[PATCH v17 00/23] Generic page walk and ptdump

[PATCH v17 00/23] Generic page walk and ptdump

[Steven Price]

This version is two patches lighter than v16:
 mm: pagewalk: Add test_p?d callbacks
 x86: mm: Convert ptdump_walk_pgd_level_core() to take an mm_struct

There is a new enum page_walk_action in struct mm_walk which allows the
callbacks to decide whether to recurse (ACTION_SUBTREE - the default),
skip (ACTION_CONTINUE) or to be called again (ACTION_AGAIN). These are
introduced in patch 11 and used for hmm.c to adapt it to the new
behaviour of the pud_entry() callback.

The new page_walk_action means that we no longer need to test_p?d()
callbacks as the p?d_entry() callbacks can simply return ACTION_CONTINUE
to skip parts of the tree.

The x86 patch is dropped because I've updated patch 20 to always use a
'fake_mm' structure which simplifies the code and avoids issues with
potentially double locking the mmap_sem of the real mm.

Previous description for the series
-----------------------------------

Many architectures current have a debugfs file for dumping the kernel
page tables. Currently each architecture has to implement custom
functions for this because the details of walking the page tables used
by the kernel are different between architectures.

This series extends the capabilities of walk_page_range() so that it can
deal with the page tables of the kernel (which have no VMAs and can
contain larger huge pages than exist for user space). A generic PTDUMP
implementation is the implemented making use of the new functionality of
walk_page_range() and finally arm64 and x86 are switch to using it,
removing the custom table walkers.

To enable a generic page table walker to walk the unusual mappings of
the kernel we need to implement a set of functions which let us know
when the walker has reached the leaf entry. After a suggestion from Will
Deacon I've chosen the name p?d_leaf() as this (hopefully) describes
the purpose (and is a new name so has no historic baggage). Some
architectures have p?d_large macros but this is easily confused with
"large pages".

This series ends with a generic PTDUMP implemention for arm64 and x86.

Mostly this is a clean up and there should be very little functional
change. The exceptions are:

* arm64 PTDUMP debugfs now displays pages which aren't present (patch 22).

* arm64 has the ability to efficiently process KASAN pages (which
  previously only x86 implemented). This means that the combination of
  KASAN and DEBUG_WX is now useable.

Also available as a git tree:
git://linux-arm.org/linux-sp.git walk_page_range/v17

Changes since v16:
https://lore.kernel.org/lkml/20191206135316.47703-1-steven.price@arm.com/
 * Introduced the ACTION_{SUBTREE,CONTINUE,AGAIN} concept suggested by
   Thomas Hellström
 * Reworked the KASAN support to avoid the need for test_p?d() callbacks
   by using ACTION_CONTINUE instead
 * powerpc: Use p?d_is_leaf rather than adding new functions
 * Simplify x86 changes by leaving ptdump_walk_pgd_level_core() taking
   a pgd

Changes since v15:
https://lore.kernel.org/lkml/20191101140942.51554-1-steven.price@arm.com/
 * Rebased onto Linus' tree, which includes the conflicting commit:
   ace88f1018b8 ("mm: pagewalk: Take the pagetable lock in walk_pte_range()")
 * New patch fixing conflict with above patch
 * Squashed in fix for ordering of "static const"
 * Squashed in fix checking p*d_present()
 * New patch fixing termination condition for walk_pte_range()

Changes since v14:
https://lore.kernel.org/lkml/20191028135910.33253-1-steven.price@arm.com/
 * Switch walk_page_range() into two functions, the existing
   walk_page_range() now still requires VMAs (and treats areas without a
   VMA as a 'hole'). The new walk_page_range_novma() ignores VMAs and
   will report the actual page table layout. This fixes the previous
   breakage of /proc/<pid>/pagemap
 * New patch at the end of the series which reduces the 'level' numbers
   by 1 to simplify the code slightly
 * Added tags

Changes since v13:
https://lore.kernel.org/lkml/20191024093716.49420-1-steven.price@arm.com/
 * Fixed typo in arc definition of pmd_leaf() spotted by the kbuild test
   robot
 * Added tags

Changes since v12:
https://lore.kernel.org/lkml/20191018101248.33727-1-steven.price@arm.com/
 * Correct code format in riscv pud_leaf()/pmd_leaf()
 * v12 may not have reached everyone because of mail server problems
   (which are now hopefully resolved!)

Changes since v11:
https://lore.kernel.org/lkml/20191007153822.16518-1-steven.price@arm.com/
 * Use "-1" as dummy depth parameter in patch 14.

Changes since v10:
https://lore.kernel.org/lkml/20190731154603.41797-1-steven.price@arm.com/
 * Rebased to v5.4-rc1 - mainly various updates to deal with the
   splitting out of ops from struct mm_walk.
 * Deal with PGD_LEVEL_MULT not always being constant on x86.

Changes since v9:
https://lore.kernel.org/lkml/20190722154210.42799-1-steven.price@arm.com/
 * Moved generic macros to first page in the series and explained the
   macro naming in the commit message.
 * mips: Moved macros to pgtable.h as they are now valid for both 32 and 64
   bit
 * x86: Dropped patch which changed the debugfs output for x86, instead
   we have...
 * new patch adding 'depth' parameter to pte_hole. This is used to
   provide the necessary information to output lines for 'holes' in the
   debugfs files
 * new patch changing arm64 debugfs output to include holes to match x86
 * generic ptdump KASAN handling has been simplified and now works with
   CONFIG_DEBUG_VIRTUAL.

Changes since v8:
https://lore.kernel.org/lkml/20190403141627.11664-1-steven.price@arm.com/
 * Rename from p?d_large() to p?d_leaf()
 * Dropped patches migrating arm64/x86 custom walkers to
   walk_page_range() in favour of adding a generic PTDUMP implementation
   and migrating arm64/x86 to that instead.
 * Rebased to v5.3-rc1

Steven Price (23):
  mm: Add generic p?d_leaf() macros
  arc: mm: Add p?d_leaf() definitions
  arm: mm: Add p?d_leaf() definitions
  arm64: mm: Add p?d_leaf() definitions
  mips: mm: Add p?d_leaf() definitions
  powerpc: mm: Add p?d_leaf() definitions
  riscv: mm: Add p?d_leaf() definitions
  s390: mm: Add p?d_leaf() definitions
  sparc: mm: Add p?d_leaf() definitions
  x86: mm: Add p?d_leaf() definitions
  mm: pagewalk: Add p4d_entry() and pgd_entry()
  mm: pagewalk: Allow walking without vma
  mm: pagewalk: Don't lock PTEs for walk_page_range_novma()
  mm: pagewalk: fix termination condition in walk_pte_range()
  mm: pagewalk: Add 'depth' parameter to pte_hole
  x86: mm: Point to struct seq_file from struct pg_state
  x86: mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct
  x86: mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct
  mm: Add generic ptdump
  x86: mm: Convert dump_pagetables to use walk_page_range
  arm64: mm: Convert mm/dump.c to use walk_page_range()
  arm64: mm: Display non-present entries in ptdump
  mm: ptdump: Reduce level numbers by 1 in note_page()

 arch/arc/include/asm/pgtable.h               |   1 +
 arch/arm/include/asm/pgtable-2level.h        |   1 +
 arch/arm/include/asm/pgtable-3level.h        |   1 +
 arch/arm64/Kconfig                           |   1 +
 arch/arm64/Kconfig.debug                     |  19 +-
 arch/arm64/include/asm/pgtable.h             |   2 +
 arch/arm64/include/asm/ptdump.h              |   8 +-
 arch/arm64/mm/Makefile                       |   4 +-
 arch/arm64/mm/dump.c                         | 148 ++++-----
 arch/arm64/mm/mmu.c                          |   4 +-
 arch/arm64/mm/ptdump_debugfs.c               |   2 +-
 arch/mips/include/asm/pgtable.h              |   5 +
 arch/powerpc/include/asm/book3s/64/pgtable.h |   3 +
 arch/riscv/include/asm/pgtable-64.h          |   7 +
 arch/riscv/include/asm/pgtable.h             |   7 +
 arch/s390/include/asm/pgtable.h              |   2 +
 arch/sparc/include/asm/pgtable_64.h          |   2 +
 arch/x86/Kconfig                             |   1 +
 arch/x86/Kconfig.debug                       |  20 +-
 arch/x86/include/asm/pgtable.h               |  10 +-
 arch/x86/mm/Makefile                         |   4 +-
 arch/x86/mm/debug_pagetables.c               |   8 +-
 arch/x86/mm/dump_pagetables.c                | 320 +++++--------------
 arch/x86/platform/efi/efi_32.c               |   2 +-
 arch/x86/platform/efi/efi_64.c               |   4 +-
 drivers/firmware/efi/arm-runtime.c           |   2 +-
 fs/proc/task_mmu.c                           |   4 +-
 include/asm-generic/pgtable.h                |  20 ++
 include/linux/pagewalk.h                     |  46 ++-
 include/linux/ptdump.h                       |  22 ++
 mm/Kconfig.debug                             |  21 ++
 mm/Makefile                                  |   1 +
 mm/hmm.c                                     |  59 ++--
 mm/migrate.c                                 |   5 +-
 mm/mincore.c                                 |   1 +
 mm/pagewalk.c                                | 156 ++++++---
 mm/ptdump.c                                  | 139 ++++++++
 37 files changed, 596 insertions(+), 466 deletions(-)
 create mode 100644 include/linux/ptdump.h
 create mode 100644 mm/ptdump.c

-- 
2.20.1


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[PATCH v17 01/23] mm: Add generic p?d_leaf() macros

[Steven Price]

Exposing the pud/pgd levels of the page tables to walk_page_range() means
we may come across the exotic large mappings that come with large areas
of contiguous memory (such as the kernel's linear map).

For architectures that don't provide all p?d_leaf() macros, provide
generic do nothing default that are suitable where there cannot be leaf
pages at that level. Futher patches will add implementations for
individual architectures.

The name p?d_leaf() is chosen to minimize the confusion with existing
uses of "large" pages and "huge" pages which do not necessary mean that
the entry is a leaf (for example it may be a set of contiguous entries
that only take 1 TLB slot). For the purpose of walking the page tables
we don't need to know how it will be represented in the TLB, but we do
need to know for sure if it is a leaf of the tree.

Signed-off-by: Steven Price <steven.price@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
---
 include/asm-generic/pgtable.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 798ea36a0549..e2e2bef07dd2 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -1238,4 +1238,24 @@ static inline bool arch_has_pfn_modify_check(void)
 #define mm_pmd_folded(mm)	__is_defined(__PAGETABLE_PMD_FOLDED)
 #endif
 
+/*
+ * p?d_leaf() - true if this entry is a final mapping to a physical address.
+ * This differs from p?d_huge() by the fact that they are always available (if
+ * the architecture supports large pages at the appropriate level) even
+ * if CONFIG_HUGETLB_PAGE is not defined.
+ * Only meaningful when called on a valid entry.
+ */
+#ifndef pgd_leaf
+#define pgd_leaf(x)	0
+#endif
+#ifndef p4d_leaf
+#define p4d_leaf(x)	0
+#endif
+#ifndef pud_leaf
+#define pud_leaf(x)	0
+#endif
+#ifndef pmd_leaf
+#define pmd_leaf(x)	0
+#endif
+
 #endif /* _ASM_GENERIC_PGTABLE_H */
-- 
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[PATCH v17 02/23] arc: mm: Add p?d_leaf() definitions

[Steven Price]

walk_page_range() is going to be allowed to walk page tables other than
those of user space. For this it needs to know when it has reached a
'leaf' entry in the page tables. This information will be provided by the
p?d_leaf() functions/macros.

For arc, we only have two levels, so only pmd_leaf() is needed.

CC: Vineet Gupta <vgupta@synopsys.com>
CC: linux-snps-arc@lists.infradead.org
Acked-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arc/include/asm/pgtable.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h
index 9019ed9f9c94..12be7e1b7cc0 100644
--- a/arch/arc/include/asm/pgtable.h
+++ b/arch/arc/include/asm/pgtable.h
@@ -273,6 +273,7 @@ static inline void pmd_set(pmd_t *pmdp, pte_t *ptep)
 #define pmd_none(x)			(!pmd_val(x))
 #define	pmd_bad(x)			((pmd_val(x) & ~PAGE_MASK))
 #define pmd_present(x)			(pmd_val(x))
+#define pmd_leaf(x)			(pmd_val(x) & _PAGE_HW_SZ)
 #define pmd_clear(xp)			do { pmd_val(*(xp)) = 0; } while (0)
 
 #define pte_page(pte)		pfn_to_page(pte_pfn(pte))
-- 
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[PATCH v17 03/23] arm: mm: Add p?d_leaf() definitions

[Steven Price]

walk_page_range() is going to be allowed to walk page tables other than
those of user space. For this it needs to know when it has reached a
'leaf' entry in the page tables. This information is provided by the
p?d_leaf() functions/macros.

For arm pmd_large() already exists and does what we want. So simply
provide the generic pmd_leaf() name.

CC: Russell King <linux@armlinux.org.uk>
CC: linux-arm-kernel@lists.infradead.org
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm/include/asm/pgtable-2level.h | 1 +
 arch/arm/include/asm/pgtable-3level.h | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/arm/include/asm/pgtable-2level.h b/arch/arm/include/asm/pgtable-2level.h
index 51beec41d48c..0d3ea35c97fe 100644
--- a/arch/arm/include/asm/pgtable-2level.h
+++ b/arch/arm/include/asm/pgtable-2level.h
@@ -189,6 +189,7 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
 }
 
 #define pmd_large(pmd)		(pmd_val(pmd) & 2)
+#define pmd_leaf(pmd)		(pmd_val(pmd) & 2)
 #define pmd_bad(pmd)		(pmd_val(pmd) & 2)
 #define pmd_present(pmd)	(pmd_val(pmd))
 
diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h
index 5b18295021a0..ad55ab068dbf 100644
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/arch/arm/include/asm/pgtable-3level.h
@@ -134,6 +134,7 @@
 #define pmd_sect(pmd)		((pmd_val(pmd) & PMD_TYPE_MASK) == \
 						 PMD_TYPE_SECT)
 #define pmd_large(pmd)		pmd_sect(pmd)
+#define pmd_leaf(pmd)		pmd_sect(pmd)
 
 #define pud_clear(pudp)			\
 	do {				\
-- 
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[PATCH v17 04/23] arm64: mm: Add p?d_leaf() definitions

[Steven Price]

walk_page_range() is going to be allowed to walk page tables other than
those of user space. For this it needs to know when it has reached a
'leaf' entry in the page tables. This information will be provided by the
p?d_leaf() functions/macros.

For arm64, we already have p?d_sect() macros which we can reuse for
p?d_leaf().

pud_sect() is defined as a dummy function when CONFIG_PGTABLE_LEVELS < 3
or CONFIG_ARM64_64K_PAGES is defined. However when the kernel is
configured this way then architecturally it isn't allowed to have a
large page at this level, and any code using these page walking macros
is implicitly relying on the page size/number of levels being the same as
the kernel. So it is safe to reuse this for p?d_leaf() as it is an
architectural restriction.

CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/pgtable.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 5d15b4735a0e..40df7e16d397 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -445,6 +445,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 				 PMD_TYPE_TABLE)
 #define pmd_sect(pmd)		((pmd_val(pmd) & PMD_TYPE_MASK) == \
 				 PMD_TYPE_SECT)
+#define pmd_leaf(pmd)		pmd_sect(pmd)
 
 #if defined(CONFIG_ARM64_64K_PAGES) || CONFIG_PGTABLE_LEVELS < 3
 static inline bool pud_sect(pud_t pud) { return false; }
@@ -529,6 +530,7 @@ static inline void pte_unmap(pte_t *pte) { }
 #define pud_none(pud)		(!pud_val(pud))
 #define pud_bad(pud)		(!(pud_val(pud) & PUD_TABLE_BIT))
 #define pud_present(pud)	pte_present(pud_pte(pud))
+#define pud_leaf(pud)		pud_sect(pud)
 #define pud_valid(pud)		pte_valid(pud_pte(pud))
 
 static inline void set_pud(pud_t *pudp, pud_t pud)
-- 
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[PATCH v17 05/23] mips: mm: Add p?d_leaf() definitions

[Steven Price]

walk_page_range() is going to be allowed to walk page tables other than
those of user space. For this it needs to know when it has reached a
'leaf' entry in the page tables. This information is provided by the
p?d_leaf() functions/macros.

If _PAGE_HUGE is defined we can simply look for it. When not defined we
can be confident that there are no leaf pages in existence and fall back
on the generic implementation (added in a later patch) which returns 0.

CC: Ralf Baechle <ralf@linux-mips.org>
CC: Paul Burton <paul.burton@mips.com>
CC: James Hogan <jhogan@kernel.org>
CC: linux-mips@vger.kernel.org
Signed-off-by: Steven Price <steven.price@arm.com>
Acked-by: Paul Burton <paul.burton@mips.com>
---
 arch/mips/include/asm/pgtable.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index 91b89aab1787..aef5378f909c 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -639,6 +639,11 @@ static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
 
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
+#ifdef _PAGE_HUGE
+#define pmd_leaf(pmd)	((pmd_val(pmd) & _PAGE_HUGE) != 0)
+#define pud_leaf(pud)	((pud_val(pud) & _PAGE_HUGE) != 0)
+#endif
+
 #define gup_fast_permitted(start, end)	(!cpu_has_dc_aliases)
 
 #include <asm-generic/pgtable.h>
-- 
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[PATCH v17 06/23] powerpc: mm: Add p?d_leaf() definitions

[Steven Price]

walk_page_range() is going to be allowed to walk page tables other than
those of user space. For this it needs to know when it has reached a
'leaf' entry in the page tables. This information is provided by the
p?d_leaf() functions/macros.

For powerpc p?d_is_leaf() functions already exist. Export them using the
new p?d_leaf() name.

CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <paulus@samba.org>
CC: Michael Ellerman <mpe@ellerman.id.au>
CC: linuxppc-dev@lists.ozlabs.org
CC: kvm-ppc@vger.kernel.org
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/powerpc/include/asm/book3s/64/pgtable.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index b01624e5c467..201a69e6a355 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -1355,18 +1355,21 @@ static inline bool is_pte_rw_upgrade(unsigned long old_val, unsigned long new_va
  * Like pmd_huge() and pmd_large(), but works regardless of config options
  */
 #define pmd_is_leaf pmd_is_leaf
+#define pmd_leaf pmd_is_leaf
 static inline bool pmd_is_leaf(pmd_t pmd)
 {
 	return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE));
 }
 
 #define pud_is_leaf pud_is_leaf
+#define pud_leaf pud_is_leaf
 static inline bool pud_is_leaf(pud_t pud)
 {
 	return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE));
 }
 
 #define pgd_is_leaf pgd_is_leaf
+#define pgd_leaf pgd_is_leaf
 static inline bool pgd_is_leaf(pgd_t pgd)
 {
 	return !!(pgd_raw(pgd) & cpu_to_be64(_PAGE_PTE));
-- 
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[PATCH v17 07/23] riscv: mm: Add p?d_leaf() definitions

[Steven Price]

walk_page_range() is going to be allowed to walk page tables other than
those of user space. For this it needs to know when it has reached a
'leaf' entry in the page tables. This information is provided by the
p?d_leaf() functions/macros.

For riscv a page is a leaf page when it has a read, write or execute bit
set on it.

CC: Palmer Dabbelt <palmer@sifive.com>
CC: Albert Ou <aou@eecs.berkeley.edu>
CC: linux-riscv@lists.infradead.org
Reviewed-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Zong Li <zong.li@sifive.com>
Acked-by: Paul Walmsley <paul.walmsley@sifive.com> # for arch/riscv
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/riscv/include/asm/pgtable-64.h | 7 +++++++
 arch/riscv/include/asm/pgtable.h    | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/arch/riscv/include/asm/pgtable-64.h b/arch/riscv/include/asm/pgtable-64.h
index 74630989006d..4c4d2c65ba6c 100644
--- a/arch/riscv/include/asm/pgtable-64.h
+++ b/arch/riscv/include/asm/pgtable-64.h
@@ -43,6 +43,13 @@ static inline int pud_bad(pud_t pud)
 	return !pud_present(pud);
 }
 
+#define pud_leaf	pud_leaf
+static inline int pud_leaf(pud_t pud)
+{
+	return pud_present(pud) &&
+	       (pud_val(pud) & (_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC));
+}
+
 static inline void set_pud(pud_t *pudp, pud_t pud)
 {
 	*pudp = pud;
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 7ff0ed4f292e..5cf96b2b4d5a 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -105,6 +105,13 @@ static inline int pmd_bad(pmd_t pmd)
 	return !pmd_present(pmd);
 }
 
+#define pmd_leaf	pmd_leaf
+static inline int pmd_leaf(pmd_t pmd)
+{
+	return pmd_present(pmd) &&
+	       (pmd_val(pmd) & (_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC));
+}
+
 static inline void set_pmd(pmd_t *pmdp, pmd_t pmd)
 {
 	*pmdp = pmd;
-- 
2.20.1


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[PATCH v17 08/23] s390: mm: Add p?d_leaf() definitions

[Steven Price]

walk_page_range() is going to be allowed to walk page tables other than
those of user space. For this it needs to know when it has reached a
'leaf' entry in the page tables. This information is provided by the
p?d_leaf() functions/macros.

For s390, pud_large() and pmd_large() are already implemented as static
inline functions. Add a macro to provide the p?d_leaf names for the
generic code to use.

CC: Heiko Carstens <heiko.carstens@de.ibm.com>
CC: Vasily Gorbik <gor@linux.ibm.com>
CC: Christian Borntraeger <borntraeger@de.ibm.com>
CC: linux-s390@vger.kernel.org
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/s390/include/asm/pgtable.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 7b03037a8475..137a3920ca36 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -673,6 +673,7 @@ static inline int pud_none(pud_t pud)
 	return pud_val(pud) == _REGION3_ENTRY_EMPTY;
 }
 
+#define pud_leaf	pud_large
 static inline int pud_large(pud_t pud)
 {
 	if ((pud_val(pud) & _REGION_ENTRY_TYPE_MASK) != _REGION_ENTRY_TYPE_R3)
@@ -690,6 +691,7 @@ static inline unsigned long pud_pfn(pud_t pud)
 	return (pud_val(pud) & origin_mask) >> PAGE_SHIFT;
 }
 
+#define pmd_leaf	pmd_large
 static inline int pmd_large(pmd_t pmd)
 {
 	return (pmd_val(pmd) & _SEGMENT_ENTRY_LARGE) != 0;
-- 
2.20.1


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[PATCH v17 09/23] sparc: mm: Add p?d_leaf() definitions

[Steven Price]

walk_page_range() is going to be allowed to walk page tables other than
those of user space. For this it needs to know when it has reached a
'leaf' entry in the page tables. This information is provided by the
p?d_leaf() functions/macros.

For sparc 64 bit, pmd_large() and pud_large() are already provided, so
add macros to provide the p?d_leaf names required by the generic code.

CC: "David S. Miller" <davem@davemloft.net>
CC: sparclinux@vger.kernel.org
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/sparc/include/asm/pgtable_64.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 6ae8016ef4ec..43206652eaf5 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -683,6 +683,7 @@ static inline unsigned long pte_special(pte_t pte)
 	return pte_val(pte) & _PAGE_SPECIAL;
 }
 
+#define pmd_leaf	pmd_large
 static inline unsigned long pmd_large(pmd_t pmd)
 {
 	pte_t pte = __pte(pmd_val(pmd));
@@ -867,6 +868,7 @@ static inline unsigned long pud_page_vaddr(pud_t pud)
 /* only used by the stubbed out hugetlb gup code, should never be called */
 #define pgd_page(pgd)			NULL
 
+#define pud_leaf	pud_large
 static inline unsigned long pud_large(pud_t pud)
 {
 	pte_t pte = __pte(pud_val(pud));
-- 
2.20.1


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[PATCH v17 10/23] x86: mm: Add p?d_leaf() definitions

[Steven Price]

walk_page_range() is going to be allowed to walk page tables other than
those of user space. For this it needs to know when it has reached a
'leaf' entry in the page tables. This information is provided by the
p?d_leaf() functions/macros.

For x86 we already have p?d_large() functions, so simply add macros to
provide the generic p?d_leaf() names for the generic code.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/x86/include/asm/pgtable.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index ad97dc155195..8091a1c62596 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -239,6 +239,7 @@ static inline unsigned long pgd_pfn(pgd_t pgd)
 	return (pgd_val(pgd) & PTE_PFN_MASK) >> PAGE_SHIFT;
 }
 
+#define p4d_leaf	p4d_large
 static inline int p4d_large(p4d_t p4d)
 {
 	/* No 512 GiB pages yet */
@@ -247,6 +248,7 @@ static inline int p4d_large(p4d_t p4d)
 
 #define pte_page(pte)	pfn_to_page(pte_pfn(pte))
 
+#define pmd_leaf	pmd_large
 static inline int pmd_large(pmd_t pte)
 {
 	return pmd_flags(pte) & _PAGE_PSE;
@@ -874,6 +876,7 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address)
 	return (pmd_t *)pud_page_vaddr(*pud) + pmd_index(address);
 }
 
+#define pud_leaf	pud_large
 static inline int pud_large(pud_t pud)
 {
 	return (pud_val(pud) & (_PAGE_PSE | _PAGE_PRESENT)) ==
@@ -885,6 +888,7 @@ static inline int pud_bad(pud_t pud)
 	return (pud_flags(pud) & ~(_KERNPG_TABLE | _PAGE_USER)) != 0;
 }
 #else
+#define pud_leaf	pud_large
 static inline int pud_large(pud_t pud)
 {
 	return 0;
@@ -1233,6 +1237,7 @@ static inline bool pgdp_maps_userspace(void *__ptr)
 	return (((ptr & ~PAGE_MASK) / sizeof(pgd_t)) < PGD_KERNEL_START);
 }
 
+#define pgd_leaf	pgd_large
 static inline int pgd_large(pgd_t pgd) { return 0; }
 
 #ifdef CONFIG_PAGE_TABLE_ISOLATION
-- 
2.20.1


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[PATCH v17 11/23] mm: pagewalk: Add p4d_entry() and pgd_entry()

[Steven Price]

pgd_entry() and pud_entry() were removed by commit 0b1fbfe50006c410
("mm/pagewalk: remove pgd_entry() and pud_entry()") because there were
no users. We're about to add users so reintroduce them, along with
p4d_entry() as we now have 5 levels of tables.

Note that commit a00cc7d9dd93d66a ("mm, x86: add support for
PUD-sized transparent hugepages") already re-added pud_entry() but with
different semantics to the other callbacks. This commit reverts the
semantics back to match the other callbacks.

To support hmm.c which now uses the new semantics of pud_entry() a new
member ('action') of struct mm_walk is added which allows the callbacks
to either descend (ACTION_SUBTREE, the default), skip (ACTION_CONTINUE)
or repeat the callback (ACTION_AGAIN). hmm.c is then updated to call
pud_trans_huge_lock() itself and make use of the splitting/retry logic
of the core code.

After this change pud_entry() is called for all entries, not just
transparent huge pages.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 include/linux/pagewalk.h | 34 ++++++++++++++++++++-----
 mm/hmm.c                 | 55 ++++++++++++++++++++++------------------
 mm/pagewalk.c            | 50 +++++++++++++++++++++++++-----------
 3 files changed, 94 insertions(+), 45 deletions(-)

diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
index 6ec82e92c87f..aa6a0b63964e 100644
--- a/include/linux/pagewalk.h
+++ b/include/linux/pagewalk.h
@@ -8,15 +8,15 @@ struct mm_walk;
 
 /**
  * mm_walk_ops - callbacks for walk_page_range
- * @pud_entry:		if set, called for each non-empty PUD (2nd-level) entry
- *			this handler should only handle pud_trans_huge() puds.
- *			the pmd_entry or pte_entry callbacks will be used for
- *			regular PUDs.
- * @pmd_entry:		if set, called for each non-empty PMD (3rd-level) entry
+ * @pgd_entry:		if set, called for each non-empty PGD (top-level) entry
+ * @p4d_entry:		if set, called for each non-empty P4D entry
+ * @pud_entry:		if set, called for each non-empty PUD entry
+ * @pmd_entry:		if set, called for each non-empty PMD entry
  *			this handler is required to be able to handle
  *			pmd_trans_huge() pmds.  They may simply choose to
  *			split_huge_page() instead of handling it explicitly.
- * @pte_entry:		if set, called for each non-empty PTE (4th-level) entry
+ * @pte_entry:		if set, called for each non-empty PTE (lowest-level)
+ *			entry
  * @pte_hole:		if set, called for each hole at all levels
  * @hugetlb_entry:	if set, called for each hugetlb entry
  * @test_walk:		caller specific callback function to determine whether
@@ -27,8 +27,15 @@ struct mm_walk;
  * @pre_vma:            if set, called before starting walk on a non-null vma.
  * @post_vma:           if set, called after a walk on a non-null vma, provided
  *                      that @pre_vma and the vma walk succeeded.
+ *
+ * p?d_entry callbacks are called even if those levels are folded on a
+ * particular architecture/configuration.
  */
 struct mm_walk_ops {
+	int (*pgd_entry)(pgd_t *pgd, unsigned long addr,
+			 unsigned long next, struct mm_walk *walk);
+	int (*p4d_entry)(p4d_t *p4d, unsigned long addr,
+			 unsigned long next, struct mm_walk *walk);
 	int (*pud_entry)(pud_t *pud, unsigned long addr,
 			 unsigned long next, struct mm_walk *walk);
 	int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
@@ -47,11 +54,25 @@ struct mm_walk_ops {
 	void (*post_vma)(struct mm_walk *walk);
 };
 
+/*
+ * Action for pud_entry / pmd_entry callbacks.
+ * ACTION_SUBTREE is the default
+ */
+enum page_walk_action {
+	/* Descend to next level, splitting huge pages if needed and possible */
+	ACTION_SUBTREE = 0,
+	/* Continue to next entry at this level (ignoring any subtree) */
+	ACTION_CONTINUE = 1,
+	/* Call again for this entry */
+	ACTION_AGAIN = 2
+};
+
 /**
  * mm_walk - walk_page_range data
  * @ops:	operation to call during the walk
  * @mm:		mm_struct representing the target process of page table walk
  * @vma:	vma currently walked (NULL if walking outside vmas)
+ * @action:	next action to perform (see enum page_walk_action)
  * @private:	private data for callbacks' usage
  *
  * (see the comment on walk_page_range() for more details)
@@ -60,6 +81,7 @@ struct mm_walk {
 	const struct mm_walk_ops *ops;
 	struct mm_struct *mm;
 	struct vm_area_struct *vma;
+	enum page_walk_action action;
 	void *private;
 };
 
diff --git a/mm/hmm.c b/mm/hmm.c
index d379cb6496ae..05241c82e05c 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -477,20 +477,30 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
 	unsigned long addr = start, next;
 	pmd_t *pmdp;
 	pud_t pud;
-	int ret;
+	int ret = 0;
+	spinlock_t *ptl = pud_trans_huge_lock(pudp, walk->vma);
+
+	if (!ptl)
+		return 0;
+
+	/* Normally we don't want to split the huge page */
+	walk->action = ACTION_CONTINUE;
 
-again:
 	pud = READ_ONCE(*pudp);
-	if (pud_none(pud))
-		return hmm_vma_walk_hole(start, end, walk);
+	if (pud_none(pud)) {
+		ret = hmm_vma_walk_hole(start, end, walk);
+		goto out_unlock;
+	}
 
 	if (pud_huge(pud) && pud_devmap(pud)) {
 		unsigned long i, npages, pfn;
 		uint64_t *pfns, cpu_flags;
 		bool fault, write_fault;
 
-		if (!pud_present(pud))
-			return hmm_vma_walk_hole(start, end, walk);
+		if (!pud_present(pud)) {
+			ret = hmm_vma_walk_hole(start, end, walk);
+			goto out_unlock;
+		}
 
 		i = (addr - range->start) >> PAGE_SHIFT;
 		npages = (end - addr) >> PAGE_SHIFT;
@@ -499,16 +509,20 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
 		cpu_flags = pud_to_hmm_pfn_flags(range, pud);
 		hmm_range_need_fault(hmm_vma_walk, pfns, npages,
 				     cpu_flags, &fault, &write_fault);
-		if (fault || write_fault)
-			return hmm_vma_walk_hole_(addr, end, fault,
-						write_fault, walk);
+		if (fault || write_fault) {
+			ret = hmm_vma_walk_hole_(addr, end, fault,
+						 write_fault, walk);
+			goto out_unlock;
+		}
 
 		pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 		for (i = 0; i < npages; ++i, ++pfn) {
 			hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
 					      hmm_vma_walk->pgmap);
-			if (unlikely(!hmm_vma_walk->pgmap))
-				return -EBUSY;
+			if (unlikely(!hmm_vma_walk->pgmap)) {
+				ret = -EBUSY;
+				goto out_unlock;
+			}
 			pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
 				  cpu_flags;
 		}
@@ -517,22 +531,15 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
 			hmm_vma_walk->pgmap = NULL;
 		}
 		hmm_vma_walk->last = end;
-		return 0;
+		goto out_unlock;
 	}
 
-	split_huge_pud(walk->vma, pudp, addr);
-	if (pud_none(*pudp))
-		goto again;
+	/* Ask for the PUD to be split */
+	walk->action = ACTION_SUBTREE;
 
-	pmdp = pmd_offset(pudp, addr);
-	do {
-		next = pmd_addr_end(addr, end);
-		ret = hmm_vma_walk_pmd(pmdp, addr, next, walk);
-		if (ret)
-			return ret;
-	} while (pmdp++, addr = next, addr != end);
-
-	return 0;
+out_unlock:
+	spin_unlock(ptl);
+	return ret;
 }
 #else
 #define hmm_vma_walk_pud	NULL
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index ea0b9e606ad1..690af44609e2 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -46,6 +46,9 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 				break;
 			continue;
 		}
+
+		walk->action = ACTION_SUBTREE;
+
 		/*
 		 * This implies that each ->pmd_entry() handler
 		 * needs to know about pmd_trans_huge() pmds
@@ -55,16 +58,21 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 		if (err)
 			break;
 
+		if (walk->action == ACTION_AGAIN)
+			goto again;
+
 		/*
 		 * Check this here so we only break down trans_huge
 		 * pages when we _need_ to
 		 */
-		if (!ops->pte_entry)
+		if (walk->action == ACTION_CONTINUE ||
+		    !(ops->pte_entry))
 			continue;
 
 		split_huge_pmd(walk->vma, pmd, addr);
 		if (pmd_trans_unstable(pmd))
 			goto again;
+
 		err = walk_pte_range(pmd, addr, next, walk);
 		if (err)
 			break;
@@ -93,24 +101,25 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 			continue;
 		}
 
-		if (ops->pud_entry) {
-			spinlock_t *ptl = pud_trans_huge_lock(pud, walk->vma);
+		walk->action = ACTION_SUBTREE;
 
-			if (ptl) {
-				err = ops->pud_entry(pud, addr, next, walk);
-				spin_unlock(ptl);
-				if (err)
-					break;
-				continue;
-			}
-		}
+		if (ops->pud_entry)
+			err = ops->pud_entry(pud, addr, next, walk);
+		if (err)
+			break;
+
+		if (walk->action == ACTION_AGAIN)
+			goto again;
+
+		if (walk->action == ACTION_CONTINUE ||
+		    !(ops->pmd_entry || ops->pte_entry))
+			continue;
 
 		split_huge_pud(walk->vma, pud, addr);
 		if (pud_none(*pud))
 			goto again;
 
-		if (ops->pmd_entry || ops->pte_entry)
-			err = walk_pmd_range(pud, addr, next, walk);
+		err = walk_pmd_range(pud, addr, next, walk);
 		if (err)
 			break;
 	} while (pud++, addr = next, addr != end);
@@ -136,7 +145,12 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
 				break;
 			continue;
 		}
-		if (ops->pmd_entry || ops->pte_entry)
+		if (ops->p4d_entry) {
+			err = ops->p4d_entry(p4d, addr, next, walk);
+			if (err)
+				break;
+		}
+		if (ops->pud_entry || ops->pmd_entry || ops->pte_entry)
 			err = walk_pud_range(p4d, addr, next, walk);
 		if (err)
 			break;
@@ -163,7 +177,13 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
 				break;
 			continue;
 		}
-		if (ops->pmd_entry || ops->pte_entry)
+		if (ops->pgd_entry) {
+			err = ops->pgd_entry(pgd, addr, next, walk);
+			if (err)
+				break;
+		}
+		if (ops->p4d_entry || ops->pud_entry || ops->pmd_entry ||
+		    ops->pte_entry)
 			err = walk_p4d_range(pgd, addr, next, walk);
 		if (err)
 			break;
-- 
2.20.1


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[PATCH v17 12/23] mm: pagewalk: Allow walking without vma

[Steven Price]

Since 48684a65b4e3: "mm: pagewalk: fix misbehavior of walk_page_range
for vma(VM_PFNMAP)", page_table_walk() will report any kernel area as
a hole, because it lacks a vma.

This means each arch has re-implemented page table walking when needed,
for example in the per-arch ptdump walker.

Remove the requirement to have a vma in the generic code and add a new
function walk_page_range_novma() which ignores the VMAs and simply walks
the page tables.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 include/linux/pagewalk.h |  5 +++++
 mm/pagewalk.c            | 40 ++++++++++++++++++++++++++++++++--------
 2 files changed, 37 insertions(+), 8 deletions(-)

diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
index aa6a0b63964e..d5d07f7a9c14 100644
--- a/include/linux/pagewalk.h
+++ b/include/linux/pagewalk.h
@@ -73,6 +73,7 @@ enum page_walk_action {
  * @mm:		mm_struct representing the target process of page table walk
  * @vma:	vma currently walked (NULL if walking outside vmas)
  * @action:	next action to perform (see enum page_walk_action)
+ * @no_vma:	walk ignoring vmas (vma will always be NULL)
  * @private:	private data for callbacks' usage
  *
  * (see the comment on walk_page_range() for more details)
@@ -82,12 +83,16 @@ struct mm_walk {
 	struct mm_struct *mm;
 	struct vm_area_struct *vma;
 	enum page_walk_action action;
+	bool no_vma;
 	void *private;
 };
 
 int walk_page_range(struct mm_struct *mm, unsigned long start,
 		unsigned long end, const struct mm_walk_ops *ops,
 		void *private);
+int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
+			  unsigned long end, const struct mm_walk_ops *ops,
+			  void *private);
 int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
 		void *private);
 int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 690af44609e2..d5773465f6da 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -39,7 +39,7 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 	do {
 again:
 		next = pmd_addr_end(addr, end);
-		if (pmd_none(*pmd) || !walk->vma) {
+		if (pmd_none(*pmd) || (!walk->vma && !walk->no_vma)) {
 			if (ops->pte_hole)
 				err = ops->pte_hole(addr, next, walk);
 			if (err)
@@ -65,13 +65,16 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 		 * Check this here so we only break down trans_huge
 		 * pages when we _need_ to
 		 */
-		if (walk->action == ACTION_CONTINUE ||
+		if ((!walk->vma && (pmd_leaf(*pmd) || !pmd_present(*pmd))) ||
+		    walk->action == ACTION_CONTINUE ||
 		    !(ops->pte_entry))
 			continue;
 
-		split_huge_pmd(walk->vma, pmd, addr);
-		if (pmd_trans_unstable(pmd))
-			goto again;
+		if (walk->vma) {
+			split_huge_pmd(walk->vma, pmd, addr);
+			if (pmd_trans_unstable(pmd))
+				goto again;
+		}
 
 		err = walk_pte_range(pmd, addr, next, walk);
 		if (err)
@@ -93,7 +96,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 	do {
  again:
 		next = pud_addr_end(addr, end);
-		if (pud_none(*pud) || !walk->vma) {
+		if (pud_none(*pud) || (!walk->vma && !walk->no_vma)) {
 			if (ops->pte_hole)
 				err = ops->pte_hole(addr, next, walk);
 			if (err)
@@ -111,11 +114,13 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 		if (walk->action == ACTION_AGAIN)
 			goto again;
 
-		if (walk->action == ACTION_CONTINUE ||
+		if ((!walk->vma && (pud_leaf(*pud) || !pud_present(*pud))) ||
+		    walk->action == ACTION_CONTINUE ||
 		    !(ops->pmd_entry || ops->pte_entry))
 			continue;
 
-		split_huge_pud(walk->vma, pud, addr);
+		if (walk->vma)
+			split_huge_pud(walk->vma, pud, addr);
 		if (pud_none(*pud))
 			goto again;
 
@@ -389,6 +394,25 @@ int walk_page_range(struct mm_struct *mm, unsigned long start,
 	return err;
 }
 
+int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
+			  unsigned long end, const struct mm_walk_ops *ops,
+			  void *private)
+{
+	struct mm_walk walk = {
+		.ops		= ops,
+		.mm		= mm,
+		.private	= private,
+		.no_vma		= true
+	};
+
+	if (start >= end || !walk.mm)
+		return -EINVAL;
+
+	lockdep_assert_held(&walk.mm->mmap_sem);
+
+	return __walk_page_range(start, end, &walk);
+}
+
 int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
 		void *private)
 {
-- 
2.20.1


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[PATCH v17 13/23] mm: pagewalk: Don't lock PTEs for walk_page_range_novma()

[Steven Price]

walk_page_range_novma() can be used to walk page tables or the kernel or
for firmware. These page tables may contain entries that are not backed
by a struct page and so it isn't (in general) possible to take the PTE
lock for the pte_entry() callback. So update walk_pte_range() to only
take the lock when no_vma==false by splitting out the inner loop to a
separate function and add a comment explaining the difference to
walk_page_range_novma().

Signed-off-by: Steven Price <steven.price@arm.com>
---
 mm/pagewalk.c | 35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index d5773465f6da..4b5ee92ba079 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -4,15 +4,12 @@
 #include <linux/sched.h>
 #include <linux/hugetlb.h>
 
-static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
-			  struct mm_walk *walk)
+static int walk_pte_range_inner(pte_t *pte, unsigned long addr,
+				unsigned long end, struct mm_walk *walk)
 {
-	pte_t *pte;
-	int err = 0;
 	const struct mm_walk_ops *ops = walk->ops;
-	spinlock_t *ptl;
+	int err = 0;
 
-	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
 	for (;;) {
 		err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
 		if (err)
@@ -22,8 +19,26 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 			break;
 		pte++;
 	}
+	return err;
+}
+
+static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
+			  struct mm_walk *walk)
+{
+	pte_t *pte;
+	int err = 0;
+	spinlock_t *ptl;
+
+	if (walk->no_vma) {
+		pte = pte_offset_map(pmd, addr);
+		err = walk_pte_range_inner(pte, addr, end, walk);
+		pte_unmap(pte);
+	} else {
+		pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+		err = walk_pte_range_inner(pte, addr, end, walk);
+		pte_unmap_unlock(pte, ptl);
+	}
 
-	pte_unmap_unlock(pte, ptl);
 	return err;
 }
 
@@ -394,6 +409,12 @@ int walk_page_range(struct mm_struct *mm, unsigned long start,
 	return err;
 }
 
+/*
+ * Similar to walk_page_range() but can walk any page tables even if they are
+ * not backed by VMAs. Because 'unusual' entries may be walked this function
+ * will also not lock the PTEs for the pte_entry() callback. This is useful for
+ * walking the kernel pages tables or page tables for firmware.
+ */
 int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
 			  unsigned long end, const struct mm_walk_ops *ops,
 			  void *private)
-- 
2.20.1


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[PATCH v17 14/23] mm: pagewalk: fix termination condition in walk_pte_range()

[Steven Price]

If walk_pte_range() is called with a 'end' argument that is beyond the
last page of memory (e.g. ~0UL) then the comparison between 'addr' and
'end' will always fail and the loop will be infinite. Instead change the
comparison to >= while accounting for overflow.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 mm/pagewalk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 4b5ee92ba079..6732fc7ac4c8 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -14,9 +14,9 @@ static int walk_pte_range_inner(pte_t *pte, unsigned long addr,
 		err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
 		if (err)
 		       break;
-		addr += PAGE_SIZE;
-		if (addr == end)
+		if (addr >= end - PAGE_SIZE)
 			break;
+		addr += PAGE_SIZE;
 		pte++;
 	}
 	return err;
-- 
2.20.1


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[PATCH v17 15/23] mm: pagewalk: Add 'depth' parameter to pte_hole

[Steven Price]

The pte_hole() callback is called at multiple levels of the page tables.
Code dumping the kernel page tables needs to know what at what depth
the missing entry is. Add this is an extra parameter to pte_hole().
When the depth isn't know (e.g. processing a vma) then -1 is passed.

The depth that is reported is the actual level where the entry is
missing (ignoring any folding that is in place), i.e. any levels where
PTRS_PER_P?D is set to 1 are ignored.

Note that depth starts at 0 for a PGD so that PUD/PMD/PTE retain their
natural numbers as levels 2/3/4.

Tested-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 fs/proc/task_mmu.c       |  4 ++--
 include/linux/pagewalk.h |  7 +++++--
 mm/hmm.c                 |  8 ++++----
 mm/migrate.c             |  5 +++--
 mm/mincore.c             |  1 +
 mm/pagewalk.c            | 31 +++++++++++++++++++++++++------
 6 files changed, 40 insertions(+), 16 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 9442631fd4af..3ba9ae83bff5 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -505,7 +505,7 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
 
 #ifdef CONFIG_SHMEM
 static int smaps_pte_hole(unsigned long addr, unsigned long end,
-		struct mm_walk *walk)
+			  __always_unused int depth, struct mm_walk *walk)
 {
 	struct mem_size_stats *mss = walk->private;
 
@@ -1282,7 +1282,7 @@ static int add_to_pagemap(unsigned long addr, pagemap_entry_t *pme,
 }
 
 static int pagemap_pte_hole(unsigned long start, unsigned long end,
-				struct mm_walk *walk)
+			    __always_unused int depth, struct mm_walk *walk)
 {
 	struct pagemapread *pm = walk->private;
 	unsigned long addr = start;
diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
index d5d07f7a9c14..745a654c6ea7 100644
--- a/include/linux/pagewalk.h
+++ b/include/linux/pagewalk.h
@@ -17,7 +17,10 @@ struct mm_walk;
  *			split_huge_page() instead of handling it explicitly.
  * @pte_entry:		if set, called for each non-empty PTE (lowest-level)
  *			entry
- * @pte_hole:		if set, called for each hole at all levels
+ * @pte_hole:		if set, called for each hole at all levels,
+ *			depth is -1 if not known, 0:PGD, 1:P4D, 2:PUD, 3:PMD
+ *			4:PTE. Any folded depths (where PTRS_PER_P?D is equal
+ *			to 1) are skipped.
  * @hugetlb_entry:	if set, called for each hugetlb entry
  * @test_walk:		caller specific callback function to determine whether
  *			we walk over the current vma or not. Returning 0 means
@@ -43,7 +46,7 @@ struct mm_walk_ops {
 	int (*pte_entry)(pte_t *pte, unsigned long addr,
 			 unsigned long next, struct mm_walk *walk);
 	int (*pte_hole)(unsigned long addr, unsigned long next,
-			struct mm_walk *walk);
+			int depth, struct mm_walk *walk);
 	int (*hugetlb_entry)(pte_t *pte, unsigned long hmask,
 			     unsigned long addr, unsigned long next,
 			     struct mm_walk *walk);
diff --git a/mm/hmm.c b/mm/hmm.c
index 05241c82e05c..a71295e99968 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -186,7 +186,7 @@ static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
 }
 
 static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
-			     struct mm_walk *walk)
+			     __always_unused int depth, struct mm_walk *walk)
 {
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
@@ -380,7 +380,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
 again:
 	pmd = READ_ONCE(*pmdp);
 	if (pmd_none(pmd))
-		return hmm_vma_walk_hole(start, end, walk);
+		return hmm_vma_walk_hole(start, end, -1, walk);
 
 	if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
 		bool fault, write_fault;
@@ -488,7 +488,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
 
 	pud = READ_ONCE(*pudp);
 	if (pud_none(pud)) {
-		ret = hmm_vma_walk_hole(start, end, walk);
+		ret = hmm_vma_walk_hole(start, end, -1, walk);
 		goto out_unlock;
 	}
 
@@ -498,7 +498,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
 		bool fault, write_fault;
 
 		if (!pud_present(pud)) {
-			ret = hmm_vma_walk_hole(start, end, walk);
+			ret = hmm_vma_walk_hole(start, end, -1, walk);
 			goto out_unlock;
 		}
 
diff --git a/mm/migrate.c b/mm/migrate.c
index eae1565285e3..616cd1ed04dd 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2119,6 +2119,7 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
 #ifdef CONFIG_DEVICE_PRIVATE
 static int migrate_vma_collect_hole(unsigned long start,
 				    unsigned long end,
+				    __always_unused int depth,
 				    struct mm_walk *walk)
 {
 	struct migrate_vma *migrate = walk->private;
@@ -2163,7 +2164,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 
 again:
 	if (pmd_none(*pmdp))
-		return migrate_vma_collect_hole(start, end, walk);
+		return migrate_vma_collect_hole(start, end, -1, walk);
 
 	if (pmd_trans_huge(*pmdp)) {
 		struct page *page;
@@ -2196,7 +2197,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 				return migrate_vma_collect_skip(start, end,
 								walk);
 			if (pmd_none(*pmdp))
-				return migrate_vma_collect_hole(start, end,
+				return migrate_vma_collect_hole(start, end, -1,
 								walk);
 		}
 	}
diff --git a/mm/mincore.c b/mm/mincore.c
index 49b6fa2f6aa1..0e6dd9948f1a 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -112,6 +112,7 @@ static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
 }
 
 static int mincore_unmapped_range(unsigned long addr, unsigned long end,
+				   __always_unused int depth,
 				   struct mm_walk *walk)
 {
 	walk->private += __mincore_unmapped_range(addr, end,
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 6732fc7ac4c8..5895ce4f1a85 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -4,6 +4,22 @@
 #include <linux/sched.h>
 #include <linux/hugetlb.h>
 
+/*
+ * We want to know the real level where a entry is located ignoring any
+ * folding of levels which may be happening. For example if p4d is folded then
+ * a missing entry found at level 1 (p4d) is actually at level 0 (pgd).
+ */
+static int real_depth(int depth)
+{
+	if (depth == 3 && PTRS_PER_PMD == 1)
+		depth = 2;
+	if (depth == 2 && PTRS_PER_PUD == 1)
+		depth = 1;
+	if (depth == 1 && PTRS_PER_P4D == 1)
+		depth = 0;
+	return depth;
+}
+
 static int walk_pte_range_inner(pte_t *pte, unsigned long addr,
 				unsigned long end, struct mm_walk *walk)
 {
@@ -49,6 +65,7 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 	unsigned long next;
 	const struct mm_walk_ops *ops = walk->ops;
 	int err = 0;
+	int depth = real_depth(3);
 
 	pmd = pmd_offset(pud, addr);
 	do {
@@ -56,7 +73,7 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 		next = pmd_addr_end(addr, end);
 		if (pmd_none(*pmd) || (!walk->vma && !walk->no_vma)) {
 			if (ops->pte_hole)
-				err = ops->pte_hole(addr, next, walk);
+				err = ops->pte_hole(addr, next, depth, walk);
 			if (err)
 				break;
 			continue;
@@ -106,6 +123,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 	unsigned long next;
 	const struct mm_walk_ops *ops = walk->ops;
 	int err = 0;
+	int depth = real_depth(2);
 
 	pud = pud_offset(p4d, addr);
 	do {
@@ -113,7 +131,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 		next = pud_addr_end(addr, end);
 		if (pud_none(*pud) || (!walk->vma && !walk->no_vma)) {
 			if (ops->pte_hole)
-				err = ops->pte_hole(addr, next, walk);
+				err = ops->pte_hole(addr, next, depth, walk);
 			if (err)
 				break;
 			continue;
@@ -154,13 +172,14 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
 	unsigned long next;
 	const struct mm_walk_ops *ops = walk->ops;
 	int err = 0;
+	int depth = real_depth(1);
 
 	p4d = p4d_offset(pgd, addr);
 	do {
 		next = p4d_addr_end(addr, end);
 		if (p4d_none_or_clear_bad(p4d)) {
 			if (ops->pte_hole)
-				err = ops->pte_hole(addr, next, walk);
+				err = ops->pte_hole(addr, next, depth, walk);
 			if (err)
 				break;
 			continue;
@@ -192,7 +211,7 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
 		next = pgd_addr_end(addr, end);
 		if (pgd_none_or_clear_bad(pgd)) {
 			if (ops->pte_hole)
-				err = ops->pte_hole(addr, next, walk);
+				err = ops->pte_hole(addr, next, 0, walk);
 			if (err)
 				break;
 			continue;
@@ -239,7 +258,7 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
 		if (pte)
 			err = ops->hugetlb_entry(pte, hmask, addr, next, walk);
 		else if (ops->pte_hole)
-			err = ops->pte_hole(addr, next, walk);
+			err = ops->pte_hole(addr, next, -1, walk);
 
 		if (err)
 			break;
@@ -283,7 +302,7 @@ static int walk_page_test(unsigned long start, unsigned long end,
 	if (vma->vm_flags & VM_PFNMAP) {
 		int err = 1;
 		if (ops->pte_hole)
-			err = ops->pte_hole(start, end, walk);
+			err = ops->pte_hole(start, end, -1, walk);
 		return err ? err : 1;
 	}
 	return 0;
-- 
2.20.1


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[PATCH v17 16/23] x86: mm: Point to struct seq_file from struct pg_state

[Steven Price]

mm/dump_pagetables.c passes both struct seq_file and struct pg_state
down the chain of walk_*_level() functions to be passed to note_page().
Instead place the struct seq_file in struct pg_state and access it from
struct pg_state (which is private to this file) in note_page().

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/x86/mm/dump_pagetables.c | 69 ++++++++++++++++++-----------------
 1 file changed, 35 insertions(+), 34 deletions(-)

diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index ab67822fd2f4..4dc6f4df40af 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -36,6 +36,7 @@ struct pg_state {
 	bool to_dmesg;
 	bool check_wx;
 	unsigned long wx_pages;
+	struct seq_file *seq;
 };
 
 struct addr_marker {
@@ -265,11 +266,12 @@ static void note_wx(struct pg_state *st)
  * of PTE entries; the next one is different so we need to
  * print what we collected so far.
  */
-static void note_page(struct seq_file *m, struct pg_state *st,
-		      pgprot_t new_prot, pgprotval_t new_eff, int level)
+static void note_page(struct pg_state *st, pgprot_t new_prot,
+		      pgprotval_t new_eff, int level)
 {
 	pgprotval_t prot, cur, eff;
 	static const char units[] = "BKMGTPE";
+	struct seq_file *m = st->seq;
 
 	/*
 	 * If we have a "break" in the series, we need to flush the state that
@@ -354,8 +356,8 @@ static inline pgprotval_t effective_prot(pgprotval_t prot1, pgprotval_t prot2)
 	       ((prot1 | prot2) & _PAGE_NX);
 }
 
-static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
-			   pgprotval_t eff_in, unsigned long P)
+static void walk_pte_level(struct pg_state *st, pmd_t addr, pgprotval_t eff_in,
+			   unsigned long P)
 {
 	int i;
 	pte_t *pte;
@@ -366,7 +368,7 @@ static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
 		pte = pte_offset_map(&addr, st->current_address);
 		prot = pte_flags(*pte);
 		eff = effective_prot(eff_in, prot);
-		note_page(m, st, __pgprot(prot), eff, 5);
+		note_page(st, __pgprot(prot), eff, 5);
 		pte_unmap(pte);
 	}
 }
@@ -379,22 +381,20 @@ static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
  * us dozens of seconds (minutes for 5-level config) while checking for
  * W+X mapping or reading kernel_page_tables debugfs file.
  */
-static inline bool kasan_page_table(struct seq_file *m, struct pg_state *st,
-				void *pt)
+static inline bool kasan_page_table(struct pg_state *st, void *pt)
 {
 	if (__pa(pt) == __pa(kasan_early_shadow_pmd) ||
 	    (pgtable_l5_enabled() &&
 			__pa(pt) == __pa(kasan_early_shadow_p4d)) ||
 	    __pa(pt) == __pa(kasan_early_shadow_pud)) {
 		pgprotval_t prot = pte_flags(kasan_early_shadow_pte[0]);
-		note_page(m, st, __pgprot(prot), 0, 5);
+		note_page(st, __pgprot(prot), 0, 5);
 		return true;
 	}
 	return false;
 }
 #else
-static inline bool kasan_page_table(struct seq_file *m, struct pg_state *st,
-				void *pt)
+static inline bool kasan_page_table(struct pg_state *st, void *pt)
 {
 	return false;
 }
@@ -402,7 +402,7 @@ static inline bool kasan_page_table(struct seq_file *m, struct pg_state *st,
 
 #if PTRS_PER_PMD > 1
 
-static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
+static void walk_pmd_level(struct pg_state *st, pud_t addr,
 			   pgprotval_t eff_in, unsigned long P)
 {
 	int i;
@@ -416,27 +416,27 @@ static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
 			prot = pmd_flags(*start);
 			eff = effective_prot(eff_in, prot);
 			if (pmd_large(*start) || !pmd_present(*start)) {
-				note_page(m, st, __pgprot(prot), eff, 4);
-			} else if (!kasan_page_table(m, st, pmd_start)) {
-				walk_pte_level(m, st, *start, eff,
+				note_page(st, __pgprot(prot), eff, 4);
+			} else if (!kasan_page_table(st, pmd_start)) {
+				walk_pte_level(st, *start, eff,
 					       P + i * PMD_LEVEL_MULT);
 			}
 		} else
-			note_page(m, st, __pgprot(0), 0, 4);
+			note_page(st, __pgprot(0), 0, 4);
 		start++;
 	}
 }
 
 #else
-#define walk_pmd_level(m,s,a,e,p) walk_pte_level(m,s,__pmd(pud_val(a)),e,p)
+#define walk_pmd_level(s,a,e,p) walk_pte_level(s,__pmd(pud_val(a)),e,p)
 #define pud_large(a) pmd_large(__pmd(pud_val(a)))
 #define pud_none(a)  pmd_none(__pmd(pud_val(a)))
 #endif
 
 #if PTRS_PER_PUD > 1
 
-static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr,
-			   pgprotval_t eff_in, unsigned long P)
+static void walk_pud_level(struct pg_state *st, p4d_t addr, pgprotval_t eff_in,
+			   unsigned long P)
 {
 	int i;
 	pud_t *start, *pud_start;
@@ -450,33 +450,33 @@ static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr,
 			prot = pud_flags(*start);
 			eff = effective_prot(eff_in, prot);
 			if (pud_large(*start) || !pud_present(*start)) {
-				note_page(m, st, __pgprot(prot), eff, 3);
-			} else if (!kasan_page_table(m, st, pud_start)) {
-				walk_pmd_level(m, st, *start, eff,
+				note_page(st, __pgprot(prot), eff, 3);
+			} else if (!kasan_page_table(st, pud_start)) {
+				walk_pmd_level(st, *start, eff,
 					       P + i * PUD_LEVEL_MULT);
 			}
 		} else
-			note_page(m, st, __pgprot(0), 0, 3);
+			note_page(st, __pgprot(0), 0, 3);
 
 		start++;
 	}
 }
 
 #else
-#define walk_pud_level(m,s,a,e,p) walk_pmd_level(m,s,__pud(p4d_val(a)),e,p)
+#define walk_pud_level(s,a,e,p) walk_pmd_level(s,__pud(p4d_val(a)),e,p)
 #define p4d_large(a) pud_large(__pud(p4d_val(a)))
 #define p4d_none(a)  pud_none(__pud(p4d_val(a)))
 #endif
 
-static void walk_p4d_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
-			   pgprotval_t eff_in, unsigned long P)
+static void walk_p4d_level(struct pg_state *st, pgd_t addr, pgprotval_t eff_in,
+			   unsigned long P)
 {
 	int i;
 	p4d_t *start, *p4d_start;
 	pgprotval_t prot, eff;
 
 	if (PTRS_PER_P4D == 1)
-		return walk_pud_level(m, st, __p4d(pgd_val(addr)), eff_in, P);
+		return walk_pud_level(st, __p4d(pgd_val(addr)), eff_in, P);
 
 	p4d_start = start = (p4d_t *)pgd_page_vaddr(addr);
 
@@ -486,13 +486,13 @@ static void walk_p4d_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
 			prot = p4d_flags(*start);
 			eff = effective_prot(eff_in, prot);
 			if (p4d_large(*start) || !p4d_present(*start)) {
-				note_page(m, st, __pgprot(prot), eff, 2);
-			} else if (!kasan_page_table(m, st, p4d_start)) {
-				walk_pud_level(m, st, *start, eff,
+				note_page(st, __pgprot(prot), eff, 2);
+			} else if (!kasan_page_table(st, p4d_start)) {
+				walk_pud_level(st, *start, eff,
 					       P + i * P4D_LEVEL_MULT);
 			}
 		} else
-			note_page(m, st, __pgprot(0), 0, 2);
+			note_page(st, __pgprot(0), 0, 2);
 
 		start++;
 	}
@@ -529,6 +529,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 	}
 
 	st.check_wx = checkwx;
+	st.seq = m;
 	if (checkwx)
 		st.wx_pages = 0;
 
@@ -542,13 +543,13 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 			eff = prot;
 #endif
 			if (pgd_large(*start) || !pgd_present(*start)) {
-				note_page(m, &st, __pgprot(prot), eff, 1);
+				note_page(&st, __pgprot(prot), eff, 1);
 			} else {
-				walk_p4d_level(m, &st, *start, eff,
+				walk_p4d_level(&st, *start, eff,
 					       i * PGD_LEVEL_MULT);
 			}
 		} else
-			note_page(m, &st, __pgprot(0), 0, 1);
+			note_page(&st, __pgprot(0), 0, 1);
 
 		cond_resched();
 		start++;
@@ -556,7 +557,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 
 	/* Flush out the last page */
 	st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
-	note_page(m, &st, __pgprot(0), 0, 0);
+	note_page(&st, __pgprot(0), 0, 0);
 	if (!checkwx)
 		return;
 	if (st.wx_pages)
-- 
2.20.1


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[PATCH v17 17/23] x86: mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct

[Steven Price]

To enable x86 to use the generic walk_page_range() function, the
callers of ptdump_walk_pgd_level() need to pass an mm_struct rather
than the raw pgd_t pointer. Luckily since commit 7e904a91bf60
("efi: Use efi_mm in x86 as well as ARM") we now have an mm_struct
for EFI on x86.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/x86/include/asm/pgtable.h | 2 +-
 arch/x86/mm/dump_pagetables.c  | 4 ++--
 arch/x86/platform/efi/efi_32.c | 2 +-
 arch/x86/platform/efi/efi_64.c | 4 ++--
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 8091a1c62596..5a30bf58156e 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -29,7 +29,7 @@
 extern pgd_t early_top_pgt[PTRS_PER_PGD];
 int __init __early_make_pgtable(unsigned long address, pmdval_t pmd);
 
-void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd);
+void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm);
 void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd, bool user);
 void ptdump_walk_pgd_level_checkwx(void);
 void ptdump_walk_user_pgd_level_checkwx(void);
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 4dc6f4df40af..24fe76325b31 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -567,9 +567,9 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 		pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages found.\n");
 }
 
-void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
+void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm)
 {
-	ptdump_walk_pgd_level_core(m, pgd, false, true);
+	ptdump_walk_pgd_level_core(m, mm->pgd, false, true);
 }
 
 void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd, bool user)
diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c
index 9959657127f4..1616074075c3 100644
--- a/arch/x86/platform/efi/efi_32.c
+++ b/arch/x86/platform/efi/efi_32.c
@@ -49,7 +49,7 @@ void efi_sync_low_kernel_mappings(void) {}
 void __init efi_dump_pagetable(void)
 {
 #ifdef CONFIG_EFI_PGT_DUMP
-	ptdump_walk_pgd_level(NULL, swapper_pg_dir);
+	ptdump_walk_pgd_level(NULL, &init_mm);
 #endif
 }
 
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 08ce8177c3af..3cb63cd369d6 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -614,9 +614,9 @@ void __init efi_dump_pagetable(void)
 {
 #ifdef CONFIG_EFI_PGT_DUMP
 	if (efi_enabled(EFI_OLD_MEMMAP))
-		ptdump_walk_pgd_level(NULL, swapper_pg_dir);
+		ptdump_walk_pgd_level(NULL, &init_mm);
 	else
-		ptdump_walk_pgd_level(NULL, efi_mm.pgd);
+		ptdump_walk_pgd_level(NULL, &efi_mm);
 #endif
 }
 
-- 
2.20.1


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[PATCH v17 18/23] x86: mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct

[Steven Price]

To enable x86 to use the generic walk_page_range() function, the
callers of ptdump_walk_pgd_level_debugfs() need to pass in the mm_struct.

This means that ptdump_walk_pgd_level_core() is now always passed a
valid pgd, so drop the support for pgd==NULL.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/x86/include/asm/pgtable.h |  3 ++-
 arch/x86/mm/debug_pagetables.c |  8 ++++----
 arch/x86/mm/dump_pagetables.c  | 14 ++++++--------
 3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 5a30bf58156e..7e118660bbd9 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -30,7 +30,8 @@ extern pgd_t early_top_pgt[PTRS_PER_PGD];
 int __init __early_make_pgtable(unsigned long address, pmdval_t pmd);
 
 void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm);
-void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd, bool user);
+void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm,
+				   bool user);
 void ptdump_walk_pgd_level_checkwx(void);
 void ptdump_walk_user_pgd_level_checkwx(void);
 
diff --git a/arch/x86/mm/debug_pagetables.c b/arch/x86/mm/debug_pagetables.c
index 39001a401eff..d0efec713c6c 100644
--- a/arch/x86/mm/debug_pagetables.c
+++ b/arch/x86/mm/debug_pagetables.c
@@ -7,7 +7,7 @@
 
 static int ptdump_show(struct seq_file *m, void *v)
 {
-	ptdump_walk_pgd_level_debugfs(m, NULL, false);
+	ptdump_walk_pgd_level_debugfs(m, &init_mm, false);
 	return 0;
 }
 
@@ -17,7 +17,7 @@ static int ptdump_curknl_show(struct seq_file *m, void *v)
 {
 	if (current->mm->pgd) {
 		down_read(&current->mm->mmap_sem);
-		ptdump_walk_pgd_level_debugfs(m, current->mm->pgd, false);
+		ptdump_walk_pgd_level_debugfs(m, current->mm, false);
 		up_read(&current->mm->mmap_sem);
 	}
 	return 0;
@@ -30,7 +30,7 @@ static int ptdump_curusr_show(struct seq_file *m, void *v)
 {
 	if (current->mm->pgd) {
 		down_read(&current->mm->mmap_sem);
-		ptdump_walk_pgd_level_debugfs(m, current->mm->pgd, true);
+		ptdump_walk_pgd_level_debugfs(m, current->mm, true);
 		up_read(&current->mm->mmap_sem);
 	}
 	return 0;
@@ -43,7 +43,7 @@ DEFINE_SHOW_ATTRIBUTE(ptdump_curusr);
 static int ptdump_efi_show(struct seq_file *m, void *v)
 {
 	if (efi_mm.pgd)
-		ptdump_walk_pgd_level_debugfs(m, efi_mm.pgd, false);
+		ptdump_walk_pgd_level_debugfs(m, &efi_mm, false);
 	return 0;
 }
 
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 24fe76325b31..2f5f32f21f81 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -518,16 +518,12 @@ static inline bool is_hypervisor_range(int idx)
 static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 				       bool checkwx, bool dmesg)
 {
-	pgd_t *start = INIT_PGD;
+	pgd_t *start = pgd;
 	pgprotval_t prot, eff;
 	int i;
 	struct pg_state st = {};
 
-	if (pgd) {
-		start = pgd;
-		st.to_dmesg = dmesg;
-	}
-
+	st.to_dmesg = dmesg;
 	st.check_wx = checkwx;
 	st.seq = m;
 	if (checkwx)
@@ -572,8 +568,10 @@ void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm)
 	ptdump_walk_pgd_level_core(m, mm->pgd, false, true);
 }
 
-void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd, bool user)
+void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm,
+				   bool user)
 {
+	pgd_t *pgd = mm->pgd;
 #ifdef CONFIG_PAGE_TABLE_ISOLATION
 	if (user && boot_cpu_has(X86_FEATURE_PTI))
 		pgd = kernel_to_user_pgdp(pgd);
@@ -599,7 +597,7 @@ void ptdump_walk_user_pgd_level_checkwx(void)
 
 void ptdump_walk_pgd_level_checkwx(void)
 {
-	ptdump_walk_pgd_level_core(NULL, NULL, true, false);
+	ptdump_walk_pgd_level_core(NULL, INIT_PGD, true, false);
 }
 
 static int __init pt_dump_init(void)
-- 
2.20.1


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[PATCH v17 19/23] mm: Add generic ptdump

[Steven Price]

Add a generic version of page table dumping that architectures can
opt-in to

Signed-off-by: Steven Price <steven.price@arm.com>
---
 include/linux/ptdump.h |  21 +++++++
 mm/Kconfig.debug       |  21 +++++++
 mm/Makefile            |   1 +
 mm/ptdump.c            | 139 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 182 insertions(+)
 create mode 100644 include/linux/ptdump.h
 create mode 100644 mm/ptdump.c

diff --git a/include/linux/ptdump.h b/include/linux/ptdump.h
new file mode 100644
index 000000000000..a0fb8dd2be97
--- /dev/null
+++ b/include/linux/ptdump.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _LINUX_PTDUMP_H
+#define _LINUX_PTDUMP_H
+
+#include <linux/mm_types.h>
+
+struct ptdump_range {
+	unsigned long start;
+	unsigned long end;
+};
+
+struct ptdump_state {
+	void (*note_page)(struct ptdump_state *st, unsigned long addr,
+			  int level, unsigned long val);
+	const struct ptdump_range *range;
+};
+
+void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm);
+
+#endif /* _LINUX_PTDUMP_H */
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 327b3ebf23bf..0271b22e063f 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -117,3 +117,24 @@ config DEBUG_RODATA_TEST
     depends on STRICT_KERNEL_RWX
     ---help---
       This option enables a testcase for the setting rodata read-only.
+
+config GENERIC_PTDUMP
+	bool
+
+config PTDUMP_CORE
+	bool
+
+config PTDUMP_DEBUGFS
+	bool "Export kernel pagetable layout to userspace via debugfs"
+	depends on DEBUG_KERNEL
+	depends on DEBUG_FS
+	depends on GENERIC_PTDUMP
+	select PTDUMP_CORE
+	help
+	  Say Y here if you want to show the kernel pagetable layout in a
+	  debugfs file. This information is only useful for kernel developers
+	  who are working in architecture specific areas of the kernel.
+	  It is probably not a good idea to enable this feature in a production
+	  kernel.
+
+	  If in doubt, say N.
diff --git a/mm/Makefile b/mm/Makefile
index 1937cc251883..a8eff811f6c4 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -108,3 +108,4 @@ obj-$(CONFIG_ZONE_DEVICE) += memremap.o
 obj-$(CONFIG_HMM_MIRROR) += hmm.o
 obj-$(CONFIG_MEMFD_CREATE) += memfd.o
 obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o
+obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
diff --git a/mm/ptdump.c b/mm/ptdump.c
new file mode 100644
index 000000000000..868638b8e404
--- /dev/null
+++ b/mm/ptdump.c
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/pagewalk.h>
+#include <linux/ptdump.h>
+#include <linux/kasan.h>
+
+#ifdef CONFIG_KASAN
+/*
+ * This is an optimization for KASAN=y case. Since all kasan page tables
+ * eventually point to the kasan_early_shadow_page we could call note_page()
+ * right away without walking through lower level page tables. This saves
+ * us dozens of seconds (minutes for 5-level config) while checking for
+ * W+X mapping or reading kernel_page_tables debugfs file.
+ */
+static inline int note_kasan_page_table(struct mm_walk *walk,
+					unsigned long addr)
+{
+	struct ptdump_state *st = walk->private;
+
+	st->note_page(st, addr, 5, pte_val(kasan_early_shadow_pte[0]));
+
+	walk->action = ACTION_CONTINUE;
+
+	return 0;
+}
+#endif
+
+static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,
+			    unsigned long next, struct mm_walk *walk)
+{
+	struct ptdump_state *st = walk->private;
+	pgd_t val = READ_ONCE(*pgd);
+
+#if CONFIG_PGTABLE_LEVELS > 4 && defined(CONFIG_KASAN)
+	if (pgd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_p4d)))
+		return note_kasan_page_table(walk, addr);
+#endif
+
+	if (pgd_leaf(val))
+		st->note_page(st, addr, 1, pgd_val(val));
+
+	return 0;
+}
+
+static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
+			    unsigned long next, struct mm_walk *walk)
+{
+	struct ptdump_state *st = walk->private;
+	p4d_t val = READ_ONCE(*p4d);
+
+#if CONFIG_PGTABLE_LEVELS > 3 && defined(CONFIG_KASAN)
+	if (p4d_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pud)))
+		return note_kasan_page_table(walk, addr);
+#endif
+
+	if (p4d_leaf(val))
+		st->note_page(st, addr, 2, p4d_val(val));
+
+	return 0;
+}
+
+static int ptdump_pud_entry(pud_t *pud, unsigned long addr,
+			    unsigned long next, struct mm_walk *walk)
+{
+	struct ptdump_state *st = walk->private;
+	pud_t val = READ_ONCE(*pud);
+
+#if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_KASAN)
+	if (pud_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pmd)))
+		return note_kasan_page_table(walk, addr);
+#endif
+
+	if (pud_leaf(val))
+		st->note_page(st, addr, 3, pud_val(val));
+
+	return 0;
+}
+
+static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,
+			    unsigned long next, struct mm_walk *walk)
+{
+	struct ptdump_state *st = walk->private;
+	pmd_t val = READ_ONCE(*pmd);
+
+#if defined(CONFIG_KASAN)
+	if (pmd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pte)))
+		return note_kasan_page_table(walk, addr);
+#endif
+
+	if (pmd_leaf(val))
+		st->note_page(st, addr, 4, pmd_val(val));
+
+	return 0;
+}
+
+static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
+			    unsigned long next, struct mm_walk *walk)
+{
+	struct ptdump_state *st = walk->private;
+
+	st->note_page(st, addr, 5, pte_val(READ_ONCE(*pte)));
+
+	return 0;
+}
+
+static int ptdump_hole(unsigned long addr, unsigned long next,
+		       int depth, struct mm_walk *walk)
+{
+	struct ptdump_state *st = walk->private;
+
+	st->note_page(st, addr, depth + 1, 0);
+
+	return 0;
+}
+
+static const struct mm_walk_ops ptdump_ops = {
+	.pgd_entry	= ptdump_pgd_entry,
+	.p4d_entry	= ptdump_p4d_entry,
+	.pud_entry	= ptdump_pud_entry,
+	.pmd_entry	= ptdump_pmd_entry,
+	.pte_entry	= ptdump_pte_entry,
+	.pte_hole	= ptdump_hole,
+};
+
+void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm)
+{
+	const struct ptdump_range *range = st->range;
+
+	down_read(&mm->mmap_sem);
+	while (range->start != range->end) {
+		walk_page_range_novma(mm, range->start, range->end,
+				      &ptdump_ops, st);
+		range++;
+	}
+	up_read(&mm->mmap_sem);
+
+	/* Flush out the last page */
+	st->note_page(st, 0, 0, 0);
+}
-- 
2.20.1


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[PATCH v17 20/23] x86: mm: Convert dump_pagetables to use walk_page_range

[Steven Price]

Make use of the new functionality in walk_page_range to remove the
arch page walking code and use the generic code to walk the page tables.

The effective permissions are passed down the chain using new fields
in struct pg_state.

The KASAN optimisation is implemented by setting action=CONTINUE in the
callbacks to skip an entire tree of entries.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/x86/Kconfig              |   1 +
 arch/x86/Kconfig.debug        |  20 +--
 arch/x86/mm/Makefile          |   4 +-
 arch/x86/mm/dump_pagetables.c | 292 ++++++++--------------------------
 4 files changed, 70 insertions(+), 247 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5e8949953660..8a9594817874 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -119,6 +119,7 @@ config X86
 	select GENERIC_IRQ_RESERVATION_MODE
 	select GENERIC_IRQ_SHOW
 	select GENERIC_PENDING_IRQ		if SMP
+	select GENERIC_PTDUMP
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_STRNCPY_FROM_USER
 	select GENERIC_STRNLEN_USER
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index c4eab8ed33a3..2e74690b028a 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -62,26 +62,10 @@ config EARLY_PRINTK_USB_XDBC
 config MCSAFE_TEST
 	def_bool n
 
-config X86_PTDUMP_CORE
-	def_bool n
-
-config X86_PTDUMP
-	tristate "Export kernel pagetable layout to userspace via debugfs"
-	depends on DEBUG_KERNEL
-	select DEBUG_FS
-	select X86_PTDUMP_CORE
-	---help---
-	  Say Y here if you want to show the kernel pagetable layout in a
-	  debugfs file. This information is only useful for kernel developers
-	  who are working in architecture specific areas of the kernel.
-	  It is probably not a good idea to enable this feature in a production
-	  kernel.
-	  If in doubt, say "N"
-
 config EFI_PGT_DUMP
 	bool "Dump the EFI pagetable"
 	depends on EFI
-	select X86_PTDUMP_CORE
+	select PTDUMP_CORE
 	---help---
 	  Enable this if you want to dump the EFI page table before
 	  enabling virtual mode. This can be used to debug miscellaneous
@@ -90,7 +74,7 @@ config EFI_PGT_DUMP
 
 config DEBUG_WX
 	bool "Warn on W+X mappings at boot"
-	select X86_PTDUMP_CORE
+	select PTDUMP_CORE
 	---help---
 	  Generate a warning if any W+X mappings are found at boot.
 
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 3b89c201ac26..ad44713b2e1e 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -28,8 +28,8 @@ obj-$(CONFIG_X86_PAT)		+= pat_interval.o
 obj-$(CONFIG_X86_32)		+= pgtable_32.o iomap_32.o
 
 obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
-obj-$(CONFIG_X86_PTDUMP_CORE)	+= dump_pagetables.o
-obj-$(CONFIG_X86_PTDUMP)	+= debug_pagetables.o
+obj-$(CONFIG_PTDUMP_CORE)	+= dump_pagetables.o
+obj-$(CONFIG_PTDUMP_DEBUGFS)	+= debug_pagetables.o
 
 obj-$(CONFIG_HIGHMEM)		+= highmem_32.o
 
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 2f5f32f21f81..a0b8ffc927bb 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -16,6 +16,7 @@
 #include <linux/seq_file.h>
 #include <linux/highmem.h>
 #include <linux/pci.h>
+#include <linux/ptdump.h>
 
 #include <asm/e820/types.h>
 #include <asm/pgtable.h>
@@ -26,11 +27,12 @@
  * when a "break" in the continuity is found.
  */
 struct pg_state {
+	struct ptdump_state ptdump;
 	int level;
-	pgprot_t current_prot;
+	pgprotval_t current_prot;
 	pgprotval_t effective_prot;
+	pgprotval_t prot_levels[5];
 	unsigned long start_address;
-	unsigned long current_address;
 	const struct addr_marker *marker;
 	unsigned long lines;
 	bool to_dmesg;
@@ -175,9 +177,8 @@ static struct addr_marker address_markers[] = {
 /*
  * Print a readable form of a pgprot_t to the seq_file
  */
-static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
+static void printk_prot(struct seq_file *m, pgprotval_t pr, int level, bool dmsg)
 {
-	pgprotval_t pr = pgprot_val(prot);
 	static const char * const level_name[] =
 		{ "cr3", "pgd", "p4d", "pud", "pmd", "pte" };
 
@@ -224,24 +225,11 @@ static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
 	pt_dump_cont_printf(m, dmsg, "%s\n", level_name[level]);
 }
 
-/*
- * On 64 bits, sign-extend the 48 bit address to 64 bit
- */
-static unsigned long normalize_addr(unsigned long u)
-{
-	int shift;
-	if (!IS_ENABLED(CONFIG_X86_64))
-		return u;
-
-	shift = 64 - (__VIRTUAL_MASK_SHIFT + 1);
-	return (signed long)(u << shift) >> shift;
-}
-
-static void note_wx(struct pg_state *st)
+static void note_wx(struct pg_state *st, unsigned long addr)
 {
 	unsigned long npages;
 
-	npages = (st->current_address - st->start_address) / PAGE_SIZE;
+	npages = (addr - st->start_address) / PAGE_SIZE;
 
 #ifdef CONFIG_PCI_BIOS
 	/*
@@ -249,7 +237,7 @@ static void note_wx(struct pg_state *st)
 	 * Inform about it, but avoid the warning.
 	 */
 	if (pcibios_enabled && st->start_address >= PAGE_OFFSET + BIOS_BEGIN &&
-	    st->current_address <= PAGE_OFFSET + BIOS_END) {
+	    addr <= PAGE_OFFSET + BIOS_END) {
 		pr_warn_once("x86/mm: PCI BIOS W+X mapping %lu pages\n", npages);
 		return;
 	}
@@ -261,25 +249,44 @@ static void note_wx(struct pg_state *st)
 		  (void *)st->start_address);
 }
 
+static inline pgprotval_t effective_prot(pgprotval_t prot1, pgprotval_t prot2)
+{
+	return (prot1 & prot2 & (_PAGE_USER | _PAGE_RW)) |
+	       ((prot1 | prot2) & _PAGE_NX);
+}
+
 /*
  * This function gets called on a break in a continuous series
  * of PTE entries; the next one is different so we need to
  * print what we collected so far.
  */
-static void note_page(struct pg_state *st, pgprot_t new_prot,
-		      pgprotval_t new_eff, int level)
+static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
+		      unsigned long val)
 {
-	pgprotval_t prot, cur, eff;
+	struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
+	pgprotval_t new_prot, new_eff;
+	pgprotval_t cur, eff;
 	static const char units[] = "BKMGTPE";
 	struct seq_file *m = st->seq;
 
+	new_prot = val & PTE_FLAGS_MASK;
+
+	if (level > 1) {
+		new_eff = effective_prot(st->prot_levels[level - 2],
+					 new_prot);
+	} else {
+		new_eff = new_prot;
+	}
+
+	if (level > 0)
+		st->prot_levels[level - 1] = new_eff;
+
 	/*
 	 * If we have a "break" in the series, we need to flush the state that
 	 * we have now. "break" is either changing perms, levels or
 	 * address space marker.
 	 */
-	prot = pgprot_val(new_prot);
-	cur = pgprot_val(st->current_prot);
+	cur = st->current_prot;
 	eff = st->effective_prot;
 
 	if (!st->level) {
@@ -291,14 +298,14 @@ static void note_page(struct pg_state *st, pgprot_t new_prot,
 		st->lines = 0;
 		pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 				   st->marker->name);
-	} else if (prot != cur || new_eff != eff || level != st->level ||
-		   st->current_address >= st->marker[1].start_address) {
+	} else if (new_prot != cur || new_eff != eff || level != st->level ||
+		   addr >= st->marker[1].start_address) {
 		const char *unit = units;
 		unsigned long delta;
 		int width = sizeof(unsigned long) * 2;
 
 		if (st->check_wx && (eff & _PAGE_RW) && !(eff & _PAGE_NX))
-			note_wx(st);
+			note_wx(st, addr);
 
 		/*
 		 * Now print the actual finished series
@@ -308,9 +315,9 @@ static void note_page(struct pg_state *st, pgprot_t new_prot,
 			pt_dump_seq_printf(m, st->to_dmesg,
 					   "0x%0*lx-0x%0*lx   ",
 					   width, st->start_address,
-					   width, st->current_address);
+					   width, addr);
 
-			delta = st->current_address - st->start_address;
+			delta = addr - st->start_address;
 			while (!(delta & 1023) && unit[1]) {
 				delta >>= 10;
 				unit++;
@@ -327,7 +334,7 @@ static void note_page(struct pg_state *st, pgprot_t new_prot,
 		 * such as the start of vmalloc space etc.
 		 * This helps in the interpretation.
 		 */
-		if (st->current_address >= st->marker[1].start_address) {
+		if (addr >= st->marker[1].start_address) {
 			if (st->marker->max_lines &&
 			    st->lines > st->marker->max_lines) {
 				unsigned long nskip =
@@ -343,217 +350,48 @@ static void note_page(struct pg_state *st, pgprot_t new_prot,
 					   st->marker->name);
 		}
 
-		st->start_address = st->current_address;
+		st->start_address = addr;
 		st->current_prot = new_prot;
 		st->effective_prot = new_eff;
 		st->level = level;
 	}
 }
 
-static inline pgprotval_t effective_prot(pgprotval_t prot1, pgprotval_t prot2)
-{
-	return (prot1 & prot2 & (_PAGE_USER | _PAGE_RW)) |
-	       ((prot1 | prot2) & _PAGE_NX);
-}
-
-static void walk_pte_level(struct pg_state *st, pmd_t addr, pgprotval_t eff_in,
-			   unsigned long P)
-{
-	int i;
-	pte_t *pte;
-	pgprotval_t prot, eff;
-
-	for (i = 0; i < PTRS_PER_PTE; i++) {
-		st->current_address = normalize_addr(P + i * PTE_LEVEL_MULT);
-		pte = pte_offset_map(&addr, st->current_address);
-		prot = pte_flags(*pte);
-		eff = effective_prot(eff_in, prot);
-		note_page(st, __pgprot(prot), eff, 5);
-		pte_unmap(pte);
-	}
-}
-#ifdef CONFIG_KASAN
-
-/*
- * This is an optimization for KASAN=y case. Since all kasan page tables
- * eventually point to the kasan_early_shadow_page we could call note_page()
- * right away without walking through lower level page tables. This saves
- * us dozens of seconds (minutes for 5-level config) while checking for
- * W+X mapping or reading kernel_page_tables debugfs file.
- */
-static inline bool kasan_page_table(struct pg_state *st, void *pt)
-{
-	if (__pa(pt) == __pa(kasan_early_shadow_pmd) ||
-	    (pgtable_l5_enabled() &&
-			__pa(pt) == __pa(kasan_early_shadow_p4d)) ||
-	    __pa(pt) == __pa(kasan_early_shadow_pud)) {
-		pgprotval_t prot = pte_flags(kasan_early_shadow_pte[0]);
-		note_page(st, __pgprot(prot), 0, 5);
-		return true;
-	}
-	return false;
-}
-#else
-static inline bool kasan_page_table(struct pg_state *st, void *pt)
-{
-	return false;
-}
-#endif
-
-#if PTRS_PER_PMD > 1
-
-static void walk_pmd_level(struct pg_state *st, pud_t addr,
-			   pgprotval_t eff_in, unsigned long P)
-{
-	int i;
-	pmd_t *start, *pmd_start;
-	pgprotval_t prot, eff;
-
-	pmd_start = start = (pmd_t *)pud_page_vaddr(addr);
-	for (i = 0; i < PTRS_PER_PMD; i++) {
-		st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
-		if (!pmd_none(*start)) {
-			prot = pmd_flags(*start);
-			eff = effective_prot(eff_in, prot);
-			if (pmd_large(*start) || !pmd_present(*start)) {
-				note_page(st, __pgprot(prot), eff, 4);
-			} else if (!kasan_page_table(st, pmd_start)) {
-				walk_pte_level(st, *start, eff,
-					       P + i * PMD_LEVEL_MULT);
-			}
-		} else
-			note_page(st, __pgprot(0), 0, 4);
-		start++;
-	}
-}
-
-#else
-#define walk_pmd_level(s,a,e,p) walk_pte_level(s,__pmd(pud_val(a)),e,p)
-#define pud_large(a) pmd_large(__pmd(pud_val(a)))
-#define pud_none(a)  pmd_none(__pmd(pud_val(a)))
-#endif
-
-#if PTRS_PER_PUD > 1
-
-static void walk_pud_level(struct pg_state *st, p4d_t addr, pgprotval_t eff_in,
-			   unsigned long P)
+static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
+				       bool checkwx, bool dmesg)
 {
-	int i;
-	pud_t *start, *pud_start;
-	pgprotval_t prot, eff;
-
-	pud_start = start = (pud_t *)p4d_page_vaddr(addr);
-
-	for (i = 0; i < PTRS_PER_PUD; i++) {
-		st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
-		if (!pud_none(*start)) {
-			prot = pud_flags(*start);
-			eff = effective_prot(eff_in, prot);
-			if (pud_large(*start) || !pud_present(*start)) {
-				note_page(st, __pgprot(prot), eff, 3);
-			} else if (!kasan_page_table(st, pud_start)) {
-				walk_pmd_level(st, *start, eff,
-					       P + i * PUD_LEVEL_MULT);
-			}
-		} else
-			note_page(st, __pgprot(0), 0, 3);
+	const struct ptdump_range ptdump_ranges[] = {
+#ifdef CONFIG_X86_64
 
-		start++;
-	}
-}
+#define normalize_addr_shift (64 - (__VIRTUAL_MASK_SHIFT + 1))
+#define normalize_addr(u) ((signed long)((u) << normalize_addr_shift) >> \
+			   normalize_addr_shift)
 
+	{0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
+	{normalize_addr(PTRS_PER_PGD * PGD_LEVEL_MULT / 2), ~0UL},
 #else
-#define walk_pud_level(s,a,e,p) walk_pmd_level(s,__pud(p4d_val(a)),e,p)
-#define p4d_large(a) pud_large(__pud(p4d_val(a)))
-#define p4d_none(a)  pud_none(__pud(p4d_val(a)))
+	{0, ~0UL},
 #endif
+	{0, 0}
+};
 
-static void walk_p4d_level(struct pg_state *st, pgd_t addr, pgprotval_t eff_in,
-			   unsigned long P)
-{
-	int i;
-	p4d_t *start, *p4d_start;
-	pgprotval_t prot, eff;
-
-	if (PTRS_PER_P4D == 1)
-		return walk_pud_level(st, __p4d(pgd_val(addr)), eff_in, P);
-
-	p4d_start = start = (p4d_t *)pgd_page_vaddr(addr);
-
-	for (i = 0; i < PTRS_PER_P4D; i++) {
-		st->current_address = normalize_addr(P + i * P4D_LEVEL_MULT);
-		if (!p4d_none(*start)) {
-			prot = p4d_flags(*start);
-			eff = effective_prot(eff_in, prot);
-			if (p4d_large(*start) || !p4d_present(*start)) {
-				note_page(st, __pgprot(prot), eff, 2);
-			} else if (!kasan_page_table(st, p4d_start)) {
-				walk_pud_level(st, *start, eff,
-					       P + i * P4D_LEVEL_MULT);
-			}
-		} else
-			note_page(st, __pgprot(0), 0, 2);
-
-		start++;
-	}
-}
+	struct pg_state st = {
+		.ptdump = {
+			.note_page	= note_page,
+			.range		= ptdump_ranges
+		},
+		.to_dmesg	= dmesg,
+		.check_wx	= checkwx,
+		.seq		= m
+	};
 
-#define pgd_large(a) (pgtable_l5_enabled() ? pgd_large(a) : p4d_large(__p4d(pgd_val(a))))
-#define pgd_none(a)  (pgtable_l5_enabled() ? pgd_none(a) : p4d_none(__p4d(pgd_val(a))))
+	struct mm_struct fake_mm = {
+		.pgd = pgd
+	};
+	init_rwsem(&fake_mm.mmap_sem);
 
-static inline bool is_hypervisor_range(int idx)
-{
-#ifdef CONFIG_X86_64
-	/*
-	 * A hole in the beginning of kernel address space reserved
-	 * for a hypervisor.
-	 */
-	return	(idx >= pgd_index(GUARD_HOLE_BASE_ADDR)) &&
-		(idx <  pgd_index(GUARD_HOLE_END_ADDR));
-#else
-	return false;
-#endif
-}
-
-static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
-				       bool checkwx, bool dmesg)
-{
-	pgd_t *start = pgd;
-	pgprotval_t prot, eff;
-	int i;
-	struct pg_state st = {};
-
-	st.to_dmesg = dmesg;
-	st.check_wx = checkwx;
-	st.seq = m;
-	if (checkwx)
-		st.wx_pages = 0;
-
-	for (i = 0; i < PTRS_PER_PGD; i++) {
-		st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
-		if (!pgd_none(*start) && !is_hypervisor_range(i)) {
-			prot = pgd_flags(*start);
-#ifdef CONFIG_X86_PAE
-			eff = _PAGE_USER | _PAGE_RW;
-#else
-			eff = prot;
-#endif
-			if (pgd_large(*start) || !pgd_present(*start)) {
-				note_page(&st, __pgprot(prot), eff, 1);
-			} else {
-				walk_p4d_level(&st, *start, eff,
-					       i * PGD_LEVEL_MULT);
-			}
-		} else
-			note_page(&st, __pgprot(0), 0, 1);
-
-		cond_resched();
-		start++;
-	}
+	ptdump_walk_pgd(&st.ptdump, &fake_mm);
 
-	/* Flush out the last page */
-	st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
-	note_page(&st, __pgprot(0), 0, 0);
 	if (!checkwx)
 		return;
 	if (st.wx_pages)
-- 
2.20.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v17 21/23] arm64: mm: Convert mm/dump.c to use walk_page_range()

[Steven Price]

Now walk_page_range() can walk kernel page tables, we can switch the
arm64 ptdump code over to using it, simplifying the code.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/Kconfig                 |   1 +
 arch/arm64/Kconfig.debug           |  19 +----
 arch/arm64/include/asm/ptdump.h    |   8 +-
 arch/arm64/mm/Makefile             |   4 +-
 arch/arm64/mm/dump.c               | 117 ++++++++++-------------------
 arch/arm64/mm/mmu.c                |   4 +-
 arch/arm64/mm/ptdump_debugfs.c     |   2 +-
 drivers/firmware/efi/arm-runtime.c |   2 +-
 8 files changed, 50 insertions(+), 107 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b1b4476ddb83..43aa1de727f4 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -103,6 +103,7 @@ config ARM64
 	select GENERIC_IRQ_SHOW
 	select GENERIC_IRQ_SHOW_LEVEL
 	select GENERIC_PCI_IOMAP
+	select GENERIC_PTDUMP
 	select GENERIC_SCHED_CLOCK
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_STRNCPY_FROM_USER
diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index cf09010d825f..1c906d932d6b 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -1,22 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
-config ARM64_PTDUMP_CORE
-	def_bool n
-
-config ARM64_PTDUMP_DEBUGFS
-	bool "Export kernel pagetable layout to userspace via debugfs"
-	depends on DEBUG_KERNEL
-	select ARM64_PTDUMP_CORE
-	select DEBUG_FS
-        help
-	  Say Y here if you want to show the kernel pagetable layout in a
-	  debugfs file. This information is only useful for kernel developers
-	  who are working in architecture specific areas of the kernel.
-	  It is probably not a good idea to enable this feature in a production
-	  kernel.
-
-	  If in doubt, say N.
-
 config PID_IN_CONTEXTIDR
 	bool "Write the current PID to the CONTEXTIDR register"
 	help
@@ -42,7 +25,7 @@ config ARM64_RANDOMIZE_TEXT_OFFSET
 
 config DEBUG_WX
 	bool "Warn on W+X mappings at boot"
-	select ARM64_PTDUMP_CORE
+	select PTDUMP_CORE
 	---help---
 	  Generate a warning if any W+X mappings are found at boot.
 
diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
index 0b8e7269ec82..38187f74e089 100644
--- a/arch/arm64/include/asm/ptdump.h
+++ b/arch/arm64/include/asm/ptdump.h
@@ -5,7 +5,7 @@
 #ifndef __ASM_PTDUMP_H
 #define __ASM_PTDUMP_H
 
-#ifdef CONFIG_ARM64_PTDUMP_CORE
+#ifdef CONFIG_PTDUMP_CORE
 
 #include <linux/mm_types.h>
 #include <linux/seq_file.h>
@@ -21,15 +21,15 @@ struct ptdump_info {
 	unsigned long			base_addr;
 };
 
-void ptdump_walk_pgd(struct seq_file *s, struct ptdump_info *info);
-#ifdef CONFIG_ARM64_PTDUMP_DEBUGFS
+void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
+#ifdef CONFIG_PTDUMP_DEBUGFS
 void ptdump_debugfs_register(struct ptdump_info *info, const char *name);
 #else
 static inline void ptdump_debugfs_register(struct ptdump_info *info,
 					   const char *name) { }
 #endif
 void ptdump_check_wx(void);
-#endif /* CONFIG_ARM64_PTDUMP_CORE */
+#endif /* CONFIG_PTDUMP_CORE */
 
 #ifdef CONFIG_DEBUG_WX
 #define debug_checkwx()	ptdump_check_wx()
diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
index 849c1df3d214..d91030f0ffee 100644
--- a/arch/arm64/mm/Makefile
+++ b/arch/arm64/mm/Makefile
@@ -4,8 +4,8 @@ obj-y				:= dma-mapping.o extable.o fault.o init.o \
 				   ioremap.o mmap.o pgd.o mmu.o \
 				   context.o proc.o pageattr.o
 obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
-obj-$(CONFIG_ARM64_PTDUMP_CORE)	+= dump.o
-obj-$(CONFIG_ARM64_PTDUMP_DEBUGFS)	+= ptdump_debugfs.o
+obj-$(CONFIG_PTDUMP_CORE)	+= dump.o
+obj-$(CONFIG_PTDUMP_DEBUGFS)	+= ptdump_debugfs.o
 obj-$(CONFIG_NUMA)		+= numa.o
 obj-$(CONFIG_DEBUG_VIRTUAL)	+= physaddr.o
 KASAN_SANITIZE_physaddr.o	+= n
diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
index 0a920b538a89..f8c3ef7903ed 100644
--- a/arch/arm64/mm/dump.c
+++ b/arch/arm64/mm/dump.c
@@ -15,6 +15,7 @@
 #include <linux/io.h>
 #include <linux/init.h>
 #include <linux/mm.h>
+#include <linux/ptdump.h>
 #include <linux/sched.h>
 #include <linux/seq_file.h>
 
@@ -75,10 +76,11 @@ static struct addr_marker address_markers[] = {
  * dumps out a description of the range.
  */
 struct pg_state {
+	struct ptdump_state ptdump;
 	struct seq_file *seq;
 	const struct addr_marker *marker;
 	unsigned long start_address;
-	unsigned level;
+	int level;
 	u64 current_prot;
 	bool check_wx;
 	unsigned long wx_pages;
@@ -179,6 +181,10 @@ static struct pg_level pg_level[] = {
 		.name	= "PGD",
 		.bits	= pte_bits,
 		.num	= ARRAY_SIZE(pte_bits),
+	}, { /* p4d */
+		.name	= "P4D",
+		.bits	= pte_bits,
+		.num	= ARRAY_SIZE(pte_bits),
 	}, { /* pud */
 		.name	= (CONFIG_PGTABLE_LEVELS > 3) ? "PUD" : "PGD",
 		.bits	= pte_bits,
@@ -241,11 +247,15 @@ static void note_prot_wx(struct pg_state *st, unsigned long addr)
 	st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
 }
 
-static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
-				u64 val)
+static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
+		      unsigned long val)
 {
+	struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
 	static const char units[] = "KMGTPE";
-	u64 prot = val & pg_level[level].mask;
+	u64 prot = 0;
+
+	if (level >= 0)
+		prot = val & pg_level[level].mask;
 
 	if (!st->level) {
 		st->level = level;
@@ -293,85 +303,27 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
 
 }
 
-static void walk_pte(struct pg_state *st, pmd_t *pmdp, unsigned long start,
-		     unsigned long end)
-{
-	unsigned long addr = start;
-	pte_t *ptep = pte_offset_kernel(pmdp, start);
-
-	do {
-		note_page(st, addr, 4, READ_ONCE(pte_val(*ptep)));
-	} while (ptep++, addr += PAGE_SIZE, addr != end);
-}
-
-static void walk_pmd(struct pg_state *st, pud_t *pudp, unsigned long start,
-		     unsigned long end)
-{
-	unsigned long next, addr = start;
-	pmd_t *pmdp = pmd_offset(pudp, start);
-
-	do {
-		pmd_t pmd = READ_ONCE(*pmdp);
-		next = pmd_addr_end(addr, end);
-
-		if (pmd_none(pmd) || pmd_sect(pmd)) {
-			note_page(st, addr, 3, pmd_val(pmd));
-		} else {
-			BUG_ON(pmd_bad(pmd));
-			walk_pte(st, pmdp, addr, next);
-		}
-	} while (pmdp++, addr = next, addr != end);
-}
-
-static void walk_pud(struct pg_state *st, pgd_t *pgdp, unsigned long start,
-		     unsigned long end)
+void ptdump_walk(struct seq_file *s, struct ptdump_info *info)
 {
-	unsigned long next, addr = start;
-	pud_t *pudp = pud_offset(pgdp, start);
-
-	do {
-		pud_t pud = READ_ONCE(*pudp);
-		next = pud_addr_end(addr, end);
-
-		if (pud_none(pud) || pud_sect(pud)) {
-			note_page(st, addr, 2, pud_val(pud));
-		} else {
-			BUG_ON(pud_bad(pud));
-			walk_pmd(st, pudp, addr, next);
-		}
-	} while (pudp++, addr = next, addr != end);
-}
+	unsigned long end = ~0UL;
+	struct pg_state st;
 
-static void walk_pgd(struct pg_state *st, struct mm_struct *mm,
-		     unsigned long start)
-{
-	unsigned long end = (start < TASK_SIZE_64) ? TASK_SIZE_64 : 0;
-	unsigned long next, addr = start;
-	pgd_t *pgdp = pgd_offset(mm, start);
-
-	do {
-		pgd_t pgd = READ_ONCE(*pgdp);
-		next = pgd_addr_end(addr, end);
-
-		if (pgd_none(pgd)) {
-			note_page(st, addr, 1, pgd_val(pgd));
-		} else {
-			BUG_ON(pgd_bad(pgd));
-			walk_pud(st, pgdp, addr, next);
-		}
-	} while (pgdp++, addr = next, addr != end);
-}
+	if (info->base_addr < TASK_SIZE_64)
+		end = TASK_SIZE_64;
 
-void ptdump_walk_pgd(struct seq_file *m, struct ptdump_info *info)
-{
-	struct pg_state st = {
-		.seq = m,
+	st = (struct pg_state){
+		.seq = s,
 		.marker = info->markers,
+		.ptdump = {
+			.note_page = note_page,
+			.range = (struct ptdump_range[]){
+				{info->base_addr, end},
+				{0, 0}
+			}
+		}
 	};
 
-	walk_pgd(&st, info->mm, info->base_addr);
-
-	note_page(&st, 0, 0, 0);
+	ptdump_walk_pgd(&st.ptdump, info->mm);
 }
 
 static void ptdump_initialize(void)
@@ -399,10 +351,17 @@ void ptdump_check_wx(void)
 			{ -1, NULL},
 		},
 		.check_wx = true,
+		.ptdump = {
+			.note_page = note_page,
+			.range = (struct ptdump_range[]) {
+				{PAGE_OFFSET, ~0UL},
+				{0, 0}
+			}
+		}
 	};
 
-	walk_pgd(&st, &init_mm, PAGE_OFFSET);
-	note_page(&st, 0, 0, 0);
+	ptdump_walk_pgd(&st.ptdump, &init_mm);
+
 	if (st.wx_pages || st.uxn_pages)
 		pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found, %lu non-UXN pages found\n",
 			st.wx_pages, st.uxn_pages);
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 5a3b15a14a7f..36e8f4f74433 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -943,13 +943,13 @@ int __init arch_ioremap_pud_supported(void)
 	 * SW table walks can't handle removal of intermediate entries.
 	 */
 	return IS_ENABLED(CONFIG_ARM64_4K_PAGES) &&
-	       !IS_ENABLED(CONFIG_ARM64_PTDUMP_DEBUGFS);
+	       !IS_ENABLED(CONFIG_PTDUMP_DEBUGFS);
 }
 
 int __init arch_ioremap_pmd_supported(void)
 {
 	/* See arch_ioremap_pud_supported() */
-	return !IS_ENABLED(CONFIG_ARM64_PTDUMP_DEBUGFS);
+	return !IS_ENABLED(CONFIG_PTDUMP_DEBUGFS);
 }
 
 int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
index 064163f25592..1f2eae3e988b 100644
--- a/arch/arm64/mm/ptdump_debugfs.c
+++ b/arch/arm64/mm/ptdump_debugfs.c
@@ -7,7 +7,7 @@
 static int ptdump_show(struct seq_file *m, void *v)
 {
 	struct ptdump_info *info = m->private;
-	ptdump_walk_pgd(m, info);
+	ptdump_walk(m, info);
 	return 0;
 }
 DEFINE_SHOW_ATTRIBUTE(ptdump);
diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
index 899b803842bb..9dda2602c862 100644
--- a/drivers/firmware/efi/arm-runtime.c
+++ b/drivers/firmware/efi/arm-runtime.c
@@ -27,7 +27,7 @@
 
 extern u64 efi_system_table;
 
-#ifdef CONFIG_ARM64_PTDUMP_DEBUGFS
+#if defined(CONFIG_PTDUMP_DEBUGFS) && defined(CONFIG_ARM64)
 #include <asm/ptdump.h>
 
 static struct ptdump_info efi_ptdump_info = {
-- 
2.20.1


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[PATCH v17 22/23] arm64: mm: Display non-present entries in ptdump

[Steven Price]

Previously the /sys/kernel/debug/kernel_page_tables file would only show
lines for entries present in the page tables. However it is useful to
also show non-present entries as this makes the size and level of the
holes more visible. This aligns the behaviour with x86 which also shows
holes.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/mm/dump.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
index f8c3ef7903ed..e5b6691c5bfc 100644
--- a/arch/arm64/mm/dump.c
+++ b/arch/arm64/mm/dump.c
@@ -270,21 +270,22 @@ static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
 		if (st->current_prot) {
 			note_prot_uxn(st, addr);
 			note_prot_wx(st, addr);
-			pt_dump_seq_printf(st->seq, "0x%016lx-0x%016lx   ",
+		}
+
+		pt_dump_seq_printf(st->seq, "0x%016lx-0x%016lx   ",
 				   st->start_address, addr);
 
-			delta = (addr - st->start_address) >> 10;
-			while (!(delta & 1023) && unit[1]) {
-				delta >>= 10;
-				unit++;
-			}
-			pt_dump_seq_printf(st->seq, "%9lu%c %s", delta, *unit,
-				   pg_level[st->level].name);
-			if (pg_level[st->level].bits)
-				dump_prot(st, pg_level[st->level].bits,
-					  pg_level[st->level].num);
-			pt_dump_seq_puts(st->seq, "\n");
+		delta = (addr - st->start_address) >> 10;
+		while (!(delta & 1023) && unit[1]) {
+			delta >>= 10;
+			unit++;
 		}
+		pt_dump_seq_printf(st->seq, "%9lu%c %s", delta, *unit,
+				   pg_level[st->level].name);
+		if (st->current_prot && pg_level[st->level].bits)
+			dump_prot(st, pg_level[st->level].bits,
+				  pg_level[st->level].num);
+		pt_dump_seq_puts(st->seq, "\n");
 
 		if (addr >= st->marker[1].start_address) {
 			st->marker++;
-- 
2.20.1


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[PATCH v17 23/23] mm: ptdump: Reduce level numbers by 1 in note_page()

[Steven Price]

Rather than having to increment the 'depth' number by 1 in
ptdump_hole(), let's change the meaning of 'level' in note_page() since
that makes the code simplier.

Note that for x86, the level numbers were previously increased by 1 in
commit 45dcd2091363 ("x86/mm/dump_pagetables: Fix printout of p4d level")
and the comment "Bit 7 has a different meaning" was not updated, so this
change also makes the code match the comment again.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/mm/dump.c          |  6 +++---
 arch/x86/mm/dump_pagetables.c | 19 ++++++++++---------
 include/linux/ptdump.h        |  1 +
 mm/ptdump.c                   | 16 ++++++++--------
 4 files changed, 22 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
index e5b6691c5bfc..ef4b3ca1e058 100644
--- a/arch/arm64/mm/dump.c
+++ b/arch/arm64/mm/dump.c
@@ -176,8 +176,7 @@ struct pg_level {
 };
 
 static struct pg_level pg_level[] = {
-	{
-	}, { /* pgd */
+	{ /* pgd */
 		.name	= "PGD",
 		.bits	= pte_bits,
 		.num	= ARRAY_SIZE(pte_bits),
@@ -257,7 +256,7 @@ static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
 	if (level >= 0)
 		prot = val & pg_level[level].mask;
 
-	if (!st->level) {
+	if (st->level == -1) {
 		st->level = level;
 		st->current_prot = prot;
 		st->start_address = addr;
@@ -351,6 +350,7 @@ void ptdump_check_wx(void)
 			{ 0, NULL},
 			{ -1, NULL},
 		},
+		.level = -1,
 		.check_wx = true,
 		.ptdump = {
 			.note_page = note_page,
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index a0b8ffc927bb..411f6a758998 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -180,7 +180,7 @@ static struct addr_marker address_markers[] = {
 static void printk_prot(struct seq_file *m, pgprotval_t pr, int level, bool dmsg)
 {
 	static const char * const level_name[] =
-		{ "cr3", "pgd", "p4d", "pud", "pmd", "pte" };
+		{ "pgd", "p4d", "pud", "pmd", "pte" };
 
 	if (!(pr & _PAGE_PRESENT)) {
 		/* Not present */
@@ -204,12 +204,12 @@ static void printk_prot(struct seq_file *m, pgprotval_t pr, int level, bool dmsg
 			pt_dump_cont_printf(m, dmsg, "    ");
 
 		/* Bit 7 has a different meaning on level 3 vs 4 */
-		if (level <= 4 && pr & _PAGE_PSE)
+		if (level <= 3 && pr & _PAGE_PSE)
 			pt_dump_cont_printf(m, dmsg, "PSE ");
 		else
 			pt_dump_cont_printf(m, dmsg, "    ");
-		if ((level == 5 && pr & _PAGE_PAT) ||
-		    ((level == 4 || level == 3) && pr & _PAGE_PAT_LARGE))
+		if ((level == 4 && pr & _PAGE_PAT) ||
+		    ((level == 3 || level == 2) && pr & _PAGE_PAT_LARGE))
 			pt_dump_cont_printf(m, dmsg, "PAT ");
 		else
 			pt_dump_cont_printf(m, dmsg, "    ");
@@ -271,15 +271,15 @@ static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
 
 	new_prot = val & PTE_FLAGS_MASK;
 
-	if (level > 1) {
-		new_eff = effective_prot(st->prot_levels[level - 2],
+	if (level > 0) {
+		new_eff = effective_prot(st->prot_levels[level - 1],
 					 new_prot);
 	} else {
 		new_eff = new_prot;
 	}
 
-	if (level > 0)
-		st->prot_levels[level - 1] = new_eff;
+	if (level >= 0)
+		st->prot_levels[level] = new_eff;
 
 	/*
 	 * If we have a "break" in the series, we need to flush the state that
@@ -289,7 +289,7 @@ static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
 	cur = st->current_prot;
 	eff = st->effective_prot;
 
-	if (!st->level) {
+	if (st->level == -1) {
 		/* First entry */
 		st->current_prot = new_prot;
 		st->effective_prot = new_eff;
@@ -380,6 +380,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 			.note_page	= note_page,
 			.range		= ptdump_ranges
 		},
+		.level = -1,
 		.to_dmesg	= dmesg,
 		.check_wx	= checkwx,
 		.seq		= m
diff --git a/include/linux/ptdump.h b/include/linux/ptdump.h
index a0fb8dd2be97..b28f3f2acf90 100644
--- a/include/linux/ptdump.h
+++ b/include/linux/ptdump.h
@@ -11,6 +11,7 @@ struct ptdump_range {
 };
 
 struct ptdump_state {
+	/* level is 0:PGD to 4:PTE, or -1 if unknown */
 	void (*note_page)(struct ptdump_state *st, unsigned long addr,
 			  int level, unsigned long val);
 	const struct ptdump_range *range;
diff --git a/mm/ptdump.c b/mm/ptdump.c
index 868638b8e404..ad18a9839d6f 100644
--- a/mm/ptdump.c
+++ b/mm/ptdump.c
@@ -17,7 +17,7 @@ static inline int note_kasan_page_table(struct mm_walk *walk,
 {
 	struct ptdump_state *st = walk->private;
 
-	st->note_page(st, addr, 5, pte_val(kasan_early_shadow_pte[0]));
+	st->note_page(st, addr, 4, pte_val(kasan_early_shadow_pte[0]));
 
 	walk->action = ACTION_CONTINUE;
 
@@ -37,7 +37,7 @@ static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,
 #endif
 
 	if (pgd_leaf(val))
-		st->note_page(st, addr, 1, pgd_val(val));
+		st->note_page(st, addr, 0, pgd_val(val));
 
 	return 0;
 }
@@ -54,7 +54,7 @@ static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
 #endif
 
 	if (p4d_leaf(val))
-		st->note_page(st, addr, 2, p4d_val(val));
+		st->note_page(st, addr, 1, p4d_val(val));
 
 	return 0;
 }
@@ -71,7 +71,7 @@ static int ptdump_pud_entry(pud_t *pud, unsigned long addr,
 #endif
 
 	if (pud_leaf(val))
-		st->note_page(st, addr, 3, pud_val(val));
+		st->note_page(st, addr, 2, pud_val(val));
 
 	return 0;
 }
@@ -88,7 +88,7 @@ static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,
 #endif
 
 	if (pmd_leaf(val))
-		st->note_page(st, addr, 4, pmd_val(val));
+		st->note_page(st, addr, 3, pmd_val(val));
 
 	return 0;
 }
@@ -98,7 +98,7 @@ static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
 {
 	struct ptdump_state *st = walk->private;
 
-	st->note_page(st, addr, 5, pte_val(READ_ONCE(*pte)));
+	st->note_page(st, addr, 4, pte_val(READ_ONCE(*pte)));
 
 	return 0;
 }
@@ -108,7 +108,7 @@ static int ptdump_hole(unsigned long addr, unsigned long next,
 {
 	struct ptdump_state *st = walk->private;
 
-	st->note_page(st, addr, depth + 1, 0);
+	st->note_page(st, addr, depth, 0);
 
 	return 0;
 }
@@ -135,5 +135,5 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm)
 	up_read(&mm->mmap_sem);
 
 	/* Flush out the last page */
-	st->note_page(st, 0, 0, 0);
+	st->note_page(st, 0, -1, 0);
 }
-- 
2.20.1


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Re: [PATCH v17 01/23] mm: Add generic p?d_leaf() macros

[Michael Ellerman]

Steven Price <steven.price@arm.com> writes:
> Exposing the pud/pgd levels of the page tables to walk_page_range() means
> we may come across the exotic large mappings that come with large areas
> of contiguous memory (such as the kernel's linear map).
>
> For architectures that don't provide all p?d_leaf() macros, provide
> generic do nothing default that are suitable where there cannot be leaf
> pages at that level. Futher patches will add implementations for
> individual architectures.
>
> The name p?d_leaf() is chosen to minimize the confusion with existing
> uses of "large" pages and "huge" pages which do not necessary mean that
> the entry is a leaf (for example it may be a set of contiguous entries
> that only take 1 TLB slot). For the purpose of walking the page tables
> we don't need to know how it will be represented in the TLB, but we do
> need to know for sure if it is a leaf of the tree.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> Acked-by: Mark Rutland <mark.rutland@arm.com>
> ---
>  include/asm-generic/pgtable.h | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
> index 798ea36a0549..e2e2bef07dd2 100644
> --- a/include/asm-generic/pgtable.h
> +++ b/include/asm-generic/pgtable.h
> @@ -1238,4 +1238,24 @@ static inline bool arch_has_pfn_modify_check(void)
>  #define mm_pmd_folded(mm)	__is_defined(__PAGETABLE_PMD_FOLDED)
>  #endif
>  
> +/*
> + * p?d_leaf() - true if this entry is a final mapping to a physical address.
> + * This differs from p?d_huge() by the fact that they are always available (if
> + * the architecture supports large pages at the appropriate level) even
> + * if CONFIG_HUGETLB_PAGE is not defined.
> + * Only meaningful when called on a valid entry.
> + */
> +#ifndef pgd_leaf
> +#define pgd_leaf(x)	0
> +#endif
> +#ifndef p4d_leaf
> +#define p4d_leaf(x)	0
> +#endif
> +#ifndef pud_leaf
> +#define pud_leaf(x)	0
> +#endif
> +#ifndef pmd_leaf
> +#define pmd_leaf(x)	0
> +#endif

Any reason you made these #defines rather than static inlines?

cheers

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Re: [PATCH v17 06/23] powerpc: mm: Add p?d_leaf() definitions

[Michael Ellerman]

Steven Price <steven.price@arm.com> writes:
> walk_page_range() is going to be allowed to walk page tables other than
> those of user space. For this it needs to know when it has reached a
> 'leaf' entry in the page tables. This information is provided by the
> p?d_leaf() functions/macros.
>
> For powerpc p?d_is_leaf() functions already exist. Export them using the
> new p?d_leaf() name.
>
> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> CC: Paul Mackerras <paulus@samba.org>
> CC: Michael Ellerman <mpe@ellerman.id.au>
> CC: linuxppc-dev@lists.ozlabs.org
> CC: kvm-ppc@vger.kernel.org
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/powerpc/include/asm/book3s/64/pgtable.h | 3 +++
>  1 file changed, 3 insertions(+)

We have fallback versions of our pmd_is_leaf() etc. in
arch/powerpc/include/asm/pgtable.h, eg:

#ifndef pmd_is_leaf
#define pmd_is_leaf pmd_is_leaf
static inline bool pmd_is_leaf(pmd_t pmd)
{
	return false;
}
#endif

Because we support several different MMUs and most of them don't need to
do anything.

So we could put the compatibility #defines to your names along with the
fallback versions in asm/pgtable.h, rather than in
asm/book3s/64/pgtable.h

But I see you also have fallbacks for your versions, so it probably
doesn't matter either way.

So I'm OK with this version, unless you think there's a compelling
reason to do the compatibility #defines in our asm/pgtable.h

Acked-by: Michael Ellerman <mpe@ellerman.id.au>

cheers


> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index b01624e5c467..201a69e6a355 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -1355,18 +1355,21 @@ static inline bool is_pte_rw_upgrade(unsigned long old_val, unsigned long new_va
>   * Like pmd_huge() and pmd_large(), but works regardless of config options
>   */
>  #define pmd_is_leaf pmd_is_leaf
> +#define pmd_leaf pmd_is_leaf
>  static inline bool pmd_is_leaf(pmd_t pmd)
>  {
>  	return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE));
>  }
>  
>  #define pud_is_leaf pud_is_leaf
> +#define pud_leaf pud_is_leaf
>  static inline bool pud_is_leaf(pud_t pud)
>  {
>  	return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE));
>  }
>  
>  #define pgd_is_leaf pgd_is_leaf
> +#define pgd_leaf pgd_is_leaf
>  static inline bool pgd_is_leaf(pgd_t pgd)
>  {
>  	return !!(pgd_raw(pgd) & cpu_to_be64(_PAGE_PTE));
> -- 
> 2.20.1

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Re: [PATCH v17 11/23] mm: pagewalk: Add p4d_entry() and pgd_entry()

[Thomas Hellström (VMware)]

Hi, Steven,


On 12/18/19 5:23 PM, Steven Price wrote:
> pgd_entry() and pud_entry() were removed by commit 0b1fbfe50006c410
> ("mm/pagewalk: remove pgd_entry() and pud_entry()") because there were
> no users. We're about to add users so reintroduce them, along with
> p4d_entry() as we now have 5 levels of tables.
>
> Note that commit a00cc7d9dd93d66a ("mm, x86: add support for
> PUD-sized transparent hugepages") already re-added pud_entry() but with
> different semantics to the other callbacks. This commit reverts the
> semantics back to match the other callbacks.
>
> To support hmm.c which now uses the new semantics of pud_entry() a new
> member ('action') of struct mm_walk is added which allows the callbacks
> to either descend (ACTION_SUBTREE, the default), skip (ACTION_CONTINUE)
> or repeat the callback (ACTION_AGAIN). hmm.c is then updated to call
> pud_trans_huge_lock() itself and make use of the splitting/retry logic
> of the core code.
>
> After this change pud_entry() is called for all entries, not just
> transparent huge pages.
>
> Signed-off-by: Steven Price <steven.price@arm.com>

I have a couple of comments that are actually mostly related to 
pre-existing bugs, but that affect code that are touched by this patch.

Perhaps this is most cleanly addressed by a follow-up patch. Up to you 
to decide.

Since these problems are pre-existing,

Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>

Thanks,

Thomas


> ---
>   include/linux/pagewalk.h | 34 ++++++++++++++++++++-----
>   mm/hmm.c                 | 55 ++++++++++++++++++++++------------------
>   mm/pagewalk.c            | 50 +++++++++++++++++++++++++-----------
>   3 files changed, 94 insertions(+), 45 deletions(-)
>
> diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
> index 6ec82e92c87f..aa6a0b63964e 100644
> --- a/include/linux/pagewalk.h
> +++ b/include/linux/pagewalk.h
> @@ -8,15 +8,15 @@ struct mm_walk;
>   
>   /**
>    * mm_walk_ops - callbacks for walk_page_range
> - * @pud_entry:		if set, called for each non-empty PUD (2nd-level) entry
> - *			this handler should only handle pud_trans_huge() puds.
> - *			the pmd_entry or pte_entry callbacks will be used for
> - *			regular PUDs.
> - * @pmd_entry:		if set, called for each non-empty PMD (3rd-level) entry
> + * @pgd_entry:		if set, called for each non-empty PGD (top-level) entry
> + * @p4d_entry:		if set, called for each non-empty P4D entry
> + * @pud_entry:		if set, called for each non-empty PUD entry
> + * @pmd_entry:		if set, called for each non-empty PMD entry
>    *			this handler is required to be able to handle
>    *			pmd_trans_huge() pmds.  They may simply choose to
>    *			split_huge_page() instead of handling it explicitly.
> - * @pte_entry:		if set, called for each non-empty PTE (4th-level) entry
> + * @pte_entry:		if set, called for each non-empty PTE (lowest-level)
> + *			entry
>    * @pte_hole:		if set, called for each hole at all levels
>    * @hugetlb_entry:	if set, called for each hugetlb entry
>    * @test_walk:		caller specific callback function to determine whether
> @@ -27,8 +27,15 @@ struct mm_walk;
>    * @pre_vma:            if set, called before starting walk on a non-null vma.
>    * @post_vma:           if set, called after a walk on a non-null vma, provided
>    *                      that @pre_vma and the vma walk succeeded.
> + *
> + * p?d_entry callbacks are called even if those levels are folded on a
> + * particular architecture/configuration.
>    */
>   struct mm_walk_ops {
> +	int (*pgd_entry)(pgd_t *pgd, unsigned long addr,
> +			 unsigned long next, struct mm_walk *walk);
> +	int (*p4d_entry)(p4d_t *p4d, unsigned long addr,
> +			 unsigned long next, struct mm_walk *walk);
>   	int (*pud_entry)(pud_t *pud, unsigned long addr,
>   			 unsigned long next, struct mm_walk *walk);
>   	int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
> @@ -47,11 +54,25 @@ struct mm_walk_ops {
>   	void (*post_vma)(struct mm_walk *walk);
>   };
>   
> +/*
> + * Action for pud_entry / pmd_entry callbacks.
> + * ACTION_SUBTREE is the default
> + */
> +enum page_walk_action {
> +	/* Descend to next level, splitting huge pages if needed and possible */
> +	ACTION_SUBTREE = 0,
> +	/* Continue to next entry at this level (ignoring any subtree) */
> +	ACTION_CONTINUE = 1,
> +	/* Call again for this entry */
> +	ACTION_AGAIN = 2
> +};
> +
>   /**
>    * mm_walk - walk_page_range data
>    * @ops:	operation to call during the walk
>    * @mm:		mm_struct representing the target process of page table walk
>    * @vma:	vma currently walked (NULL if walking outside vmas)
> + * @action:	next action to perform (see enum page_walk_action)
>    * @private:	private data for callbacks' usage
>    *
>    * (see the comment on walk_page_range() for more details)
> @@ -60,6 +81,7 @@ struct mm_walk {
>   	const struct mm_walk_ops *ops;
>   	struct mm_struct *mm;
>   	struct vm_area_struct *vma;
> +	enum page_walk_action action;
>   	void *private;
>   };
>   
> diff --git a/mm/hmm.c b/mm/hmm.c
> index d379cb6496ae..05241c82e05c 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -477,20 +477,30 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
>   	unsigned long addr = start, next;
>   	pmd_t *pmdp;
>   	pud_t pud;
> -	int ret;
> +	int ret = 0;
> +	spinlock_t *ptl = pud_trans_huge_lock(pudp, walk->vma);
> +
> +	if (!ptl)
> +		return 0;

Since if we didn't get the PTL here, the pud might be unstable in which 
case we want to retry:

if (!ptl) {
	if (pud_trans_unstable(pudp))
		walk->action = ACTION_AGAIN;
	return 0;
}


> +
> +	/* Normally we don't want to split the huge page */
> +	walk->action = ACTION_CONTINUE;
>   
> -again:
>   	pud = READ_ONCE(*pudp);

We have the lock now, so READ_ONCE could probably be a simple dereference.

> -	if (pud_none(pud))
> -		return hmm_vma_walk_hole(start, end, walk);
> +	if (pud_none(pud)) {
> +		ret = hmm_vma_walk_hole(start, end, walk);
> +		goto out_unlock;
> +	}

pud_trans_huge_lock() successful return means pud_none() is always false.


>   
>   	if (pud_huge(pud) && pud_devmap(pud)) {
>   		unsigned long i, npages, pfn;
>   		uint64_t *pfns, cpu_flags;
>   		bool fault, write_fault;
>   
> -		if (!pud_present(pud))
> -			return hmm_vma_walk_hole(start, end, walk);
> +		if (!pud_present(pud)) {
> +			ret = hmm_vma_walk_hole(start, end, walk);
> +			goto out_unlock;
> +		}

Can't see !pud_present happening either after a succesful 
pud_trans_huge_lock().

>   
>   		i = (addr - range->start) >> PAGE_SHIFT;
>   		npages = (end - addr) >> PAGE_SHIFT;
> @@ -499,16 +509,20 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
>   		cpu_flags = pud_to_hmm_pfn_flags(range, pud);
>   		hmm_range_need_fault(hmm_vma_walk, pfns, npages,
>   				     cpu_flags, &fault, &write_fault);
> -		if (fault || write_fault)
> -			return hmm_vma_walk_hole_(addr, end, fault,
> -						write_fault, walk);
> +		if (fault || write_fault) {
> +			ret = hmm_vma_walk_hole_(addr, end, fault,
> +						 write_fault, walk);
> +			goto out_unlock;
> +		}
>   
>   		pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
>   		for (i = 0; i < npages; ++i, ++pfn) {
>   			hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
>   					      hmm_vma_walk->pgmap);
> -			if (unlikely(!hmm_vma_walk->pgmap))
> -				return -EBUSY;
> +			if (unlikely(!hmm_vma_walk->pgmap)) {
> +				ret = -EBUSY;
> +				goto out_unlock;
> +			}
>   			pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
>   				  cpu_flags;
>   		}
> @@ -517,22 +531,15 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
>   			hmm_vma_walk->pgmap = NULL;
>   		}
>   		hmm_vma_walk->last = end;
> -		return 0;
> +		goto out_unlock;
>   	}
>   
> -	split_huge_pud(walk->vma, pudp, addr);
> -	if (pud_none(*pudp))
> -		goto again;
> +	/* Ask for the PUD to be split */
> +	walk->action = ACTION_SUBTREE;
>   
> -	pmdp = pmd_offset(pudp, addr);
> -	do {
> -		next = pmd_addr_end(addr, end);
> -		ret = hmm_vma_walk_pmd(pmdp, addr, next, walk);
> -		if (ret)
> -			return ret;
> -	} while (pmdp++, addr = next, addr != end);
> -
> -	return 0;
> +out_unlock:
> +	spin_unlock(ptl);
> +	return ret;
>   }
>   #else
>   #define hmm_vma_walk_pud	NULL
> diff --git a/mm/pagewalk.c b/mm/pagewalk.c
> index ea0b9e606ad1..690af44609e2 100644
> --- a/mm/pagewalk.c
> +++ b/mm/pagewalk.c
> @@ -46,6 +46,9 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
>   				break;
>   			continue;
>   		}
> +
> +		walk->action = ACTION_SUBTREE;
> +
>   		/*
>   		 * This implies that each ->pmd_entry() handler
>   		 * needs to know about pmd_trans_huge() pmds
> @@ -55,16 +58,21 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
>   		if (err)
>   			break;
>   
> +		if (walk->action == ACTION_AGAIN)
> +			goto again;
> +
>   		/*
>   		 * Check this here so we only break down trans_huge
>   		 * pages when we _need_ to
>   		 */
> -		if (!ops->pte_entry)
> +		if (walk->action == ACTION_CONTINUE ||
> +		    !(ops->pte_entry))
>   			continue;
>   
>   		split_huge_pmd(walk->vma, pmd, addr);
>   		if (pmd_trans_unstable(pmd))
>   			goto again;
> +
>   		err = walk_pte_range(pmd, addr, next, walk);
>   		if (err)
>   			break;
> @@ -93,24 +101,25 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
>   			continue;
>   		}
>   
> -		if (ops->pud_entry) {
> -			spinlock_t *ptl = pud_trans_huge_lock(pud, walk->vma);
> +		walk->action = ACTION_SUBTREE;
>   
> -			if (ptl) {
> -				err = ops->pud_entry(pud, addr, next, walk);
> -				spin_unlock(ptl);
> -				if (err)
> -					break;
> -				continue;
> -			}
> -		}
> +		if (ops->pud_entry)
> +			err = ops->pud_entry(pud, addr, next, walk);
> +		if (err)
> +			break;
> +
> +		if (walk->action == ACTION_AGAIN)
> +			goto again;
> +
> +		if (walk->action == ACTION_CONTINUE ||
> +		    !(ops->pmd_entry || ops->pte_entry))
> +			continue;
>   
>   		split_huge_pud(walk->vma, pud, addr);
>   		if (pud_none(*pud))

Here we should really have

if (pud_trans_unstable(pud))

Thanks,

Thomas



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Re: [PATCH v17 01/23] mm: Add generic p?d_leaf() macros

[Steven Price]

On 19/12/2019 11:43, Michael Ellerman wrote:
> Steven Price <steven.price@arm.com> writes:
>> Exposing the pud/pgd levels of the page tables to walk_page_range() means
>> we may come across the exotic large mappings that come with large areas
>> of contiguous memory (such as the kernel's linear map).
>>
>> For architectures that don't provide all p?d_leaf() macros, provide
>> generic do nothing default that are suitable where there cannot be leaf
>> pages at that level. Futher patches will add implementations for
>> individual architectures.
>>
>> The name p?d_leaf() is chosen to minimize the confusion with existing
>> uses of "large" pages and "huge" pages which do not necessary mean that
>> the entry is a leaf (for example it may be a set of contiguous entries
>> that only take 1 TLB slot). For the purpose of walking the page tables
>> we don't need to know how it will be represented in the TLB, but we do
>> need to know for sure if it is a leaf of the tree.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> Acked-by: Mark Rutland <mark.rutland@arm.com>
>> ---
>>  include/asm-generic/pgtable.h | 20 ++++++++++++++++++++
>>  1 file changed, 20 insertions(+)
>>
>> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
>> index 798ea36a0549..e2e2bef07dd2 100644
>> --- a/include/asm-generic/pgtable.h
>> +++ b/include/asm-generic/pgtable.h
>> @@ -1238,4 +1238,24 @@ static inline bool arch_has_pfn_modify_check(void)
>>  #define mm_pmd_folded(mm)	__is_defined(__PAGETABLE_PMD_FOLDED)
>>  #endif
>>  
>> +/*
>> + * p?d_leaf() - true if this entry is a final mapping to a physical address.
>> + * This differs from p?d_huge() by the fact that they are always available (if
>> + * the architecture supports large pages at the appropriate level) even
>> + * if CONFIG_HUGETLB_PAGE is not defined.
>> + * Only meaningful when called on a valid entry.
>> + */
>> +#ifndef pgd_leaf
>> +#define pgd_leaf(x)	0
>> +#endif
>> +#ifndef p4d_leaf
>> +#define p4d_leaf(x)	0
>> +#endif
>> +#ifndef pud_leaf
>> +#define pud_leaf(x)	0
>> +#endif
>> +#ifndef pmd_leaf
>> +#define pmd_leaf(x)	0
>> +#endif
> 
> Any reason you made these #defines rather than static inlines?

No strong reason - but these have to be #defines in the arch overrides
so the #ifndef works, so I was being consistent here. I guess a static
inline might avoid warnings although I haven't seen any.

Steve

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Re: [PATCH v17 06/23] powerpc: mm: Add p?d_leaf() definitions

[Steven Price]

On 19/12/2019 11:49, Michael Ellerman wrote:
> Steven Price <steven.price@arm.com> writes:
>> walk_page_range() is going to be allowed to walk page tables other than
>> those of user space. For this it needs to know when it has reached a
>> 'leaf' entry in the page tables. This information is provided by the
>> p?d_leaf() functions/macros.
>>
>> For powerpc p?d_is_leaf() functions already exist. Export them using the
>> new p?d_leaf() name.
>>
>> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>> CC: Paul Mackerras <paulus@samba.org>
>> CC: Michael Ellerman <mpe@ellerman.id.au>
>> CC: linuxppc-dev@lists.ozlabs.org
>> CC: kvm-ppc@vger.kernel.org
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>  arch/powerpc/include/asm/book3s/64/pgtable.h | 3 +++
>>  1 file changed, 3 insertions(+)
> 
> We have fallback versions of our pmd_is_leaf() etc. in
> arch/powerpc/include/asm/pgtable.h, eg:
> 
> #ifndef pmd_is_leaf
> #define pmd_is_leaf pmd_is_leaf
> static inline bool pmd_is_leaf(pmd_t pmd)
> {
> 	return false;
> }
> #endif
> 
> Because we support several different MMUs and most of them don't need to
> do anything.
> 
> So we could put the compatibility #defines to your names along with the
> fallback versions in asm/pgtable.h, rather than in
> asm/book3s/64/pgtable.h
> 
> But I see you also have fallbacks for your versions, so it probably
> doesn't matter either way.
> 
> So I'm OK with this version, unless you think there's a compelling
> reason to do the compatibility #defines in our asm/pgtable.h

I was thinking that (assuming this series actually gets merged this
time), the p?d_is_leaf() versions could be removed and replaced by
p?d_leaf() in the future. Since the fallbacks are in the asm-generic
code it makes sense for the pmd_leaf() definitions to be next to the
non-fallback versions.

> Acked-by: Michael Ellerman <mpe@ellerman.id.au>

Thanks!

Steve

> cheers
> 
> 
>> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> index b01624e5c467..201a69e6a355 100644
>> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
>> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> @@ -1355,18 +1355,21 @@ static inline bool is_pte_rw_upgrade(unsigned long old_val, unsigned long new_va
>>   * Like pmd_huge() and pmd_large(), but works regardless of config options
>>   */
>>  #define pmd_is_leaf pmd_is_leaf
>> +#define pmd_leaf pmd_is_leaf
>>  static inline bool pmd_is_leaf(pmd_t pmd)
>>  {
>>  	return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE));
>>  }
>>  
>>  #define pud_is_leaf pud_is_leaf
>> +#define pud_leaf pud_is_leaf
>>  static inline bool pud_is_leaf(pud_t pud)
>>  {
>>  	return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE));
>>  }
>>  
>>  #define pgd_is_leaf pgd_is_leaf
>> +#define pgd_leaf pgd_is_leaf
>>  static inline bool pgd_is_leaf(pgd_t pgd)
>>  {
>>  	return !!(pgd_raw(pgd) & cpu_to_be64(_PAGE_PTE));
>> -- 
>> 2.20.1
> 
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> 


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Re: [PATCH v17 11/23] mm: pagewalk: Add p4d_entry() and pgd_entry()

[Steven Price]

On 19/12/2019 14:25, Thomas Hellström (VMware) wrote:
> Hi, Steven,
> 
> 
> On 12/18/19 5:23 PM, Steven Price wrote:
>> pgd_entry() and pud_entry() were removed by commit 0b1fbfe50006c410
>> ("mm/pagewalk: remove pgd_entry() and pud_entry()") because there were
>> no users. We're about to add users so reintroduce them, along with
>> p4d_entry() as we now have 5 levels of tables.
>>
>> Note that commit a00cc7d9dd93d66a ("mm, x86: add support for
>> PUD-sized transparent hugepages") already re-added pud_entry() but with
>> different semantics to the other callbacks. This commit reverts the
>> semantics back to match the other callbacks.
>>
>> To support hmm.c which now uses the new semantics of pud_entry() a new
>> member ('action') of struct mm_walk is added which allows the callbacks
>> to either descend (ACTION_SUBTREE, the default), skip (ACTION_CONTINUE)
>> or repeat the callback (ACTION_AGAIN). hmm.c is then updated to call
>> pud_trans_huge_lock() itself and make use of the splitting/retry logic
>> of the core code.
>>
>> After this change pud_entry() is called for all entries, not just
>> transparent huge pages.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
> 
> I have a couple of comments that are actually mostly related to
> pre-existing bugs, but that affect code that are touched by this patch.
> 
> Perhaps this is most cleanly addressed by a follow-up patch. Up to you
> to decide.
> 
> Since these problems are pre-existing,
> 
> Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>

Thanks, I'll send out an extra patch with these changes.

Steve

> Thanks,
> 
> Thomas
> 
> 
>> ---
>>   include/linux/pagewalk.h | 34 ++++++++++++++++++++-----
>>   mm/hmm.c                 | 55 ++++++++++++++++++++++------------------
>>   mm/pagewalk.c            | 50 +++++++++++++++++++++++++-----------
>>   3 files changed, 94 insertions(+), 45 deletions(-)
>>
>> diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
>> index 6ec82e92c87f..aa6a0b63964e 100644
>> --- a/include/linux/pagewalk.h
>> +++ b/include/linux/pagewalk.h
>> @@ -8,15 +8,15 @@ struct mm_walk;
>>     /**
>>    * mm_walk_ops - callbacks for walk_page_range
>> - * @pud_entry:        if set, called for each non-empty PUD
>> (2nd-level) entry
>> - *            this handler should only handle pud_trans_huge() puds.
>> - *            the pmd_entry or pte_entry callbacks will be used for
>> - *            regular PUDs.
>> - * @pmd_entry:        if set, called for each non-empty PMD
>> (3rd-level) entry
>> + * @pgd_entry:        if set, called for each non-empty PGD
>> (top-level) entry
>> + * @p4d_entry:        if set, called for each non-empty P4D entry
>> + * @pud_entry:        if set, called for each non-empty PUD entry
>> + * @pmd_entry:        if set, called for each non-empty PMD entry
>>    *            this handler is required to be able to handle
>>    *            pmd_trans_huge() pmds.  They may simply choose to
>>    *            split_huge_page() instead of handling it explicitly.
>> - * @pte_entry:        if set, called for each non-empty PTE
>> (4th-level) entry
>> + * @pte_entry:        if set, called for each non-empty PTE
>> (lowest-level)
>> + *            entry
>>    * @pte_hole:        if set, called for each hole at all levels
>>    * @hugetlb_entry:    if set, called for each hugetlb entry
>>    * @test_walk:        caller specific callback function to determine
>> whether
>> @@ -27,8 +27,15 @@ struct mm_walk;
>>    * @pre_vma:            if set, called before starting walk on a
>> non-null vma.
>>    * @post_vma:           if set, called after a walk on a non-null
>> vma, provided
>>    *                      that @pre_vma and the vma walk succeeded.
>> + *
>> + * p?d_entry callbacks are called even if those levels are folded on a
>> + * particular architecture/configuration.
>>    */
>>   struct mm_walk_ops {
>> +    int (*pgd_entry)(pgd_t *pgd, unsigned long addr,
>> +             unsigned long next, struct mm_walk *walk);
>> +    int (*p4d_entry)(p4d_t *p4d, unsigned long addr,
>> +             unsigned long next, struct mm_walk *walk);
>>       int (*pud_entry)(pud_t *pud, unsigned long addr,
>>                unsigned long next, struct mm_walk *walk);
>>       int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
>> @@ -47,11 +54,25 @@ struct mm_walk_ops {
>>       void (*post_vma)(struct mm_walk *walk);
>>   };
>>   +/*
>> + * Action for pud_entry / pmd_entry callbacks.
>> + * ACTION_SUBTREE is the default
>> + */
>> +enum page_walk_action {
>> +    /* Descend to next level, splitting huge pages if needed and
>> possible */
>> +    ACTION_SUBTREE = 0,
>> +    /* Continue to next entry at this level (ignoring any subtree) */
>> +    ACTION_CONTINUE = 1,
>> +    /* Call again for this entry */
>> +    ACTION_AGAIN = 2
>> +};
>> +
>>   /**
>>    * mm_walk - walk_page_range data
>>    * @ops:    operation to call during the walk
>>    * @mm:        mm_struct representing the target process of page
>> table walk
>>    * @vma:    vma currently walked (NULL if walking outside vmas)
>> + * @action:    next action to perform (see enum page_walk_action)
>>    * @private:    private data for callbacks' usage
>>    *
>>    * (see the comment on walk_page_range() for more details)
>> @@ -60,6 +81,7 @@ struct mm_walk {
>>       const struct mm_walk_ops *ops;
>>       struct mm_struct *mm;
>>       struct vm_area_struct *vma;
>> +    enum page_walk_action action;
>>       void *private;
>>   };
>>   diff --git a/mm/hmm.c b/mm/hmm.c
>> index d379cb6496ae..05241c82e05c 100644
>> --- a/mm/hmm.c
>> +++ b/mm/hmm.c
>> @@ -477,20 +477,30 @@ static int hmm_vma_walk_pud(pud_t *pudp,
>> unsigned long start, unsigned long end,
>>       unsigned long addr = start, next;
>>       pmd_t *pmdp;
>>       pud_t pud;
>> -    int ret;
>> +    int ret = 0;
>> +    spinlock_t *ptl = pud_trans_huge_lock(pudp, walk->vma);
>> +
>> +    if (!ptl)
>> +        return 0;
> 
> Since if we didn't get the PTL here, the pud might be unstable in which
> case we want to retry:
> 
> if (!ptl) {
>     if (pud_trans_unstable(pudp))
>         walk->action = ACTION_AGAIN;
>     return 0;
> }
> 
> 
>> +
>> +    /* Normally we don't want to split the huge page */
>> +    walk->action = ACTION_CONTINUE;
>>   -again:
>>       pud = READ_ONCE(*pudp);
> 
> We have the lock now, so READ_ONCE could probably be a simple dereference.
> 
>> -    if (pud_none(pud))
>> -        return hmm_vma_walk_hole(start, end, walk);
>> +    if (pud_none(pud)) {
>> +        ret = hmm_vma_walk_hole(start, end, walk);
>> +        goto out_unlock;
>> +    }
> 
> pud_trans_huge_lock() successful return means pud_none() is always false.
> 
> 
>>         if (pud_huge(pud) && pud_devmap(pud)) {
>>           unsigned long i, npages, pfn;
>>           uint64_t *pfns, cpu_flags;
>>           bool fault, write_fault;
>>   -        if (!pud_present(pud))
>> -            return hmm_vma_walk_hole(start, end, walk);
>> +        if (!pud_present(pud)) {
>> +            ret = hmm_vma_walk_hole(start, end, walk);
>> +            goto out_unlock;
>> +        }
> 
> Can't see !pud_present happening either after a succesful
> pud_trans_huge_lock().
> 
>>             i = (addr - range->start) >> PAGE_SHIFT;
>>           npages = (end - addr) >> PAGE_SHIFT;
>> @@ -499,16 +509,20 @@ static int hmm_vma_walk_pud(pud_t *pudp,
>> unsigned long start, unsigned long end,
>>           cpu_flags = pud_to_hmm_pfn_flags(range, pud);
>>           hmm_range_need_fault(hmm_vma_walk, pfns, npages,
>>                        cpu_flags, &fault, &write_fault);
>> -        if (fault || write_fault)
>> -            return hmm_vma_walk_hole_(addr, end, fault,
>> -                        write_fault, walk);
>> +        if (fault || write_fault) {
>> +            ret = hmm_vma_walk_hole_(addr, end, fault,
>> +                         write_fault, walk);
>> +            goto out_unlock;
>> +        }
>>             pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
>>           for (i = 0; i < npages; ++i, ++pfn) {
>>               hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
>>                             hmm_vma_walk->pgmap);
>> -            if (unlikely(!hmm_vma_walk->pgmap))
>> -                return -EBUSY;
>> +            if (unlikely(!hmm_vma_walk->pgmap)) {
>> +                ret = -EBUSY;
>> +                goto out_unlock;
>> +            }
>>               pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
>>                     cpu_flags;
>>           }
>> @@ -517,22 +531,15 @@ static int hmm_vma_walk_pud(pud_t *pudp,
>> unsigned long start, unsigned long end,
>>               hmm_vma_walk->pgmap = NULL;
>>           }
>>           hmm_vma_walk->last = end;
>> -        return 0;
>> +        goto out_unlock;
>>       }
>>   -    split_huge_pud(walk->vma, pudp, addr);
>> -    if (pud_none(*pudp))
>> -        goto again;
>> +    /* Ask for the PUD to be split */
>> +    walk->action = ACTION_SUBTREE;
>>   -    pmdp = pmd_offset(pudp, addr);
>> -    do {
>> -        next = pmd_addr_end(addr, end);
>> -        ret = hmm_vma_walk_pmd(pmdp, addr, next, walk);
>> -        if (ret)
>> -            return ret;
>> -    } while (pmdp++, addr = next, addr != end);
>> -
>> -    return 0;
>> +out_unlock:
>> +    spin_unlock(ptl);
>> +    return ret;
>>   }
>>   #else
>>   #define hmm_vma_walk_pud    NULL
>> diff --git a/mm/pagewalk.c b/mm/pagewalk.c
>> index ea0b9e606ad1..690af44609e2 100644
>> --- a/mm/pagewalk.c
>> +++ b/mm/pagewalk.c
>> @@ -46,6 +46,9 @@ static int walk_pmd_range(pud_t *pud, unsigned long
>> addr, unsigned long end,
>>                   break;
>>               continue;
>>           }
>> +
>> +        walk->action = ACTION_SUBTREE;
>> +
>>           /*
>>            * This implies that each ->pmd_entry() handler
>>            * needs to know about pmd_trans_huge() pmds
>> @@ -55,16 +58,21 @@ static int walk_pmd_range(pud_t *pud, unsigned
>> long addr, unsigned long end,
>>           if (err)
>>               break;
>>   +        if (walk->action == ACTION_AGAIN)
>> +            goto again;
>> +
>>           /*
>>            * Check this here so we only break down trans_huge
>>            * pages when we _need_ to
>>            */
>> -        if (!ops->pte_entry)
>> +        if (walk->action == ACTION_CONTINUE ||
>> +            !(ops->pte_entry))
>>               continue;
>>             split_huge_pmd(walk->vma, pmd, addr);
>>           if (pmd_trans_unstable(pmd))
>>               goto again;
>> +
>>           err = walk_pte_range(pmd, addr, next, walk);
>>           if (err)
>>               break;
>> @@ -93,24 +101,25 @@ static int walk_pud_range(p4d_t *p4d, unsigned
>> long addr, unsigned long end,
>>               continue;
>>           }
>>   -        if (ops->pud_entry) {
>> -            spinlock_t *ptl = pud_trans_huge_lock(pud, walk->vma);
>> +        walk->action = ACTION_SUBTREE;
>>   -            if (ptl) {
>> -                err = ops->pud_entry(pud, addr, next, walk);
>> -                spin_unlock(ptl);
>> -                if (err)
>> -                    break;
>> -                continue;
>> -            }
>> -        }
>> +        if (ops->pud_entry)
>> +            err = ops->pud_entry(pud, addr, next, walk);
>> +        if (err)
>> +            break;
>> +
>> +        if (walk->action == ACTION_AGAIN)
>> +            goto again;
>> +
>> +        if (walk->action == ACTION_CONTINUE ||
>> +            !(ops->pmd_entry || ops->pte_entry))
>> +            continue;
>>             split_huge_pud(walk->vma, pud, addr);
>>           if (pud_none(*pud))
> 
> Here we should really have
> 
> if (pud_trans_unstable(pud))
> 
> Thanks,
> 
> Thomas
> 
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel


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Re: [PATCH v17 01/23] mm: Add generic p?d_leaf() macros

[Michael Ellerman]

Steven Price <steven.price@arm.com> writes:
> On 19/12/2019 11:43, Michael Ellerman wrote:
>> Steven Price <steven.price@arm.com> writes:
>>> Exposing the pud/pgd levels of the page tables to walk_page_range() means
>>> we may come across the exotic large mappings that come with large areas
>>> of contiguous memory (such as the kernel's linear map).
>>>
>>> For architectures that don't provide all p?d_leaf() macros, provide
>>> generic do nothing default that are suitable where there cannot be leaf
>>> pages at that level. Futher patches will add implementations for
>>> individual architectures.
>>>
>>> The name p?d_leaf() is chosen to minimize the confusion with existing
>>> uses of "large" pages and "huge" pages which do not necessary mean that
>>> the entry is a leaf (for example it may be a set of contiguous entries
>>> that only take 1 TLB slot). For the purpose of walking the page tables
>>> we don't need to know how it will be represented in the TLB, but we do
>>> need to know for sure if it is a leaf of the tree.
>>>
>>> Signed-off-by: Steven Price <steven.price@arm.com>
>>> Acked-by: Mark Rutland <mark.rutland@arm.com>
>>> ---
>>>  include/asm-generic/pgtable.h | 20 ++++++++++++++++++++
>>>  1 file changed, 20 insertions(+)
>>>
>>> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
>>> index 798ea36a0549..e2e2bef07dd2 100644
>>> --- a/include/asm-generic/pgtable.h
>>> +++ b/include/asm-generic/pgtable.h
>>> @@ -1238,4 +1238,24 @@ static inline bool arch_has_pfn_modify_check(void)
>>>  #define mm_pmd_folded(mm)	__is_defined(__PAGETABLE_PMD_FOLDED)
>>>  #endif
>>>  
>>> +/*
>>> + * p?d_leaf() - true if this entry is a final mapping to a physical address.
>>> + * This differs from p?d_huge() by the fact that they are always available (if
>>> + * the architecture supports large pages at the appropriate level) even
>>> + * if CONFIG_HUGETLB_PAGE is not defined.
>>> + * Only meaningful when called on a valid entry.
>>> + */
>>> +#ifndef pgd_leaf
>>> +#define pgd_leaf(x)	0
>>> +#endif
>>> +#ifndef p4d_leaf
>>> +#define p4d_leaf(x)	0
>>> +#endif
>>> +#ifndef pud_leaf
>>> +#define pud_leaf(x)	0
>>> +#endif
>>> +#ifndef pmd_leaf
>>> +#define pmd_leaf(x)	0
>>> +#endif
>> 
>> Any reason you made these #defines rather than static inlines?
>
> No strong reason - but these have to be #defines in the arch overrides
> so the #ifndef works, so I was being consistent here.

We handle that usually just with eg:

static inline bool pgd_leaf(pgd_t pgd)
{
	...
}
#define pgd_leaf pgd_leaf

> I guess a static inline might avoid warnings although I haven't seen
> any.

If anything I'd expect it to cause warnings, for example if someone is
doing pgd_leaf(pmd), but that would be good to catch.

cheers

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Re: [PATCH v17 21/23] arm64: mm: Convert mm/dump.c to use walk_page_range()

[Ard Biesheuvel]

On Wed, 18 Dec 2019 at 17:25, Steven Price <steven.price@arm.com> wrote:
>
> Now walk_page_range() can walk kernel page tables, we can switch the
> arm64 ptdump code over to using it, simplifying the code.
>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>

I did not realize this at the time, but this patch removes the ability
to dump the EFI page tables on 32-bit ARM. Was that intentional?


> ---
>  arch/arm64/Kconfig                 |   1 +
>  arch/arm64/Kconfig.debug           |  19 +----
>  arch/arm64/include/asm/ptdump.h    |   8 +-
>  arch/arm64/mm/Makefile             |   4 +-
>  arch/arm64/mm/dump.c               | 117 ++++++++++-------------------
>  arch/arm64/mm/mmu.c                |   4 +-
>  arch/arm64/mm/ptdump_debugfs.c     |   2 +-
>  drivers/firmware/efi/arm-runtime.c |   2 +-
>  8 files changed, 50 insertions(+), 107 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index b1b4476ddb83..43aa1de727f4 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -103,6 +103,7 @@ config ARM64
>         select GENERIC_IRQ_SHOW
>         select GENERIC_IRQ_SHOW_LEVEL
>         select GENERIC_PCI_IOMAP
> +       select GENERIC_PTDUMP
>         select GENERIC_SCHED_CLOCK
>         select GENERIC_SMP_IDLE_THREAD
>         select GENERIC_STRNCPY_FROM_USER
> diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
> index cf09010d825f..1c906d932d6b 100644
> --- a/arch/arm64/Kconfig.debug
> +++ b/arch/arm64/Kconfig.debug
> @@ -1,22 +1,5 @@
>  # SPDX-License-Identifier: GPL-2.0-only
>
> -config ARM64_PTDUMP_CORE
> -       def_bool n
> -
> -config ARM64_PTDUMP_DEBUGFS
> -       bool "Export kernel pagetable layout to userspace via debugfs"
> -       depends on DEBUG_KERNEL
> -       select ARM64_PTDUMP_CORE
> -       select DEBUG_FS
> -        help
> -         Say Y here if you want to show the kernel pagetable layout in a
> -         debugfs file. This information is only useful for kernel developers
> -         who are working in architecture specific areas of the kernel.
> -         It is probably not a good idea to enable this feature in a production
> -         kernel.
> -
> -         If in doubt, say N.
> -
>  config PID_IN_CONTEXTIDR
>         bool "Write the current PID to the CONTEXTIDR register"
>         help
> @@ -42,7 +25,7 @@ config ARM64_RANDOMIZE_TEXT_OFFSET
>
>  config DEBUG_WX
>         bool "Warn on W+X mappings at boot"
> -       select ARM64_PTDUMP_CORE
> +       select PTDUMP_CORE
>         ---help---
>           Generate a warning if any W+X mappings are found at boot.
>
> diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> index 0b8e7269ec82..38187f74e089 100644
> --- a/arch/arm64/include/asm/ptdump.h
> +++ b/arch/arm64/include/asm/ptdump.h
> @@ -5,7 +5,7 @@
>  #ifndef __ASM_PTDUMP_H
>  #define __ASM_PTDUMP_H
>
> -#ifdef CONFIG_ARM64_PTDUMP_CORE
> +#ifdef CONFIG_PTDUMP_CORE
>
>  #include <linux/mm_types.h>
>  #include <linux/seq_file.h>
> @@ -21,15 +21,15 @@ struct ptdump_info {
>         unsigned long                   base_addr;
>  };
>
> -void ptdump_walk_pgd(struct seq_file *s, struct ptdump_info *info);
> -#ifdef CONFIG_ARM64_PTDUMP_DEBUGFS
> +void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
> +#ifdef CONFIG_PTDUMP_DEBUGFS
>  void ptdump_debugfs_register(struct ptdump_info *info, const char *name);
>  #else
>  static inline void ptdump_debugfs_register(struct ptdump_info *info,
>                                            const char *name) { }
>  #endif
>  void ptdump_check_wx(void);
> -#endif /* CONFIG_ARM64_PTDUMP_CORE */
> +#endif /* CONFIG_PTDUMP_CORE */
>
>  #ifdef CONFIG_DEBUG_WX
>  #define debug_checkwx()        ptdump_check_wx()
> diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
> index 849c1df3d214..d91030f0ffee 100644
> --- a/arch/arm64/mm/Makefile
> +++ b/arch/arm64/mm/Makefile
> @@ -4,8 +4,8 @@ obj-y                           := dma-mapping.o extable.o fault.o init.o \
>                                    ioremap.o mmap.o pgd.o mmu.o \
>                                    context.o proc.o pageattr.o
>  obj-$(CONFIG_HUGETLB_PAGE)     += hugetlbpage.o
> -obj-$(CONFIG_ARM64_PTDUMP_CORE)        += dump.o
> -obj-$(CONFIG_ARM64_PTDUMP_DEBUGFS)     += ptdump_debugfs.o
> +obj-$(CONFIG_PTDUMP_CORE)      += dump.o
> +obj-$(CONFIG_PTDUMP_DEBUGFS)   += ptdump_debugfs.o
>  obj-$(CONFIG_NUMA)             += numa.o
>  obj-$(CONFIG_DEBUG_VIRTUAL)    += physaddr.o
>  KASAN_SANITIZE_physaddr.o      += n
> diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
> index 0a920b538a89..f8c3ef7903ed 100644
> --- a/arch/arm64/mm/dump.c
> +++ b/arch/arm64/mm/dump.c
> @@ -15,6 +15,7 @@
>  #include <linux/io.h>
>  #include <linux/init.h>
>  #include <linux/mm.h>
> +#include <linux/ptdump.h>
>  #include <linux/sched.h>
>  #include <linux/seq_file.h>
>
> @@ -75,10 +76,11 @@ static struct addr_marker address_markers[] = {
>   * dumps out a description of the range.
>   */
>  struct pg_state {
> +       struct ptdump_state ptdump;
>         struct seq_file *seq;
>         const struct addr_marker *marker;
>         unsigned long start_address;
> -       unsigned level;
> +       int level;
>         u64 current_prot;
>         bool check_wx;
>         unsigned long wx_pages;
> @@ -179,6 +181,10 @@ static struct pg_level pg_level[] = {
>                 .name   = "PGD",
>                 .bits   = pte_bits,
>                 .num    = ARRAY_SIZE(pte_bits),
> +       }, { /* p4d */
> +               .name   = "P4D",
> +               .bits   = pte_bits,
> +               .num    = ARRAY_SIZE(pte_bits),
>         }, { /* pud */
>                 .name   = (CONFIG_PGTABLE_LEVELS > 3) ? "PUD" : "PGD",
>                 .bits   = pte_bits,
> @@ -241,11 +247,15 @@ static void note_prot_wx(struct pg_state *st, unsigned long addr)
>         st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
>  }
>
> -static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
> -                               u64 val)
> +static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
> +                     unsigned long val)
>  {
> +       struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
>         static const char units[] = "KMGTPE";
> -       u64 prot = val & pg_level[level].mask;
> +       u64 prot = 0;
> +
> +       if (level >= 0)
> +               prot = val & pg_level[level].mask;
>
>         if (!st->level) {
>                 st->level = level;
> @@ -293,85 +303,27 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
>
>  }
>
> -static void walk_pte(struct pg_state *st, pmd_t *pmdp, unsigned long start,
> -                    unsigned long end)
> -{
> -       unsigned long addr = start;
> -       pte_t *ptep = pte_offset_kernel(pmdp, start);
> -
> -       do {
> -               note_page(st, addr, 4, READ_ONCE(pte_val(*ptep)));
> -       } while (ptep++, addr += PAGE_SIZE, addr != end);
> -}
> -
> -static void walk_pmd(struct pg_state *st, pud_t *pudp, unsigned long start,
> -                    unsigned long end)
> -{
> -       unsigned long next, addr = start;
> -       pmd_t *pmdp = pmd_offset(pudp, start);
> -
> -       do {
> -               pmd_t pmd = READ_ONCE(*pmdp);
> -               next = pmd_addr_end(addr, end);
> -
> -               if (pmd_none(pmd) || pmd_sect(pmd)) {
> -                       note_page(st, addr, 3, pmd_val(pmd));
> -               } else {
> -                       BUG_ON(pmd_bad(pmd));
> -                       walk_pte(st, pmdp, addr, next);
> -               }
> -       } while (pmdp++, addr = next, addr != end);
> -}
> -
> -static void walk_pud(struct pg_state *st, pgd_t *pgdp, unsigned long start,
> -                    unsigned long end)
> +void ptdump_walk(struct seq_file *s, struct ptdump_info *info)
>  {
> -       unsigned long next, addr = start;
> -       pud_t *pudp = pud_offset(pgdp, start);
> -
> -       do {
> -               pud_t pud = READ_ONCE(*pudp);
> -               next = pud_addr_end(addr, end);
> -
> -               if (pud_none(pud) || pud_sect(pud)) {
> -                       note_page(st, addr, 2, pud_val(pud));
> -               } else {
> -                       BUG_ON(pud_bad(pud));
> -                       walk_pmd(st, pudp, addr, next);
> -               }
> -       } while (pudp++, addr = next, addr != end);
> -}
> +       unsigned long end = ~0UL;
> +       struct pg_state st;
>
> -static void walk_pgd(struct pg_state *st, struct mm_struct *mm,
> -                    unsigned long start)
> -{
> -       unsigned long end = (start < TASK_SIZE_64) ? TASK_SIZE_64 : 0;
> -       unsigned long next, addr = start;
> -       pgd_t *pgdp = pgd_offset(mm, start);
> -
> -       do {
> -               pgd_t pgd = READ_ONCE(*pgdp);
> -               next = pgd_addr_end(addr, end);
> -
> -               if (pgd_none(pgd)) {
> -                       note_page(st, addr, 1, pgd_val(pgd));
> -               } else {
> -                       BUG_ON(pgd_bad(pgd));
> -                       walk_pud(st, pgdp, addr, next);
> -               }
> -       } while (pgdp++, addr = next, addr != end);
> -}
> +       if (info->base_addr < TASK_SIZE_64)
> +               end = TASK_SIZE_64;
>
> -void ptdump_walk_pgd(struct seq_file *m, struct ptdump_info *info)
> -{
> -       struct pg_state st = {
> -               .seq = m,
> +       st = (struct pg_state){
> +               .seq = s,
>                 .marker = info->markers,
> +               .ptdump = {
> +                       .note_page = note_page,
> +                       .range = (struct ptdump_range[]){
> +                               {info->base_addr, end},
> +                               {0, 0}
> +                       }
> +               }
>         };
>
> -       walk_pgd(&st, info->mm, info->base_addr);
> -
> -       note_page(&st, 0, 0, 0);
> +       ptdump_walk_pgd(&st.ptdump, info->mm);
>  }
>
>  static void ptdump_initialize(void)
> @@ -399,10 +351,17 @@ void ptdump_check_wx(void)
>                         { -1, NULL},
>                 },
>                 .check_wx = true,
> +               .ptdump = {
> +                       .note_page = note_page,
> +                       .range = (struct ptdump_range[]) {
> +                               {PAGE_OFFSET, ~0UL},
> +                               {0, 0}
> +                       }
> +               }
>         };
>
> -       walk_pgd(&st, &init_mm, PAGE_OFFSET);
> -       note_page(&st, 0, 0, 0);
> +       ptdump_walk_pgd(&st.ptdump, &init_mm);
> +
>         if (st.wx_pages || st.uxn_pages)
>                 pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found, %lu non-UXN pages found\n",
>                         st.wx_pages, st.uxn_pages);
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 5a3b15a14a7f..36e8f4f74433 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -943,13 +943,13 @@ int __init arch_ioremap_pud_supported(void)
>          * SW table walks can't handle removal of intermediate entries.
>          */
>         return IS_ENABLED(CONFIG_ARM64_4K_PAGES) &&
> -              !IS_ENABLED(CONFIG_ARM64_PTDUMP_DEBUGFS);
> +              !IS_ENABLED(CONFIG_PTDUMP_DEBUGFS);
>  }
>
>  int __init arch_ioremap_pmd_supported(void)
>  {
>         /* See arch_ioremap_pud_supported() */
> -       return !IS_ENABLED(CONFIG_ARM64_PTDUMP_DEBUGFS);
> +       return !IS_ENABLED(CONFIG_PTDUMP_DEBUGFS);
>  }
>
>  int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
> diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
> index 064163f25592..1f2eae3e988b 100644
> --- a/arch/arm64/mm/ptdump_debugfs.c
> +++ b/arch/arm64/mm/ptdump_debugfs.c
> @@ -7,7 +7,7 @@
>  static int ptdump_show(struct seq_file *m, void *v)
>  {
>         struct ptdump_info *info = m->private;
> -       ptdump_walk_pgd(m, info);
> +       ptdump_walk(m, info);
>         return 0;
>  }
>  DEFINE_SHOW_ATTRIBUTE(ptdump);
> diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
> index 899b803842bb..9dda2602c862 100644
> --- a/drivers/firmware/efi/arm-runtime.c
> +++ b/drivers/firmware/efi/arm-runtime.c
> @@ -27,7 +27,7 @@
>
>  extern u64 efi_system_table;
>
> -#ifdef CONFIG_ARM64_PTDUMP_DEBUGFS
> +#if defined(CONFIG_PTDUMP_DEBUGFS) && defined(CONFIG_ARM64)
>  #include <asm/ptdump.h>
>
>  static struct ptdump_info efi_ptdump_info = {
> --
> 2.20.1
>

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Re: [PATCH v17 21/23] arm64: mm: Convert mm/dump.c to use walk_page_range()

[Steven Price]

On 16/02/2020 16:25, Ard Biesheuvel wrote:
> On Wed, 18 Dec 2019 at 17:25, Steven Price <steven.price@arm.com> wrote:
>>
>> Now walk_page_range() can walk kernel page tables, we can switch the
>> arm64 ptdump code over to using it, simplifying the code.
>>
>> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
>> Signed-off-by: Steven Price <steven.price@arm.com>
> 
> I did not realize this at the time, but this patch removes the ability
> to dump the EFI page tables on 32-bit ARM. Was that intentional?

No that wasn't intentional, but I can't instantly see how this change
affects 32-bit ARM.

<snip (files in arch/arm64)>
>> diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
>> index 899b803842bb..9dda2602c862 100644
>> --- a/drivers/firmware/efi/arm-runtime.c
>> +++ b/drivers/firmware/efi/arm-runtime.c
>> @@ -27,7 +27,7 @@
>>
>>  extern u64 efi_system_table;
>>
>> -#ifdef CONFIG_ARM64_PTDUMP_DEBUGFS
>> +#if defined(CONFIG_PTDUMP_DEBUGFS) && defined(CONFIG_ARM64)

The previous define was *ARM64* so should never have been true when
building for arm. The new condition should be equivalent (arm64 &&
ptdump enabled).

Am I missing something?

Steve

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Re: [PATCH v17 21/23] arm64: mm: Convert mm/dump.c to use walk_page_range()

[Ard Biesheuvel]

On Mon, 17 Feb 2020 at 11:01, Steven Price <steven.price@arm.com> wrote:
>
> On 16/02/2020 16:25, Ard Biesheuvel wrote:
> > On Wed, 18 Dec 2019 at 17:25, Steven Price <steven.price@arm.com> wrote:
> >>
> >> Now walk_page_range() can walk kernel page tables, we can switch the
> >> arm64 ptdump code over to using it, simplifying the code.
> >>
> >> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> >> Signed-off-by: Steven Price <steven.price@arm.com>
> >
> > I did not realize this at the time, but this patch removes the ability
> > to dump the EFI page tables on 32-bit ARM. Was that intentional?
>
> No that wasn't intentional, but I can't instantly see how this change
> affects 32-bit ARM.
>
> <snip (files in arch/arm64)>
> >> diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
> >> index 899b803842bb..9dda2602c862 100644
> >> --- a/drivers/firmware/efi/arm-runtime.c
> >> +++ b/drivers/firmware/efi/arm-runtime.c
> >> @@ -27,7 +27,7 @@
> >>
> >>  extern u64 efi_system_table;
> >>
> >> -#ifdef CONFIG_ARM64_PTDUMP_DEBUGFS
> >> +#if defined(CONFIG_PTDUMP_DEBUGFS) && defined(CONFIG_ARM64)
>
> The previous define was *ARM64* so should never have been true when
> building for arm. The new condition should be equivalent (arm64 &&
> ptdump enabled).
>
> Am I missing something?
>

Not at all, I just got confused.

IIRC we did have support for dumping the EFI pages tables on 32-bit
ARM at *some* point, but it obviously wasn't your patch that removed
it.

Apologies for the noise.

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