qemu

x86_mmu.c (6873B)

---

 /*
  * Copyright (C) 2016 Veertu Inc,
  * Copyright (C) 2017 Google Inc,
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * This program 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
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this program; if not, see <http://www.gnu.org/licenses/>.
  */
 
 #include "qemu/osdep.h"
 #include "panic.h"
 #include "cpu.h"
 #include "x86.h"
 #include "x86_mmu.h"
 #include "vmcs.h"
 #include "vmx.h"
 
 #define pte_present(pte) (pte & PT_PRESENT)
 #define pte_write_access(pte) (pte & PT_WRITE)
 #define pte_user_access(pte) (pte & PT_USER)
 #define pte_exec_access(pte) (!(pte & PT_NX))
 
 #define pte_large_page(pte) (pte & PT_PS)
 #define pte_global_access(pte) (pte & PT_GLOBAL)
 
 #define PAE_CR3_MASK                (~0x1fllu)
 #define LEGACY_CR3_MASK             (0xffffffff)
 
 #define LEGACY_PTE_PAGE_MASK        (0xffffffffllu << 12)
 #define PAE_PTE_PAGE_MASK           ((-1llu << 12) & ((1llu << 52) - 1))
 #define PAE_PTE_LARGE_PAGE_MASK     ((-1llu << (21)) & ((1llu << 52) - 1))
 
 struct gpt_translation {
     target_ulong  gva;
     uint64_t gpa;
     int    err_code;
     uint64_t pte[5];
     bool write_access;
     bool user_access;
     bool exec_access;
 };
 
 static int gpt_top_level(struct CPUState *cpu, bool pae)
 {
     if (!pae) {
         return 2;
     }
     if (x86_is_long_mode(cpu)) {
         return 4;
     }
 
     return 3;
 }
 
 static inline int gpt_entry(target_ulong addr, int level, bool pae)
 {
     int level_shift = pae ? 9 : 10;
     return (addr >> (level_shift * (level - 1) + 12)) & ((1 << level_shift) - 1);
 }
 
 static inline int pte_size(bool pae)
 {
     return pae ? 8 : 4;
 }
 
 
 static bool get_pt_entry(struct CPUState *cpu, struct gpt_translation *pt,
                          int level, bool pae)
 {
     int index;
     uint64_t pte = 0;
     uint64_t page_mask = pae ? PAE_PTE_PAGE_MASK : LEGACY_PTE_PAGE_MASK;
     uint64_t gpa = pt->pte[level] & page_mask;
 
     if (level == 3 && !x86_is_long_mode(cpu)) {
         gpa = pt->pte[level];
     }
 
     index = gpt_entry(pt->gva, level, pae);
     address_space_read(&address_space_memory, gpa + index * pte_size(pae),
                        MEMTXATTRS_UNSPECIFIED, &pte, pte_size(pae));
 
     pt->pte[level - 1] = pte;
 
     return true;
 }
 
 /* test page table entry */
 static bool test_pt_entry(struct CPUState *cpu, struct gpt_translation *pt,
                           int level, bool *is_large, bool pae)
 {
     uint64_t pte = pt->pte[level];
 
     if (pt->write_access) {
         pt->err_code |= MMU_PAGE_WT;
     }
     if (pt->user_access) {
         pt->err_code |= MMU_PAGE_US;
     }
     if (pt->exec_access) {
         pt->err_code |= MMU_PAGE_NX;
     }
 
     if (!pte_present(pte)) {
         return false;
     }
 
     if (pae && !x86_is_long_mode(cpu) && 2 == level) {
         goto exit;
     }
 
     if (1 == level && pte_large_page(pte)) {
         pt->err_code |= MMU_PAGE_PT;
         *is_large = true;
     }
     if (!level) {
         pt->err_code |= MMU_PAGE_PT;
     }
 
     uint32_t cr0 = rvmcs(cpu->hvf->fd, VMCS_GUEST_CR0);
     /* check protection */
     if (cr0 & CR0_WP_MASK) {
         if (pt->write_access && !pte_write_access(pte)) {
             return false;
         }
     }
 
     if (pt->user_access && !pte_user_access(pte)) {
         return false;
     }
 
     if (pae && pt->exec_access && !pte_exec_access(pte)) {
         return false;
     }
     
 exit:
     /* TODO: check reserved bits */
     return true;
 }
 
 static inline uint64_t pse_pte_to_page(uint64_t pte)
 {
     return ((pte & 0x1fe000) << 19) | (pte & 0xffc00000);
 }
 
 static inline uint64_t large_page_gpa(struct gpt_translation *pt, bool pae)
 {
     VM_PANIC_ON(!pte_large_page(pt->pte[1]))
     /* 2Mb large page  */
     if (pae) {
         return (pt->pte[1] & PAE_PTE_LARGE_PAGE_MASK) | (pt->gva & 0x1fffff);
     }
 
     /* 4Mb large page */
     return pse_pte_to_page(pt->pte[1]) | (pt->gva & 0x3fffff);
 }
 
 
 
 static bool walk_gpt(struct CPUState *cpu, target_ulong addr, int err_code,
                      struct gpt_translation *pt, bool pae)
 {
     int top_level, level;
     bool is_large = false;
     target_ulong cr3 = rvmcs(cpu->hvf->fd, VMCS_GUEST_CR3);
     uint64_t page_mask = pae ? PAE_PTE_PAGE_MASK : LEGACY_PTE_PAGE_MASK;
     
     memset(pt, 0, sizeof(*pt));
     top_level = gpt_top_level(cpu, pae);
 
     pt->pte[top_level] = pae ? (cr3 & PAE_CR3_MASK) : (cr3 & LEGACY_CR3_MASK);
     pt->gva = addr;
     pt->user_access = (err_code & MMU_PAGE_US);
     pt->write_access = (err_code & MMU_PAGE_WT);
     pt->exec_access = (err_code & MMU_PAGE_NX);
     
     for (level = top_level; level > 0; level--) {
         get_pt_entry(cpu, pt, level, pae);
 
         if (!test_pt_entry(cpu, pt, level - 1, &is_large, pae)) {
             return false;
         }
 
         if (is_large) {
             break;
         }
     }
 
     if (!is_large) {
         pt->gpa = (pt->pte[0] & page_mask) | (pt->gva & 0xfff);
     } else {
         pt->gpa = large_page_gpa(pt, pae);
     }
 
     return true;
 }
 
 
 bool mmu_gva_to_gpa(struct CPUState *cpu, target_ulong gva, uint64_t *gpa)
 {
     bool res;
     struct gpt_translation pt;
     int err_code = 0;
 
     if (!x86_is_paging_mode(cpu)) {
         *gpa = gva;
         return true;
     }
 
     res = walk_gpt(cpu, gva, err_code, &pt, x86_is_pae_enabled(cpu));
     if (res) {
         *gpa = pt.gpa;
         return true;
     }
 
     return false;
 }
 
 void vmx_write_mem(struct CPUState *cpu, target_ulong gva, void *data, int bytes)
 {
     uint64_t gpa;
 
     while (bytes > 0) {
         /* copy page */
         int copy = MIN(bytes, 0x1000 - (gva & 0xfff));
 
         if (!mmu_gva_to_gpa(cpu, gva, &gpa)) {
             VM_PANIC_EX("%s: mmu_gva_to_gpa %llx failed\n", __func__, gva);
         } else {
             address_space_write(&address_space_memory, gpa,
                                 MEMTXATTRS_UNSPECIFIED, data, copy);
         }
 
         bytes -= copy;
         gva += copy;
         data += copy;
     }
 }
 
 void vmx_read_mem(struct CPUState *cpu, void *data, target_ulong gva, int bytes)
 {
     uint64_t gpa;
 
     while (bytes > 0) {
         /* copy page */
         int copy = MIN(bytes, 0x1000 - (gva & 0xfff));
 
         if (!mmu_gva_to_gpa(cpu, gva, &gpa)) {
             VM_PANIC_EX("%s: mmu_gva_to_gpa %llx failed\n", __func__, gva);
         }
         address_space_read(&address_space_memory, gpa, MEMTXATTRS_UNSPECIFIED,
                            data, copy);
 
         bytes -= copy;
         gva += copy;
         data += copy;
     }
 }