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-rw-r--r--arch/riscv/mm/pmap.cc361
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diff --git a/arch/riscv/mm/pmap.cc b/arch/riscv/mm/pmap.cc
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-/* SPDX-License-Identifier: GPL-2.0-or-later */
-/* Copyright (C) 2026 Richard Qin */
-
-/*
- * pmap.cc — SV39 page table operations (MD layer)
- *
- * Implements the pmap namespace interface for RISC-V SV39.
- * 3-level page table: VPN[2] (9 bits) -> VPN[1] (9 bits) -> VPN[0] (9 bits)
- * Each level is a 4KB page containing 512 PTEs of 8 bytes each.
- *
- * Address conversion: all page table operations work with physical addresses.
- * To read/write page table entries we must convert PA to VA via pa_to_va().
- *
- * Reference: docs/specs/vmm.md
- */
-
-#include <lume/types.h>
-#include <lume/addr.h>
-#include <lume/config.h>
-#include <lume/pmm.h>
-#include <lume/memblock.h>
-#include <arch/mmu.h>
-#include <lume/klog.h>
-#include <lume/errno.h>
-
-namespace pmap {
-
-/*
- * Before the first pmap::activate(), CPU runs on entry.S bootstrap page table
- * (fixed direct-map base). After activation, runtime (KASLR) base is valid.
- */
-static bool g_runtime_mapping_ready = false;
-
-/* PTE bit definitions */
-inline constexpr uint64 PTE_V = 1ULL << 0;
-inline constexpr uint64 PTE_R = 1ULL << 1;
-inline constexpr uint64 PTE_W = 1ULL << 2;
-inline constexpr uint64 PTE_X = 1ULL << 3;
-inline constexpr uint64 PTE_U = 1ULL << 4;
-inline constexpr uint64 PTE_G = 1ULL << 5;
-inline constexpr uint64 PTE_A = 1ULL << 6;
-inline constexpr uint64 PTE_D = 1ULL << 7;
-inline constexpr uint64 PTE_COW = 1ULL << 8;
-
-/* SV39: 3 levels, 9 bits per level, 12-bit page offset */
-inline constexpr int kLevels = 3;
-inline constexpr int kPtePerPage = 512;
-
-/* SV39: upper half of VA space (kernel) starts at L2 index 256 */
-inline constexpr int kKernelPgdStart = kPtePerPage / 2;
-
-/* SATP PPN mask (44 bits) and page shift */
-inline constexpr uint64 kSatpPpnMask = 0xFFFFFFFFFFFULL;
-inline constexpr int kPageShift = 12;
-
-/* Extract VPN[level] from a virtual address */
-static inline uint64 vpn(uint64 va, int level)
-{
- return (va >> (12 + 9 * level)) & 0x1FF;
-}
-
-/* Extract PA from a PTE */
-static inline uint64 pte_to_pa(uint64 pte)
-{
- return ((pte >> 10) & 0xFFFFFFFFFFFULL) << 12;
-}
-
-/* Create a PTE from a PA and flags */
-static inline uint64 pa_to_pte(uint64 pa, uint64 flags)
-{
- return ((pa >> 12) << 10) | flags;
-}
-
-/* Convert PA to kernel VA for accessing page table contents */
-static inline uint64 *pa_to_ptr(uint64 pa)
-{
- uint64 va = g_runtime_mapping_ready
- ? pa_to_va(phys_addr(pa)).raw
- : boot_pa_to_va(phys_addr(pa)).raw;
- return reinterpret_cast<uint64 *>(va);
-}
-
-/* Allocate a zeroed page for a page table level.
- * During early boot (before PMM), uses memblock.
- * After PMM init, uses the buddy allocator.
- * Returns PA of the new page, or 0 on failure. */
-static uint64 alloc_pt_page()
-{
- uint64 pa;
- if (memblock_is_active()) {
- pa = memblock_alloc(kPageSize, kPageSize);
- } else {
- Page *page = pmm_alloc_page();
- if (!page) {
- return 0;
- }
- pa = page_to_pa(page).raw;
- }
- if (!pa) {
- return 0;
- }
- /* Zero the page */
- uint64 *ptr = pa_to_ptr(pa);
- for (int i = 0; i < kPtePerPage; i++) {
- ptr[i] = 0;
- }
- return pa;
-}
-
-uint64 create()
-{
- uint64 new_root = alloc_pt_page();
- if (!new_root) return 0;
-
- /* Copy kernel mappings from the current kernel page table.
- * In SV39, entries 256..511 (VPN[2] >= 256) cover the upper
- * half of the 64-bit VA space where the kernel lives.
- * Without these, switching to the new page table would
- * immediately fault on any kernel VA access.
- *
- * Only do this after the runtime page table is active —
- * during early boot the bootstrap PT doesn't cover all of
- * RAM so pa_to_ptr on the kernel root would fault. */
- if (g_runtime_mapping_ready) {
- uint64 kernel_satp;
- asm volatile("csrr %0, satp" : "=r"(kernel_satp));
- uint64 kernel_root_pa = (kernel_satp & kSatpPpnMask) << kPageShift;
-
- uint64 *new_l2 = pa_to_ptr(new_root);
- uint64 *kern_l2 = pa_to_ptr(kernel_root_pa);
-
- for (int i = kKernelPgdStart; i < kPtePerPage; i++) {
- new_l2[i] = kern_l2[i];
- }
- }
-
- return new_root;
-}
-
-void destroy(uint64 root_pa)
-{
- uint64 *l2 = pa_to_ptr(root_pa);
-
- /* Only free the user half (entries 0..255).
- * Entries 256..511 are shared kernel PGD pointers copied
- * from the kernel page table — freeing them would corrupt
- * the kernel's own mappings. */
- for (int i = 0; i < kKernelPgdStart; i++) {
- if (!(l2[i] & PTE_V))
- continue;
- /* Non-leaf L2 entry? (no R/W/X bits = pointer to L1 table) */
- if (!(l2[i] & (PTE_R | PTE_W | PTE_X))) {
- uint64 l1_pa = pte_to_pa(l2[i]);
- uint64 *l1 = pa_to_ptr(l1_pa);
- for (int j = 0; j < kPtePerPage; j++) {
- if (!(l1[j] & PTE_V))
- continue;
- if (!(l1[j] & (PTE_R | PTE_W | PTE_X))) {
- /* L0 page table */
- uint64 l0_pa = pte_to_pa(l1[j]);
- pmm_free_page(pa_to_page(phys_addr(l0_pa)));
- }
- }
- pmm_free_page(pa_to_page(phys_addr(l1_pa)));
- }
- }
- pmm_free_page(pa_to_page(phys_addr(root_pa)));
-}
-
-int map(uint64 root_pa, uint64 va, uint64 pa, uint64 perm)
-{
- uint64 *table = pa_to_ptr(root_pa);
-
- /* Walk levels 2 -> 1, creating intermediate tables as needed */
- for (int level = 2; level > 0; level--) {
- uint64 idx = vpn(va, level);
- if (!(table[idx] & PTE_V)) {
- uint64 child_pa = alloc_pt_page();
- if (!child_pa)
- return -ENOMEM; /* -ENOMEM */
- table[idx] = pa_to_pte(child_pa, PTE_V);
- }
- table = pa_to_ptr(pte_to_pa(table[idx]));
- }
-
- /* Level 0: install the leaf PTE */
- uint64 idx = vpn(va, 0);
- table[idx] = pa_to_pte(pa, perm | PTE_V | PTE_A | PTE_D);
- return 0;
-}
-
-int map_2mb(uint64 root_pa, uint64 va, uint64 pa, uint64 perm)
-{
- /* VA and PA must be 2MB-aligned */
- constexpr uint64 k2MB = 2ULL * 1024 * 1024;
- if ((va & (k2MB - 1)) != 0 || (pa & (k2MB - 1)) != 0) {
- return -EINVAL; /* -EINVAL */
- }
-
- uint64 *table = pa_to_ptr(root_pa);
-
- /* Walk L2: create intermediate table if needed */
- uint64 idx2 = vpn(va, 2);
- if (!(table[idx2] & PTE_V)) {
- uint64 child_pa = alloc_pt_page();
- if (!child_pa) {
- return -ENOMEM; /* -ENOMEM */
- }
- table[idx2] = pa_to_pte(child_pa, PTE_V);
- }
- table = pa_to_ptr(pte_to_pa(table[idx2]));
-
- /* L1: install leaf PTE (2MB mega page) */
- uint64 idx1 = vpn(va, 1);
- table[idx1] = pa_to_pte(pa, perm | PTE_V | PTE_A | PTE_D);
- return 0;
-}
-
-void unmap(uint64 root_pa, uint64 va)
-{
- uint64 *table = pa_to_ptr(root_pa);
- for (int level = 2; level > 0; level--) {
- uint64 idx = vpn(va, level);
- if (!(table[idx] & PTE_V))
- return;
- table = pa_to_ptr(pte_to_pa(table[idx]));
- }
- table[vpn(va, 0)] = 0;
-}
-
-int protect(uint64 root_pa, uint64 va, uint64 perm)
-{
- uint64 *table = pa_to_ptr(root_pa);
- for (int level = 2; level >= 0; level--) {
- uint64 idx = vpn(va, level);
- uint64 pte = table[idx];
- if (!(pte & PTE_V))
- return -EFAULT; /* -EFAULT */
- if (pte & (PTE_R | PTE_W | PTE_X)) {
- uint64 pa = pte_to_pa(pte);
- table[idx] = pa_to_pte(pa, perm | PTE_V);
- return 0;
- }
- table = pa_to_ptr(pte_to_pa(pte));
- }
- return -EFAULT;
-}
-
-int protect_range(uint64 root_pa, uint64 start, uint64 end, uint64 perm)
-{
- if (end <= start) {
- return 0;
- }
-
- uint64 va = page_align_down(start);
- uint64 va_end = page_align_up(end);
-
- for (; va < va_end; va += kPageSize) {
- int ret = protect(root_pa, va, perm);
- if (ret == -14) {
- continue; /* unmapped page: skip */
- }
- if (ret < 0) {
- return ret;
- }
- }
-
- arch::mmu::flush_tlb_all();
- return 0;
-}
-
-bool lookup(uint64 root_pa, uint64 va, uint64 *pa_out)
-{
- uint64 *table = pa_to_ptr(root_pa);
- for (int level = 2; level >= 0; level--) {
- uint64 idx = vpn(va, level);
- uint64 pte = table[idx];
- if (!(pte & PTE_V))
- return false;
- /* Leaf PTE? (has R, W, or X) */
- if (pte & (PTE_R | PTE_W | PTE_X)) {
- if (pa_out)
- *pa_out = pte_to_pa(pte);
- return true;
- }
- table = pa_to_ptr(pte_to_pa(pte));
- }
- return false;
-}
-
-uint64 lookup_pte(uint64 root_pa, uint64 va)
-{
- uint64 *table = pa_to_ptr(root_pa);
- for (int level = 2; level >= 0; level--) {
- uint64 idx = vpn(va, level);
- uint64 pte = table[idx];
- if (!(pte & PTE_V))
- return 0;
- if (pte & (PTE_R | PTE_W | PTE_X))
- return pte; // leaf PTE raw value
- table = pa_to_ptr(pte_to_pa(pte));
- }
- return 0;
-}
-
-bool is_cow(uint64 root_pa, uint64 va)
-{
- uint64 *table = pa_to_ptr(root_pa);
- for (int level = 2; level >= 0; level--) {
- uint64 idx = vpn(va, level);
- uint64 pte = table[idx];
- if (!(pte & PTE_V))
- return false;
- if (pte & (PTE_R | PTE_W | PTE_X)) {
- return (pte & PTE_COW) != 0;
- }
- table = pa_to_ptr(pte_to_pa(pte));
- }
- return false;
-}
-
-int make_cow(uint64 root_pa, uint64 va)
-{
- uint64 *table = pa_to_ptr(root_pa);
- for (int level = 2; level >= 0; level--) {
- uint64 idx = vpn(va, level);
- uint64 pte = table[idx];
- if (!(pte & PTE_V))
- return -EFAULT; /* -EFAULT */
- if (pte & (PTE_R | PTE_W | PTE_X)) {
- /* Clear write bit, set COW bit */
- pte &= ~PTE_W;
- pte |= PTE_COW;
- table[idx] = pte;
- return 0;
- }
- table = pa_to_ptr(pte_to_pa(pte));
- }
- return -EFAULT;
-}
-
-void activate(uint64 root_pa)
-{
- arch::mmu::set_page_table(root_pa);
- arch::mmu::flush_tlb_all();
- g_runtime_mapping_ready = true;
-}
-
-uint64 vm_perm_to_pte(uint64 vm_perm)
-{
- /* Translate MI VM_* flags to SV39 PTE bits.
- * The MI flags are defined in <lume/vmm.h>. */
- uint64 pte = PTE_V | PTE_A | PTE_D; // Valid + Accessed + Dirty (avoid HW A/D faults)
- if (vm_perm & (1ULL << 0)) pte |= PTE_R; // VM_READ
- if (vm_perm & (1ULL << 1)) pte |= PTE_W; // VM_WRITE
- if (vm_perm & (1ULL << 2)) pte |= PTE_X; // VM_EXEC
- if (vm_perm & (1ULL << 3)) pte |= PTE_U; // VM_USER
- return pte;
-}
-
-} // namespace pmap
generated by cgit v1.2.3 (git 2.46.0) at 2026-10-29 00:38:17 +0000