Contributors: 42
| Author |
Tokens |
Token Proportion |
Commits |
Commit Proportion |
| Aneesh Kumar K.V |
1456 |
59.89% |
48 |
35.82% |
| Nicholas Piggin |
193 |
7.94% |
9 |
6.72% |
| Paul Mackerras |
148 |
6.09% |
6 |
4.48% |
| Benjamin Herrenschmidt |
84 |
3.46% |
9 |
6.72% |
| Peter Zijlstra |
52 |
2.14% |
2 |
1.49% |
| Anshuman Khandual |
47 |
1.93% |
1 |
0.75% |
| David Gibson |
46 |
1.89% |
3 |
2.24% |
| Michael Anderson |
45 |
1.85% |
1 |
0.75% |
| Dan J Williams |
39 |
1.60% |
2 |
1.49% |
| Reza Arbab |
36 |
1.48% |
3 |
2.24% |
| Vishal Moola (Oracle) |
29 |
1.19% |
1 |
0.75% |
| Anton Blanchard |
25 |
1.03% |
4 |
2.99% |
| Russell Currey |
22 |
0.90% |
1 |
0.75% |
| Balbir Singh |
18 |
0.74% |
1 |
0.75% |
| David S. Miller |
18 |
0.74% |
1 |
0.75% |
| Mike Kravetz |
17 |
0.70% |
1 |
0.75% |
| Alistair Popple |
16 |
0.66% |
1 |
0.75% |
| Linus Torvalds |
15 |
0.62% |
3 |
2.24% |
| Linus Torvalds (pre-git) |
14 |
0.58% |
4 |
2.99% |
| Mike Rapoport |
13 |
0.53% |
3 |
2.24% |
| Kumar Gala |
12 |
0.49% |
2 |
1.49% |
| Oliver O'Halloran |
12 |
0.49% |
1 |
0.75% |
| Christophe Leroy |
8 |
0.33% |
4 |
2.99% |
| Michael Ellerman |
7 |
0.29% |
2 |
1.49% |
| Logan Gunthorpe |
7 |
0.29% |
1 |
0.75% |
| Ram Pai |
7 |
0.29% |
2 |
1.49% |
| Dave Kleikamp |
6 |
0.25% |
1 |
0.75% |
| Andrew Morton |
6 |
0.25% |
2 |
1.49% |
| Ryan Roberts |
5 |
0.21% |
1 |
0.75% |
| Li Zhong |
4 |
0.16% |
1 |
0.75% |
| Will Deacon |
3 |
0.12% |
1 |
0.75% |
| Arnd Bergmann |
3 |
0.12% |
1 |
0.75% |
| Rusty Russell |
3 |
0.12% |
1 |
0.75% |
| Mauricio Faria de Oliveira |
2 |
0.08% |
1 |
0.75% |
| Thomas Gleixner |
2 |
0.08% |
1 |
0.75% |
| Stephen Rothwell |
2 |
0.08% |
1 |
0.75% |
| Peter Xu |
2 |
0.08% |
2 |
1.49% |
| Christoph Hellwig |
2 |
0.08% |
1 |
0.75% |
| Hari Bathini |
2 |
0.08% |
1 |
0.75% |
| Claudio Carvalho |
1 |
0.04% |
1 |
0.75% |
| Yinghai Lu |
1 |
0.04% |
1 |
0.75% |
| Badari Pulavarty |
1 |
0.04% |
1 |
0.75% |
| Total |
2431 |
|
134 |
|
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright 2015-2016, Aneesh Kumar K.V, IBM Corporation.
*/
#include <linux/sched.h>
#include <linux/mm_types.h>
#include <linux/memblock.h>
#include <linux/memremap.h>
#include <linux/pkeys.h>
#include <linux/debugfs.h>
#include <linux/proc_fs.h>
#include <misc/cxl-base.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>
#include <asm/trace.h>
#include <asm/powernv.h>
#include <asm/firmware.h>
#include <asm/ultravisor.h>
#include <asm/kexec.h>
#include <mm/mmu_decl.h>
#include <trace/events/thp.h>
#include "internal.h"
struct mmu_psize_def mmu_psize_defs[MMU_PAGE_COUNT];
EXPORT_SYMBOL_GPL(mmu_psize_defs);
#ifdef CONFIG_SPARSEMEM_VMEMMAP
int mmu_vmemmap_psize = MMU_PAGE_4K;
#endif
unsigned long __pmd_frag_nr;
EXPORT_SYMBOL(__pmd_frag_nr);
unsigned long __pmd_frag_size_shift;
EXPORT_SYMBOL(__pmd_frag_size_shift);
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
/*
* This is called when relaxing access to a hugepage. It's also called in the page
* fault path when we don't hit any of the major fault cases, ie, a minor
* update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have
* handled those two for us, we additionally deal with missing execute
* permission here on some processors
*/
int pmdp_set_access_flags(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp, pmd_t entry, int dirty)
{
int changed;
#ifdef CONFIG_DEBUG_VM
WARN_ON(!pmd_trans_huge(*pmdp) && !pmd_devmap(*pmdp));
assert_spin_locked(pmd_lockptr(vma->vm_mm, pmdp));
#endif
changed = !pmd_same(*(pmdp), entry);
if (changed) {
/*
* We can use MMU_PAGE_2M here, because only radix
* path look at the psize.
*/
__ptep_set_access_flags(vma, pmdp_ptep(pmdp),
pmd_pte(entry), address, MMU_PAGE_2M);
}
return changed;
}
int pudp_set_access_flags(struct vm_area_struct *vma, unsigned long address,
pud_t *pudp, pud_t entry, int dirty)
{
int changed;
#ifdef CONFIG_DEBUG_VM
WARN_ON(!pud_devmap(*pudp));
assert_spin_locked(pud_lockptr(vma->vm_mm, pudp));
#endif
changed = !pud_same(*(pudp), entry);
if (changed) {
/*
* We can use MMU_PAGE_1G here, because only radix
* path look at the psize.
*/
__ptep_set_access_flags(vma, pudp_ptep(pudp),
pud_pte(entry), address, MMU_PAGE_1G);
}
return changed;
}
int pmdp_test_and_clear_young(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp)
{
return __pmdp_test_and_clear_young(vma->vm_mm, address, pmdp);
}
int pudp_test_and_clear_young(struct vm_area_struct *vma,
unsigned long address, pud_t *pudp)
{
return __pudp_test_and_clear_young(vma->vm_mm, address, pudp);
}
/*
* set a new huge pmd. We should not be called for updating
* an existing pmd entry. That should go via pmd_hugepage_update.
*/
void set_pmd_at(struct mm_struct *mm, unsigned long addr,
pmd_t *pmdp, pmd_t pmd)
{
#ifdef CONFIG_DEBUG_VM
/*
* Make sure hardware valid bit is not set. We don't do
* tlb flush for this update.
*/
WARN_ON(pte_hw_valid(pmd_pte(*pmdp)) && !pte_protnone(pmd_pte(*pmdp)));
assert_spin_locked(pmd_lockptr(mm, pmdp));
WARN_ON(!(pmd_leaf(pmd)));
#endif
trace_hugepage_set_pmd(addr, pmd_val(pmd));
return set_pte_at(mm, addr, pmdp_ptep(pmdp), pmd_pte(pmd));
}
void set_pud_at(struct mm_struct *mm, unsigned long addr,
pud_t *pudp, pud_t pud)
{
#ifdef CONFIG_DEBUG_VM
/*
* Make sure hardware valid bit is not set. We don't do
* tlb flush for this update.
*/
WARN_ON(pte_hw_valid(pud_pte(*pudp)));
assert_spin_locked(pud_lockptr(mm, pudp));
WARN_ON(!(pud_leaf(pud)));
#endif
trace_hugepage_set_pud(addr, pud_val(pud));
return set_pte_at(mm, addr, pudp_ptep(pudp), pud_pte(pud));
}
static void do_serialize(void *arg)
{
/* We've taken the IPI, so try to trim the mask while here */
if (radix_enabled()) {
struct mm_struct *mm = arg;
exit_lazy_flush_tlb(mm, false);
}
}
/*
* Serialize against __find_linux_pte() which does lock-less
* lookup in page tables with local interrupts disabled. For huge pages
* it casts pmd_t to pte_t. Since format of pte_t is different from
* pmd_t we want to prevent transit from pmd pointing to page table
* to pmd pointing to huge page (and back) while interrupts are disabled.
* We clear pmd to possibly replace it with page table pointer in
* different code paths. So make sure we wait for the parallel
* __find_linux_pte() to finish.
*/
void serialize_against_pte_lookup(struct mm_struct *mm)
{
smp_mb();
smp_call_function_many(mm_cpumask(mm), do_serialize, mm, 1);
}
/*
* We use this to invalidate a pmdp entry before switching from a
* hugepte to regular pmd entry.
*/
pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp)
{
unsigned long old_pmd;
VM_WARN_ON_ONCE(!pmd_present(*pmdp));
old_pmd = pmd_hugepage_update(vma->vm_mm, address, pmdp, _PAGE_PRESENT, _PAGE_INVALID);
flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
return __pmd(old_pmd);
}
pmd_t pmdp_huge_get_and_clear_full(struct vm_area_struct *vma,
unsigned long addr, pmd_t *pmdp, int full)
{
pmd_t pmd;
VM_BUG_ON(addr & ~HPAGE_PMD_MASK);
VM_BUG_ON((pmd_present(*pmdp) && !pmd_trans_huge(*pmdp) &&
!pmd_devmap(*pmdp)) || !pmd_present(*pmdp));
pmd = pmdp_huge_get_and_clear(vma->vm_mm, addr, pmdp);
/*
* if it not a fullmm flush, then we can possibly end up converting
* this PMD pte entry to a regular level 0 PTE by a parallel page fault.
* Make sure we flush the tlb in this case.
*/
if (!full)
flush_pmd_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE);
return pmd;
}
pud_t pudp_huge_get_and_clear_full(struct vm_area_struct *vma,
unsigned long addr, pud_t *pudp, int full)
{
pud_t pud;
VM_BUG_ON(addr & ~HPAGE_PMD_MASK);
VM_BUG_ON((pud_present(*pudp) && !pud_devmap(*pudp)) ||
!pud_present(*pudp));
pud = pudp_huge_get_and_clear(vma->vm_mm, addr, pudp);
/*
* if it not a fullmm flush, then we can possibly end up converting
* this PMD pte entry to a regular level 0 PTE by a parallel page fault.
* Make sure we flush the tlb in this case.
*/
if (!full)
flush_pud_tlb_range(vma, addr, addr + HPAGE_PUD_SIZE);
return pud;
}
static pmd_t pmd_set_protbits(pmd_t pmd, pgprot_t pgprot)
{
return __pmd(pmd_val(pmd) | pgprot_val(pgprot));
}
static pud_t pud_set_protbits(pud_t pud, pgprot_t pgprot)
{
return __pud(pud_val(pud) | pgprot_val(pgprot));
}
/*
* At some point we should be able to get rid of
* pmd_mkhuge() and mk_huge_pmd() when we update all the
* other archs to mark the pmd huge in pfn_pmd()
*/
pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot)
{
unsigned long pmdv;
pmdv = (pfn << PAGE_SHIFT) & PTE_RPN_MASK;
return __pmd_mkhuge(pmd_set_protbits(__pmd(pmdv), pgprot));
}
pud_t pfn_pud(unsigned long pfn, pgprot_t pgprot)
{
unsigned long pudv;
pudv = (pfn << PAGE_SHIFT) & PTE_RPN_MASK;
return __pud_mkhuge(pud_set_protbits(__pud(pudv), pgprot));
}
pmd_t mk_pmd(struct page *page, pgprot_t pgprot)
{
return pfn_pmd(page_to_pfn(page), pgprot);
}
pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
{
unsigned long pmdv;
pmdv = pmd_val(pmd);
pmdv &= _HPAGE_CHG_MASK;
return pmd_set_protbits(__pmd(pmdv), newprot);
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
/* For use by kexec, called with MMU off */
notrace void mmu_cleanup_all(void)
{
if (radix_enabled())
radix__mmu_cleanup_all();
else if (mmu_hash_ops.hpte_clear_all)
mmu_hash_ops.hpte_clear_all();
reset_sprs();
}
#ifdef CONFIG_MEMORY_HOTPLUG
int __meminit create_section_mapping(unsigned long start, unsigned long end,
int nid, pgprot_t prot)
{
if (radix_enabled())
return radix__create_section_mapping(start, end, nid, prot);
return hash__create_section_mapping(start, end, nid, prot);
}
int __meminit remove_section_mapping(unsigned long start, unsigned long end)
{
if (radix_enabled())
return radix__remove_section_mapping(start, end);
return hash__remove_section_mapping(start, end);
}
#endif /* CONFIG_MEMORY_HOTPLUG */
void __init mmu_partition_table_init(void)
{
unsigned long patb_size = 1UL << PATB_SIZE_SHIFT;
unsigned long ptcr;
/* Initialize the Partition Table with no entries */
partition_tb = memblock_alloc(patb_size, patb_size);
if (!partition_tb)
panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
__func__, patb_size, patb_size);
ptcr = __pa(partition_tb) | (PATB_SIZE_SHIFT - 12);
set_ptcr_when_no_uv(ptcr);
powernv_set_nmmu_ptcr(ptcr);
}
static void flush_partition(unsigned int lpid, bool radix)
{
if (radix) {
radix__flush_all_lpid(lpid);
radix__flush_all_lpid_guest(lpid);
} else {
asm volatile("ptesync" : : : "memory");
asm volatile(PPC_TLBIE_5(%0,%1,2,0,0) : :
"r" (TLBIEL_INVAL_SET_LPID), "r" (lpid));
/* do we need fixup here ?*/
asm volatile("eieio; tlbsync; ptesync" : : : "memory");
trace_tlbie(lpid, 0, TLBIEL_INVAL_SET_LPID, lpid, 2, 0, 0);
}
}
void mmu_partition_table_set_entry(unsigned int lpid, unsigned long dw0,
unsigned long dw1, bool flush)
{
unsigned long old = be64_to_cpu(partition_tb[lpid].patb0);
/*
* When ultravisor is enabled, the partition table is stored in secure
* memory and can only be accessed doing an ultravisor call. However, we
* maintain a copy of the partition table in normal memory to allow Nest
* MMU translations to occur (for normal VMs).
*
* Therefore, here we always update partition_tb, regardless of whether
* we are running under an ultravisor or not.
*/
partition_tb[lpid].patb0 = cpu_to_be64(dw0);
partition_tb[lpid].patb1 = cpu_to_be64(dw1);
/*
* If ultravisor is enabled, we do an ultravisor call to register the
* partition table entry (PATE), which also do a global flush of TLBs
* and partition table caches for the lpid. Otherwise, just do the
* flush. The type of flush (hash or radix) depends on what the previous
* use of the partition ID was, not the new use.
*/
if (firmware_has_feature(FW_FEATURE_ULTRAVISOR)) {
uv_register_pate(lpid, dw0, dw1);
pr_info("PATE registered by ultravisor: dw0 = 0x%lx, dw1 = 0x%lx\n",
dw0, dw1);
} else if (flush) {
/*
* Boot does not need to flush, because MMU is off and each
* CPU does a tlbiel_all() before switching them on, which
* flushes everything.
*/
flush_partition(lpid, (old & PATB_HR));
}
}
EXPORT_SYMBOL_GPL(mmu_partition_table_set_entry);
static pmd_t *get_pmd_from_cache(struct mm_struct *mm)
{
void *pmd_frag, *ret;
if (PMD_FRAG_NR == 1)
return NULL;
spin_lock(&mm->page_table_lock);
ret = mm->context.pmd_frag;
if (ret) {
pmd_frag = ret + PMD_FRAG_SIZE;
/*
* If we have taken up all the fragments mark PTE page NULL
*/
if (((unsigned long)pmd_frag & ~PAGE_MASK) == 0)
pmd_frag = NULL;
mm->context.pmd_frag = pmd_frag;
}
spin_unlock(&mm->page_table_lock);
return (pmd_t *)ret;
}
static pmd_t *__alloc_for_pmdcache(struct mm_struct *mm)
{
void *ret = NULL;
struct ptdesc *ptdesc;
gfp_t gfp = GFP_KERNEL_ACCOUNT | __GFP_ZERO;
if (mm == &init_mm)
gfp &= ~__GFP_ACCOUNT;
ptdesc = pagetable_alloc(gfp, 0);
if (!ptdesc)
return NULL;
if (!pagetable_pmd_ctor(ptdesc)) {
pagetable_free(ptdesc);
return NULL;
}
atomic_set(&ptdesc->pt_frag_refcount, 1);
ret = ptdesc_address(ptdesc);
/*
* if we support only one fragment just return the
* allocated page.
*/
if (PMD_FRAG_NR == 1)
return ret;
spin_lock(&mm->page_table_lock);
/*
* If we find ptdesc_page set, we return
* the allocated page with single fragment
* count.
*/
if (likely(!mm->context.pmd_frag)) {
atomic_set(&ptdesc->pt_frag_refcount, PMD_FRAG_NR);
mm->context.pmd_frag = ret + PMD_FRAG_SIZE;
}
spin_unlock(&mm->page_table_lock);
return (pmd_t *)ret;
}
pmd_t *pmd_fragment_alloc(struct mm_struct *mm, unsigned long vmaddr)
{
pmd_t *pmd;
pmd = get_pmd_from_cache(mm);
if (pmd)
return pmd;
return __alloc_for_pmdcache(mm);
}
void pmd_fragment_free(unsigned long *pmd)
{
struct ptdesc *ptdesc = virt_to_ptdesc(pmd);
if (pagetable_is_reserved(ptdesc))
return free_reserved_ptdesc(ptdesc);
BUG_ON(atomic_read(&ptdesc->pt_frag_refcount) <= 0);
if (atomic_dec_and_test(&ptdesc->pt_frag_refcount)) {
pagetable_pmd_dtor(ptdesc);
pagetable_free(ptdesc);
}
}
static inline void pgtable_free(void *table, int index)
{
switch (index) {
case PTE_INDEX:
pte_fragment_free(table, 0);
break;
case PMD_INDEX:
pmd_fragment_free(table);
break;
case PUD_INDEX:
__pud_free(table);
break;
/* We don't free pgd table via RCU callback */
default:
BUG();
}
}
void pgtable_free_tlb(struct mmu_gather *tlb, void *table, int index)
{
unsigned long pgf = (unsigned long)table;
BUG_ON(index > MAX_PGTABLE_INDEX_SIZE);
pgf |= index;
tlb_remove_table(tlb, (void *)pgf);
}
void __tlb_remove_table(void *_table)
{
void *table = (void *)((unsigned long)_table & ~MAX_PGTABLE_INDEX_SIZE);
unsigned int index = (unsigned long)_table & MAX_PGTABLE_INDEX_SIZE;
return pgtable_free(table, index);
}
#ifdef CONFIG_PROC_FS
atomic_long_t direct_pages_count[MMU_PAGE_COUNT];
void arch_report_meminfo(struct seq_file *m)
{
/*
* Hash maps the memory with one size mmu_linear_psize.
* So don't bother to print these on hash
*/
if (!radix_enabled())
return;
seq_printf(m, "DirectMap4k: %8lu kB\n",
atomic_long_read(&direct_pages_count[MMU_PAGE_4K]) << 2);
seq_printf(m, "DirectMap64k: %8lu kB\n",
atomic_long_read(&direct_pages_count[MMU_PAGE_64K]) << 6);
seq_printf(m, "DirectMap2M: %8lu kB\n",
atomic_long_read(&direct_pages_count[MMU_PAGE_2M]) << 11);
seq_printf(m, "DirectMap1G: %8lu kB\n",
atomic_long_read(&direct_pages_count[MMU_PAGE_1G]) << 20);
}
#endif /* CONFIG_PROC_FS */
pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr,
pte_t *ptep)
{
unsigned long pte_val;
/*
* Clear the _PAGE_PRESENT so that no hardware parallel update is
* possible. Also keep the pte_present true so that we don't take
* wrong fault.
*/
pte_val = pte_update(vma->vm_mm, addr, ptep, _PAGE_PRESENT, _PAGE_INVALID, 0);
return __pte(pte_val);
}
void ptep_modify_prot_commit(struct vm_area_struct *vma, unsigned long addr,
pte_t *ptep, pte_t old_pte, pte_t pte)
{
if (radix_enabled())
return radix__ptep_modify_prot_commit(vma, addr,
ptep, old_pte, pte);
set_pte_at(vma->vm_mm, addr, ptep, pte);
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
/*
* For hash translation mode, we use the deposited table to store hash slot
* information and they are stored at PTRS_PER_PMD offset from related pmd
* location. Hence a pmd move requires deposit and withdraw.
*
* For radix translation with split pmd ptl, we store the deposited table in the
* pmd page. Hence if we have different pmd page we need to withdraw during pmd
* move.
*
* With hash we use deposited table always irrespective of anon or not.
* With radix we use deposited table only for anonymous mapping.
*/
int pmd_move_must_withdraw(struct spinlock *new_pmd_ptl,
struct spinlock *old_pmd_ptl,
struct vm_area_struct *vma)
{
if (radix_enabled())
return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
return true;
}
#endif
/*
* Does the CPU support tlbie?
*/
bool tlbie_capable __read_mostly = true;
EXPORT_SYMBOL(tlbie_capable);
/*
* Should tlbie be used for management of CPU TLBs, for kernel and process
* address spaces? tlbie may still be used for nMMU accelerators, and for KVM
* guest address spaces.
*/
bool tlbie_enabled __read_mostly = true;
static int __init setup_disable_tlbie(char *str)
{
if (!radix_enabled()) {
pr_err("disable_tlbie: Unable to disable TLBIE with Hash MMU.\n");
return 1;
}
tlbie_capable = false;
tlbie_enabled = false;
return 1;
}
__setup("disable_tlbie", setup_disable_tlbie);
static int __init pgtable_debugfs_setup(void)
{
if (!tlbie_capable)
return 0;
/*
* There is no locking vs tlb flushing when changing this value.
* The tlb flushers will see one value or another, and use either
* tlbie or tlbiel with IPIs. In both cases the TLBs will be
* invalidated as expected.
*/
debugfs_create_bool("tlbie_enabled", 0600,
arch_debugfs_dir,
&tlbie_enabled);
return 0;
}
arch_initcall(pgtable_debugfs_setup);
#if defined(CONFIG_ZONE_DEVICE) && defined(CONFIG_ARCH_HAS_MEMREMAP_COMPAT_ALIGN)
/*
* Override the generic version in mm/memremap.c.
*
* With hash translation, the direct-map range is mapped with just one
* page size selected by htab_init_page_sizes(). Consult
* mmu_psize_defs[] to determine the minimum page size alignment.
*/
unsigned long memremap_compat_align(void)
{
if (!radix_enabled()) {
unsigned int shift = mmu_psize_defs[mmu_linear_psize].shift;
return max(SUBSECTION_SIZE, 1UL << shift);
}
return SUBSECTION_SIZE;
}
EXPORT_SYMBOL_GPL(memremap_compat_align);
#endif
pgprot_t vm_get_page_prot(unsigned long vm_flags)
{
unsigned long prot;
/* Radix supports execute-only, but protection_map maps X -> RX */
if (!radix_enabled() && ((vm_flags & VM_ACCESS_FLAGS) == VM_EXEC))
vm_flags |= VM_READ;
prot = pgprot_val(protection_map[vm_flags & (VM_ACCESS_FLAGS | VM_SHARED)]);
if (vm_flags & VM_SAO)
prot |= _PAGE_SAO;
#ifdef CONFIG_PPC_MEM_KEYS
prot |= vmflag_to_pte_pkey_bits(vm_flags);
#endif
return __pgprot(prot);
}
EXPORT_SYMBOL(vm_get_page_prot);