On 8/2/21 11:34 AM, 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 tests functions need is the
> struct. In this way, the code is simplified and 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
> or kernel crash on accessing unmapped page when CONFIG_DEBUG_PAGEALLOC
> is enabled.
>
> This introduces "struct pgtable_debug_args". The struct is initialized
> and destroyed, but the information in the struct isn't used yet. It will
> be used in subsequent patches.
>
> Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
> Reviewed-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
> mm/debug_vm_pgtable.c | 269 +++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 268 insertions(+), 1 deletion(-)
>
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index 1c922691aa61..6a825f0e7cd7 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -58,6 +58,37 @@
> #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;
> +
> + bool is_contiguous_page;
> + 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 +986,238 @@ 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) {
> + if (args->is_contiguous_page) {
> + free_contig_range(args->pud_pfn,
> + (1 << (HPAGE_PUD_SHIFT - PAGE_SHIFT)));
> + } else {
> + page = pfn_to_page(args->pud_pfn);
> + __free_pages(page, HPAGE_PUD_SHIFT - PAGE_SHIFT);
> + }
> +
> + args->pud_pfn = ULONG_MAX;
> + args->pmd_pfn = ULONG_MAX;
> + args->pte_pfn = ULONG_MAX;
> + }
> +
> + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> + has_transparent_hugepage() &&
> + args->pmd_pfn != ULONG_MAX) {
> + if (args->is_contiguous_page) {
> + free_contig_range(args->pmd_pfn, (1 << HPAGE_PMD_ORDER));
> + } else {
> + page = pfn_to_page(args->pmd_pfn);
> + __free_pages(page, HPAGE_PMD_ORDER);
> + }
> +
> + args->pmd_pfn = ULONG_MAX;
> + args->pte_pfn = ULONG_MAX;
> + }
> +
> + if (args->pte_pfn != ULONG_MAX) {
> + page = pfn_to_page(args->pte_pfn);
> + __free_pages(page, 0);
args->pte_pfn = ULONG_MAX ?
> + }
> +
> + /* Free page table entries */
> + 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->start_p4dp);
> +
> + /* Free vma and mm struct */
> + if (args->vma)
> + vm_area_free(args->vma);
> +
> + if (args->mm)
> + mmdrop(args->mm);
> +}
> +
> +static struct page * __init debug_vm_pgtable_alloc_huge_page(
> + struct pgtable_debug_args *args, int order)
Small nit, formatting like below would have been better. But dont change yet
unless there is a respin.
static struct page * __init
debug_vm_pgtable_alloc_huge_page(struct pgtable_debug_args *args, int order)
> +{
> + struct page *page = NULL;
> +
> +#ifdef CONFIG_CONTIG_ALLOC
> + if (order >= MAX_ORDER) {
> + page = alloc_contig_pages((1 << order), GFP_KERNEL,
> + first_online_node, NULL);
> + if (page) {
> + args->is_contiguous_page = true;
> + return page;
> + }
> + }
> +#endif
> +
> + if (order < MAX_ORDER)
> + page = alloc_pages(GFP_KERNEL, order);
> +
> + return page;
> +}
> +
> +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.
> + *
> + * __P000 (or even __S000) will help create page table entries with
> + * PROT_NONE permission as required for pxx_protnone_tests().
> + */
> + memset(args, 0, sizeof(*args));
> + args->vaddr = get_random_vaddr();
> + args->page_prot = vm_get_page_prot(VMFLAGS);
> + args->page_prot_none = __P000;
> + args->is_contiguous_page = false;
> + 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;
> + }
> +
> + /*
> + * Allocate page table entries. They will be modified in the tests.
> + * Lets save the page table entries so that they can be released
> + * when the tests are completed.
> + */
> + args->pgdp = pgd_offset(args->mm, args->vaddr);
> + args->p4dp = p4d_alloc(args->mm, args->pgdp, args->vaddr);
> + args->start_p4dp = p4d_offset(args->pgdp, 0UL);
> + WARN_ON(!args->start_p4dp);
> + if (!args->p4dp) {
> + pr_err("Failed to allocate p4d entries\n");
> + ret = -ENOMEM;
> + goto error;
> + }
Expected like this instead. 'args->start_p4dp' should not be evaluated
unless 'args->p4dp' allocation succeeds. Otherwise on the error path,
it would call p4d_free(args->mm, args->start_p4dp) freeing up a page
table page which was never allocated !
args->pgdp = pgd_offset(args->mm, args->vaddr);
args->p4dp = p4d_alloc(args->mm, args->pgdp, args->vaddr);
if (!args->p4dp) {
pr_err("Failed to allocate p4d entries\n");
ret = -ENOMEM;
goto error;
}
args->start_p4dp = p4d_offset(args->pgdp, 0UL);
WARN_ON(!args->start_p4dp);
I had requested just to move these two sentences into the previous code
block, without changing any order. This is also applicable for all other
page table levels below.
> +
> + args->pudp = pud_alloc(args->mm, args->p4dp, args->vaddr);
> + args->start_pudp = pud_offset(args->p4dp, 0UL);
> + WARN_ON(!args->start_pudp);
> + if (!args->pudp) {
> + pr_err("Failed to allocate pud entries\n");
> + ret = -ENOMEM;
> + goto error;
> + }
> +
> + args->pmdp = pmd_alloc(args->mm, args->pudp, args->vaddr);
> + args->start_pmdp = pmd_offset(args->pudp, 0UL);
> + WARN_ON(!args->start_pmdp);
> + if (!args->pmdp) {
> + pr_err("Failed to allocate pmd entries\n");
> + ret = -ENOMEM;
> + goto error;
> + }
> +
> + args->ptep = pte_alloc_map(args->mm, args->pmdp, args->vaddr);
> + args->start_ptep = pmd_pgtable(READ_ONCE(*args->pmdp));
> + WARN_ON(!args->start_ptep);
> + if (!args->ptep) {
> + pr_err("Failed to allocate pte entries\n");
> + ret = -ENOMEM;
> + goto error;
> + }
> +
> + /*
> + * PFN for mapping at PTE level is determined from a standard kernel
> + * text symbol. But pfns for higher page table levels are derived by
> + * masking lower bits of this real pfn. These derived pfns might not
> + * exist on the platform but that does not really matter as pfn_pxx()
> + * helpers will still create appropriate entries for the test. This
> + * helps avoid large memory block allocations to be used for mapping
> + * at higher page table levels in some of the tests.
> + */
> + 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);
> + WARN_ON(!pfn_valid(args->fixed_pte_pfn));
> +
> + /*
> + * 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 = debug_vm_pgtable_alloc_huge_page(args,
> + 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 = debug_vm_pgtable_alloc_huge_page(args, HPAGE_PMD_ORDER);
> + if (page) {
> + args->pmd_pfn = page_to_pfn(page);
> + args->pte_pfn = args->pmd_pfn;
> + return 0;
> + }
> + }
> +
> + 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 +1231,13 @@ 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 +1392,8 @@ 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);
>
