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/* -------------------------------------------
Copyright SoftwareLabs
------------------------------------------- */
#include <ArchKit/ArchKit.hpp>
#include <HALKit/AMD64/HalPageAlloc.hpp>
#include <NewKit/Defines.hpp>
#include <NewKit/KernelCheck.hpp>
STATIC NewOS::Boolean kAllocationInProgress = false;
namespace NewOS
{
namespace HAL
{
namespace Detail
{
struct VirtualMemoryHeader
{
UInt32 Magic;
Boolean Present;
Boolean ReadWrite;
Boolean User;
SizeT PageSize;
};
struct VirtualMemoryHeaderTraits
{
/// @brief Get next header.
/// @param current
/// @return
VirtualMemoryHeader* Next(VirtualMemoryHeader* current)
{
return current + sizeof(PTE) + current->PageSize;
}
/// @brief Get previous header.
/// @param current
/// @return
VirtualMemoryHeader* Prev(VirtualMemoryHeader* current)
{
return current - sizeof(PTE) - current->PageSize;
}
};
} // namespace Detail
/// @brief Allocates a new page of memory.
/// @param sz the size of it.
/// @param rw read/write flag.
/// @param user user flag.
/// @return the page table of it.
STATIC auto hal_try_alloc_new_page(Boolean rw, Boolean user, SizeT size) -> VoidPtr
{
if (kAllocationInProgress)
return nullptr;
kAllocationInProgress = true;
constexpr auto cVMTMagic = 0xDEEFD00D;
///! fetch from the start.
Detail::VirtualMemoryHeader* vmHeader = reinterpret_cast<Detail::VirtualMemoryHeader*>(kKernelVirtualStart);
Detail::VirtualMemoryHeaderTraits traits;
while (vmHeader->Present &&
vmHeader->Magic != cVMTMagic)
{
vmHeader = traits.Next(vmHeader);
}
vmHeader->Magic = cVMTMagic;
vmHeader->Present = true;
vmHeader->ReadWrite = rw;
vmHeader->User = user;
vmHeader->PageSize = size;
kAllocationInProgress = false;
return reinterpret_cast<VoidPtr>(vmHeader);
}
/// @brief Allocate a new page to be used by the OS.
/// @param rw read/write bit.
/// @param user user bit.
/// @return
auto hal_alloc_page(Boolean rw, Boolean user, SizeT size) -> VoidPtr
{
/// Wait for a ongoing allocation to complete.
while (kAllocationInProgress)
{
;
}
if (size == 0)
++size;
/// allocate new page.
return hal_try_alloc_new_page(rw, user, size);
}
} // namespace HAL
} // namespace NewOS
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