[PATCH v2 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args

[Gavin Shan]

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@xxxxxxxxxx>
---
 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;
+		}
+	}
+
+	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);
-- 
2.23.0