forked from Minki/linux
20273941f2
Christoph reported a nice splat which illustrated a race in the new stack based kmap_atomic implementation. The problem is that we pop our stack slot before we're completely done resetting its state -- in particular clearing the PTE (sometimes that's CONFIG_DEBUG_HIGHMEM). If an interrupt happens before we actually clear the PTE used for the last slot, that interrupt can reuse the slot in a dirty state, which triggers a BUG in kmap_atomic(). Fix this by introducing kmap_atomic_idx() which reports the current slot index without actually releasing it and use that to find the PTE and delay the _pop() until after we're completely done. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Reported-by: Christoph Hellwig <hch@infradead.org> Acked-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
138 lines
2.9 KiB
C
138 lines
2.9 KiB
C
#include <linux/module.h>
|
|
#include <linux/highmem.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/smp.h>
|
|
#include <asm/fixmap.h>
|
|
#include <asm/tlbflush.h>
|
|
|
|
static pte_t *kmap_pte;
|
|
|
|
unsigned long highstart_pfn, highend_pfn;
|
|
|
|
void *kmap(struct page *page)
|
|
{
|
|
void *addr;
|
|
|
|
might_sleep();
|
|
if (!PageHighMem(page))
|
|
return page_address(page);
|
|
addr = kmap_high(page);
|
|
flush_tlb_one((unsigned long)addr);
|
|
|
|
return addr;
|
|
}
|
|
EXPORT_SYMBOL(kmap);
|
|
|
|
void kunmap(struct page *page)
|
|
{
|
|
BUG_ON(in_interrupt());
|
|
if (!PageHighMem(page))
|
|
return;
|
|
kunmap_high(page);
|
|
}
|
|
EXPORT_SYMBOL(kunmap);
|
|
|
|
/*
|
|
* kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
|
|
* no global lock is needed and because the kmap code must perform a global TLB
|
|
* invalidation when the kmap pool wraps.
|
|
*
|
|
* However when holding an atomic kmap is is not legal to sleep, so atomic
|
|
* kmaps are appropriate for short, tight code paths only.
|
|
*/
|
|
|
|
void *__kmap_atomic(struct page *page)
|
|
{
|
|
unsigned long vaddr;
|
|
int idx, type;
|
|
|
|
/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
|
|
pagefault_disable();
|
|
if (!PageHighMem(page))
|
|
return page_address(page);
|
|
|
|
type = kmap_atomic_idx_push();
|
|
idx = type + KM_TYPE_NR*smp_processor_id();
|
|
vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
|
|
#ifdef CONFIG_DEBUG_HIGHMEM
|
|
BUG_ON(!pte_none(*(kmap_pte - idx)));
|
|
#endif
|
|
set_pte(kmap_pte-idx, mk_pte(page, PAGE_KERNEL));
|
|
local_flush_tlb_one((unsigned long)vaddr);
|
|
|
|
return (void*) vaddr;
|
|
}
|
|
EXPORT_SYMBOL(__kmap_atomic);
|
|
|
|
void __kunmap_atomic(void *kvaddr)
|
|
{
|
|
unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
|
|
int type;
|
|
|
|
if (vaddr < FIXADDR_START) { // FIXME
|
|
pagefault_enable();
|
|
return;
|
|
}
|
|
|
|
type = kmap_atomic_idx();
|
|
#ifdef CONFIG_DEBUG_HIGHMEM
|
|
{
|
|
int idx = type + KM_TYPE_NR * smp_processor_id();
|
|
|
|
BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
|
|
|
|
/*
|
|
* force other mappings to Oops if they'll try to access
|
|
* this pte without first remap it
|
|
*/
|
|
pte_clear(&init_mm, vaddr, kmap_pte-idx);
|
|
local_flush_tlb_one(vaddr);
|
|
}
|
|
#endif
|
|
kmap_atomic_idx_pop();
|
|
pagefault_enable();
|
|
}
|
|
EXPORT_SYMBOL(__kunmap_atomic);
|
|
|
|
/*
|
|
* This is the same as kmap_atomic() but can map memory that doesn't
|
|
* have a struct page associated with it.
|
|
*/
|
|
void *kmap_atomic_pfn(unsigned long pfn)
|
|
{
|
|
unsigned long vaddr;
|
|
int idx, type;
|
|
|
|
pagefault_disable();
|
|
|
|
type = kmap_atomic_idx_push();
|
|
idx = type + KM_TYPE_NR*smp_processor_id();
|
|
vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
|
|
set_pte(kmap_pte-idx, pfn_pte(pfn, PAGE_KERNEL));
|
|
flush_tlb_one(vaddr);
|
|
|
|
return (void*) vaddr;
|
|
}
|
|
|
|
struct page *kmap_atomic_to_page(void *ptr)
|
|
{
|
|
unsigned long idx, vaddr = (unsigned long)ptr;
|
|
pte_t *pte;
|
|
|
|
if (vaddr < FIXADDR_START)
|
|
return virt_to_page(ptr);
|
|
|
|
idx = virt_to_fix(vaddr);
|
|
pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
|
|
return pte_page(*pte);
|
|
}
|
|
|
|
void __init kmap_init(void)
|
|
{
|
|
unsigned long kmap_vstart;
|
|
|
|
/* cache the first kmap pte */
|
|
kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
|
|
kmap_pte = kmap_get_fixmap_pte(kmap_vstart);
|
|
}
|