Kernel/Core/Memory/StackGuard.cpp

/*
   This file is part of Fennix Kernel.

   Fennix Kernel is free software: you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation, either version 3 of
   the License, or (at your option) any later version.

   Fennix Kernel is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with Fennix Kernel. If not, see <https://www.gnu.org/licenses/>.
*/

#include <memory.hpp>

#include <debug.h>

namespace Memory
{
    bool StackGuard::Expand(uintptr_t FaultAddress)
    {
        if (this->UserMode)
        {
            if (FaultAddress < (uintptr_t)this->StackBottom - USER_STACK_SIZE ||
                FaultAddress > (uintptr_t)this->StackTop)
            {
                info("Fault address %#lx is not in range of stack %#lx - %#lx", FaultAddress,
                     (uintptr_t)this->StackBottom - USER_STACK_SIZE, (uintptr_t)this->StackTop);
                return false; /* It's not about the stack. */
            }
            else
            {
                void *AllocatedStack = KernelAllocator.RequestPages(TO_PAGES(USER_STACK_SIZE + 1));
                debug("AllocatedStack: %#lx", AllocatedStack);
                memset(AllocatedStack, 0, USER_STACK_SIZE);

                Virtual va = Virtual(this->Table);
                for (size_t i = 0; i < TO_PAGES(USER_STACK_SIZE); i++)
                {
                    void *VirtualPage = (void *)((uintptr_t)this->StackBottom - (i * PAGE_SIZE));
                    void *PhysicalPage = (void *)((uintptr_t)AllocatedStack + (i * PAGE_SIZE));

                    va.Map(VirtualPage, PhysicalPage, PTFlag::RW | PTFlag::US);
                    AllocatedPages pa = {
                        .PhysicalAddress = PhysicalPage,
                        .VirtualAddress = VirtualPage,
                    };
                    AllocatedPagesList.push_back(pa);
                    debug("Mapped %#lx to %#lx", PhysicalPage, VirtualPage);
                }

                this->StackBottom = (void *)((uintptr_t)this->StackBottom - USER_STACK_SIZE);
                this->Size += USER_STACK_SIZE;
                info("Stack expanded to %#lx", this->StackBottom);
                this->Expanded = true;
                return true;
            }
        }
        else
        {
            fixme("Not implemented and probably not needed");
            return false;
        }
    }

    void StackGuard::Fork(StackGuard *Parent)
    {
        this->UserMode = Parent->GetUserMode();
        this->StackBottom = Parent->GetStackBottom();
        this->StackTop = Parent->GetStackTop();
        this->StackPhysicalBottom = Parent->GetStackPhysicalBottom();
        this->StackPhysicalTop = Parent->GetStackPhysicalTop();
        this->Size = Parent->GetSize();
        this->Expanded = Parent->IsExpanded();

        if (this->UserMode)
        {
            std::vector<AllocatedPages> ParentAllocatedPages = Parent->GetAllocatedPages();

            Virtual va = Virtual(Table);

            foreach (auto Page in AllocatedPagesList)
            {
                va.Unmap(Page.VirtualAddress);
                KernelAllocator.FreePage(Page.PhysicalAddress);
                debug("Freed %#lx and unmapped %#lx", Page.PhysicalAddress, Page.VirtualAddress);
            }

            foreach (auto Page in ParentAllocatedPages)
            {
                void *NewPhysical = KernelAllocator.RequestPage();
                memcpy(NewPhysical, Page.PhysicalAddress, PAGE_SIZE);
                va.Map(Page.VirtualAddress, NewPhysical, PTFlag::RW | PTFlag::US);

                AllocatedPages pa = {
                    .PhysicalAddress = NewPhysical,
                    .VirtualAddress = Page.VirtualAddress,
                };
                AllocatedPagesList.push_back(pa);
                debug("Mapped %#lx to %#lx", NewPhysical, Page.VirtualAddress);
            }
        }
        else
        {
            fixme("Kernel mode stack fork not implemented");
        }
    }

    StackGuard::StackGuard(bool User, PageTable *Table)
    {
        this->UserMode = User;
        this->Table = Table;

        if (this->UserMode)
        {
            void *AllocatedStack = KernelAllocator.RequestPages(TO_PAGES(USER_STACK_SIZE + 1));
            memset(AllocatedStack, 0, USER_STACK_SIZE);
            debug("AllocatedStack: %#lx", AllocatedStack);

            Virtual va = Virtual(Table);
            for (size_t i = 0; i < TO_PAGES(USER_STACK_SIZE); i++)
            {
                void *VirtualPage = (void *)(USER_STACK_BASE + (i * PAGE_SIZE));
                void *PhysicalPage = (void *)((uintptr_t)AllocatedStack + (i * PAGE_SIZE));
                va.Map(VirtualPage, PhysicalPage, PTFlag::RW | PTFlag::US);

                AllocatedPages pa = {
                    .PhysicalAddress = PhysicalPage,
                    .VirtualAddress = VirtualPage,
                };
                AllocatedPagesList.push_back(pa);
                debug("Mapped %#lx to %#lx", PhysicalPage, VirtualPage);
            }

            this->StackBottom = (void *)USER_STACK_BASE;
            this->StackTop = (void *)(USER_STACK_BASE + USER_STACK_SIZE);

            this->StackPhysicalBottom = AllocatedStack;
            this->StackPhysicalTop = (void *)((uintptr_t)AllocatedStack + USER_STACK_SIZE);

            this->Size = USER_STACK_SIZE;
        }
        else
        {
            this->StackBottom = KernelAllocator.RequestPages(TO_PAGES(STACK_SIZE + 1));
            memset(this->StackBottom, 0, STACK_SIZE);
            debug("StackBottom: %#lx", this->StackBottom);

            this->StackTop = (void *)((uintptr_t)this->StackBottom + STACK_SIZE);

            this->StackPhysicalBottom = this->StackBottom;
            this->StackPhysicalTop = this->StackTop;

            this->Size = STACK_SIZE;

            for (size_t i = 0; i < TO_PAGES(STACK_SIZE); i++)
            {
                AllocatedPages pa = {
                    .PhysicalAddress = (void *)((uintptr_t)this->StackBottom + (i * PAGE_SIZE)),
                    .VirtualAddress = (void *)((uintptr_t)this->StackBottom + (i * PAGE_SIZE)),
                };
                AllocatedPagesList.push_back(pa);
            }
        }

        debug("Allocated stack at %#lx", this->StackBottom);
    }

    StackGuard::~StackGuard()
    {
        foreach (auto Page in AllocatedPagesList)
        {
            KernelAllocator.FreePage(Page.PhysicalAddress);
            debug("Freed page at %#lx", Page.PhysicalAddress);
        }
    }
}