cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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page_vma_mapped.c (8842B)


      1// SPDX-License-Identifier: GPL-2.0
      2#include <linux/mm.h>
      3#include <linux/rmap.h>
      4#include <linux/hugetlb.h>
      5#include <linux/swap.h>
      6#include <linux/swapops.h>
      7
      8#include "internal.h"
      9
     10static inline bool not_found(struct page_vma_mapped_walk *pvmw)
     11{
     12	page_vma_mapped_walk_done(pvmw);
     13	return false;
     14}
     15
     16static bool map_pte(struct page_vma_mapped_walk *pvmw)
     17{
     18	pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address);
     19	if (!(pvmw->flags & PVMW_SYNC)) {
     20		if (pvmw->flags & PVMW_MIGRATION) {
     21			if (!is_swap_pte(*pvmw->pte))
     22				return false;
     23		} else {
     24			/*
     25			 * We get here when we are trying to unmap a private
     26			 * device page from the process address space. Such
     27			 * page is not CPU accessible and thus is mapped as
     28			 * a special swap entry, nonetheless it still does
     29			 * count as a valid regular mapping for the page (and
     30			 * is accounted as such in page maps count).
     31			 *
     32			 * So handle this special case as if it was a normal
     33			 * page mapping ie lock CPU page table and returns
     34			 * true.
     35			 *
     36			 * For more details on device private memory see HMM
     37			 * (include/linux/hmm.h or mm/hmm.c).
     38			 */
     39			if (is_swap_pte(*pvmw->pte)) {
     40				swp_entry_t entry;
     41
     42				/* Handle un-addressable ZONE_DEVICE memory */
     43				entry = pte_to_swp_entry(*pvmw->pte);
     44				if (!is_device_private_entry(entry) &&
     45				    !is_device_exclusive_entry(entry))
     46					return false;
     47			} else if (!pte_present(*pvmw->pte))
     48				return false;
     49		}
     50	}
     51	pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd);
     52	spin_lock(pvmw->ptl);
     53	return true;
     54}
     55
     56/**
     57 * check_pte - check if @pvmw->page is mapped at the @pvmw->pte
     58 * @pvmw: page_vma_mapped_walk struct, includes a pair pte and page for checking
     59 *
     60 * page_vma_mapped_walk() found a place where @pvmw->page is *potentially*
     61 * mapped. check_pte() has to validate this.
     62 *
     63 * pvmw->pte may point to empty PTE, swap PTE or PTE pointing to
     64 * arbitrary page.
     65 *
     66 * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration
     67 * entry that points to @pvmw->page or any subpage in case of THP.
     68 *
     69 * If PVMW_MIGRATION flag is not set, returns true if pvmw->pte points to
     70 * pvmw->page or any subpage in case of THP.
     71 *
     72 * Otherwise, return false.
     73 *
     74 */
     75static bool check_pte(struct page_vma_mapped_walk *pvmw)
     76{
     77	unsigned long pfn;
     78
     79	if (pvmw->flags & PVMW_MIGRATION) {
     80		swp_entry_t entry;
     81		if (!is_swap_pte(*pvmw->pte))
     82			return false;
     83		entry = pte_to_swp_entry(*pvmw->pte);
     84
     85		if (!is_migration_entry(entry) &&
     86		    !is_device_exclusive_entry(entry))
     87			return false;
     88
     89		pfn = swp_offset(entry);
     90	} else if (is_swap_pte(*pvmw->pte)) {
     91		swp_entry_t entry;
     92
     93		/* Handle un-addressable ZONE_DEVICE memory */
     94		entry = pte_to_swp_entry(*pvmw->pte);
     95		if (!is_device_private_entry(entry) &&
     96		    !is_device_exclusive_entry(entry))
     97			return false;
     98
     99		pfn = swp_offset(entry);
    100	} else {
    101		if (!pte_present(*pvmw->pte))
    102			return false;
    103
    104		pfn = pte_pfn(*pvmw->pte);
    105	}
    106
    107	return (pfn - pvmw->pfn) < pvmw->nr_pages;
    108}
    109
    110/* Returns true if the two ranges overlap.  Careful to not overflow. */
    111static bool check_pmd(unsigned long pfn, struct page_vma_mapped_walk *pvmw)
    112{
    113	if ((pfn + HPAGE_PMD_NR - 1) < pvmw->pfn)
    114		return false;
    115	if (pfn > pvmw->pfn + pvmw->nr_pages - 1)
    116		return false;
    117	return true;
    118}
    119
    120static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size)
    121{
    122	pvmw->address = (pvmw->address + size) & ~(size - 1);
    123	if (!pvmw->address)
    124		pvmw->address = ULONG_MAX;
    125}
    126
    127/**
    128 * page_vma_mapped_walk - check if @pvmw->pfn is mapped in @pvmw->vma at
    129 * @pvmw->address
    130 * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
    131 * must be set. pmd, pte and ptl must be NULL.
    132 *
    133 * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
    134 * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
    135 * adjusted if needed (for PTE-mapped THPs).
    136 *
    137 * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
    138 * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
    139 * a loop to find all PTEs that map the THP.
    140 *
    141 * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
    142 * regardless of which page table level the page is mapped at. @pvmw->pmd is
    143 * NULL.
    144 *
    145 * Returns false if there are no more page table entries for the page in
    146 * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
    147 *
    148 * If you need to stop the walk before page_vma_mapped_walk() returned false,
    149 * use page_vma_mapped_walk_done(). It will do the housekeeping.
    150 */
    151bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
    152{
    153	struct vm_area_struct *vma = pvmw->vma;
    154	struct mm_struct *mm = vma->vm_mm;
    155	unsigned long end;
    156	pgd_t *pgd;
    157	p4d_t *p4d;
    158	pud_t *pud;
    159	pmd_t pmde;
    160
    161	/* The only possible pmd mapping has been handled on last iteration */
    162	if (pvmw->pmd && !pvmw->pte)
    163		return not_found(pvmw);
    164
    165	if (unlikely(is_vm_hugetlb_page(vma))) {
    166		struct hstate *hstate = hstate_vma(vma);
    167		unsigned long size = huge_page_size(hstate);
    168		/* The only possible mapping was handled on last iteration */
    169		if (pvmw->pte)
    170			return not_found(pvmw);
    171
    172		/* when pud is not present, pte will be NULL */
    173		pvmw->pte = huge_pte_offset(mm, pvmw->address, size);
    174		if (!pvmw->pte)
    175			return false;
    176
    177		pvmw->ptl = huge_pte_lockptr(hstate, mm, pvmw->pte);
    178		spin_lock(pvmw->ptl);
    179		if (!check_pte(pvmw))
    180			return not_found(pvmw);
    181		return true;
    182	}
    183
    184	end = vma_address_end(pvmw);
    185	if (pvmw->pte)
    186		goto next_pte;
    187restart:
    188	do {
    189		pgd = pgd_offset(mm, pvmw->address);
    190		if (!pgd_present(*pgd)) {
    191			step_forward(pvmw, PGDIR_SIZE);
    192			continue;
    193		}
    194		p4d = p4d_offset(pgd, pvmw->address);
    195		if (!p4d_present(*p4d)) {
    196			step_forward(pvmw, P4D_SIZE);
    197			continue;
    198		}
    199		pud = pud_offset(p4d, pvmw->address);
    200		if (!pud_present(*pud)) {
    201			step_forward(pvmw, PUD_SIZE);
    202			continue;
    203		}
    204
    205		pvmw->pmd = pmd_offset(pud, pvmw->address);
    206		/*
    207		 * Make sure the pmd value isn't cached in a register by the
    208		 * compiler and used as a stale value after we've observed a
    209		 * subsequent update.
    210		 */
    211		pmde = READ_ONCE(*pvmw->pmd);
    212
    213		if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) ||
    214		    (pmd_present(pmde) && pmd_devmap(pmde))) {
    215			pvmw->ptl = pmd_lock(mm, pvmw->pmd);
    216			pmde = *pvmw->pmd;
    217			if (!pmd_present(pmde)) {
    218				swp_entry_t entry;
    219
    220				if (!thp_migration_supported() ||
    221				    !(pvmw->flags & PVMW_MIGRATION))
    222					return not_found(pvmw);
    223				entry = pmd_to_swp_entry(pmde);
    224				if (!is_migration_entry(entry) ||
    225				    !check_pmd(swp_offset(entry), pvmw))
    226					return not_found(pvmw);
    227				return true;
    228			}
    229			if (likely(pmd_trans_huge(pmde) || pmd_devmap(pmde))) {
    230				if (pvmw->flags & PVMW_MIGRATION)
    231					return not_found(pvmw);
    232				if (!check_pmd(pmd_pfn(pmde), pvmw))
    233					return not_found(pvmw);
    234				return true;
    235			}
    236			/* THP pmd was split under us: handle on pte level */
    237			spin_unlock(pvmw->ptl);
    238			pvmw->ptl = NULL;
    239		} else if (!pmd_present(pmde)) {
    240			/*
    241			 * If PVMW_SYNC, take and drop THP pmd lock so that we
    242			 * cannot return prematurely, while zap_huge_pmd() has
    243			 * cleared *pmd but not decremented compound_mapcount().
    244			 */
    245			if ((pvmw->flags & PVMW_SYNC) &&
    246			    transparent_hugepage_active(vma) &&
    247			    (pvmw->nr_pages >= HPAGE_PMD_NR)) {
    248				spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
    249
    250				spin_unlock(ptl);
    251			}
    252			step_forward(pvmw, PMD_SIZE);
    253			continue;
    254		}
    255		if (!map_pte(pvmw))
    256			goto next_pte;
    257this_pte:
    258		if (check_pte(pvmw))
    259			return true;
    260next_pte:
    261		do {
    262			pvmw->address += PAGE_SIZE;
    263			if (pvmw->address >= end)
    264				return not_found(pvmw);
    265			/* Did we cross page table boundary? */
    266			if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
    267				if (pvmw->ptl) {
    268					spin_unlock(pvmw->ptl);
    269					pvmw->ptl = NULL;
    270				}
    271				pte_unmap(pvmw->pte);
    272				pvmw->pte = NULL;
    273				goto restart;
    274			}
    275			pvmw->pte++;
    276			if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) {
    277				pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
    278				spin_lock(pvmw->ptl);
    279			}
    280		} while (pte_none(*pvmw->pte));
    281
    282		if (!pvmw->ptl) {
    283			pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
    284			spin_lock(pvmw->ptl);
    285		}
    286		goto this_pte;
    287	} while (pvmw->address < end);
    288
    289	return false;
    290}
    291
    292/**
    293 * page_mapped_in_vma - check whether a page is really mapped in a VMA
    294 * @page: the page to test
    295 * @vma: the VMA to test
    296 *
    297 * Returns 1 if the page is mapped into the page tables of the VMA, 0
    298 * if the page is not mapped into the page tables of this VMA.  Only
    299 * valid for normal file or anonymous VMAs.
    300 */
    301int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
    302{
    303	struct page_vma_mapped_walk pvmw = {
    304		.pfn = page_to_pfn(page),
    305		.nr_pages = 1,
    306		.vma = vma,
    307		.flags = PVMW_SYNC,
    308	};
    309
    310	pvmw.address = vma_address(page, vma);
    311	if (pvmw.address == -EFAULT)
    312		return 0;
    313	if (!page_vma_mapped_walk(&pvmw))
    314		return 0;
    315	page_vma_mapped_walk_done(&pvmw);
    316	return 1;
    317}