\r
STATIC BOOLEAN mAddressEncMaskChecked = FALSE;\r
STATIC UINT64 mAddressEncMask;\r
+STATIC PAGE_TABLE_POOL *mPageTablePool = NULL;\r
\r
typedef enum {\r
SetCBit,\r
return mAddressEncMask;\r
}\r
\r
+/**\r
+ Initialize a buffer pool for page table use only.\r
+\r
+ To reduce the potential split operation on page table, the pages reserved for\r
+ page table should be allocated in the times of PAGE_TABLE_POOL_UNIT_PAGES and\r
+ at the boundary of PAGE_TABLE_POOL_ALIGNMENT. So the page pool is always\r
+ initialized with number of pages greater than or equal to the given PoolPages.\r
+\r
+ Once the pages in the pool are used up, this method should be called again to\r
+ reserve at least another PAGE_TABLE_POOL_UNIT_PAGES. Usually this won't happen\r
+ often in practice.\r
+\r
+ @param[in] PoolPages The least page number of the pool to be created.\r
+\r
+ @retval TRUE The pool is initialized successfully.\r
+ @retval FALSE The memory is out of resource.\r
+**/\r
+STATIC\r
+BOOLEAN\r
+InitializePageTablePool (\r
+ IN UINTN PoolPages\r
+ )\r
+{\r
+ VOID *Buffer;\r
+\r
+ //\r
+ // Always reserve at least PAGE_TABLE_POOL_UNIT_PAGES, including one page for\r
+ // header.\r
+ //\r
+ PoolPages += 1; // Add one page for header.\r
+ PoolPages = ((PoolPages - 1) / PAGE_TABLE_POOL_UNIT_PAGES + 1) *\r
+ PAGE_TABLE_POOL_UNIT_PAGES;\r
+ Buffer = AllocateAlignedPages (PoolPages, PAGE_TABLE_POOL_ALIGNMENT);\r
+ if (Buffer == NULL) {\r
+ DEBUG ((DEBUG_ERROR, "ERROR: Out of aligned pages\r\n"));\r
+ return FALSE;\r
+ }\r
+\r
+ //\r
+ // Link all pools into a list for easier track later.\r
+ //\r
+ if (mPageTablePool == NULL) {\r
+ mPageTablePool = Buffer;\r
+ mPageTablePool->NextPool = mPageTablePool;\r
+ } else {\r
+ ((PAGE_TABLE_POOL *)Buffer)->NextPool = mPageTablePool->NextPool;\r
+ mPageTablePool->NextPool = Buffer;\r
+ mPageTablePool = Buffer;\r
+ }\r
+\r
+ //\r
+ // Reserve one page for pool header.\r
+ //\r
+ mPageTablePool->FreePages = PoolPages - 1;\r
+ mPageTablePool->Offset = EFI_PAGES_TO_SIZE (1);\r
+\r
+ return TRUE;\r
+}\r
+\r
+/**\r
+ This API provides a way to allocate memory for page table.\r
+\r
+ This API can be called more than once to allocate memory for page tables.\r
+\r
+ Allocates the number of 4KB pages and returns a pointer to the allocated\r
+ buffer. The buffer returned is aligned on a 4KB boundary.\r
+\r
+ If Pages is 0, then NULL is returned.\r
+ If there is not enough memory remaining to satisfy the request, then NULL is\r
+ returned.\r
+\r
+ @param Pages The number of 4 KB pages to allocate.\r
+\r
+ @return A pointer to the allocated buffer or NULL if allocation fails.\r
+\r
+**/\r
+STATIC\r
+VOID *\r
+EFIAPI\r
+AllocatePageTableMemory (\r
+ IN UINTN Pages\r
+ )\r
+{\r
+ VOID *Buffer;\r
+\r
+ if (Pages == 0) {\r
+ return NULL;\r
+ }\r
+\r
+ //\r
+ // Renew the pool if necessary.\r
+ //\r
+ if (mPageTablePool == NULL ||\r
+ Pages > mPageTablePool->FreePages) {\r
+ if (!InitializePageTablePool (Pages)) {\r
+ return NULL;\r
+ }\r
+ }\r
+\r
+ Buffer = (UINT8 *)mPageTablePool + mPageTablePool->Offset;\r
+\r
+ mPageTablePool->Offset += EFI_PAGES_TO_SIZE (Pages);\r
+ mPageTablePool->FreePages -= Pages;\r
+\r
+ DEBUG ((\r
+ DEBUG_VERBOSE,\r
+ "%a:%a: Buffer=0x%Lx Pages=%ld\n",\r
+ gEfiCallerBaseName,\r
+ __FUNCTION__,\r
+ Buffer,\r
+ Pages\r
+ ));\r
+\r
+ return Buffer;\r
+}\r
+\r
+\r
/**\r
Split 2M page to 4K.\r
\r
PAGE_TABLE_4K_ENTRY *PageTableEntry, *PageTableEntry1;\r
UINT64 AddressEncMask;\r
\r
- PageTableEntry = AllocatePages(1);\r
+ PageTableEntry = AllocatePageTableMemory(1);\r
\r
PageTableEntry1 = PageTableEntry;\r
\r
*PageEntry2M = (UINT64) (UINTN) PageTableEntry1 | IA32_PG_P | IA32_PG_RW | AddressEncMask;\r
}\r
\r
+/**\r
+ Set one page of page table pool memory to be read-only.\r
+\r
+ @param[in] PageTableBase Base address of page table (CR3).\r
+ @param[in] Address Start address of a page to be set as read-only.\r
+ @param[in] Level4Paging Level 4 paging flag.\r
+\r
+**/\r
+STATIC\r
+VOID\r
+SetPageTablePoolReadOnly (\r
+ IN UINTN PageTableBase,\r
+ IN EFI_PHYSICAL_ADDRESS Address,\r
+ IN BOOLEAN Level4Paging\r
+ )\r
+{\r
+ UINTN Index;\r
+ UINTN EntryIndex;\r
+ UINT64 AddressEncMask;\r
+ EFI_PHYSICAL_ADDRESS PhysicalAddress;\r
+ UINT64 *PageTable;\r
+ UINT64 *NewPageTable;\r
+ UINT64 PageAttr;\r
+ UINT64 LevelSize[5];\r
+ UINT64 LevelMask[5];\r
+ UINTN LevelShift[5];\r
+ UINTN Level;\r
+ UINT64 PoolUnitSize;\r
+\r
+ ASSERT (PageTableBase != 0);\r
+\r
+ //\r
+ // Since the page table is always from page table pool, which is always\r
+ // located at the boundary of PcdPageTablePoolAlignment, we just need to\r
+ // set the whole pool unit to be read-only.\r
+ //\r
+ Address = Address & PAGE_TABLE_POOL_ALIGN_MASK;\r
+\r
+ LevelShift[1] = PAGING_L1_ADDRESS_SHIFT;\r
+ LevelShift[2] = PAGING_L2_ADDRESS_SHIFT;\r
+ LevelShift[3] = PAGING_L3_ADDRESS_SHIFT;\r
+ LevelShift[4] = PAGING_L4_ADDRESS_SHIFT;\r
+\r
+ LevelMask[1] = PAGING_4K_ADDRESS_MASK_64;\r
+ LevelMask[2] = PAGING_2M_ADDRESS_MASK_64;\r
+ LevelMask[3] = PAGING_1G_ADDRESS_MASK_64;\r
+ LevelMask[4] = PAGING_1G_ADDRESS_MASK_64;\r
+\r
+ LevelSize[1] = SIZE_4KB;\r
+ LevelSize[2] = SIZE_2MB;\r
+ LevelSize[3] = SIZE_1GB;\r
+ LevelSize[4] = SIZE_512GB;\r
+\r
+ AddressEncMask = GetMemEncryptionAddressMask() &\r
+ PAGING_1G_ADDRESS_MASK_64;\r
+ PageTable = (UINT64 *)(UINTN)PageTableBase;\r
+ PoolUnitSize = PAGE_TABLE_POOL_UNIT_SIZE;\r
+\r
+ for (Level = (Level4Paging) ? 4 : 3; Level > 0; --Level) {\r
+ Index = ((UINTN)RShiftU64 (Address, LevelShift[Level]));\r
+ Index &= PAGING_PAE_INDEX_MASK;\r
+\r
+ PageAttr = PageTable[Index];\r
+ if ((PageAttr & IA32_PG_PS) == 0) {\r
+ //\r
+ // Go to next level of table.\r
+ //\r
+ PageTable = (UINT64 *)(UINTN)(PageAttr & ~AddressEncMask &\r
+ PAGING_4K_ADDRESS_MASK_64);\r
+ continue;\r
+ }\r
+\r
+ if (PoolUnitSize >= LevelSize[Level]) {\r
+ //\r
+ // Clear R/W bit if current page granularity is not larger than pool unit\r
+ // size.\r
+ //\r
+ if ((PageAttr & IA32_PG_RW) != 0) {\r
+ while (PoolUnitSize > 0) {\r
+ //\r
+ // PAGE_TABLE_POOL_UNIT_SIZE and PAGE_TABLE_POOL_ALIGNMENT are fit in\r
+ // one page (2MB). Then we don't need to update attributes for pages\r
+ // crossing page directory. ASSERT below is for that purpose.\r
+ //\r
+ ASSERT (Index < EFI_PAGE_SIZE/sizeof (UINT64));\r
+\r
+ PageTable[Index] &= ~(UINT64)IA32_PG_RW;\r
+ PoolUnitSize -= LevelSize[Level];\r
+\r
+ ++Index;\r
+ }\r
+ }\r
+\r
+ break;\r
+\r
+ } else {\r
+ //\r
+ // The smaller granularity of page must be needed.\r
+ //\r
+ ASSERT (Level > 1);\r
+\r
+ NewPageTable = AllocatePageTableMemory (1);\r
+ ASSERT (NewPageTable != NULL);\r
+\r
+ PhysicalAddress = PageAttr & LevelMask[Level];\r
+ for (EntryIndex = 0;\r
+ EntryIndex < EFI_PAGE_SIZE/sizeof (UINT64);\r
+ ++EntryIndex) {\r
+ NewPageTable[EntryIndex] = PhysicalAddress | AddressEncMask |\r
+ IA32_PG_P | IA32_PG_RW;\r
+ if (Level > 2) {\r
+ NewPageTable[EntryIndex] |= IA32_PG_PS;\r
+ }\r
+ PhysicalAddress += LevelSize[Level - 1];\r
+ }\r
+\r
+ PageTable[Index] = (UINT64)(UINTN)NewPageTable | AddressEncMask |\r
+ IA32_PG_P | IA32_PG_RW;\r
+ PageTable = NewPageTable;\r
+ }\r
+ }\r
+}\r
+\r
+/**\r
+ Prevent the memory pages used for page table from been overwritten.\r
+\r
+ @param[in] PageTableBase Base address of page table (CR3).\r
+ @param[in] Level4Paging Level 4 paging flag.\r
+\r
+**/\r
+STATIC\r
+VOID\r
+EnablePageTableProtection (\r
+ IN UINTN PageTableBase,\r
+ IN BOOLEAN Level4Paging\r
+ )\r
+{\r
+ PAGE_TABLE_POOL *HeadPool;\r
+ PAGE_TABLE_POOL *Pool;\r
+ UINT64 PoolSize;\r
+ EFI_PHYSICAL_ADDRESS Address;\r
+\r
+ if (mPageTablePool == NULL) {\r
+ return;\r
+ }\r
+\r
+ //\r
+ // SetPageTablePoolReadOnly might update mPageTablePool. It's safer to\r
+ // remember original one in advance.\r
+ //\r
+ HeadPool = mPageTablePool;\r
+ Pool = HeadPool;\r
+ do {\r
+ Address = (EFI_PHYSICAL_ADDRESS)(UINTN)Pool;\r
+ PoolSize = Pool->Offset + EFI_PAGES_TO_SIZE (Pool->FreePages);\r
+\r
+ //\r
+ // The size of one pool must be multiple of PAGE_TABLE_POOL_UNIT_SIZE, which\r
+ // is one of page size of the processor (2MB by default). Let's apply the\r
+ // protection to them one by one.\r
+ //\r
+ while (PoolSize > 0) {\r
+ SetPageTablePoolReadOnly(PageTableBase, Address, Level4Paging);\r
+ Address += PAGE_TABLE_POOL_UNIT_SIZE;\r
+ PoolSize -= PAGE_TABLE_POOL_UNIT_SIZE;\r
+ }\r
+\r
+ Pool = Pool->NextPool;\r
+ } while (Pool != HeadPool);\r
+\r
+}\r
+\r
+\r
/**\r
Split 1G page to 2M.\r
\r
PAGE_TABLE_ENTRY *PageDirectoryEntry;\r
UINT64 AddressEncMask;\r
\r
- PageDirectoryEntry = AllocatePages(1);\r
+ PageDirectoryEntry = AllocatePageTableMemory(1);\r
\r
AddressEncMask = GetMemEncryptionAddressMask ();\r
ASSERT (PageDirectoryEntry != NULL);\r
\r
}\r
\r
+/**\r
+ Check the WP status in CR0 register. This bit is used to lock or unlock write\r
+ access to pages marked as read-only.\r
+\r
+ @retval TRUE Write protection is enabled.\r
+ @retval FALSE Write protection is disabled.\r
+**/\r
+STATIC\r
+BOOLEAN\r
+IsReadOnlyPageWriteProtected (\r
+ VOID\r
+ )\r
+{\r
+ return ((AsmReadCr0 () & BIT16) != 0);\r
+}\r
+\r
+\r
+/**\r
+ Disable Write Protect on pages marked as read-only.\r
+**/\r
+STATIC\r
+VOID\r
+DisableReadOnlyPageWriteProtect (\r
+ VOID\r
+ )\r
+{\r
+ AsmWriteCr0 (AsmReadCr0() & ~BIT16);\r
+}\r
+\r
+/**\r
+ Enable Write Protect on pages marked as read-only.\r
+**/\r
+VOID\r
+EnableReadOnlyPageWriteProtect (\r
+ VOID\r
+ )\r
+{\r
+ AsmWriteCr0 (AsmReadCr0() | BIT16);\r
+}\r
+\r
+\r
/**\r
This function either sets or clears memory encryption bit for the memory region\r
specified by PhysicalAddress and length from the current page table context.\r
PAGE_TABLE_4K_ENTRY *PageTableEntry;\r
UINT64 PgTableMask;\r
UINT64 AddressEncMask;\r
+ BOOLEAN IsWpEnabled;\r
+ RETURN_STATUS Status;\r
\r
DEBUG ((\r
DEBUG_VERBOSE,\r
WriteBackInvalidateDataCacheRange((VOID*) (UINTN)PhysicalAddress, Length);\r
}\r
\r
+ //\r
+ // Make sure that the page table is changeable.\r
+ //\r
+ IsWpEnabled = IsReadOnlyPageWriteProtected ();\r
+ if (IsWpEnabled) {\r
+ DisableReadOnlyPageWriteProtect ();\r
+ }\r
+\r
+ Status = EFI_SUCCESS;\r
+\r
while (Length)\r
{\r
//\r
__FUNCTION__,\r
PhysicalAddress\r
));\r
- return RETURN_NO_MAPPING;\r
+ Status = RETURN_NO_MAPPING;\r
+ goto Done;\r
}\r
\r
PageDirectory1GEntry = (VOID*) ((PageMapLevel4Entry->Bits.PageTableBaseAddress<<12) & ~PgTableMask);\r
__FUNCTION__,\r
PhysicalAddress\r
));\r
- return RETURN_NO_MAPPING;\r
+ Status = RETURN_NO_MAPPING;\r
+ goto Done;\r
}\r
\r
//\r
__FUNCTION__,\r
PhysicalAddress\r
));\r
- return RETURN_NO_MAPPING;\r
+ Status = RETURN_NO_MAPPING;\r
+ goto Done;\r
}\r
//\r
// If the MustBe1 bit is not a 1, it's not a 2MB entry\r
__FUNCTION__,\r
PhysicalAddress\r
));\r
- return RETURN_NO_MAPPING;\r
+ Status = RETURN_NO_MAPPING;\r
+ goto Done;\r
}\r
SetOrClearCBit (&PageTableEntry->Uint64, Mode);\r
PhysicalAddress += EFI_PAGE_SIZE;\r
}\r
}\r
\r
+ //\r
+ // Protect the page table by marking the memory used for page table to be\r
+ // read-only.\r
+ //\r
+ if (IsWpEnabled) {\r
+ EnablePageTableProtection ((UINTN)PageMapLevel4Entry, TRUE);\r
+ }\r
+\r
//\r
// Flush TLB\r
//\r
CpuFlushTlb();\r
\r
- return RETURN_SUCCESS;\r
+Done:\r
+ //\r
+ // Restore page table write protection, if any.\r
+ //\r
+ if (IsWpEnabled) {\r
+ EnableReadOnlyPageWriteProtect ();\r
+ }\r
+\r
+ return Status;\r
}\r
\r
/**\r
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