278 lines
6.8 KiB
C
278 lines
6.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* Lockless get_user_pages_fast for SuperH
|
|
*
|
|
* Copyright (C) 2009 - 2010 Paul Mundt
|
|
*
|
|
* Cloned from the x86 and PowerPC versions, by:
|
|
*
|
|
* Copyright (C) 2008 Nick Piggin
|
|
* Copyright (C) 2008 Novell Inc.
|
|
*/
|
|
#include <linux/sched.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/vmstat.h>
|
|
#include <linux/highmem.h>
|
|
#include <asm/pgtable.h>
|
|
|
|
static inline pte_t gup_get_pte(pte_t *ptep)
|
|
{
|
|
#ifndef CONFIG_X2TLB
|
|
return READ_ONCE(*ptep);
|
|
#else
|
|
/*
|
|
* With get_user_pages_fast, we walk down the pagetables without
|
|
* taking any locks. For this we would like to load the pointers
|
|
* atomically, but that is not possible with 64-bit PTEs. What
|
|
* we do have is the guarantee that a pte will only either go
|
|
* from not present to present, or present to not present or both
|
|
* -- it will not switch to a completely different present page
|
|
* without a TLB flush in between; something that we are blocking
|
|
* by holding interrupts off.
|
|
*
|
|
* Setting ptes from not present to present goes:
|
|
* ptep->pte_high = h;
|
|
* smp_wmb();
|
|
* ptep->pte_low = l;
|
|
*
|
|
* And present to not present goes:
|
|
* ptep->pte_low = 0;
|
|
* smp_wmb();
|
|
* ptep->pte_high = 0;
|
|
*
|
|
* We must ensure here that the load of pte_low sees l iff pte_high
|
|
* sees h. We load pte_high *after* loading pte_low, which ensures we
|
|
* don't see an older value of pte_high. *Then* we recheck pte_low,
|
|
* which ensures that we haven't picked up a changed pte high. We might
|
|
* have got rubbish values from pte_low and pte_high, but we are
|
|
* guaranteed that pte_low will not have the present bit set *unless*
|
|
* it is 'l'. And get_user_pages_fast only operates on present ptes, so
|
|
* we're safe.
|
|
*
|
|
* gup_get_pte should not be used or copied outside gup.c without being
|
|
* very careful -- it does not atomically load the pte or anything that
|
|
* is likely to be useful for you.
|
|
*/
|
|
pte_t pte;
|
|
|
|
retry:
|
|
pte.pte_low = ptep->pte_low;
|
|
smp_rmb();
|
|
pte.pte_high = ptep->pte_high;
|
|
smp_rmb();
|
|
if (unlikely(pte.pte_low != ptep->pte_low))
|
|
goto retry;
|
|
|
|
return pte;
|
|
#endif
|
|
}
|
|
|
|
/*
|
|
* The performance critical leaf functions are made noinline otherwise gcc
|
|
* inlines everything into a single function which results in too much
|
|
* register pressure.
|
|
*/
|
|
static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
|
|
unsigned long end, int write, struct page **pages, int *nr)
|
|
{
|
|
u64 mask, result;
|
|
pte_t *ptep;
|
|
|
|
#ifdef CONFIG_X2TLB
|
|
result = _PAGE_PRESENT | _PAGE_EXT(_PAGE_EXT_KERN_READ | _PAGE_EXT_USER_READ);
|
|
if (write)
|
|
result |= _PAGE_EXT(_PAGE_EXT_KERN_WRITE | _PAGE_EXT_USER_WRITE);
|
|
#elif defined(CONFIG_SUPERH64)
|
|
result = _PAGE_PRESENT | _PAGE_USER | _PAGE_READ;
|
|
if (write)
|
|
result |= _PAGE_WRITE;
|
|
#else
|
|
result = _PAGE_PRESENT | _PAGE_USER;
|
|
if (write)
|
|
result |= _PAGE_RW;
|
|
#endif
|
|
|
|
mask = result | _PAGE_SPECIAL;
|
|
|
|
ptep = pte_offset_map(&pmd, addr);
|
|
do {
|
|
pte_t pte = gup_get_pte(ptep);
|
|
struct page *page;
|
|
|
|
if ((pte_val(pte) & mask) != result) {
|
|
pte_unmap(ptep);
|
|
return 0;
|
|
}
|
|
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
|
|
page = pte_page(pte);
|
|
get_page(page);
|
|
__flush_anon_page(page, addr);
|
|
flush_dcache_page(page);
|
|
pages[*nr] = page;
|
|
(*nr)++;
|
|
|
|
} while (ptep++, addr += PAGE_SIZE, addr != end);
|
|
pte_unmap(ptep - 1);
|
|
|
|
return 1;
|
|
}
|
|
|
|
static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
|
|
int write, struct page **pages, int *nr)
|
|
{
|
|
unsigned long next;
|
|
pmd_t *pmdp;
|
|
|
|
pmdp = pmd_offset(&pud, addr);
|
|
do {
|
|
pmd_t pmd = *pmdp;
|
|
|
|
next = pmd_addr_end(addr, end);
|
|
if (pmd_none(pmd))
|
|
return 0;
|
|
if (!gup_pte_range(pmd, addr, next, write, pages, nr))
|
|
return 0;
|
|
} while (pmdp++, addr = next, addr != end);
|
|
|
|
return 1;
|
|
}
|
|
|
|
static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
|
|
int write, struct page **pages, int *nr)
|
|
{
|
|
unsigned long next;
|
|
pud_t *pudp;
|
|
|
|
pudp = pud_offset(&pgd, addr);
|
|
do {
|
|
pud_t pud = *pudp;
|
|
|
|
next = pud_addr_end(addr, end);
|
|
if (pud_none(pud))
|
|
return 0;
|
|
if (!gup_pmd_range(pud, addr, next, write, pages, nr))
|
|
return 0;
|
|
} while (pudp++, addr = next, addr != end);
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Like get_user_pages_fast() except its IRQ-safe in that it won't fall
|
|
* back to the regular GUP.
|
|
* Note a difference with get_user_pages_fast: this always returns the
|
|
* number of pages pinned, 0 if no pages were pinned.
|
|
*/
|
|
int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
|
|
struct page **pages)
|
|
{
|
|
struct mm_struct *mm = current->mm;
|
|
unsigned long addr, len, end;
|
|
unsigned long next;
|
|
unsigned long flags;
|
|
pgd_t *pgdp;
|
|
int nr = 0;
|
|
|
|
start &= PAGE_MASK;
|
|
addr = start;
|
|
len = (unsigned long) nr_pages << PAGE_SHIFT;
|
|
end = start + len;
|
|
if (unlikely(!access_ok((void __user *)start, len)))
|
|
return 0;
|
|
|
|
/*
|
|
* This doesn't prevent pagetable teardown, but does prevent
|
|
* the pagetables and pages from being freed.
|
|
*/
|
|
local_irq_save(flags);
|
|
pgdp = pgd_offset(mm, addr);
|
|
do {
|
|
pgd_t pgd = *pgdp;
|
|
|
|
next = pgd_addr_end(addr, end);
|
|
if (pgd_none(pgd))
|
|
break;
|
|
if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
|
|
break;
|
|
} while (pgdp++, addr = next, addr != end);
|
|
local_irq_restore(flags);
|
|
|
|
return nr;
|
|
}
|
|
|
|
/**
|
|
* get_user_pages_fast() - pin user pages in memory
|
|
* @start: starting user address
|
|
* @nr_pages: number of pages from start to pin
|
|
* @gup_flags: flags modifying pin behaviour
|
|
* @pages: array that receives pointers to the pages pinned.
|
|
* Should be at least nr_pages long.
|
|
*
|
|
* Attempt to pin user pages in memory without taking mm->mmap_sem.
|
|
* If not successful, it will fall back to taking the lock and
|
|
* calling get_user_pages().
|
|
*
|
|
* Returns number of pages pinned. This may be fewer than the number
|
|
* requested. If nr_pages is 0 or negative, returns 0. If no pages
|
|
* were pinned, returns -errno.
|
|
*/
|
|
int get_user_pages_fast(unsigned long start, int nr_pages,
|
|
unsigned int gup_flags, struct page **pages)
|
|
{
|
|
struct mm_struct *mm = current->mm;
|
|
unsigned long addr, len, end;
|
|
unsigned long next;
|
|
pgd_t *pgdp;
|
|
int nr = 0;
|
|
|
|
start &= PAGE_MASK;
|
|
addr = start;
|
|
len = (unsigned long) nr_pages << PAGE_SHIFT;
|
|
|
|
end = start + len;
|
|
if (end < start)
|
|
goto slow_irqon;
|
|
|
|
local_irq_disable();
|
|
pgdp = pgd_offset(mm, addr);
|
|
do {
|
|
pgd_t pgd = *pgdp;
|
|
|
|
next = pgd_addr_end(addr, end);
|
|
if (pgd_none(pgd))
|
|
goto slow;
|
|
if (!gup_pud_range(pgd, addr, next, gup_flags & FOLL_WRITE,
|
|
pages, &nr))
|
|
goto slow;
|
|
} while (pgdp++, addr = next, addr != end);
|
|
local_irq_enable();
|
|
|
|
VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
|
|
return nr;
|
|
|
|
{
|
|
int ret;
|
|
|
|
slow:
|
|
local_irq_enable();
|
|
slow_irqon:
|
|
/* Try to get the remaining pages with get_user_pages */
|
|
start += nr << PAGE_SHIFT;
|
|
pages += nr;
|
|
|
|
ret = get_user_pages_unlocked(start,
|
|
(end - start) >> PAGE_SHIFT, pages,
|
|
gup_flags);
|
|
|
|
/* Have to be a bit careful with return values */
|
|
if (nr > 0) {
|
|
if (ret < 0)
|
|
ret = nr;
|
|
else
|
|
ret += nr;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
}
|