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Everywhere: Fix some alignment issues

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When creating uninitialized storage for variables, we need to make sure
that the alignment is correct. Fixes a KUBSAN failure when running
kernels compiled with Clang.

In `Syscalls/socket.cpp`, we can simply use local variables, as
`sockaddr_un` is a POD type.

Along with moving the `alignas` specifier to the correct member,
`AK::Optional`'s internal buffer has been made non-zeroed by default.
GCC emitted bogus uninitialized memory access warnings, so we now use
`__builtin_launder` to tell the compiler that we know what we are doing.
This might disable some optimizations, but judging by how GCC failed to
notice that the memory's initialization is dependent on `m_has_value`,
I'm not sure that's a bad thing.
This commit is contained in:
Daniel Bertalan 2021-07-01 11:29:28 +02:00 • committed by Ali Mohammad Pur
parent 45a82b2a5b
commit b9f30c6f2a
5 changed files with 17 additions and 17 deletions
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8
Userland/Libraries/LibC/malloc.cpp
View file

@ -26,8 +26,8 @@
static Threading::Lock& malloc_lock()
{
static u32 lock_storage[sizeof(Threading::Lock) / sizeof(u32)];
return *reinterpret_cast<Threading::Lock*>(&lock_storage);
alignas(Threading::Lock) static u8 lock_storage[sizeof(Threading::Lock)];
return *reinterpret_cast<Threading::Lock*>(lock_storage);
}
constexpr size_t number_of_hot_chunked_blocks_to_keep_around = 16;
@ -111,8 +111,8 @@ struct BigAllocator {
// are run. Similarly, we can not allow global destructors to destruct
// them. We could have used AK::NeverDestoyed to prevent the latter,
// but it would have not helped with the former.
static u8 g_allocators_storage[sizeof(Allocator) * num_size_classes];
static u8 g_big_allocators_storage[sizeof(BigAllocator)];
alignas(Allocator) static u8 g_allocators_storage[sizeof(Allocator) * num_size_classes];
alignas(BigAllocator) static u8 g_big_allocators_storage[sizeof(BigAllocator)];
static inline Allocator (&allocators())[num_size_classes]
{