_for_name(const StringView& name)
{
auto result = m_dynamic_object->hash_section().lookup_symbol(name, compute_gnu_hash(name), compute_sysv_hash(name));
auto result = m_dynamic_object->hash_section().lookup_symbol(name);
if (!result.has_value())
return nullptr;
auto symbol = result.value();

25
Userland/Libraries/LibELF/DynamicObject.cpp
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@ -428,18 +428,18 @@ static const char* name_for_dtag(Elf32_Sword d_tag)
auto DynamicObject::lookup_symbol(const StringView& name) const -> Optional<SymbolLookupResult>
{
return lookup_symbol(name, compute_gnu_hash(name), compute_sysv_hash(name));
return lookup_symbol(HashSymbol { name });
}
auto DynamicObject::lookup_symbol(const StringView& name, u32 gnu_hash, u32 sysv_hash) const -> Optional<SymbolLookupResult>
auto DynamicObject::lookup_symbol(const HashSymbol& symbol) const -> Optional<SymbolLookupResult>
{
auto result = hash_section().lookup_symbol(name, gnu_hash, sysv_hash);
auto result = hash_section().lookup_symbol(symbol);
if (!result.has_value())
return {};
auto symbol = result.value();
if (symbol.is_undefined())
auto symbol_result = result.value();
if (symbol_result.is_undefined())
return {};
return SymbolLookupResult { symbol.value(), symbol.address(), symbol.bind(), this };
return SymbolLookupResult { symbol_result.value(), symbol_result.address(), symbol_result.bind(), this };
}
NonnullRefPtr<DynamicObject> DynamicObject::create(const String& filename, VirtualAddress base_address, VirtualAddress dynamic_section_address)
@ -469,4 +469,17 @@ VirtualAddress DynamicObject::patch_plt_entry(u32 relocation_offset)
return symbol_location;
}
u32 DynamicObject::HashSymbol::gnu_hash() const
{
if (!m_gnu_hash.has_value())
m_gnu_hash = compute_gnu_hash(m_name);
return m_gnu_hash.value();
}
u32 DynamicObject::HashSymbol::sysv_hash() const
{
if (!m_sysv_hash.has_value())
m_sysv_hash = compute_sysv_hash(m_name);
return m_sysv_hash.value();
}
} // end namespace ELF

25
Userland/Libraries/LibELF/DynamicObject.h
View File

@ -162,6 +162,23 @@ public:
GNU
};
class HashSymbol {
public:
HashSymbol(const StringView& name)
: m_name(name)
{
}
StringView name() const { return m_name; }
u32 gnu_hash() const;
u32 sysv_hash() const;
private:
StringView m_name;
mutable Optional<u32> m_gnu_hash;
mutable Optional<u32> m_sysv_hash;
};
class HashSection : public Section {
public:
HashSection(const Section& section, HashType hash_type)
@ -170,11 +187,11 @@ public:
{
}
Optional<Symbol> lookup_symbol(const StringView& name, u32 gnu_hash, u32 sysv_hash) const
Optional<Symbol> lookup_symbol(const HashSymbol& symbol) const
{
if (m_hash_type == HashType::SYSV)
return lookup_sysv_symbol(name, sysv_hash);
return lookup_gnu_symbol(name, gnu_hash);
return lookup_sysv_symbol(symbol.name(), symbol.sysv_hash());
return lookup_gnu_symbol(symbol.name(), symbol.gnu_hash());
}
private:
@ -253,7 +270,7 @@ public:
};
Optional<SymbolLookupResult> lookup_symbol(const StringView& name) const;
Optional<SymbolLookupResult> lookup_symbol(const StringView& name, u32 gnu_hash, u32 sysv_hash) const;
Optional<SymbolLookupResult> lookup_symbol(const HashSymbol& symbol) const;
// Will be called from _fixup_plt_entry, as part of the PLT trampoline
VirtualAddress patch_plt_entry(u32 relocation_offset);