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linux/arch/x86/mm/pageattr.c

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/*
* Copyright 2002 Andi Kleen, SuSE Labs.
* Thanks to Ben LaHaise for precious feedback.
*/
#include <linux/highmem.h>
#include <linux/bootmem.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <asm/e820.h>
#include <asm/processor.h>
#include <asm/tlbflush.h>
#include <asm/sections.h>
#include <asm/uaccess.h>
#include <asm/pgalloc.h>
struct cpa_data {
unsigned long vaddr;
pgprot_t mask_set;
pgprot_t mask_clr;
int numpages;
int flushtlb;
};
enum {
CPA_NO_SPLIT = 0,
CPA_SPLIT,
};
static inline int
within(unsigned long addr, unsigned long start, unsigned long end)
{
return addr >= start && addr < end;
}
/*
* Flushing functions
*/
/**
* clflush_cache_range - flush a cache range with clflush
* @addr: virtual start address
* @size: number of bytes to flush
*
* clflush is an unordered instruction which needs fencing with mfence
* to avoid ordering issues.
*/
void clflush_cache_range(void *vaddr, unsigned int size)
{
void *vend = vaddr + size - 1;
mb();
for (; vaddr < vend; vaddr += boot_cpu_data.x86_clflush_size)
clflush(vaddr);
/*
* Flush any possible final partial cacheline:
*/
clflush(vend);
mb();
}
static void __cpa_flush_all(void *arg)
{
unsigned long cache = (unsigned long)arg;
/*
* Flush all to work around Errata in early athlons regarding
* large page flushing.
*/
__flush_tlb_all();
if (cache && boot_cpu_data.x86_model >= 4)
wbinvd();
}
static void cpa_flush_all(unsigned long cache)
{
BUG_ON(irqs_disabled());
on_each_cpu(__cpa_flush_all, (void *) cache, 1, 1);
}
static void __cpa_flush_range(void *arg)
{
/*
* We could optimize that further and do individual per page
* tlb invalidates for a low number of pages. Caveat: we must
* flush the high aliases on 64bit as well.
*/
__flush_tlb_all();
}
static void cpa_flush_range(unsigned long start, int numpages, int cache)
{
unsigned int i, level;
unsigned long addr;
BUG_ON(irqs_disabled());
WARN_ON(PAGE_ALIGN(start) != start);
on_each_cpu(__cpa_flush_range, NULL, 1, 1);
if (!cache)
return;
/*
* We only need to flush on one CPU,
* clflush is a MESI-coherent instruction that
* will cause all other CPUs to flush the same
* cachelines:
*/
for (i = 0, addr = start; i < numpages; i++, addr += PAGE_SIZE) {
pte_t *pte = lookup_address(addr, &level);
/*
* Only flush present addresses:
*/
if (pte && (pte_val(*pte) & _PAGE_PRESENT))
clflush_cache_range((void *) addr, PAGE_SIZE);
}
}
#define HIGH_MAP_START __START_KERNEL_map
#define HIGH_MAP_END (__START_KERNEL_map + KERNEL_TEXT_SIZE)
/*
* Converts a virtual address to a X86-64 highmap address
*/
static unsigned long virt_to_highmap(void *address)
{
#ifdef CONFIG_X86_64
return __pa((unsigned long)address) + HIGH_MAP_START - phys_base;
#else
return (unsigned long)address;
#endif
}
/*
* Certain areas of memory on x86 require very specific protection flags,
* for example the BIOS area or kernel text. Callers don't always get this
* right (again, ioremap() on BIOS memory is not uncommon) so this function
* checks and fixes these known static required protection bits.
*/
static inline pgprot_t static_protections(pgprot_t prot, unsigned long address)
{
pgprot_t forbidden = __pgprot(0);
/*
* The BIOS area between 640k and 1Mb needs to be executable for
* PCI BIOS based config access (CONFIG_PCI_GOBIOS) support.
*/
if (within(__pa(address), BIOS_BEGIN, BIOS_END))
pgprot_val(forbidden) |= _PAGE_NX;
/*
* The kernel text needs to be executable for obvious reasons
* Does not cover __inittext since that is gone later on
*/
if (within(address, (unsigned long)_text, (unsigned long)_etext))
pgprot_val(forbidden) |= _PAGE_NX;
/*
* Do the same for the x86-64 high kernel mapping
*/
if (within(address, virt_to_highmap(_text), virt_to_highmap(_etext)))
pgprot_val(forbidden) |= _PAGE_NX;
#ifdef CONFIG_DEBUG_RODATA
/* The .rodata section needs to be read-only */
if (within(address, (unsigned long)__start_rodata,
(unsigned long)__end_rodata))
pgprot_val(forbidden) |= _PAGE_RW;
/*
* Do the same for the x86-64 high kernel mapping
*/
if (within(address, virt_to_highmap(__start_rodata),
virt_to_highmap(__end_rodata)))
pgprot_val(forbidden) |= _PAGE_RW;
#endif
prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));
return prot;
}
/*
* Lookup the page table entry for a virtual address. Return a pointer
* to the entry and the level of the mapping.
*
* Note: We return pud and pmd either when the entry is marked large
* or when the present bit is not set. Otherwise we would return a
* pointer to a nonexisting mapping.
*/
pte_t *lookup_address(unsigned long address, int *level)
{
pgd_t *pgd = pgd_offset_k(address);
pud_t *pud;
pmd_t *pmd;
*level = PG_LEVEL_NONE;
if (pgd_none(*pgd))
return NULL;
pud = pud_offset(pgd, address);
if (pud_none(*pud))
return NULL;
pmd = pmd_offset(pud, address);
if (pmd_none(*pmd))
return NULL;
*level = PG_LEVEL_2M;
if (pmd_large(*pmd) || !pmd_present(*pmd))
return (pte_t *)pmd;
*level = PG_LEVEL_4K;
return pte_offset_kernel(pmd, address);
}
static void __set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte)
{
/* change init_mm */
set_pte_atomic(kpte, pte);
#ifdef CONFIG_X86_32
if (!SHARED_KERNEL_PMD) {
struct page *page;
list_for_each_entry(page, &pgd_list, lru) {
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pgd = (pgd_t *)page_address(page) + pgd_index(address);
pud = pud_offset(pgd, address);
pmd = pmd_offset(pud, address);
set_pte_atomic((pte_t *)pmd, pte);
}
}
#endif
}
static int try_preserve_large_page(pte_t *kpte, unsigned long address,
struct cpa_data *cpa)
{
unsigned long nextpage_addr, numpages, pmask, psize, flags;
pte_t new_pte, old_pte, *tmp;
pgprot_t old_prot, new_prot;
int level, res = CPA_SPLIT;
/*
* An Athlon 64 X2 showed hard hangs if we tried to preserve
* largepages and changed the PSE entry from RW to RO.
*
* As AMD CPUs have a long series of erratas in this area,
* (and none of the known ones seem to explain this hang),
* disable this code until the hang can be debugged:
*/
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
return res;
spin_lock_irqsave(&pgd_lock, flags);
/*
* Check for races, another CPU might have split this page
* up already:
*/
tmp = lookup_address(address, &level);
if (tmp != kpte)
goto out_unlock;
switch (level) {
case PG_LEVEL_2M:
psize = PMD_PAGE_SIZE;
pmask = PMD_PAGE_MASK;
break;
case PG_LEVEL_1G:
default:
res = -EINVAL;
goto out_unlock;
}
/*
* Calculate the number of pages, which fit into this large
* page starting at address:
*/
nextpage_addr = (address + psize) & pmask;
numpages = (nextpage_addr - address) >> PAGE_SHIFT;
if (numpages < cpa->numpages)
cpa->numpages = numpages;
/*
* We are safe now. Check whether the new pgprot is the same:
*/
old_pte = *kpte;
old_prot = new_prot = pte_pgprot(old_pte);
pgprot_val(new_prot) &= ~pgprot_val(cpa->mask_clr);
pgprot_val(new_prot) |= pgprot_val(cpa->mask_set);
new_prot = static_protections(new_prot, address);
/*
* If there are no changes, return. maxpages has been updated
* above:
*/
if (pgprot_val(new_prot) == pgprot_val(old_prot)) {
res = CPA_NO_SPLIT;
goto out_unlock;
}
/*
* We need to change the attributes. Check, whether we can
* change the large page in one go. We request a split, when
* the address is not aligned and the number of pages is
* smaller than the number of pages in the large page. Note
* that we limited the number of possible pages already to
* the number of pages in the large page.
*/
if (address == (nextpage_addr - psize) && cpa->numpages == numpages) {
/*
* The address is aligned and the number of pages
* covers the full page.
*/
new_pte = pfn_pte(pte_pfn(old_pte), canon_pgprot(new_prot));
__set_pmd_pte(kpte, address, new_pte);
cpa->flushtlb = 1;
res = CPA_NO_SPLIT;
}
out_unlock:
spin_unlock_irqrestore(&pgd_lock, flags);
return res;
}
static int split_large_page(pte_t *kpte, unsigned long address)
{
pgprot_t ref_prot;
gfp_t gfp_flags = GFP_KERNEL;
unsigned long flags, addr, pfn;
pte_t *pbase, *tmp;
struct page *base;
unsigned int i, level;
#ifdef CONFIG_DEBUG_PAGEALLOC
gfp_flags = GFP_ATOMIC | __GFP_NOWARN;
#endif
base = alloc_pages(gfp_flags, 0);
if (!base)
return -ENOMEM;
spin_lock_irqsave(&pgd_lock, flags);
/*
* Check for races, another CPU might have split this page
* up for us already:
*/
tmp = lookup_address(address, &level);
if (tmp != kpte)
goto out_unlock;
address = __pa(address);
addr = address & PMD_PAGE_MASK;
pbase = (pte_t *)page_address(base);
#ifdef CONFIG_X86_32
paravirt_alloc_pt(&init_mm, page_to_pfn(base));
#endif
ref_prot = pte_pgprot(pte_clrhuge(*kpte));
/*
* Get the target pfn from the original entry:
*/
pfn = pte_pfn(*kpte);
for (i = 0; i < PTRS_PER_PTE; i++, pfn++)
set_pte(&pbase[i], pfn_pte(pfn, ref_prot));
/*
* Install the new, split up pagetable. Important details here:
*
* On Intel the NX bit of all levels must be cleared to make a
* page executable. See section 4.13.2 of Intel 64 and IA-32
* Architectures Software Developer's Manual).
*
* Mark the entry present. The current mapping might be
* set to not present, which we preserved above.
*/
ref_prot = pte_pgprot(pte_mkexec(pte_clrhuge(*kpte)));
pgprot_val(ref_prot) |= _PAGE_PRESENT;
__set_pmd_pte(kpte, address, mk_pte(base, ref_prot));
base = NULL;
out_unlock:
spin_unlock_irqrestore(&pgd_lock, flags);
if (base)
__free_pages(base, 0);
return 0;
}
static int __change_page_attr(unsigned long address, struct cpa_data *cpa)
{
struct page *kpte_page;
int level, res;
pte_t *kpte;
repeat:
kpte = lookup_address(address, &level);
if (!kpte)
return -EINVAL;
kpte_page = virt_to_page(kpte);
BUG_ON(PageLRU(kpte_page));
BUG_ON(PageCompound(kpte_page));
if (level == PG_LEVEL_4K) {
pte_t new_pte, old_pte = *kpte;
pgprot_t new_prot = pte_pgprot(old_pte);
if(!pte_val(old_pte)) {
printk(KERN_WARNING "CPA: called for zero pte. "
"vaddr = %lx cpa->vaddr = %lx\n", address,
cpa->vaddr);
WARN_ON(1);
return -EINVAL;
}
pgprot_val(new_prot) &= ~pgprot_val(cpa->mask_clr);
pgprot_val(new_prot) |= pgprot_val(cpa->mask_set);
new_prot = static_protections(new_prot, address);
/*
* We need to keep the pfn from the existing PTE,
* after all we're only going to change it's attributes
* not the memory it points to
*/
new_pte = pfn_pte(pte_pfn(old_pte), canon_pgprot(new_prot));
/*
* Do we really change anything ?
*/
if (pte_val(old_pte) != pte_val(new_pte)) {
set_pte_atomic(kpte, new_pte);
cpa->flushtlb = 1;
}
cpa->numpages = 1;
return 0;
}
/*
* Check, whether we can keep the large page intact
* and just change the pte:
*/
res = try_preserve_large_page(kpte, address, cpa);
if (res < 0)
return res;
/*
* When the range fits into the existing large page,
* return. cp->numpages and cpa->tlbflush have been updated in
* try_large_page:
*/
if (res == CPA_NO_SPLIT)
return 0;
/*
* We have to split the large page:
*/
res = split_large_page(kpte, address);
if (res)
return res;
cpa->flushtlb = 1;
goto repeat;
}
/**
* change_page_attr_addr - Change page table attributes in linear mapping
* @address: Virtual address in linear mapping.
* @prot: New page table attribute (PAGE_*)
*
* Change page attributes of a page in the direct mapping. This is a variant
* of change_page_attr() that also works on memory holes that do not have
* mem_map entry (pfn_valid() is false).
*
* See change_page_attr() documentation for more details.
*
* Modules and drivers should use the set_memory_* APIs instead.
*/
static int change_page_attr_addr(struct cpa_data *cpa)
{
int err;
unsigned long address = cpa->vaddr;
#ifdef CONFIG_X86_64
unsigned long phys_addr = __pa(address);
/*
* If we are inside the high mapped kernel range, then we
* fixup the low mapping first. __va() returns the virtual
* address in the linear mapping:
*/
if (within(address, HIGH_MAP_START, HIGH_MAP_END))
address = (unsigned long) __va(phys_addr);
#endif
err = __change_page_attr(address, cpa);
if (err)
return err;
#ifdef CONFIG_X86_64
/*
* If the physical address is inside the kernel map, we need
* to touch the high mapped kernel as well:
*/
if (within(phys_addr, 0, KERNEL_TEXT_SIZE)) {
/*
* Calc the high mapping address. See __phys_addr()
* for the non obvious details.
*
* Note that NX and other required permissions are
* checked in static_protections().
*/
address = phys_addr + HIGH_MAP_START - phys_base;
/*
* Our high aliases are imprecise, because we check
* everything between 0 and KERNEL_TEXT_SIZE, so do
* not propagate lookup failures back to users:
*/
__change_page_attr(address, cpa);
}
#endif
return err;
}
static int __change_page_attr_set_clr(struct cpa_data *cpa)
{
int ret, numpages = cpa->numpages;
while (numpages) {
/*
* Store the remaining nr of pages for the large page
* preservation check.
*/
cpa->numpages = numpages;
ret = change_page_attr_addr(cpa);
if (ret)
return ret;
/*
* Adjust the number of pages with the result of the
* CPA operation. Either a large page has been
* preserved or a single page update happened.
*/
BUG_ON(cpa->numpages > numpages);
numpages -= cpa->numpages;
cpa->vaddr += cpa->numpages * PAGE_SIZE;
}
return 0;
}
static inline int cache_attr(pgprot_t attr)
{
return pgprot_val(attr) &
(_PAGE_PAT | _PAGE_PAT_LARGE | _PAGE_PWT | _PAGE_PCD);
}
static int change_page_attr_set_clr(unsigned long addr, int numpages,
pgprot_t mask_set, pgprot_t mask_clr)
{
struct cpa_data cpa;
int ret, cache;
/*
* Check, if we are requested to change a not supported
* feature:
*/
mask_set = canon_pgprot(mask_set);
mask_clr = canon_pgprot(mask_clr);
if (!pgprot_val(mask_set) && !pgprot_val(mask_clr))
return 0;
cpa.vaddr = addr;
cpa.numpages = numpages;
cpa.mask_set = mask_set;
cpa.mask_clr = mask_clr;
cpa.flushtlb = 0;
ret = __change_page_attr_set_clr(&cpa);
/*
* Check whether we really changed something:
*/
if (!cpa.flushtlb)
return ret;
/*
* No need to flush, when we did not set any of the caching
* attributes:
*/
cache = cache_attr(mask_set);
/*
* On success we use clflush, when the CPU supports it to
* avoid the wbindv. If the CPU does not support it and in the
* error case we fall back to cpa_flush_all (which uses
* wbindv):
*/
if (!ret && cpu_has_clflush)
cpa_flush_range(addr, numpages, cache);
else
cpa_flush_all(cache);
return ret;
}
static inline int change_page_attr_set(unsigned long addr, int numpages,
pgprot_t mask)
{
return change_page_attr_set_clr(addr, numpages, mask, __pgprot(0));
}
static inline int change_page_attr_clear(unsigned long addr, int numpages,
pgprot_t mask)
{
return change_page_attr_set_clr(addr, numpages, __pgprot(0), mask);
}
int set_memory_uc(unsigned long addr, int numpages)
{
return change_page_attr_set(addr, numpages,
__pgprot(_PAGE_PCD | _PAGE_PWT));
}
EXPORT_SYMBOL(set_memory_uc);
int set_memory_wb(unsigned long addr, int numpages)
{
return change_page_attr_clear(addr, numpages,
__pgprot(_PAGE_PCD | _PAGE_PWT));
}
EXPORT_SYMBOL(set_memory_wb);
int set_memory_x(unsigned long addr, int numpages)
{
return change_page_attr_clear(addr, numpages, __pgprot(_PAGE_NX));
}
EXPORT_SYMBOL(set_memory_x);
int set_memory_nx(unsigned long addr, int numpages)
{
return change_page_attr_set(addr, numpages, __pgprot(_PAGE_NX));
}
EXPORT_SYMBOL(set_memory_nx);
int set_memory_ro(unsigned long addr, int numpages)
{
return change_page_attr_clear(addr, numpages, __pgprot(_PAGE_RW));
}
int set_memory_rw(unsigned long addr, int numpages)
{
return change_page_attr_set(addr, numpages, __pgprot(_PAGE_RW));
}
int set_memory_np(unsigned long addr, int numpages)
{
return change_page_attr_clear(addr, numpages, __pgprot(_PAGE_PRESENT));
}
int set_pages_uc(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);
return set_memory_uc(addr, numpages);
}
EXPORT_SYMBOL(set_pages_uc);
int set_pages_wb(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);
return set_memory_wb(addr, numpages);
}
EXPORT_SYMBOL(set_pages_wb);
int set_pages_x(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);
return set_memory_x(addr, numpages);
}
EXPORT_SYMBOL(set_pages_x);
int set_pages_nx(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);
return set_memory_nx(addr, numpages);
}
EXPORT_SYMBOL(set_pages_nx);
int set_pages_ro(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);
return set_memory_ro(addr, numpages);
}
int set_pages_rw(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);
return set_memory_rw(addr, numpages);
}
#ifdef CONFIG_DEBUG_PAGEALLOC
static int __set_pages_p(struct page *page, int numpages)
{
struct cpa_data cpa = { .vaddr = (unsigned long) page_address(page),
.numpages = numpages,
.mask_set = __pgprot(_PAGE_PRESENT | _PAGE_RW),
.mask_clr = __pgprot(0)};
return __change_page_attr_set_clr(&cpa);
}
static int __set_pages_np(struct page *page, int numpages)
{
struct cpa_data cpa = { .vaddr = (unsigned long) page_address(page),
.numpages = numpages,
.mask_set = __pgprot(0),
.mask_clr = __pgprot(_PAGE_PRESENT | _PAGE_RW)};
return __change_page_attr_set_clr(&cpa);
}
void kernel_map_pages(struct page *page, int numpages, int enable)
{
if (PageHighMem(page))
return;
if (!enable) {
debug_check_no_locks_freed(page_address(page),
numpages * PAGE_SIZE);
}
/*
* If page allocator is not up yet then do not call c_p_a():
*/
if (!debug_pagealloc_enabled)
return;
/*
* The return value is ignored - the calls cannot fail,
* large pages are disabled at boot time:
*/
if (enable)
__set_pages_p(page, numpages);
else
__set_pages_np(page, numpages);
/*
* We should perform an IPI and flush all tlbs,
* but that can deadlock->flush only current cpu:
*/
__flush_tlb_all();
}
#endif
/*
* The testcases use internal knowledge of the implementation that shouldn't
* be exposed to the rest of the kernel. Include these directly here.
*/
#ifdef CONFIG_CPA_DEBUG
#include "pageattr-test.c"
#endif