Commit 667c2759 authored by Catalin Marinas's avatar Catalin Marinas
Browse files

Revert "arm64: Mark kernel page ranges contiguous" 



This reverts commit 348a65cd.

Incorrect page table manipulation that does not respect the ARM ARM
recommended break-before-make sequence may lead to TLB conflicts. The
contiguous PTE patch makes the system even more susceptible to such
errors by changing the mapping from a single page to a contiguous range
of pages. An additional TLB invalidation would reduce the risk window,
however, the correct fix is to switch to a temporary swapper_pg_dir.
Once the correct workaround is done, the reverted commit will be
re-applied.

Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Reported-by: default avatarJeremy Linton <jeremy.linton@arm.com>
parent 0ebea808

arch/arm64/mm/mmu.c

+8 −61
Original line number Diff line number Diff line
@@ -85,55 +85,19 @@ static void split_pmd(pmd_t *pmd, pte_t *pte) 
	do {

		/*

		 * Need to have the least restrictive permissions available

		 * permissions will be fixed up later. Default the new page

		 * range as contiguous ptes.

		 * permissions will be fixed up later

		 */

		set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC_CONT));

		set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));

		pfn++;

	} while (pte++, i++, i < PTRS_PER_PTE);

}



/*

 * Given a PTE with the CONT bit set, determine where the CONT range

 * starts, and clear the entire range of PTE CONT bits.

 */

static void clear_cont_pte_range(pte_t *pte, unsigned long addr)

{

	int i;



	pte -= CONT_RANGE_OFFSET(addr);

	for (i = 0; i < CONT_PTES; i++) {

		set_pte(pte, pte_mknoncont(*pte));

		pte++;

	}

	flush_tlb_all();

}



/*

 * Given a range of PTEs set the pfn and provided page protection flags

 */

static void __populate_init_pte(pte_t *pte, unsigned long addr,

				unsigned long end, phys_addr_t phys,

				pgprot_t prot)

{

	unsigned long pfn = __phys_to_pfn(phys);



	do {

		/* clear all the bits except the pfn, then apply the prot */

		set_pte(pte, pfn_pte(pfn, prot));

		pte++;

		pfn++;

		addr += PAGE_SIZE;

	} while (addr != end);

}



static void alloc_init_pte(pmd_t *pmd, unsigned long addr,

				  unsigned long end, phys_addr_t phys,

				  unsigned long end, unsigned long pfn,

				  pgprot_t prot,

				  void *(*alloc)(unsigned long size))

{

	pte_t *pte;

	unsigned long next;



	if (pmd_none(*pmd) || pmd_sect(*pmd)) {

		pte = alloc(PTRS_PER_PTE * sizeof(pte_t));
@@ -146,27 +110,9 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr, 


	pte = pte_offset_kernel(pmd, addr);

	do {

		next = min(end, (addr + CONT_SIZE) & CONT_MASK);

		if (((addr | next | phys) & ~CONT_MASK) == 0) {

			/* a block of CONT_PTES  */

			__populate_init_pte(pte, addr, next, phys,

					    __pgprot(pgprot_val(prot) | PTE_CONT));

		} else {

			/*

			 * If the range being split is already inside of a

			 * contiguous range but this PTE isn't going to be

			 * contiguous, then we want to unmark the adjacent

			 * ranges, then update the portion of the range we

			 * are interrested in.

			 */

			 clear_cont_pte_range(pte, addr);

			 __populate_init_pte(pte, addr, next, phys, prot);

		}



		pte += (next - addr) >> PAGE_SHIFT;

		phys += next - addr;

		addr = next;

	} while (addr != end);

		set_pte(pte, pfn_pte(pfn, prot));

		pfn++;

	} while (pte++, addr += PAGE_SIZE, addr != end);

}



static void split_pud(pud_t *old_pud, pmd_t *pmd)
@@ -227,7 +173,8 @@ static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud, 
				}

			}

		} else {

			alloc_init_pte(pmd, addr, next, phys, prot, alloc);

			alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),

				       prot, alloc);

		}

		phys += next - addr;

	} while (pmd++, addr = next, addr != end);

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