From: Gavin Shan <gshan@redhat.com>
To: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org, anshuman.khandual@arm.com,
catalin.marinas@arm.com, will@kernel.org,
akpm@linux-foundation.org, chuhu@redhat.com,
shan.gavin@gmail.com
Subject: Re: [PATCH v2 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args
Date: Mon, 19 Jul 2021 23:01:03 +1000 [thread overview]
Message-ID: <8d754894-5c21-1287-82b6-7ac3b064af3d@redhat.com> (raw)
In-Reply-To: <20210719054138.198373-2-gshan@redhat.com>
On 7/19/21 3:41 PM, Gavin Shan wrote:
> In debug_vm_pgtable(), there are many local variables introduced to
> track the needed information and they are passed to the functions for
> various test cases. It'd better to introduce a struct as place holder
> for these information. With it, what the functions for various test
> cases need is the struct, to simplify the code. It also makes code
> easier to be maintained.
>
> Besides, set_xxx_at() could access the data on the corresponding pages
> in the page table modifying tests. So the accessed pages in the tests
> should have been allocated from buddy. Otherwise, we're accessing pages
> that aren't owned by us. This causes issues like page flag corruption.
>
> This introduces "struct pgtable_debug_args". The struct is initialized
> and destroyed, but the information in the struct isn't used yet. They
> will be used in subsequent patches.
>
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
> mm/debug_vm_pgtable.c | 196 +++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 195 insertions(+), 1 deletion(-)
>
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index 1c922691aa61..0cc44e7c166e 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -58,6 +58,36 @@
> #define RANDOM_ORVALUE (GENMASK(BITS_PER_LONG - 1, 0) & ~ARCH_SKIP_MASK)
> #define RANDOM_NZVALUE GENMASK(7, 0)
>
> +struct pgtable_debug_args {
> + struct mm_struct *mm;
> + struct vm_area_struct *vma;
> +
> + pgd_t *pgdp;
> + p4d_t *p4dp;
> + pud_t *pudp;
> + pmd_t *pmdp;
> + pte_t *ptep;
> +
> + p4d_t *start_p4dp;
> + pud_t *start_pudp;
> + pmd_t *start_pmdp;
> + pgtable_t start_ptep;
> +
> + unsigned long vaddr;
> + pgprot_t page_prot;
> + pgprot_t page_prot_none;
> +
> + unsigned long pud_pfn;
> + unsigned long pmd_pfn;
> + unsigned long pte_pfn;
> +
> + unsigned long fixed_pgd_pfn;
> + unsigned long fixed_p4d_pfn;
> + unsigned long fixed_pud_pfn;
> + unsigned long fixed_pmd_pfn;
> + unsigned long fixed_pte_pfn;
> +};
> +
> static void __init pte_basic_tests(unsigned long pfn, int idx)
> {
> pgprot_t prot = protection_map[idx];
> @@ -955,8 +985,166 @@ static unsigned long __init get_random_vaddr(void)
> return random_vaddr;
> }
>
> +static void __init destroy_args(struct pgtable_debug_args *args)
> +{
> + struct page *page = NULL;
> +
> + /* Free (huge) page */
> + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> + IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) &&
> + has_transparent_hugepage() &&
> + args->pud_pfn != ULONG_MAX) {
> + page = pfn_to_page(args->pud_pfn);
> + __free_pages(page, HPAGE_PUD_SHIFT - PAGE_SHIFT);
> + } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> + has_transparent_hugepage() &&
> + args->pmd_pfn != ULONG_MAX) {
> + page = pfn_to_page(args->pmd_pfn);
> + __free_pages(page, HPAGE_PMD_ORDER);
> + } else if (args->pte_pfn != ULONG_MAX) {
> + page = pfn_to_page(args->pte_pfn);
> + __free_pages(page, 0);
> + }
> +
> + /* Free page table */
> + if (args->start_ptep) {
> + pte_free(args->mm, args->start_ptep);
> + mm_dec_nr_ptes(args->mm);
> + }
> +
> + if (args->start_pmdp) {
> + pmd_free(args->mm, args->start_pmdp);
> + mm_dec_nr_pmds(args->mm);
> + }
> +
> + if (args->start_pudp) {
> + pud_free(args->mm, args->start_pudp);
> + mm_dec_nr_puds(args->mm);
> + }
> +
> + if (args->start_p4dp)
> + p4d_free(args->mm, args->p4dp);
> +
> + /* Free vma and mm struct */
> + if (args->vma)
> + vm_area_free(args->vma);
> + if (args->mm)
> + mmdrop(args->mm);
> +}
> +
> +static int __init init_args(struct pgtable_debug_args *args)
> +{
> + struct page *page = NULL;
> + phys_addr_t phys;
> + int ret = 0;
> +
> + /* Initialize the debugging data */
> + memset(args, 0, sizeof(*args));
> + args->page_prot = vm_get_page_prot(VMFLAGS);
> + args->page_prot_none = __P000;
> + args->pud_pfn = ULONG_MAX;
> + args->pmd_pfn = ULONG_MAX;
> + args->pte_pfn = ULONG_MAX;
> + args->fixed_pgd_pfn = ULONG_MAX;
> + args->fixed_p4d_pfn = ULONG_MAX;
> + args->fixed_pud_pfn = ULONG_MAX;
> + args->fixed_pmd_pfn = ULONG_MAX;
> + args->fixed_pte_pfn = ULONG_MAX;
> +
> + /* Allocate mm and vma */
> + args->mm = mm_alloc();
> + if (!args->mm) {
> + pr_err("Failed to allocate mm struct\n");
> + ret = -ENOMEM;
> + goto error;
> + }
> +
> + args->vma = vm_area_alloc(args->mm);
> + if (!args->vma) {
> + pr_err("Failed to allocate vma\n");
> + ret = -ENOMEM;
> + goto error;
> + }
> +
> + /* Figure out the virtual address and allocate page table entries */
> + args->vaddr = get_random_vaddr();
> + args->pgdp = pgd_offset(args->mm, args->vaddr);
> + args->p4dp = p4d_alloc(args->mm, args->pgdp, args->vaddr);
> + args->pudp = args->p4dp ?
> + pud_alloc(args->mm, args->p4dp, args->vaddr) : NULL;
> + args->pmdp = args->pudp ?
> + pmd_alloc(args->mm, args->pudp, args->vaddr) : NULL;
> + args->ptep = args->pmdp ?
> + pte_alloc_map(args->mm, args->pmdp, args->vaddr) : NULL;
> + if (!args->ptep) {
> + pr_err("Failed to allocate page table\n");
> + ret = -ENOMEM;
> + goto error;
> + }
> +
> + /*
> + * The above page table entries will be modified. Lets save the
> + * page table entries so that they can be released when the tests
> + * are completed.
> + */
> + args->start_p4dp = p4d_offset(args->pgdp, 0UL);
> + args->start_pudp = pud_offset(args->p4dp, 0UL);
> + args->start_pmdp = pmd_offset(args->pudp, 0UL);
> + args->start_ptep = pmd_pgtable(READ_ONCE(*(args->pmdp)));
> +
> + /*
> + * Figure out the fixed addresses, which are all around the kernel
> + * symbol (@start_kernel). The corresponding PFNs might be invalid,
> + * but it's fine as the following tests won't access the pages.
> + */
> + phys = __pa_symbol(&start_kernel);
> + args->fixed_pgd_pfn = __phys_to_pfn(phys & PGDIR_MASK);
> + args->fixed_p4d_pfn = __phys_to_pfn(phys & P4D_MASK);
> + args->fixed_pud_pfn = __phys_to_pfn(phys & PUD_MASK);
> + args->fixed_pmd_pfn = __phys_to_pfn(phys & PMD_MASK);
> + args->fixed_pte_pfn = __phys_to_pfn(phys & PAGE_MASK);
> +
> + /*
> + * Allocate (huge) pages because some of the tests need to access
> + * the data in the pages. The corresponding tests will be skipped
> + * if we fail to allocate (huge) pages.
> + */
> + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> + IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) &&
> + has_transparent_hugepage()) {
> + page = alloc_pages(GFP_KERNEL, HPAGE_PUD_SHIFT - PAGE_SHIFT);
> + if (page) {
> + args->pud_pfn = page_to_pfn(page);
> + args->pmd_pfn = args->pud_pfn;
> + args->pte_pfn = args->pud_pfn;
> + return 0;
> + }
> + }
> +
> + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> + has_transparent_hugepage()) {
> + page = alloc_pages(GFP_KERNEL, HPAGE_PMD_ORDER);
> + if (page) {
> + args->pmd_pfn = page_to_pfn(page);
> + args->pte_pfn = args->pmd_pfn;
> + return 0;
> + }
> + }
> +
As syzbot reported against v1 series, we could allocate pages larger than (1 << (MAX_ORDER - 1)) here.
So __GFP_NOWARN is needed here. I will fix it in v3 series.
> + page = alloc_pages(GFP_KERNEL, 0);
> + if (page)
> + args->pte_pfn = page_to_pfn(page);
> +
> + return 0;
> +
> +error:
> + destroy_args(args);
> + return ret;
> +}
> +
> static int __init debug_vm_pgtable(void)
> {
> + struct pgtable_debug_args args;
> struct vm_area_struct *vma;
> struct mm_struct *mm;
> pgd_t *pgdp;
> @@ -970,9 +1158,13 @@ static int __init debug_vm_pgtable(void)
> unsigned long vaddr, pte_aligned, pmd_aligned;
> unsigned long pud_aligned, p4d_aligned, pgd_aligned;
> spinlock_t *ptl = NULL;
> - int idx;
> + int idx, ret;
>
> pr_info("Validating architecture page table helpers\n");
> + ret = init_args(&args);
> + if (ret)
> + return ret;
> +
> prot = vm_get_page_prot(VMFLAGS);
> vaddr = get_random_vaddr();
> mm = mm_alloc();
> @@ -1127,6 +1319,8 @@ static int __init debug_vm_pgtable(void)
> mm_dec_nr_pmds(mm);
> mm_dec_nr_ptes(mm);
> mmdrop(mm);
> +
> + destroy_args(&args);
> return 0;
> }
> late_initcall(debug_vm_pgtable);
>
Thanks,
Gavin
next prev parent reply other threads:[~2021-07-19 13:00 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-19 5:41 [PATCH v2 00/12] mm/debug_vm_pgtable: Enhancements Gavin Shan
2021-07-19 5:41 ` [PATCH v2 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args Gavin Shan
2021-07-19 13:01 ` Gavin Shan [this message]
2021-07-20 6:42 ` Anshuman Khandual
2021-07-20 23:29 ` Gavin Shan
2021-07-21 4:50 ` Anshuman Khandual
2021-07-21 12:09 ` Gavin Shan
2021-07-19 5:41 ` [PATCH v2 02/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in basic tests Gavin Shan
2021-07-19 5:41 ` [PATCH v2 03/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in leaf and savewrite tests Gavin Shan
2021-07-19 5:41 ` [PATCH v2 04/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in protnone and devmap tests Gavin Shan
2021-07-19 5:41 ` [PATCH v2 05/12] mm/vm_debug_pgtable: Use struct pgtable_debug_args in soft_dirty and swap tests Gavin Shan
2021-07-19 5:41 ` [PATCH v2 06/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in migration and thp tests Gavin Shan
2021-07-19 5:41 ` [PATCH v2 07/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PTE modifying tests Gavin Shan
2021-07-19 5:41 ` [PATCH v2 08/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PMD Gavin Shan
2021-07-19 5:41 ` [PATCH v2 09/12] mm/vm_debug_pgtable: Use struct pgtable_debug_args in PUD modifying tests Gavin Shan
2021-07-19 9:13 ` kernel test robot
2021-07-19 11:30 ` Gavin Shan
2021-07-20 2:46 ` kernel test robot
2021-07-20 23:09 ` Gavin Shan
2021-07-19 5:41 ` [PATCH v2 10/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PGD and P4D " Gavin Shan
2021-07-19 5:41 ` [PATCH v2 11/12] mm/debug_vm_pgtable: Remove unused code Gavin Shan
2021-07-19 5:41 ` [PATCH v2 12/12] mm/debug_vm_pgtable: Fix corrupted page flag Gavin Shan
2021-07-19 11:34 ` [PATCH v2 00/12] mm/debug_vm_pgtable: Enhancements Gavin Shan
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