Commit 8b11ec1b authored by Linus Torvalds's avatar Linus Torvalds
Browse files

mm: do not initialize TLB stack vma's with vma_init() 



Commit 2c4541e2 ("mm: use vma_init() to initialize VMAs on stack and
data segments") tried to initialize various left-over ad-hoc vma's
"properly", but actually made things worse for the temporary vma's used
for TLB flushing.

vma_init() doesn't actually initialize all of the vma, just a few
fields, so doing something like

   -       struct vm_area_struct vma = { .vm_mm = tlb->mm, };
   +       struct vm_area_struct vma;
   +
   +       vma_init(&vma, tlb->mm);

was actually very bad: instead of having a nicely initialized vma with
every field but "vm_mm" zeroed, you'd have an entirely uninitialized vma
with only a couple of fields initialized.  And they weren't even fields
that the code in question mostly cared about.

The flush_tlb_range() function takes a "struct vma" rather than a
"struct mm_struct", because a few architectures actually care about what
kind of range it is - being able to only do an ITLB flush if it's a
range that doesn't have data accesses enabled, for example.  And all the
normal users already have the vma for doing the range invalidation.

But a few people want to call flush_tlb_range() with a range they just
made up, so they also end up using a made-up vma.  x86 just has a
special "flush_tlb_mm_range()" function for this, but other
architectures (arm and ia64) do the "use fake vma" thing instead, and
thus got caught up in the vma_init() changes.

At the same time, the TLB flushing code really doesn't care about most
other fields in the vma, so vma_init() is just unnecessary and
pointless.

This fixes things by having an explicit "this is just an initializer for
the TLB flush" initializer macro, which is used by the arm/arm64/ia64
people who mis-use this interface with just a dummy vma.

Fixes: 2c4541e2 ("mm: use vma_init() to initialize VMAs on stack and data segments")
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 53406ed1

arch/arm/mach-rpc/ecard.c

+1 −4
Original line number Diff line number Diff line
@@ -212,7 +212,7 @@ static DEFINE_MUTEX(ecard_mutex); 
 */

static void ecard_init_pgtables(struct mm_struct *mm)

{

	struct vm_area_struct vma;

	struct vm_area_struct vma = TLB_FLUSH_VMA(mm, VM_EXEC);



	/* We want to set up the page tables for the following mapping:

	 *  Virtual	Physical
@@ -237,9 +237,6 @@ static void ecard_init_pgtables(struct mm_struct *mm) 


	memcpy(dst_pgd, src_pgd, sizeof(pgd_t) * (EASI_SIZE / PGDIR_SIZE));



	vma_init(&vma, mm);

	vma.vm_flags = VM_EXEC;



	flush_tlb_range(&vma, IO_START, IO_START + IO_SIZE);

	flush_tlb_range(&vma, EASI_START, EASI_START + EASI_SIZE);

}

arch/arm64/include/asm/tlb.h

+1 −3
Original line number Diff line number Diff line
@@ -37,9 +37,7 @@ static inline void __tlb_remove_table(void *_table) 


static inline void tlb_flush(struct mmu_gather *tlb)

{

	struct vm_area_struct vma;



	vma_init(&vma, tlb->mm);

	struct vm_area_struct vma = TLB_FLUSH_VMA(tlb->mm, 0);



	/*

	 * The ASID allocator will either invalidate the ASID or mark

arch/arm64/mm/hugetlbpage.c

+4 −6
Original line number Diff line number Diff line
@@ -108,13 +108,10 @@ static pte_t get_clear_flush(struct mm_struct *mm, 
			     unsigned long pgsize,

			     unsigned long ncontig)

{

	struct vm_area_struct vma;

	pte_t orig_pte = huge_ptep_get(ptep);

	bool valid = pte_valid(orig_pte);

	unsigned long i, saddr = addr;



	vma_init(&vma, mm);



	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++) {

		pte_t pte = ptep_get_and_clear(mm, addr, ptep);
@@ -127,8 +124,10 @@ static pte_t get_clear_flush(struct mm_struct *mm, 
			orig_pte = pte_mkdirty(orig_pte);

	}



	if (valid)

	if (valid) {

		struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);

		flush_tlb_range(&vma, saddr, addr);

	}

	return orig_pte;

}
@@ -147,10 +146,9 @@ static void clear_flush(struct mm_struct *mm, 
			     unsigned long pgsize,

			     unsigned long ncontig)

{

	struct vm_area_struct vma;

	struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);

	unsigned long i, saddr = addr;



	vma_init(&vma, mm);

	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)

		pte_clear(mm, addr, ptep);

arch/ia64/include/asm/tlb.h

+3 −4
Original line number Diff line number Diff line
@@ -115,12 +115,11 @@ ia64_tlb_flush_mmu_tlbonly(struct mmu_gather *tlb, unsigned long start, unsigned 
		flush_tlb_all();

	} else {

		/*

		 * XXX fix me: flush_tlb_range() should take an mm pointer instead of a

		 * vma pointer.

		 * flush_tlb_range() takes a vma instead of a mm pointer because

		 * some architectures want the vm_flags for ITLB/DTLB flush.

		 */

		struct vm_area_struct vma;

		struct vm_area_struct vma = TLB_FLUSH_VMA(tlb->mm, 0);



		vma_init(&vma, tlb->mm);

		/* flush the address range from the tlb: */

		flush_tlb_range(&vma, start, end);

		/* now flush the virt. page-table area mapping the address range: */

include/linux/mm.h

+3 −0
Original line number Diff line number Diff line
@@ -466,6 +466,9 @@ static inline void vma_set_anonymous(struct vm_area_struct *vma) 
	vma->vm_ops = NULL;

}



/* flush_tlb_range() takes a vma, not a mm, and can care about flags */

#define TLB_FLUSH_VMA(mm,flags) { .vm_mm = (mm), .vm_flags = (flags) }



struct mmu_gather;

struct inode;

CRA Git | Maintained and supported by SUSTech CRA and CCSE