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Kernel: Consolidate kmalloc_aligned() and use kfree_sized() within

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This patch does two things:

- Combines kmalloc_aligned() and kmalloc_aligned_cxx(). Templatizing
  the alignment parameter doesn't seem like a valuable enough
  optimization to justify having two almost-identical implementations.

- Stores the real allocation size of an aligned allocation along with
  the other alignment metadata, and uses it to call kfree_sized()
  instead of kfree().
This commit is contained in:
Andreas Kling 2021-12-26 18:08:55 +01:00
parent 1c2aa7396d
commit 6eb48f7df6
2 changed files with 12 additions and 20 deletions
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12
Kernel/Heap/kmalloc.cpp
View file

@ -305,15 +305,19 @@ size_t kmalloc_good_size(size_t size)
return size;
}
[[gnu::malloc, gnu::alloc_size(1), gnu::alloc_align(2)]] static void* kmalloc_aligned_cxx(size_t size, size_t alignment)
void* kmalloc_aligned(size_t size, size_t alignment)
{
VERIFY(alignment <= 4096);
void* ptr = kmalloc(size + alignment + sizeof(ptrdiff_t));
Checked<size_t> real_allocation_size = size;
real_allocation_size += alignment;
real_allocation_size += sizeof(ptrdiff_t) + sizeof(size_t);
void* ptr = kmalloc(real_allocation_size.value());
if (ptr == nullptr)
return nullptr;
size_t max_addr = (size_t)ptr + alignment;
void* aligned_ptr = (void*)(max_addr - (max_addr % alignment));
((ptrdiff_t*)aligned_ptr)[-1] = (ptrdiff_t)((u8*)aligned_ptr - (u8*)ptr);
((size_t*)aligned_ptr)[-2] = real_allocation_size.value();
return aligned_ptr;
}
@ -331,14 +335,14 @@ void* operator new(size_t size, const std::nothrow_t&) noexcept
void* operator new(size_t size, std::align_val_t al)
{
void* ptr = kmalloc_aligned_cxx(size, (size_t)al);
void* ptr = kmalloc_aligned(size, (size_t)al);
VERIFY(ptr);
return ptr;
}
void* operator new(size_t size, std::align_val_t al, const std::nothrow_t&) noexcept
{
return kmalloc_aligned_cxx(size, (size_t)al);
return kmalloc_aligned(size, (size_t)al);
}
void* operator new[](size_t size)

20
Kernel/Heap/kmalloc.h
View file

@ -17,11 +17,11 @@
public: \
[[nodiscard]] void* operator new(size_t) \
{ \
void* ptr = kmalloc_aligned<alignment>(sizeof(type)); \
void* ptr = kmalloc_aligned(sizeof(type), alignment); \
VERIFY(ptr); \
return ptr; \
} \
[[nodiscard]] void* operator new(size_t, const std::nothrow_t&) noexcept { return kmalloc_aligned<alignment>(sizeof(type)); } \
[[nodiscard]] void* operator new(size_t, const std::nothrow_t&) noexcept { return kmalloc_aligned(sizeof(type), alignment); } \
void operator delete(void* ptr) noexcept { kfree_aligned(ptr); } \
\
private:
@ -76,25 +76,13 @@ void operator delete[](void* ptr, size_t) noexcept;
[[gnu::malloc, gnu::alloc_size(1)]] void* kmalloc(size_t);
template<size_t ALIGNMENT>
[[gnu::malloc, gnu::alloc_size(1)]] inline void* kmalloc_aligned(size_t size)
{
static_assert(ALIGNMENT > sizeof(ptrdiff_t));
static_assert(ALIGNMENT <= 4096);
void* ptr = kmalloc(size + ALIGNMENT + sizeof(ptrdiff_t));
if (ptr == nullptr)
return ptr;
size_t max_addr = (size_t)ptr + ALIGNMENT;
void* aligned_ptr = (void*)(max_addr - (max_addr % ALIGNMENT));
((ptrdiff_t*)aligned_ptr)[-1] = (ptrdiff_t)((u8*)aligned_ptr - (u8*)ptr);
return aligned_ptr;
}
[[gnu::malloc, gnu::alloc_size(1), gnu::alloc_align(2)]] void* kmalloc_aligned(size_t size, size_t alignment);
inline void kfree_aligned(void* ptr)
{
if (ptr == nullptr)
return;
kfree((u8*)ptr - ((const ptrdiff_t*)ptr)[-1]);
kfree_sized((u8*)ptr - ((ptrdiff_t const*)ptr)[-1], ((size_t const*)ptr)[-2]);
}
size_t kmalloc_good_size(size_t);