[PATCH V7] mm/debug: Add tests validating architecture page table helpers
Christophe Leroy
christophe.leroy at c-s.fr
Tue Oct 22 18:11:07 AEDT 2019
On 10/21/2019 02:42 AM, Anshuman Khandual wrote:
> This adds tests which will validate architecture page table helpers and
> other accessors in their compliance with expected generic MM semantics.
> This will help various architectures in validating changes to existing
> page table helpers or addition of new ones.
>
> This test covers basic page table entry transformations including but not
> limited to old, young, dirty, clean, write, write protect etc at various
> level along with populating intermediate entries with next page table page
> and validating them.
>
> Test page table pages are allocated from system memory with required size
> and alignments. The mapped pfns at page table levels are derived from a
> real pfn representing a valid kernel text symbol. This test gets called
> right after page_alloc_init_late().
>
> This gets build and run when CONFIG_DEBUG_VM_PGTABLE is selected along with
> CONFIG_VM_DEBUG. Architectures willing to subscribe this test also need to
> select CONFIG_ARCH_HAS_DEBUG_VM_PGTABLE which for now is limited to x86 and
> arm64. Going forward, other architectures too can enable this after fixing
> build or runtime problems (if any) with their page table helpers.
>
> Folks interested in making sure that a given platform's page table helpers
> conform to expected generic MM semantics should enable the above config
> which will just trigger this test during boot. Any non conformity here will
> be reported as an warning which would need to be fixed. This test will help
> catch any changes to the agreed upon semantics expected from generic MM and
> enable platforms to accommodate it thereafter.
>
> Cc: Andrew Morton <akpm at linux-foundation.org>
> Cc: Vlastimil Babka <vbabka at suse.cz>
> Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: Mike Rapoport <rppt at linux.vnet.ibm.com>
> Cc: Jason Gunthorpe <jgg at ziepe.ca>
> Cc: Dan Williams <dan.j.williams at intel.com>
> Cc: Peter Zijlstra <peterz at infradead.org>
> Cc: Michal Hocko <mhocko at kernel.org>
> Cc: Mark Rutland <mark.rutland at arm.com>
> Cc: Mark Brown <broonie at kernel.org>
> Cc: Steven Price <Steven.Price at arm.com>
> Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> Cc: Masahiro Yamada <yamada.masahiro at socionext.com>
> Cc: Kees Cook <keescook at chromium.org>
> Cc: Tetsuo Handa <penguin-kernel at i-love.sakura.ne.jp>
> Cc: Matthew Wilcox <willy at infradead.org>
> Cc: Sri Krishna chowdary <schowdary at nvidia.com>
> Cc: Dave Hansen <dave.hansen at intel.com>
> Cc: Russell King - ARM Linux <linux at armlinux.org.uk>
> Cc: Michael Ellerman <mpe at ellerman.id.au>
> Cc: Paul Mackerras <paulus at samba.org>
> Cc: Martin Schwidefsky <schwidefsky at de.ibm.com>
> Cc: Heiko Carstens <heiko.carstens at de.ibm.com>
> Cc: "David S. Miller" <davem at davemloft.net>
> Cc: Vineet Gupta <vgupta at synopsys.com>
> Cc: James Hogan <jhogan at kernel.org>
> Cc: Paul Burton <paul.burton at mips.com>
> Cc: Ralf Baechle <ralf at linux-mips.org>
> Cc: Kirill A. Shutemov <kirill at shutemov.name>
> Cc: Gerald Schaefer <gerald.schaefer at de.ibm.com>
> Cc: Christophe Leroy <christophe.leroy at c-s.fr>
> Cc: Ingo Molnar <mingo at kernel.org>
> Cc: linux-snps-arc at lists.infradead.org
> Cc: linux-mips at vger.kernel.org
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: linux-ia64 at vger.kernel.org
> Cc: linuxppc-dev at lists.ozlabs.org
> Cc: linux-s390 at vger.kernel.org
> Cc: linux-sh at vger.kernel.org
> Cc: sparclinux at vger.kernel.org
> Cc: x86 at kernel.org
> Cc: linux-kernel at vger.kernel.org
>
> Tested-by: Christophe Leroy <christophe.leroy at c-s.fr> #PPC32
> Suggested-by: Catalin Marinas <catalin.marinas at arm.com>
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
> Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>
> Signed-off-by: Anshuman Khandual <anshuman.khandual at arm.com>
> ---
The cover letter have the exact same title as this patch. I think a
cover letter is not necessary for a singleton series.
The history (and any other information you don't want to include in the
commit message) can be added here, below the '---'. That way it is in
the mail but won't be included in the commit.
> .../debug/debug-vm-pgtable/arch-support.txt | 34 ++
> arch/arm64/Kconfig | 1 +
> arch/x86/Kconfig | 1 +
> arch/x86/include/asm/pgtable_64.h | 6 +
> include/asm-generic/pgtable.h | 6 +
> init/main.c | 1 +
> lib/Kconfig.debug | 21 ++
> mm/Makefile | 1 +
> mm/debug_vm_pgtable.c | 388 +++++++++++++++++++++
> 9 files changed, 459 insertions(+)
> create mode 100644 Documentation/features/debug/debug-vm-pgtable/arch-support.txt
> create mode 100644 mm/debug_vm_pgtable.c
>
> diff --git a/Documentation/features/debug/debug-vm-pgtable/arch-support.txt b/Documentation/features/debug/debug-vm-pgtable/arch-support.txt
> new file mode 100644
> index 0000000..d6b8185
> --- /dev/null
> +++ b/Documentation/features/debug/debug-vm-pgtable/arch-support.txt
> @@ -0,0 +1,34 @@
> +#
> +# Feature name: debug-vm-pgtable
> +# Kconfig: ARCH_HAS_DEBUG_VM_PGTABLE
> +# description: arch supports pgtable tests for semantics compliance
> +#
> + -----------------------
> + | arch |status|
> + -----------------------
> + | alpha: | TODO |
> + | arc: | TODO |
> + | arm: | TODO |
> + | arm64: | ok |
> + | c6x: | TODO |
> + | csky: | TODO |
> + | h8300: | TODO |
> + | hexagon: | TODO |
> + | ia64: | TODO |
> + | m68k: | TODO |
> + | microblaze: | TODO |
> + | mips: | TODO |
> + | nds32: | TODO |
> + | nios2: | TODO |
> + | openrisc: | TODO |
> + | parisc: | TODO |
> + | powerpc: | TODO |
Say ok on ppc32
> + | riscv: | TODO |
> + | s390: | TODO |
> + | sh: | TODO |
> + | sparc: | TODO |
> + | um: | TODO |
> + | unicore32: | TODO |
> + | x86: | ok |
> + | xtensa: | TODO |
> + -----------------------
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 1b6ea5a..ea62c87 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -11,6 +11,7 @@ config ARM64
> select ACPI_PPTT if ACPI
> select ARCH_CLOCKSOURCE_DATA
> select ARCH_HAS_DEBUG_VIRTUAL
> + select ARCH_HAS_DEBUG_VM_PGTABLE
> select ARCH_HAS_DEVMEM_IS_ALLOWED
> select ARCH_HAS_DMA_COHERENT_TO_PFN
> select ARCH_HAS_DMA_PREP_COHERENT
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index abe822d..13c9bd9 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -61,6 +61,7 @@ config X86
> select ARCH_CLOCKSOURCE_INIT
> select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
> select ARCH_HAS_DEBUG_VIRTUAL
> + select ARCH_HAS_DEBUG_VM_PGTABLE
> select ARCH_HAS_DEVMEM_IS_ALLOWED
> select ARCH_HAS_ELF_RANDOMIZE
> select ARCH_HAS_FAST_MULTIPLIER
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 3e56c9c2f16e..c50d7cfa566b 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -120,6 +120,7 @@ config PPC
#
select ARCH_32BIT_OFF_T if PPC32
select ARCH_HAS_DEBUG_VIRTUAL
+ select ARCH_HAS_DEBUG_VM_PGTABLE if PPC32
select ARCH_HAS_DEVMEM_IS_ALLOWED
select ARCH_HAS_ELF_RANDOMIZE
select ARCH_HAS_FORTIFY_SOURCE
> diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
> index 0b6c4042..fb0e76d 100644
> --- a/arch/x86/include/asm/pgtable_64.h
> +++ b/arch/x86/include/asm/pgtable_64.h
> @@ -53,6 +53,12 @@ static inline void sync_initial_page_table(void) { }
>
> struct mm_struct;
>
> +#define mm_p4d_folded mm_p4d_folded
> +static inline bool mm_p4d_folded(struct mm_struct *mm)
> +{
> + return !pgtable_l5_enabled();
> +}
> +
> void set_pte_vaddr_p4d(p4d_t *p4d_page, unsigned long vaddr, pte_t new_pte);
> void set_pte_vaddr_pud(pud_t *pud_page, unsigned long vaddr, pte_t new_pte);
>
> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
> index 9cdcbc7..9eb02e1 100644
> --- a/include/asm-generic/pgtable.h
> +++ b/include/asm-generic/pgtable.h
> @@ -1168,6 +1168,12 @@ static inline bool arch_has_pfn_modify_check(void)
> # define PAGE_KERNEL_EXEC PAGE_KERNEL
> #endif
>
> +#ifdef CONFIG_DEBUG_VM_PGTABLE
> +extern void debug_vm_pgtable(void);
> +#else
> +static inline void debug_vm_pgtable(void) { }
> +#endif
> +
> #endif /* !__ASSEMBLY__ */
>
> #ifndef io_remap_pfn_range
> diff --git a/init/main.c b/init/main.c
> index 91f6ebb..af8379e 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1185,6 +1185,7 @@ static noinline void __init kernel_init_freeable(void)
> sched_init_smp();
>
> page_alloc_init_late();
> + debug_vm_pgtable();
> /* Initialize page ext after all struct pages are initialized. */
> page_ext_init();
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 9c60d7d..cf48d95 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -690,6 +690,27 @@ config DEBUG_VM_PGFLAGS
>
> If unsure, say N.
>
> +config ARCH_HAS_DEBUG_VM_PGTABLE
> + bool
> + help
> + An architecture should select this when it can successfully
> + build and run DEBUG_VM_PGTABLE.
> +
> +config DEBUG_VM_PGTABLE
> + bool "Debug arch page table for semantics compliance"
> + depends on MMU
> + depends on DEBUG_VM
> + depends on ARCH_HAS_DEBUG_VM_PGTABLE
> + help
> + This option provides a debug method which can be used to test
> + architecture page table helper functions on various platforms in
> + verifying if they comply with expected generic MM semantics. This
> + will help architecture code in making sure that any changes or
> + new additions of these helpers still conform to expected
> + semantics of the generic MM.
> +
> + If unsure, say N.
> +
Would be nice to have that one also indented like the other
DEBUG_VM_XXXXX (see below).
Stack utilization instrumentation (DEBUG_STACK_USAGE) [N/y/?] n
Debug VM (DEBUG_VM) [N/y/?] (NEW) y
Debug VMA caching (DEBUG_VM_VMACACHE) [N/y/?] (NEW)
Debug VM red-black trees (DEBUG_VM_RB) [N/y/?] (NEW)
Debug page-flags operations (DEBUG_VM_PGFLAGS) [N/y/?] (NEW)
Debug arch page table for semantics compliance (DEBUG_VM_PGTABLE)
[N/y/?] (NEW)
Debug VM translations (DEBUG_VIRTUAL) [N/y/?] n
For that, just move config ARCH_HAS_DEBUG_VM_PGTABLE somewhere else,
maybe before DEBUG_VM or just after DEBUG_VM_PGTABLE
> config ARCH_HAS_DEBUG_VIRTUAL
> bool
>
> diff --git a/mm/Makefile b/mm/Makefile
> index d996846..2f085b9 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -86,6 +86,7 @@ obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o
> obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o
> obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o
> obj-$(CONFIG_DEBUG_RODATA_TEST) += rodata_test.o
> +obj-$(CONFIG_DEBUG_VM_PGTABLE) += debug_vm_pgtable.o
> obj-$(CONFIG_PAGE_OWNER) += page_owner.o
> obj-$(CONFIG_CLEANCACHE) += cleancache.o
> obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> new file mode 100644
> index 0000000..9472566
> --- /dev/null
> +++ b/mm/debug_vm_pgtable.c
> @@ -0,0 +1,388 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * This kernel test validates architecture page table helpers and
> + * accessors and helps in verifying their continued compliance with
> + * expected generic MM semantics.
> + *
> + * Copyright (C) 2019 ARM Ltd.
> + *
> + * Author: Anshuman Khandual <anshuman.khandual at arm.com>
> + */
> +#define pr_fmt(fmt) "arch_pgtable_test: %s " fmt, __func__
> +
> +#include <linux/gfp.h>
> +#include <linux/highmem.h>
> +#include <linux/hugetlb.h>
> +#include <linux/kernel.h>
> +#include <linux/kconfig.h>
> +#include <linux/mm.h>
> +#include <linux/mman.h>
> +#include <linux/mm_types.h>
> +#include <linux/module.h>
> +#include <linux/pfn_t.h>
> +#include <linux/printk.h>
> +#include <linux/random.h>
> +#include <linux/spinlock.h>
> +#include <linux/swap.h>
> +#include <linux/swapops.h>
> +#include <linux/start_kernel.h>
> +#include <linux/sched/mm.h>
> +#include <asm/pgalloc.h>
> +#include <asm/pgtable.h>
> +
> +/*
> + * Basic operations
> + *
> + * mkold(entry) = An old and not a young entry
> + * mkyoung(entry) = A young and not an old entry
> + * mkdirty(entry) = A dirty and not a clean entry
> + * mkclean(entry) = A clean and not a dirty entry
> + * mkwrite(entry) = A write and not a write protected entry
> + * wrprotect(entry) = A write protected and not a write entry
> + * pxx_bad(entry) = A mapped and non-table entry
> + * pxx_same(entry1, entry2) = Both entries hold the exact same value
> + */
> +#define VMFLAGS (VM_READ|VM_WRITE|VM_EXEC)
> +
> +/*
> + * On s390 platform, the lower 12 bits are used to identify given page table
> + * entry type and for other arch specific requirements. But these bits might
> + * affect the ability to clear entries with pxx_clear(). So while loading up
> + * the entries skip all lower 12 bits in order to accommodate s390 platform.
> + * It does not have affect any other platform.
> + */
> +#define RANDOM_ORVALUE (0xfffffffffffff000UL)
> +#define RANDOM_NZVALUE (0xff)
> +
> +static void __init pte_basic_tests(unsigned long pfn, pgprot_t prot)
> +{
> + pte_t pte = pfn_pte(pfn, prot);
> +
> + WARN_ON(!pte_same(pte, pte));
> + WARN_ON(!pte_young(pte_mkyoung(pte)));
> + WARN_ON(!pte_dirty(pte_mkdirty(pte)));
> + WARN_ON(!pte_write(pte_mkwrite(pte)));
> + WARN_ON(pte_young(pte_mkold(pte)));
> + WARN_ON(pte_dirty(pte_mkclean(pte)));
> + WARN_ON(pte_write(pte_wrprotect(pte)));
> +}
> +
> +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE
> +static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot)
> +{
> + pmd_t pmd = pfn_pmd(pfn, prot);
> +
> + WARN_ON(!pmd_same(pmd, pmd));
> + WARN_ON(!pmd_young(pmd_mkyoung(pmd)));
> + WARN_ON(!pmd_dirty(pmd_mkdirty(pmd)));
> + WARN_ON(!pmd_write(pmd_mkwrite(pmd)));
> + WARN_ON(pmd_young(pmd_mkold(pmd)));
> + WARN_ON(pmd_dirty(pmd_mkclean(pmd)));
> + WARN_ON(pmd_write(pmd_wrprotect(pmd)));
> + /*
> + * A huge page does not point to next level page table
> + * entry. Hence this must qualify as pmd_bad().
> + */
> + WARN_ON(!pmd_bad(pmd_mkhuge(pmd)));
> +}
> +#else
> +static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot) { }
> +#endif
> +
> +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
> +static void __init pud_basic_tests(unsigned long pfn, pgprot_t prot)
> +{
> + pud_t pud = pfn_pud(pfn, prot);
> +
> + WARN_ON(!pud_same(pud, pud));
> + WARN_ON(!pud_young(pud_mkyoung(pud)));
> + WARN_ON(!pud_write(pud_mkwrite(pud)));
> + WARN_ON(pud_write(pud_wrprotect(pud)));
> + WARN_ON(pud_young(pud_mkold(pud)));
> +
> + if (mm_pmd_folded(mm) || __is_defined(ARCH_HAS_4LEVEL_HACK))
> + return;
> +
> + /*
> + * A huge page does not point to next level page table
> + * entry. Hence this must qualify as pud_bad().
> + */
> + WARN_ON(!pud_bad(pud_mkhuge(pud)));
> +}
> +#else
> +static void __init pud_basic_tests(unsigned long pfn, pgprot_t prot) { }
> +#endif
> +
> +static void __init p4d_basic_tests(unsigned long pfn, pgprot_t prot)
> +{
> + p4d_t p4d;
> +
> + memset(&p4d, RANDOM_NZVALUE, sizeof(p4d_t));
> + WARN_ON(!p4d_same(p4d, p4d));
> +}
> +
> +static void __init pgd_basic_tests(unsigned long pfn, pgprot_t prot)
> +{
> + pgd_t pgd;
> +
> + memset(&pgd, RANDOM_NZVALUE, sizeof(pgd_t));
> + WARN_ON(!pgd_same(pgd, pgd));
> +}
> +
> +#ifndef __ARCH_HAS_4LEVEL_HACK
> +static void __init pud_clear_tests(struct mm_struct *mm, pud_t *pudp)
> +{
> + pud_t pud = READ_ONCE(*pudp);
> +
> + if (mm_pmd_folded(mm))
> + return;
> +
> + pud = __pud(pud_val(pud) | RANDOM_ORVALUE);
> + WRITE_ONCE(*pudp, pud);
> + pud_clear(pudp);
> + pud = READ_ONCE(*pudp);
> + WARN_ON(!pud_none(pud));
> +}
> +
> +static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp,
> + pmd_t *pmdp)
> +{
> + pud_t pud;
> +
> + if (mm_pmd_folded(mm))
> + return;
> + /*
> + * This entry points to next level page table page.
> + * Hence this must not qualify as pud_bad().
> + */
> + pmd_clear(pmdp);
> + pud_clear(pudp);
> + pud_populate(mm, pudp, pmdp);
> + pud = READ_ONCE(*pudp);
> + WARN_ON(pud_bad(pud));
> +}
> +#else
> +static void __init pud_clear_tests(struct mm_struct *mm, pud_t *pudp) { }
> +static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp,
> + pmd_t *pmdp)
> +{
> +}
> +#endif
> +
> +#ifndef __ARCH_HAS_5LEVEL_HACK
> +static void __init p4d_clear_tests(struct mm_struct *mm, p4d_t *p4dp)
> +{
> + p4d_t p4d = READ_ONCE(*p4dp);
> +
> + if (mm_pud_folded(mm))
> + return;
> +
> + p4d = __p4d(p4d_val(p4d) | RANDOM_ORVALUE);
> + WRITE_ONCE(*p4dp, p4d);
> + p4d_clear(p4dp);
> + p4d = READ_ONCE(*p4dp);
> + WARN_ON(!p4d_none(p4d));
> +}
> +
> +static void __init p4d_populate_tests(struct mm_struct *mm, p4d_t *p4dp,
> + pud_t *pudp)
> +{
> + p4d_t p4d;
> +
> + if (mm_pud_folded(mm))
> + return;
> +
> + /*
> + * This entry points to next level page table page.
> + * Hence this must not qualify as p4d_bad().
> + */
> + pud_clear(pudp);
> + p4d_clear(p4dp);
> + p4d_populate(mm, p4dp, pudp);
> + p4d = READ_ONCE(*p4dp);
> + WARN_ON(p4d_bad(p4d));
> +}
> +
> +static void __init pgd_clear_tests(struct mm_struct *mm, pgd_t *pgdp)
> +{
> + pgd_t pgd = READ_ONCE(*pgdp);
> +
> + if (mm_p4d_folded(mm))
> + return;
> +
> + pgd = __pgd(pgd_val(pgd) | RANDOM_ORVALUE);
> + WRITE_ONCE(*pgdp, pgd);
> + pgd_clear(pgdp);
> + pgd = READ_ONCE(*pgdp);
> + WARN_ON(!pgd_none(pgd));
> +}
> +
> +static void __init pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp,
> + p4d_t *p4dp)
> +{
> + pgd_t pgd;
> +
> + if (mm_p4d_folded(mm))
> + return;
> +
> + /*
> + * This entry points to next level page table page.
> + * Hence this must not qualify as pgd_bad().
> + */
> + p4d_clear(p4dp);
> + pgd_clear(pgdp);
> + pgd_populate(mm, pgdp, p4dp);
> + pgd = READ_ONCE(*pgdp);
> + WARN_ON(pgd_bad(pgd));
> +}
> +#else
> +static void __init p4d_clear_tests(struct mm_struct *mm, p4d_t *p4dp) { }
> +static void __init pgd_clear_tests(struct mm_struct *mm, pgd_t *pgdp) { }
> +static void __init p4d_populate_tests(struct mm_struct *mm, p4d_t *p4dp,
> + pud_t *pudp)
> +{
> +}
> +static void __init pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp,
> + p4d_t *p4dp)
> +{
> +}
> +#endif
> +
> +static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep)
> +{
> + pte_t pte = READ_ONCE(*ptep);
> +
> + pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
> + WRITE_ONCE(*ptep, pte);
> + pte_clear(mm, 0, ptep);
> + pte = READ_ONCE(*ptep);
> + WARN_ON(!pte_none(pte));
> +}
> +
> +static void __init pmd_clear_tests(struct mm_struct *mm, pmd_t *pmdp)
> +{
> + pmd_t pmd = READ_ONCE(*pmdp);
> +
> + pmd = __pmd(pmd_val(pmd) | RANDOM_ORVALUE);
> + WRITE_ONCE(*pmdp, pmd);
> + pmd_clear(pmdp);
> + pmd = READ_ONCE(*pmdp);
> + WARN_ON(!pmd_none(pmd));
> +}
> +
> +static void __init pmd_populate_tests(struct mm_struct *mm, pmd_t *pmdp,
> + pgtable_t pgtable)
> +{
> + pmd_t pmd;
> +
> + /*
> + * This entry points to next level page table page.
> + * Hence this must not qualify as pmd_bad().
> + */
> + pmd_clear(pmdp);
> + pmd_populate(mm, pmdp, pgtable);
> + pmd = READ_ONCE(*pmdp);
> + WARN_ON(pmd_bad(pmd));
> +}
> +
> +static unsigned long __init get_random_vaddr(void)
> +{
> + unsigned long random_vaddr, random_pages, total_user_pages;
> +
> + total_user_pages = (TASK_SIZE - FIRST_USER_ADDRESS) / PAGE_SIZE;
> +
> + random_pages = get_random_long() % total_user_pages;
> + random_vaddr = FIRST_USER_ADDRESS + random_pages * PAGE_SIZE;
> +
> + WARN_ON((random_vaddr > TASK_SIZE) ||
> + (random_vaddr < FIRST_USER_ADDRESS));
> + return random_vaddr;
> +}
> +
> +void __init debug_vm_pgtable(void)
> +{
> + struct mm_struct *mm;
> + pgd_t *pgdp;
> + p4d_t *p4dp, *saved_p4dp;
> + pud_t *pudp, *saved_pudp;
> + pmd_t *pmdp, *saved_pmdp, pmd;
> + pte_t *ptep;
> + pgtable_t saved_ptep;
> + pgprot_t prot;
> + phys_addr_t paddr;
> + unsigned long vaddr, pte_aligned, pmd_aligned;
> + unsigned long pud_aligned, p4d_aligned, pgd_aligned;
I think an information message would be nice:
diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 9472566b7e53..ed7cc3dfc968 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -313,6 +313,8 @@ void __init debug_vm_pgtable(void)
unsigned long vaddr, pte_aligned, pmd_aligned;
unsigned long pud_aligned, p4d_aligned, pgd_aligned;
+ pr_info("Validating architecture page table helpers\n");
+
prot = vm_get_page_prot(VMFLAGS);
vaddr = get_random_vaddr();
mm = mm_alloc();
Christophe
> +
> + prot = vm_get_page_prot(VMFLAGS);
> + vaddr = get_random_vaddr();
> + mm = mm_alloc();
> + if (!mm) {
> + pr_err("mm_struct allocation failed\n");
> + return;
> + }
> +
> + /*
> + * 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.
> + */
> + WARN_ON(!virt_addr_valid(&start_kernel));
> + paddr = __pa(&start_kernel);
> +
> + pte_aligned = (paddr & PAGE_MASK) >> PAGE_SHIFT;
> + pmd_aligned = (paddr & PMD_MASK) >> PAGE_SHIFT;
> + pud_aligned = (paddr & PUD_MASK) >> PAGE_SHIFT;
> + p4d_aligned = (paddr & P4D_MASK) >> PAGE_SHIFT;
> + pgd_aligned = (paddr & PGDIR_MASK) >> PAGE_SHIFT;
> +
> + pgdp = pgd_offset(mm, vaddr);
> + p4dp = p4d_alloc(mm, pgdp, vaddr);
> + pudp = pud_alloc(mm, p4dp, vaddr);
> + pmdp = pmd_alloc(mm, pudp, vaddr);
> + ptep = pte_alloc_map(mm, pmdp, vaddr);
> +
> + /*
> + * Save all the page table page addresses as the page table
> + * entries will be used for testing with random or garbage
> + * values. These saved addresses will be used for freeing
> + * page table pages.
> + */
> + pmd = READ_ONCE(*pmdp);
> + saved_p4dp = p4d_offset(pgdp, 0UL);
> + saved_pudp = pud_offset(p4dp, 0UL);
> + saved_pmdp = pmd_offset(pudp, 0UL);
> + saved_ptep = pmd_pgtable(pmd);
> +
> + pte_basic_tests(pte_aligned, prot);
> + pmd_basic_tests(pmd_aligned, prot);
> + pud_basic_tests(pud_aligned, prot);
> + p4d_basic_tests(p4d_aligned, prot);
> + pgd_basic_tests(pgd_aligned, prot);
> +
> + pte_clear_tests(mm, ptep);
> + pmd_clear_tests(mm, pmdp);
> + pud_clear_tests(mm, pudp);
> + p4d_clear_tests(mm, p4dp);
> + pgd_clear_tests(mm, pgdp);
> +
> + pte_unmap(ptep);
> +
> + pmd_populate_tests(mm, pmdp, saved_ptep);
> + pud_populate_tests(mm, pudp, saved_pmdp);
> + p4d_populate_tests(mm, p4dp, saved_pudp);
> + pgd_populate_tests(mm, pgdp, saved_p4dp);
> +
> + p4d_free(mm, saved_p4dp);
> + pud_free(mm, saved_pudp);
> + pmd_free(mm, saved_pmdp);
> + pte_free(mm, saved_ptep);
> +
> + mm_dec_nr_puds(mm);
> + mm_dec_nr_pmds(mm);
> + mm_dec_nr_ptes(mm);
> + __mmdrop(mm);
> +}
>
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