vmm.h

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// MIT License
//
// Copyright (c) 2026 Christian Spoo
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
 
#ifndef _MINIOS_MM_VMM_H_
#define _MINIOS_MM_VMM_H_
 
#include <miniOS/types.h> 
 
 
#define PAGE_PRESENT  (1ULL << 0)
#define PAGE_WRITE    (1ULL << 1)
#define PAGE_USER     (1ULL << 2)
#define PAGE_COW      (1ULL << 9)   /* software: copy-on-write pending */
 
/* ------------------------------------------------------------------ */
/*  Higher-half kernel virtual address layout                          */
/* ------------------------------------------------------------------ */
/* KERNEL_VMA: base of higher-half kernel window (PML4[256]).          *
 * Physical address P maps to virtual P + KERNEL_VMA.                 *
 * NOTE: Also defined as KERNEL_VMA equ in src/arch/x86_64/main64.asm *
 *       (ASM boot code cannot include C headers). Keep in sync.      */
#define KERNEL_VMA          0xFFFF800000000000ULL
 
/* HEAP_START: kernel heap virtual base (PML4[260]).                   *
 * src/kernel/mm/heap.c honours #ifndef HEAP_START so test builds     *
 * can override this value via -D on the compiler command line.       */
#ifndef HEAP_START
#define HEAP_START          0xFFFF820000000000ULL
#endif
 
/* HEAP_MAX: upper bound of heap (4 MiB above HEAP_START).            */
#ifndef HEAP_MAX
#define HEAP_MAX            (HEAP_START + 4ULL * 1024 * 1024)
#endif
 
/* DMA_BUFFER_VA: 4 KiB DMA bounce buffer virtual address (PML4[262]).*/
#define DMA_BUFFER_VA       0xFFFF830000000000ULL
 
/* GOP_FB_VA: linear framebuffer virtual base (PML4[264]).              *
 * Mapped at boot by gop_init_from_mb2() when CONSOLE_GOP is defined.  */
#define GOP_FB_VA           0xFFFF840000000000ULL
 
/* VGA_BUFFER_VA: text-mode VGA framebuffer virtual address.           *
 * Physical 0xB8000 mapped via the KERNEL_VMA identity window.        */
#define VGA_BUFFER_VA       (KERNEL_VMA + 0xB8000ULL)
 
/* ------------------------------------------------------------------ */
/*  x86_64 page size                                                   */
/* ------------------------------------------------------------------ */
/* PAGE_SIZE: 4 KiB frame size for this kernel (4-level paging).      */
#define PAGE_SIZE           4096ULL
 
/* ------------------------------------------------------------------ */
/*  Page-table index extraction (4-level paging, 9-bit indices)       */
/* ------------------------------------------------------------------ */
#define PML4_SHIFT      39   /* bits [47:39] index PML4 */
#define PDPT_SHIFT      30   /* bits [38:30] index PDPT */
#define PD_SHIFT        21   /* bits [29:21] index PD   */
#define PT_SHIFT        12   /* bits [20:12] index PT   */
#define PT_INDEX_MASK   0x1FFULL  /* 9-bit mask for any level index */
 
/* ------------------------------------------------------------------ */
/*  PTE physical address mask                                          */
/* ------------------------------------------------------------------ */
/* PTE_ADDR_MASK: bits [51:12] hold the physical frame address in a PTE. */
#define PTE_ADDR_MASK   0x000FFFFFFFFFF000ULL

int vmm_map_page(uint64_t virt, uint64_t phys, uint64_t flags);

void vmm_unmap_page(uint64_t virt);

uint64_t vmm_virt_to_phys(uint64_t virt);
uint64_t vmm_virt_to_pte(uint64_t virt);

int vmm_resolve_user_fault(uint64_t cr2, uint64_t error_code);

uint64_t vmm_new_address_space(void);

void vmm_free_address_space(uint64_t pml4_phys);
 
/* PML4-parameterized variants of the four core VMM primitives — operate on
 * an explicit address space instead of the live CR3. Used to build a new
 * process's page tables (fork) or inspect another process's memory (ptrace,
 * once implemented) without ever loading that process's CR3. */
int      vmm_map_page_in(uint64_t pml4_phys, uint64_t virt, uint64_t phys, uint64_t flags);
void     vmm_unmap_page_in(uint64_t pml4_phys, uint64_t virt);
uint64_t vmm_virt_to_phys_in(uint64_t pml4_phys, uint64_t virt);
uint64_t vmm_virt_to_pte_in(uint64_t pml4_phys, uint64_t virt);
 
#endif /* _MINIOS_MM_VMM_H_ */