From f61c5ba2885eabc7bc4b0b2f5232f475216ba446 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 17 Sep 2018 16:29:14 +0200 Subject: [PATCH] x86/mm/cpa: Add sanity check for existing mappings With the range check it is possible to do a quick verification that the current mapping is correct vs. the static protection areas. In case a incorrect mapping is detected a warning is emitted and the large page is split up. If the large page is a 2M page, then the split code is forced to check the static protections for the PTE entries to fix up the incorrectness. For 1G pages this can't be done easily because that would require to either find the offending 2M areas before the split or afterwards. For now just warn about that case and revisit it when reported. Signed-off-by: Thomas Gleixner Reviewed-by: Dave Hansen Cc: Peter Zijlstra Cc: Bin Yang Cc: Mark Gross Link: https://lkml.kernel.org/r/20180917143546.331408643@linutronix.de --- arch/x86/mm/pageattr.c | 77 ++++++++++++++++++++++++++++++++++++------ 1 file changed, 67 insertions(+), 10 deletions(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 8f9083eb21ac..19781b0ab4b4 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -37,12 +37,14 @@ struct cpa_data { unsigned long numpages; int flags; unsigned long pfn; - unsigned force_split : 1; + unsigned force_split : 1, + force_static_prot : 1; int curpage; struct page **pages; }; enum cpa_warn { + CPA_CONFLICT, CPA_PROTECT, CPA_DETECT, }; @@ -501,6 +503,7 @@ static inline void check_conflict(int warnlvl, pgprot_t prot, pgprotval_t val, unsigned long pfn, const char *txt) { static const char *lvltxt[] = { + [CPA_CONFLICT] = "conflict", [CPA_PROTECT] = "protect", [CPA_DETECT] = "detect", }; @@ -743,7 +746,7 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address, struct cpa_data *cpa) { unsigned long numpages, pmask, psize, lpaddr, addr, pfn, old_pfn; - pgprot_t old_prot, new_prot, req_prot; + pgprot_t old_prot, new_prot, req_prot, chk_prot; pte_t new_pte, old_pte, *tmp; enum pg_level level; int i; @@ -819,6 +822,23 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address, lpaddr = address & pmask; numpages = psize >> PAGE_SHIFT; + /* + * Sanity check that the existing mapping is correct versus the static + * protections. static_protections() guards against !PRESENT, so no + * extra conditional required here. + */ + chk_prot = static_protections(old_prot, lpaddr, old_pfn, numpages, + CPA_CONFLICT); + + if (WARN_ON_ONCE(pgprot_val(chk_prot) != pgprot_val(old_prot))) { + /* + * Split the large page and tell the split code to + * enforce static protections. + */ + cpa->force_static_prot = 1; + return 1; + } + /* * Make sure that the requested pgprot does not violate the static * protections. Check the full large page whether one of the pages @@ -828,8 +848,8 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address, new_prot = static_protections(req_prot, address, pfn, 1, CPA_DETECT); pfn = old_pfn; for (i = 0, addr = lpaddr; i < numpages; i++, addr += PAGE_SIZE, pfn++) { - pgprot_t chk_prot = static_protections(req_prot, addr, pfn, 1, - CPA_DETECT); + chk_prot = static_protections(req_prot, addr, pfn, 1, + CPA_DETECT); cpa_inc_4k_checked(); if (pgprot_val(chk_prot) != pgprot_val(new_prot)) return 1; @@ -871,15 +891,50 @@ static int should_split_large_page(pte_t *kpte, unsigned long address, return do_split; } +static void split_set_pte(struct cpa_data *cpa, pte_t *pte, unsigned long pfn, + pgprot_t ref_prot, unsigned long address, + unsigned long size) +{ + unsigned int npg = PFN_DOWN(size); + pgprot_t prot; + + /* + * If should_split_large_page() discovered an inconsistent mapping, + * remove the invalid protection in the split mapping. + */ + if (!cpa->force_static_prot) + goto set; + + prot = static_protections(ref_prot, address, pfn, npg, CPA_PROTECT); + + if (pgprot_val(prot) == pgprot_val(ref_prot)) + goto set; + + /* + * If this is splitting a PMD, fix it up. PUD splits cannot be + * fixed trivially as that would require to rescan the newly + * installed PMD mappings after returning from split_large_page() + * so an eventual further split can allocate the necessary PTE + * pages. Warn for now and revisit it in case this actually + * happens. + */ + if (size == PAGE_SIZE) + ref_prot = prot; + else + pr_warn_once("CPA: Cannot fixup static protections for PUD split\n"); +set: + set_pte(pte, pfn_pte(pfn, ref_prot)); +} + static int __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address, struct page *base) { + unsigned long lpaddr, lpinc, ref_pfn, pfn, pfninc = 1; pte_t *pbase = (pte_t *)page_address(base); - unsigned long ref_pfn, pfn, pfninc = 1; unsigned int i, level; - pte_t *tmp; pgprot_t ref_prot; + pte_t *tmp; spin_lock(&pgd_lock); /* @@ -902,15 +957,17 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address, * PAT bit to correct position. */ ref_prot = pgprot_large_2_4k(ref_prot); - ref_pfn = pmd_pfn(*(pmd_t *)kpte); + lpaddr = address & PMD_MASK; + lpinc = PAGE_SIZE; break; case PG_LEVEL_1G: ref_prot = pud_pgprot(*(pud_t *)kpte); ref_pfn = pud_pfn(*(pud_t *)kpte); pfninc = PMD_PAGE_SIZE >> PAGE_SHIFT; - + lpaddr = address & PUD_MASK; + lpinc = PMD_SIZE; /* * Clear the PSE flags if the PRESENT flag is not set * otherwise pmd_present/pmd_huge will return true @@ -931,8 +988,8 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address, * Get the target pfn from the original entry: */ pfn = ref_pfn; - for (i = 0; i < PTRS_PER_PTE; i++, pfn += pfninc) - set_pte(&pbase[i], pfn_pte(pfn, ref_prot)); + for (i = 0; i < PTRS_PER_PTE; i++, pfn += pfninc, lpaddr += lpinc) + split_set_pte(cpa, pbase + i, pfn, ref_prot, lpaddr, lpinc); if (virt_addr_valid(address)) { unsigned long pfn = PFN_DOWN(__pa(address));