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util/delegate.cpp: Recognise a couple more MSVC thunks.

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The MSVC C++ ABI doesn't reserve the first vtable entry for classes
without a virtual destructor, so the instruction to load the virtual
member function address may not need an immediate displacement.

Also recognise virtual member function call thunks for AArch64.
This commit is contained in:
Vas Crabb 2021-09-22 09:42:10 +10:00
parent 2bfa21eb2a
commit 45d893eaa5
1 changed files with 29 additions and 6 deletions
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35
src/lib/util/delegate.cpp
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@ -142,25 +142,27 @@ delegate_generic_function delegate_mfp_msvc::adjust_this_pointer(delegate_generi
object = reinterpret_cast<delegate_generic_class *>(byteptr);
// walk past recognisable thunks
std::uint8_t const *func = reinterpret_cast<std::uint8_t const *>(m_function);
#if defined(__x86_64__) || defined(_M_X64)
std::uint8_t const *func = reinterpret_cast<std::uint8_t const *>(m_function);
while (true)
{
if (0xe9 == func[0])
{
// absolute jump with 32-bit displacement
// relative jump with 32-bit displacement (typically a resolved PLT entry)
LOG("Found relative jump at %p ", func);
func += 5 + *reinterpret_cast<std::int32_t const *>(func + 1);
LOG("redirecting to %p\n", func);
}
else if ((0x48 == func[0]) && (0x8b == func[1]) && (0x01 == func[2]) && (0xff == func[3]) && ((0x60 == func[4]) || (0xa0 == func[4])))
else if ((0x48 == func[0]) && (0x8b == func[1]) && (0x01 == func[2]) && (0xff == func[3]) && ((0x20 == func[4]) || (0x60 == func[4]) || (0xa0 == func[4])))
{
// virtual function call thunk - mov rax,QWORD PTR [rcx] ; jmp QWORD PTR [rax+...]
LOG("Found virtual member function thunk at %p ", func);
std::uint8_t const *const vptr = *reinterpret_cast<std::uint8_t const *const *>(object);
if (0x60 == func[4])
if (0x20 == func[4]) // no displacement
func = *reinterpret_cast<std::uint8_t const *const *>(vptr);
else if (0x60 == func[4]) // 8-bit displacement
func = *reinterpret_cast<std::uint8_t const *const *>(vptr + *reinterpret_cast<std::int8_t const *>(func + 5));
else
else // 32-bit displacement
func = *reinterpret_cast<std::uint8_t const *const *>(vptr + *reinterpret_cast<std::int32_t const *>(func + 5));
LOG("redirecting to %p\n", func);
}
@ -170,8 +172,29 @@ delegate_generic_function delegate_mfp_msvc::adjust_this_pointer(delegate_generi
break;
}
}
#endif
return reinterpret_cast<delegate_generic_function>(std::uintptr_t(func));
#elif defined(__aarch64__) || defined(_M_ARM64)
std::uint32_t const *func = reinterpret_cast<std::uint32_t const *>(m_function);
while (true)
{
if ((0xf9400010 == func[0]) && (0xf9400210 == (func[1] & 0xffc003ff)) && (0xd61f0200 == func[2]))
{
// virtual function call thunk - ldr xip0,[x0] ; ldr xip0,[x0,#...] ; br xip0
LOG("Found virtual member function thunk at %p ", func);
std::uint32_t const *const *const vptr = *reinterpret_cast<std::uint32_t const *const *const *>(object);
func = vptr[(func[1] & 0x003ffc00) >> 10];
LOG("redirecting to %p\n", func);
}
else
{
// not something we can easily bypass
break;
}
}
return reinterpret_cast<delegate_generic_function>(std::uintptr_t(func));
#else
return reinterpret_cast<delegate_generic_function>(m_function);
#endif
}
} // namespace util::detail