linux/arch/s390/mm/pgtable.c
Christian Borntraeger 74b6b522ec KVM: s390: fix locking order problem in enable_sie
There are potential locking problem in enable_sie. We take the task_lock
and the mmap_sem. As exit_mm uses the same locks vice versa, this triggers
a lockdep warning.
The second problem is that dup_mm and mmput might sleep, so we must not
hold the task_lock at that moment.

The solution is to dup the mm unconditional and use the task_lock before and
afterwards to check  if we can use the new mm. dup_mm and mmput are called
outside the task_lock, but we run update_mm while holding the task_lock,
protection us against ptrace.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-06 21:08:26 +03:00

299 lines
7.4 KiB
C

/*
* arch/s390/mm/pgtable.c
*
* Copyright IBM Corp. 2007
* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
*/
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/smp.h>
#include <linux/highmem.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/quicklist.h>
#include <asm/system.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#ifndef CONFIG_64BIT
#define ALLOC_ORDER 1
#define TABLES_PER_PAGE 4
#define FRAG_MASK 15UL
#define SECOND_HALVES 10UL
void clear_table_pgstes(unsigned long *table)
{
clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/4);
memset(table + 256, 0, PAGE_SIZE/4);
clear_table(table + 512, _PAGE_TYPE_EMPTY, PAGE_SIZE/4);
memset(table + 768, 0, PAGE_SIZE/4);
}
#else
#define ALLOC_ORDER 2
#define TABLES_PER_PAGE 2
#define FRAG_MASK 3UL
#define SECOND_HALVES 2UL
void clear_table_pgstes(unsigned long *table)
{
clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/2);
memset(table + 256, 0, PAGE_SIZE/2);
}
#endif
unsigned long *crst_table_alloc(struct mm_struct *mm, int noexec)
{
struct page *page = alloc_pages(GFP_KERNEL, ALLOC_ORDER);
if (!page)
return NULL;
page->index = 0;
if (noexec) {
struct page *shadow = alloc_pages(GFP_KERNEL, ALLOC_ORDER);
if (!shadow) {
__free_pages(page, ALLOC_ORDER);
return NULL;
}
page->index = page_to_phys(shadow);
}
spin_lock(&mm->page_table_lock);
list_add(&page->lru, &mm->context.crst_list);
spin_unlock(&mm->page_table_lock);
return (unsigned long *) page_to_phys(page);
}
void crst_table_free(struct mm_struct *mm, unsigned long *table)
{
unsigned long *shadow = get_shadow_table(table);
struct page *page = virt_to_page(table);
spin_lock(&mm->page_table_lock);
list_del(&page->lru);
spin_unlock(&mm->page_table_lock);
if (shadow)
free_pages((unsigned long) shadow, ALLOC_ORDER);
free_pages((unsigned long) table, ALLOC_ORDER);
}
#ifdef CONFIG_64BIT
int crst_table_upgrade(struct mm_struct *mm, unsigned long limit)
{
unsigned long *table, *pgd;
unsigned long entry;
BUG_ON(limit > (1UL << 53));
repeat:
table = crst_table_alloc(mm, mm->context.noexec);
if (!table)
return -ENOMEM;
spin_lock(&mm->page_table_lock);
if (mm->context.asce_limit < limit) {
pgd = (unsigned long *) mm->pgd;
if (mm->context.asce_limit <= (1UL << 31)) {
entry = _REGION3_ENTRY_EMPTY;
mm->context.asce_limit = 1UL << 42;
mm->context.asce_bits = _ASCE_TABLE_LENGTH |
_ASCE_USER_BITS |
_ASCE_TYPE_REGION3;
} else {
entry = _REGION2_ENTRY_EMPTY;
mm->context.asce_limit = 1UL << 53;
mm->context.asce_bits = _ASCE_TABLE_LENGTH |
_ASCE_USER_BITS |
_ASCE_TYPE_REGION2;
}
crst_table_init(table, entry);
pgd_populate(mm, (pgd_t *) table, (pud_t *) pgd);
mm->pgd = (pgd_t *) table;
table = NULL;
}
spin_unlock(&mm->page_table_lock);
if (table)
crst_table_free(mm, table);
if (mm->context.asce_limit < limit)
goto repeat;
update_mm(mm, current);
return 0;
}
void crst_table_downgrade(struct mm_struct *mm, unsigned long limit)
{
pgd_t *pgd;
if (mm->context.asce_limit <= limit)
return;
__tlb_flush_mm(mm);
while (mm->context.asce_limit > limit) {
pgd = mm->pgd;
switch (pgd_val(*pgd) & _REGION_ENTRY_TYPE_MASK) {
case _REGION_ENTRY_TYPE_R2:
mm->context.asce_limit = 1UL << 42;
mm->context.asce_bits = _ASCE_TABLE_LENGTH |
_ASCE_USER_BITS |
_ASCE_TYPE_REGION3;
break;
case _REGION_ENTRY_TYPE_R3:
mm->context.asce_limit = 1UL << 31;
mm->context.asce_bits = _ASCE_TABLE_LENGTH |
_ASCE_USER_BITS |
_ASCE_TYPE_SEGMENT;
break;
default:
BUG();
}
mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN);
crst_table_free(mm, (unsigned long *) pgd);
}
update_mm(mm, current);
}
#endif
/*
* page table entry allocation/free routines.
*/
unsigned long *page_table_alloc(struct mm_struct *mm)
{
struct page *page;
unsigned long *table;
unsigned long bits;
bits = (mm->context.noexec || mm->context.pgstes) ? 3UL : 1UL;
spin_lock(&mm->page_table_lock);
page = NULL;
if (!list_empty(&mm->context.pgtable_list)) {
page = list_first_entry(&mm->context.pgtable_list,
struct page, lru);
if ((page->flags & FRAG_MASK) == ((1UL << TABLES_PER_PAGE) - 1))
page = NULL;
}
if (!page) {
spin_unlock(&mm->page_table_lock);
page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
if (!page)
return NULL;
pgtable_page_ctor(page);
page->flags &= ~FRAG_MASK;
table = (unsigned long *) page_to_phys(page);
if (mm->context.pgstes)
clear_table_pgstes(table);
else
clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE);
spin_lock(&mm->page_table_lock);
list_add(&page->lru, &mm->context.pgtable_list);
}
table = (unsigned long *) page_to_phys(page);
while (page->flags & bits) {
table += 256;
bits <<= 1;
}
page->flags |= bits;
if ((page->flags & FRAG_MASK) == ((1UL << TABLES_PER_PAGE) - 1))
list_move_tail(&page->lru, &mm->context.pgtable_list);
spin_unlock(&mm->page_table_lock);
return table;
}
void page_table_free(struct mm_struct *mm, unsigned long *table)
{
struct page *page;
unsigned long bits;
bits = (mm->context.noexec || mm->context.pgstes) ? 3UL : 1UL;
bits <<= (__pa(table) & (PAGE_SIZE - 1)) / 256 / sizeof(unsigned long);
page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
spin_lock(&mm->page_table_lock);
page->flags ^= bits;
if (page->flags & FRAG_MASK) {
/* Page now has some free pgtable fragments. */
list_move(&page->lru, &mm->context.pgtable_list);
page = NULL;
} else
/* All fragments of the 4K page have been freed. */
list_del(&page->lru);
spin_unlock(&mm->page_table_lock);
if (page) {
pgtable_page_dtor(page);
__free_page(page);
}
}
void disable_noexec(struct mm_struct *mm, struct task_struct *tsk)
{
struct page *page;
spin_lock(&mm->page_table_lock);
/* Free shadow region and segment tables. */
list_for_each_entry(page, &mm->context.crst_list, lru)
if (page->index) {
free_pages((unsigned long) page->index, ALLOC_ORDER);
page->index = 0;
}
/* "Free" second halves of page tables. */
list_for_each_entry(page, &mm->context.pgtable_list, lru)
page->flags &= ~SECOND_HALVES;
spin_unlock(&mm->page_table_lock);
mm->context.noexec = 0;
update_mm(mm, tsk);
}
/*
* switch on pgstes for its userspace process (for kvm)
*/
int s390_enable_sie(void)
{
struct task_struct *tsk = current;
struct mm_struct *mm, *old_mm;
/* Do we have pgstes? if yes, we are done */
if (tsk->mm->context.pgstes)
return 0;
/* lets check if we are allowed to replace the mm */
task_lock(tsk);
if (!tsk->mm || atomic_read(&tsk->mm->mm_users) > 1 ||
tsk->mm != tsk->active_mm || tsk->mm->ioctx_list) {
task_unlock(tsk);
return -EINVAL;
}
task_unlock(tsk);
/* we copy the mm with pgstes enabled */
tsk->mm->context.pgstes = 1;
mm = dup_mm(tsk);
tsk->mm->context.pgstes = 0;
if (!mm)
return -ENOMEM;
/* Now lets check again if somebody attached ptrace etc */
task_lock(tsk);
if (!tsk->mm || atomic_read(&tsk->mm->mm_users) > 1 ||
tsk->mm != tsk->active_mm || tsk->mm->ioctx_list) {
mmput(mm);
task_unlock(tsk);
return -EINVAL;
}
/* ok, we are alone. No ptrace, no threads, etc. */
old_mm = tsk->mm;
tsk->mm = tsk->active_mm = mm;
preempt_disable();
update_mm(mm, tsk);
cpu_set(smp_processor_id(), mm->cpu_vm_mask);
preempt_enable();
task_unlock(tsk);
mmput(old_mm);
return 0;
}
EXPORT_SYMBOL_GPL(s390_enable_sie);