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author | Christian Borntraeger <borntraeger@de.ibm.com> | 2008-10-28 10:10:15 (GMT) |
---|---|---|
committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2008-10-28 10:12:03 (GMT) |
commit | 250cf776f74b5932a1977d0489cae9206e2351dd (patch) | |
tree | 71bb6778e65e8efbdd0cac09a64e4e1194b98c3f /arch/s390/mm | |
parent | 2c78091405d6f54748b1fac78c45f2a799e3073a (diff) | |
download | linux-250cf776f74b5932a1977d0489cae9206e2351dd.tar.xz |
[S390] pgtables: Fix race in enable_sie vs. page table ops
The current enable_sie code sets the mm->context.pgstes bit to tell
dup_mm that the new mm should have extended page tables. This bit is also
used by the s390 specific page table primitives to decide about the page
table layout - which means context.pgstes has two meanings. This can cause
any kind of bugs. For example - e.g. shrink_zone can call
ptep_clear_flush_young while enable_sie is running. ptep_clear_flush_young
will test for context.pgstes. Since enable_sie changed that value of the old
struct mm without changing the page table layout ptep_clear_flush_young will
do the wrong thing.
The solution is to split pgstes into two bits
- one for the allocation
- one for the current state
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/mm')
-rw-r--r-- | arch/s390/mm/pgtable.c | 16 |
1 files changed, 8 insertions, 8 deletions
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index 3d98ba8..ef3635b 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -169,7 +169,7 @@ unsigned long *page_table_alloc(struct mm_struct *mm) unsigned long *table; unsigned long bits; - bits = (mm->context.noexec || mm->context.pgstes) ? 3UL : 1UL; + bits = (mm->context.noexec || mm->context.has_pgste) ? 3UL : 1UL; spin_lock(&mm->page_table_lock); page = NULL; if (!list_empty(&mm->context.pgtable_list)) { @@ -186,7 +186,7 @@ unsigned long *page_table_alloc(struct mm_struct *mm) pgtable_page_ctor(page); page->flags &= ~FRAG_MASK; table = (unsigned long *) page_to_phys(page); - if (mm->context.pgstes) + if (mm->context.has_pgste) clear_table_pgstes(table); else clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE); @@ -210,7 +210,7 @@ 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 = (mm->context.noexec || mm->context.has_pgste) ? 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); @@ -257,7 +257,7 @@ int s390_enable_sie(void) struct mm_struct *mm, *old_mm; /* Do we have pgstes? if yes, we are done */ - if (tsk->mm->context.pgstes) + if (tsk->mm->context.has_pgste) return 0; /* lets check if we are allowed to replace the mm */ @@ -269,14 +269,14 @@ int s390_enable_sie(void) } task_unlock(tsk); - /* we copy the mm with pgstes enabled */ - tsk->mm->context.pgstes = 1; + /* we copy the mm and let dup_mm create the page tables with_pgstes */ + tsk->mm->context.alloc_pgste = 1; mm = dup_mm(tsk); - tsk->mm->context.pgstes = 0; + tsk->mm->context.alloc_pgste = 0; if (!mm) return -ENOMEM; - /* Now lets check again if somebody attached ptrace etc */ + /* Now lets check again if something happened */ task_lock(tsk); if (!tsk->mm || atomic_read(&tsk->mm->mm_users) > 1 || tsk->mm != tsk->active_mm || tsk->mm->ioctx_list) { |