From: Anshuman Khandual anshuman.khandual@arm.com
[ Upstream commit bb5c47ced46797409f4791d0380db3116d93134c ]
Patch series "mm/debug_vm_pgtable: Some minor updates", v3.
This series contains some cleanups and new test suggestions from Catalin from an earlier discussion.
https://lore.kernel.org/linux-mm/20201123142237.GF17833@gaia/
This patch (of 2):
This adds validation tests for dirtiness after write protect conversion for each page table level. There are two new separate test types involved here.
The first test ensures that a given page table entry does not become dirty after pxx_wrprotect(). This is important for platforms like arm64 which transfers and drops the hardware dirty bit (!PTE_RDONLY) to the software dirty bit while making it an write protected one. This test ensures that no fresh page table entry could be created with hardware dirty bit set. The second test ensures that a given page table entry always preserve the dirty information across pxx_wrprotect().
This adds two previously missing PUD level basic tests and while here fixes pxx_wrprotect() related typos in the documentation file.
Link: https://lkml.kernel.org/r/1611137241-26220-1-git-send-email-anshuman.khandua... Link: https://lkml.kernel.org/r/1611137241-26220-2-git-send-email-anshuman.khandua... Signed-off-by: Anshuman Khandual anshuman.khandual@arm.com Suggested-by: Catalin Marinas catalin.marinas@arm.com Tested-by: Gerald Schaefer gerald.schaefer@de.ibm.com [s390] Cc: Christophe Leroy christophe.leroy@csgroup.eu Cc: Gerald Schaefer gerald.schaefer@linux.ibm.com Cc: Vineet Gupta vgupta@synopsys.com Cc: Paul Walmsley paul.walmsley@sifive.com Cc: Steven Price steven.price@arm.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- Documentation/vm/arch_pgtable_helpers.rst | 8 ++--- mm/debug_vm_pgtable.c | 39 +++++++++++++++++++++++ 2 files changed, 43 insertions(+), 4 deletions(-)
diff --git a/Documentation/vm/arch_pgtable_helpers.rst b/Documentation/vm/arch_pgtable_helpers.rst index f3591ee3aaa8..552567d863b8 100644 --- a/Documentation/vm/arch_pgtable_helpers.rst +++ b/Documentation/vm/arch_pgtable_helpers.rst @@ -50,7 +50,7 @@ PTE Page Table Helpers +---------------------------+--------------------------------------------------+ | pte_mkwrite | Creates a writable PTE | +---------------------------+--------------------------------------------------+ -| pte_mkwrprotect | Creates a write protected PTE | +| pte_wrprotect | Creates a write protected PTE | +---------------------------+--------------------------------------------------+ | pte_mkspecial | Creates a special PTE | +---------------------------+--------------------------------------------------+ @@ -120,7 +120,7 @@ PMD Page Table Helpers +---------------------------+--------------------------------------------------+ | pmd_mkwrite | Creates a writable PMD | +---------------------------+--------------------------------------------------+ -| pmd_mkwrprotect | Creates a write protected PMD | +| pmd_wrprotect | Creates a write protected PMD | +---------------------------+--------------------------------------------------+ | pmd_mkspecial | Creates a special PMD | +---------------------------+--------------------------------------------------+ @@ -186,7 +186,7 @@ PUD Page Table Helpers +---------------------------+--------------------------------------------------+ | pud_mkwrite | Creates a writable PUD | +---------------------------+--------------------------------------------------+ -| pud_mkwrprotect | Creates a write protected PUD | +| pud_wrprotect | Creates a write protected PUD | +---------------------------+--------------------------------------------------+ | pud_mkdevmap | Creates a ZONE_DEVICE mapped PUD | +---------------------------+--------------------------------------------------+ @@ -224,7 +224,7 @@ HugeTLB Page Table Helpers +---------------------------+--------------------------------------------------+ | huge_pte_mkwrite | Creates a writable HugeTLB | +---------------------------+--------------------------------------------------+ -| huge_pte_mkwrprotect | Creates a write protected HugeTLB | +| huge_pte_wrprotect | Creates a write protected HugeTLB | +---------------------------+--------------------------------------------------+ | huge_ptep_get_and_clear | Clears a HugeTLB | +---------------------------+--------------------------------------------------+ diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c index 750bfef26be3..79480fd18443 100644 --- a/mm/debug_vm_pgtable.c +++ b/mm/debug_vm_pgtable.c @@ -63,6 +63,16 @@ static void __init pte_basic_tests(unsigned long pfn, pgprot_t prot) pte_t pte = pfn_pte(pfn, prot);
pr_debug("Validating PTE basic\n"); + + /* + * This test needs to be executed after the given page table entry + * is created with pfn_pte() to make sure that protection_map[idx] + * does not have the dirty bit enabled from the beginning. This is + * important for platforms like arm64 where (!PTE_RDONLY) indicate + * dirty bit being set. + */ + WARN_ON(pte_dirty(pte_wrprotect(pte))); + WARN_ON(!pte_same(pte, pte)); WARN_ON(!pte_young(pte_mkyoung(pte_mkold(pte)))); WARN_ON(!pte_dirty(pte_mkdirty(pte_mkclean(pte)))); @@ -70,6 +80,8 @@ static void __init pte_basic_tests(unsigned long pfn, pgprot_t prot) WARN_ON(pte_young(pte_mkold(pte_mkyoung(pte)))); WARN_ON(pte_dirty(pte_mkclean(pte_mkdirty(pte)))); WARN_ON(pte_write(pte_wrprotect(pte_mkwrite(pte)))); + WARN_ON(pte_dirty(pte_wrprotect(pte_mkclean(pte)))); + WARN_ON(!pte_dirty(pte_wrprotect(pte_mkdirty(pte)))); }
static void __init pte_advanced_tests(struct mm_struct *mm, @@ -137,6 +149,17 @@ static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot) return;
pr_debug("Validating PMD basic\n"); + + /* + * This test needs to be executed after the given page table entry + * is created with pfn_pmd() to make sure that protection_map[idx] + * does not have the dirty bit enabled from the beginning. This is + * important for platforms like arm64 where (!PTE_RDONLY) indicate + * dirty bit being set. + */ + WARN_ON(pmd_dirty(pmd_wrprotect(pmd))); + + WARN_ON(!pmd_same(pmd, pmd)); WARN_ON(!pmd_young(pmd_mkyoung(pmd_mkold(pmd)))); WARN_ON(!pmd_dirty(pmd_mkdirty(pmd_mkclean(pmd)))); @@ -144,6 +167,8 @@ static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot) WARN_ON(pmd_young(pmd_mkold(pmd_mkyoung(pmd)))); WARN_ON(pmd_dirty(pmd_mkclean(pmd_mkdirty(pmd)))); WARN_ON(pmd_write(pmd_wrprotect(pmd_mkwrite(pmd)))); + WARN_ON(pmd_dirty(pmd_wrprotect(pmd_mkclean(pmd)))); + WARN_ON(!pmd_dirty(pmd_wrprotect(pmd_mkdirty(pmd)))); /* * A huge page does not point to next level page table * entry. Hence this must qualify as pmd_bad(). @@ -257,11 +282,25 @@ static void __init pud_basic_tests(unsigned long pfn, pgprot_t prot) return;
pr_debug("Validating PUD basic\n"); + + /* + * This test needs to be executed after the given page table entry + * is created with pfn_pud() to make sure that protection_map[idx] + * does not have the dirty bit enabled from the beginning. This is + * important for platforms like arm64 where (!PTE_RDONLY) indicate + * dirty bit being set. + */ + WARN_ON(pud_dirty(pud_wrprotect(pud))); + WARN_ON(!pud_same(pud, pud)); WARN_ON(!pud_young(pud_mkyoung(pud_mkold(pud)))); + WARN_ON(!pud_dirty(pud_mkdirty(pud_mkclean(pud)))); + WARN_ON(pud_dirty(pud_mkclean(pud_mkdirty(pud)))); WARN_ON(!pud_write(pud_mkwrite(pud_wrprotect(pud)))); WARN_ON(pud_write(pud_wrprotect(pud_mkwrite(pud)))); WARN_ON(pud_young(pud_mkold(pud_mkyoung(pud)))); + WARN_ON(pud_dirty(pud_wrprotect(pud_mkclean(pud)))); + WARN_ON(!pud_dirty(pud_wrprotect(pud_mkdirty(pud))));
if (mm_pmd_folded(mm)) return;