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LibELF: Only call IFUNC resolvers after populating the PLT

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As IFUNC resolvers may call arbitrary functions though the PLT, they can
only be called after the PLT has been populated. This is true of the
`[[gnu::target_clones]]` attribute, which makes a call to
`__cpu_indicator_init`, which is defined in `libgcc_s.so`, through the
PLT.

`do_plt_relocation` and `do_direct_relocation` are given a parameter
that controls whether IFUNCs are immediately resolved. In the first
pass, relocations pointing to IFUNCs are put on a worklist, while all
other relocations are performed. Only after non-IFUNC relocations are
done and the PLT is set up do we deal with these.
This commit is contained in:
Daniel Bertalan 2023-04-22 12:09:00 +02:00 • committed by Andreas Kling
parent cd45c2d295
commit e2b1f9447c
2 changed files with 53 additions and 15 deletions
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17
Userland/Libraries/LibELF/DynamicLoader.h
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@ -40,6 +40,11 @@ enum class ShouldInitializeWeak {
No
};
enum class ShouldCallIfuncResolver {
Yes,
No
};
extern "C" FlatPtr _fixup_plt_entry(DynamicObject* object, u32 relocation_offset);
class DynamicLoader : public RefCounted<DynamicLoader> {
@ -115,8 +120,6 @@ private:
ElfW(Phdr) m_program_header; // Explicitly a copy of the PHDR in the image
};
friend FlatPtr _fixup_plt_entry(DynamicObject*, u32);
// Stage 1
void load_program_headers();
@ -132,13 +135,17 @@ private:
bool validate();
friend FlatPtr _fixup_plt_entry(DynamicObject*, u32);
enum class RelocationResult : uint8_t {
Failed = 0,
Success = 1,
ResolveLater = 2,
CallIfuncResolver = 3,
};
RelocationResult do_direct_relocation(DynamicObject::Relocation const&, ShouldInitializeWeak);
static RelocationResult do_plt_relocation(DynamicObject::Relocation const&);
RelocationResult do_direct_relocation(DynamicObject::Relocation const&, ShouldInitializeWeak, ShouldCallIfuncResolver);
// Will be called from _fixup_plt_entry, as part of the PLT trampoline
static RelocationResult do_plt_relocation(DynamicObject::Relocation const&, ShouldCallIfuncResolver);
void do_relr_relocations();
void find_tls_size_and_alignment();
@ -164,6 +171,8 @@ private:
size_t m_tls_alignment_of_current_object { 0 };
Vector<DynamicObject::Relocation> m_unresolved_relocations;
Vector<DynamicObject::Relocation> m_direct_ifunc_relocations;
Vector<DynamicObject::Relocation> m_plt_ifunc_relocations;
mutable RefPtr<DynamicObject> m_cached_dynamic_object;