Commit 499069e1 authored by Carsten Otte's avatar Carsten Otte Committed by Martin Schwidefsky
Browse files

[S390] take mmap_sem when walking guest page table 



gmap_fault needs to walk the guest page table. However, parts of
that may change if some other thread does munmap. In that case
gmap_unmap_notifier will also unmap the corresponding parts from
the guest page table. We need to take mmap_sem in order to serialize
these operations.
do_exception now calls __gmap_fault with mmap_sem held which does
not get exported to modules. The exported function, which is called
from KVM, now takes mmap_sem.

Reported-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarCarsten Otte <cotte@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent cc772456

arch/s390/include/asm/pgtable.h

+1 −0
Original line number Diff line number Diff line
@@ -696,6 +696,7 @@ void gmap_disable(struct gmap *gmap); 
int gmap_map_segment(struct gmap *gmap, unsigned long from,

		     unsigned long to, unsigned long length);

int gmap_unmap_segment(struct gmap *gmap, unsigned long to, unsigned long len);

unsigned long __gmap_fault(unsigned long address, struct gmap *);

unsigned long gmap_fault(unsigned long address, struct gmap *);



/*

arch/s390/mm/fault.c

+1 −1
Original line number Diff line number Diff line
@@ -307,7 +307,7 @@ static inline int do_exception(struct pt_regs *regs, int access, 


#ifdef CONFIG_PGSTE

	if (test_tsk_thread_flag(current, TIF_SIE) && S390_lowcore.gmap) {

		address = gmap_fault(address,

		address = __gmap_fault(address,

				     (struct gmap *) S390_lowcore.gmap);

		if (address == -EFAULT) {

			fault = VM_FAULT_BADMAP;

arch/s390/mm/pgtable.c

+14 −1
Original line number Diff line number Diff line
@@ -393,7 +393,10 @@ out_unmap: 
}

EXPORT_SYMBOL_GPL(gmap_map_segment);



unsigned long gmap_fault(unsigned long address, struct gmap *gmap)

/*

 * this function is assumed to be called with mmap_sem held

 */

unsigned long __gmap_fault(unsigned long address, struct gmap *gmap)

{

	unsigned long *table, vmaddr, segment;

	struct mm_struct *mm;
@@ -461,7 +464,17 @@ unsigned long gmap_fault(unsigned long address, struct gmap *gmap) 
		return vmaddr | (address & ~PMD_MASK);

	}

	return -EFAULT;

}



unsigned long gmap_fault(unsigned long address, struct gmap *gmap)

{

	unsigned long rc;



	down_read(&gmap->mm->mmap_sem);

	rc = __gmap_fault(address, gmap);

	up_read(&gmap->mm->mmap_sem);



	return rc;

}

EXPORT_SYMBOL_GPL(gmap_fault);

CRA Git | Maintained and supported by SUSTech CRA and CCSE