x86: cpa, micro-optimization

[linux-2.6/kmemtrace.git] / arch / x86 / mm / pageattr.c

/*
 * 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>

/*
 * The current flushing context - we pass it instead of 5 arguments:
 */
struct cpa_data {
        unsigned long   vaddr;
        pgprot_t        mask_set;
        pgprot_t        mask_clr;
        int             numpages;
        int             flushtlb;
};

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;

        *level = PG_LEVEL_1G;
        if (pud_large(*pud) || !pud_present(*pud))
                return (pte_t *)pud;

        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);
}

/*
 * Set the new pmd in all the pgds we know about:
 */
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;

                address = __pa(address);
                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, do_split = 1;

        /*
         * 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 1;

        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;
#ifdef CONFIG_X86_64
        case PG_LEVEL_1G:
                psize = PMD_PAGE_SIZE;
                pmask = PMD_PAGE_MASK;
                break;
#endif
        default:
                do_split = -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)) {
                do_split = 0;
                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;
                do_split = 0;
        }

out_unlock:
        spin_unlock_irqrestore(&pgd_lock, flags);

        return do_split;
}

static int split_large_page(pte_t *kpte, unsigned long address)
{
        unsigned long flags, pfn, pfninc = 1;
        gfp_t gfp_flags = GFP_KERNEL;
        unsigned int i, level;
        pte_t *pbase, *tmp;
        pgprot_t ref_prot;
        struct page *base;

#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;

        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));

#ifdef CONFIG_X86_64
        if (level == PG_LEVEL_1G) {
                pfninc = PMD_PAGE_SIZE >> PAGE_SHIFT;
                pgprot_val(ref_prot) |= _PAGE_PSE;
        }
#endif

        /*
         * Get the target pfn from the original entry:
         */
        pfn = pte_pfn(*kpte);
        for (i = 0; i < PTRS_PER_PTE; i++, pfn += pfninc)
                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)
{
        int level, do_split, err;
        struct page *kpte_page;
        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:
         */
        do_split = try_preserve_large_page(kpte, address, cpa);
        /*
         * When the range fits into the existing large page,
         * return. cp->numpages and cpa->tlbflush have been updated in
         * try_large_page:
         */
        if (do_split <= 0)
                return do_split;

        /*
         * We have to split the large page:
         */
        err = split_large_page(kpte, address);
        if (!err) {
                cpa->flushtlb = 1;
                goto repeat;
        }

        return err;
}

/**
 * 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