/* Contains macros and constants for the kernel VM mapping, page tables,
 * definitions for the RISC-V MMU, etc. */

#pragma once

/* **************************************** */
/* Kernel Virtual Memory Mapping  (not really an MMU thing) */

// All physical memory mapped at this address
#ifdef __riscv64
# define KERNBASE       0xFFFFFC0000000000
# define ULIM           0x0000040000000000
# define KERN_LOAD_ADDR 0xFFFFFFFF80000000
# define KERN_VMAP_TOP    	KERN_LOAD_ADDR // upper 2GB reserved (see mmu_init)
# define NPTLEVELS                       3
# define L1PGSHIFT              (13+10+10)
# define L1PGSIZE        (1L << L1PGSHIFT)
# define L2PGSHIFT                 (13+10)
# define L2PGSIZE        (1L << L2PGSHIFT)
# define L3PGSHIFT                    (13)
# define L3PGSIZE        (1L << L3PGSHIFT)
# define PGSHIFT                 L3PGSHIFT
# define PTSIZE                   L2PGSIZE
#else
# define KERNBASE               0x80000000
# define ULIM                   0x7F000000
# define KERN_LOAD_ADDR           KERNBASE
# define KERN_VMAP_TOP    		0xfec00000
# define NPTLEVELS                       2
# define L1PGSHIFT                 (13+11)
# define L1PGSIZE         (1 << L1PGSHIFT)
# define L2PGSHIFT                      13
# define L2PGSIZE         (1 << L2PGSHIFT)
# define PGSHIFT                 L2PGSHIFT
# define PTSIZE                   L1PGSIZE
#endif

/* All arches must define this, which is the lower limit of their static
 * mappings, and where the dynamic mappings will start. */
#define KERN_DYN_TOP    KERNBASE

/* **************************************** */
/* Page table constants, macros, etc */

#define PGSIZE (1 << PGSHIFT)

// RV64 virtual addresses are 48 bits, sign-extended out to 64 bits,
// creating a hole between 0x0000 7FFF FFFF FFFF and 0xFFFF 8000 0000 0000.
// Bits 11-0 are the page offset; L1/L2/L3/L4 page table indices are given
// by bits 47-39, 38-30, 29-21, and 20-12, respectively.
//
// In RV32, virtual addresses are 32 bits; bits 11-0 are the page offset;
// and L1/L2 page table indices are given by bits 31-22 and 21-12,
// respectively.
//
// In both cases, the last-level page size is 4KB, as is the page table size.

// page number field of address
#define LA2PPN(la)	(((uintptr_t) (la)) >> PGSHIFT)

// page number field of PPN
#define PTE2PPN(pte)	(((uintptr_t) (pte)) >> PTE_PPN_SHIFT)

// index into L1 PT
#define L1X(la)		((((uintptr_t) (la)) >> L1PGSHIFT) & (NPTENTRIES-1))

// index into L2 PT
#define L2X(la)		((((uintptr_t) (la)) >> L2PGSHIFT) & (NPTENTRIES-1))

#ifdef __riscv64
// index into L3 PT
#define L3X(la)		((((uintptr_t) (la)) >> L3PGSHIFT) & (NPTENTRIES-1))

// index into L4 PT
#define L4X(la)		((((uintptr_t) (la)) >> L4PGSHIFT) & (NPTENTRIES-1))

#endif

// offset in page
#define PGOFF(la)	(((uintptr_t) (la)) & (PGSIZE-1))

// construct PTD from physical address
#define PTD(pa) (((uintptr_t)(pa) >> PGSHIFT << PTE_PPN_SHIFT) | PTE_T)

// Page directory and page table constants
#define NPTENTRIES (PGSIZE/sizeof(pte_t))

// Page table/directory entry flags.
#define PTE_T    0x001 // Entry is a page Table descriptor
#define PTE_E    0x002 // Entry is a page table Entry
#define PTE_R    0x004 // Referenced
#define PTE_D    0x008 // Dirty
#define PTE_UX   0x010 // User eXecute permission
#define PTE_UW   0x020 // User Read permission
#define PTE_UR   0x040 // User Write permission
#define PTE_SX   0x080 // Supervisor eXecute permission
#define PTE_SW   0x100 // Supervisor Read permission
#define PTE_SR   0x200 // Supervisor Write permission
#define PTE_PERM (PTE_SR | PTE_SW | PTE_SX | PTE_UR | PTE_UW | PTE_UX)
#define PTE_PPN_SHIFT 13
#warning "Review RISCV PTE_modes, like NOCACHE/WRITECOMB"
#define PTE_NOCACHE	0 // PTE bits to turn off caching, if possible
#define PTE_WRITECOMB	0 // PTE bits to turn on write-combining, if possible

// commly used access modes

#warning "Review RISCV PTEs.  Maybe want PTE_E/PTE_R?"
	/* arch-indep code doesn't set PTE_P, it just sets a perm */


#define PTE_KERN_RW	(PTE_SR | PTE_SW | PTE_SX)
#define PTE_KERN_RO	(PTE_SR | PTE_SX)
#define PTE_USER_RW	(PTE_SR | PTE_SW | PTE_UR | PTE_UW | PTE_UX)
#define PTE_USER_RO	(PTE_SR | PTE_UR | PTE_UX)
#define PTE_NONE	0

#warning "probably remove this"
// x86 equivalencies
#define PTE_P      PTE_E

// address in page table entry
#define PTE_ADDR(pte)	((physaddr_t) (pte) & ~(PGSIZE-1))

// address in page table descriptor
#define PTD_ADDR(ptd)	PTE_ADDR(ptd)

// MMU Control Register flags
#define MMU_CR_E	0x00000001	// Protection Enable
#define MMU_CR_NF	0x00000002	// No Fault mode
#define MMU_CR_PSO	0x00000080	// Partial Store Order (TSO disabled)

// MMU Fault Status Register flags
#define MMU_FSR_USER	0x00000020	// Fault caused by user-space access
#define MMU_FSR_EX	0x00000040	// Fault occured in instruction-space
#define MMU_FSR_WR	0x00000080	// Fault caused by a store

// MMU Register Addresses
#define MMU_REG_CTRL	0x00000000	// MMU Control Register
#define MMU_REG_CTXTBL	0x00000100	// MMU Context Table Pointer Register
#define MMU_REG_CTX	0x00000200	// MMU Context Register
#define MMU_REG_FSR	0x00000300	// MMU Fault Status Register
#define MMU_REG_FAR	0x00000400	// MMU Fault Address Register

// we must guarantee that for any PTE, exactly one of the following is true
#define PAGE_PRESENT(pte) ((pte) & PTE_P)
#define PAGE_UNMAPPED(pte) ((pte) == 0)
#define PAGE_PAGED_OUT(pte) (!PAGE_PRESENT(pte) && !PAGE_UNMAPPED(pte))
#define NOVPT

#ifndef __ASSEMBLER__
typedef unsigned long pte_t;
typedef unsigned long pgdir_t;
#endif

/* Same as VPT but read-only for users */
#define UVPT		(ULIM - PTSIZE)

/* Arbitrary boundary between the break and the start of
 * memory returned by calls to mmap with addr = 0 */
#define BRK_END 0x40000000