[PATCH 1/3] x86/mm: factor out conditional pageattr PTE bit setting code

[Dave Hansen]

From: Dave Hansen 

The pageattr code has a pattern repeated where it sets a PTE bit
for present PTEs but clears it for non-present PTEs.  This helps
to keep pte_none() from getting messed up.  _PAGE_GLOBAL is the
most frequent target of this pattern.

This pattern also includes a nice, copy-and-pasted comment.

I want to do some special stuff with _PAGE_GLOBAL in a moment,
so refactor this a _bit_ to centralize the comment and the
bit operations.

Signed-off-by: Dave Hansen 
Cc: Andy Lutomirski 
Cc: Linus Torvalds 
Cc: Kees Cook 
Cc: Hugh Dickins 
Cc: Juergen Gross 
Cc: x...@kernel.org
---

 b/arch/x86/mm/pageattr.c |   65 ++-
 1 file changed, 20 insertions(+), 45 deletions(-)

diff -puN arch/x86/mm/pageattr.c~kpti-centralize-global-setting 
arch/x86/mm/pageattr.c
--- a/arch/x86/mm/pageattr.c~kpti-centralize-global-setting 2018-02-13 
15:17:55.602210062 -0800
+++ b/arch/x86/mm/pageattr.c2018-02-13 15:17:55.606210062 -0800
@@ -512,6 +512,22 @@ static void __set_pmd_pte(pte_t *kpte, u
 #endif
 }
 
+static pgprot_t pgprot_set_on_present(pgprot_t prot, pteval_t flags)
+{
+   /*
+* Set 'flags' only if PRESENT.  Ensures that we do not
+* set flags in an otherwise empty PTE breaking pte_none().
+* A later function (such as canon_pgprot()) must clear
+* possibly unsupported flags (like _PAGE_GLOBAL).
+*/
+   if (pgprot_val(prot) & _PAGE_PRESENT)
+   pgprot_val(prot) |= flags;
+   else
+   pgprot_val(prot) &= ~flags;
+
+   return prot;
+}
+
 static int
 try_preserve_large_page(pte_t *kpte, unsigned long address,
struct cpa_data *cpa)
@@ -577,18 +593,7 @@ try_preserve_large_page(pte_t *kpte, uns
 * different bit positions in the two formats.
 */
req_prot = pgprot_4k_2_large(req_prot);
-
-   /*
-* Set the PSE and GLOBAL flags only if the PRESENT flag is
-* set otherwise pmd_present/pmd_huge will return true even on
-* a non present pmd. The canon_pgprot will clear _PAGE_GLOBAL
-* for the ancient hardware that doesn't support it.
-*/
-   if (pgprot_val(req_prot) & _PAGE_PRESENT)
-   pgprot_val(req_prot) |= _PAGE_PSE | _PAGE_GLOBAL;
-   else
-   pgprot_val(req_prot) &= ~(_PAGE_PSE | _PAGE_GLOBAL);
-
+   req_prot = pgprot_set_on_present(req_prot, _PAGE_GLOBAL | _PAGE_PSE);
req_prot = canon_pgprot(req_prot);
 
/*
@@ -698,16 +703,7 @@ __split_large_page(struct cpa_data *cpa,
return 1;
}
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is set
-* otherwise pmd/pte_present will return true even on a non
-* present pmd/pte. The canon_pgprot will clear _PAGE_GLOBAL
-* for the ancient hardware that doesn't support it.
-*/
-   if (pgprot_val(ref_prot) & _PAGE_PRESENT)
-   pgprot_val(ref_prot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(ref_prot) &= ~_PAGE_GLOBAL;
+   ref_prot = pgprot_set_on_present(ref_prot, _PAGE_GLOBAL);
 
/*
 * Get the target pfn from the original entry:
@@ -930,18 +926,7 @@ static void populate_pte(struct cpa_data
 
pte = pte_offset_kernel(pmd, start);
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is
-* set otherwise pte_present will return true even on
-* a non present pte. The canon_pgprot will clear
-* _PAGE_GLOBAL for the ancient hardware that doesn't
-* support it.
-*/
-   if (pgprot_val(pgprot) & _PAGE_PRESENT)
-   pgprot_val(pgprot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(pgprot) &= ~_PAGE_GLOBAL;
-
+   pgprot = pgprot_set_on_present(pgprot, _PAGE_GLOBAL);
pgprot = canon_pgprot(pgprot);
 
while (num_pages-- && start < end) {
@@ -1234,17 +1219,7 @@ repeat:
 
new_prot = static_protections(new_prot, address, pfn);
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is
-* set otherwise pte_present will return true even on
-* a non present pte. The canon_pgprot will clear
-* _PAGE_GLOBAL for the ancient hardware that doesn't
-* support it.
-*/
-   if (pgprot_val(new_prot) & _PAGE_PRESENT)
-   pgprot_val(new_prot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(new_prot) &= ~_PAGE_GLOBAL;
+   new_prot = pgprot_set_on_present(new_prot, _PAGE_GLOBAL);
 
/*
 * We need to keep the pfn from the existing PTE,
_

[PATCH 1/3] x86/mm: factor out conditional pageattr PTE bit setting code

[Dave Hansen]

From: Dave Hansen 

The pageattr code has a pattern repeated where it sets a PTE bit
for present PTEs but clears it for non-present PTEs.  This helps
to keep pte_none() from getting messed up.  _PAGE_GLOBAL is the
most frequent target of this pattern.

This pattern also includes a nice, copy-and-pasted comment.

I want to do some special stuff with _PAGE_GLOBAL in a moment,
so refactor this a _bit_ to centralize the comment and the
bit operations.

Signed-off-by: Dave Hansen 
Cc: Andy Lutomirski 
Cc: Linus Torvalds 
Cc: Kees Cook 
Cc: Hugh Dickins 
Cc: Juergen Gross 
Cc: x...@kernel.org
---

 b/arch/x86/mm/pageattr.c |   65 ++-
 1 file changed, 20 insertions(+), 45 deletions(-)

diff -puN arch/x86/mm/pageattr.c~kpti-centralize-global-setting 
arch/x86/mm/pageattr.c
--- a/arch/x86/mm/pageattr.c~kpti-centralize-global-setting 2018-02-13 
15:17:55.602210062 -0800
+++ b/arch/x86/mm/pageattr.c2018-02-13 15:17:55.606210062 -0800
@@ -512,6 +512,22 @@ static void __set_pmd_pte(pte_t *kpte, u
 #endif
 }
 
+static pgprot_t pgprot_set_on_present(pgprot_t prot, pteval_t flags)
+{
+   /*
+* Set 'flags' only if PRESENT.  Ensures that we do not
+* set flags in an otherwise empty PTE breaking pte_none().
+* A later function (such as canon_pgprot()) must clear
+* possibly unsupported flags (like _PAGE_GLOBAL).
+*/
+   if (pgprot_val(prot) & _PAGE_PRESENT)
+   pgprot_val(prot) |= flags;
+   else
+   pgprot_val(prot) &= ~flags;
+
+   return prot;
+}
+
 static int
 try_preserve_large_page(pte_t *kpte, unsigned long address,
struct cpa_data *cpa)
@@ -577,18 +593,7 @@ try_preserve_large_page(pte_t *kpte, uns
 * different bit positions in the two formats.
 */
req_prot = pgprot_4k_2_large(req_prot);
-
-   /*
-* Set the PSE and GLOBAL flags only if the PRESENT flag is
-* set otherwise pmd_present/pmd_huge will return true even on
-* a non present pmd. The canon_pgprot will clear _PAGE_GLOBAL
-* for the ancient hardware that doesn't support it.
-*/
-   if (pgprot_val(req_prot) & _PAGE_PRESENT)
-   pgprot_val(req_prot) |= _PAGE_PSE | _PAGE_GLOBAL;
-   else
-   pgprot_val(req_prot) &= ~(_PAGE_PSE | _PAGE_GLOBAL);
-
+   req_prot = pgprot_set_on_present(req_prot, _PAGE_GLOBAL | _PAGE_PSE);
req_prot = canon_pgprot(req_prot);
 
/*
@@ -698,16 +703,7 @@ __split_large_page(struct cpa_data *cpa,
return 1;
}
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is set
-* otherwise pmd/pte_present will return true even on a non
-* present pmd/pte. The canon_pgprot will clear _PAGE_GLOBAL
-* for the ancient hardware that doesn't support it.
-*/
-   if (pgprot_val(ref_prot) & _PAGE_PRESENT)
-   pgprot_val(ref_prot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(ref_prot) &= ~_PAGE_GLOBAL;
+   ref_prot = pgprot_set_on_present(ref_prot, _PAGE_GLOBAL);
 
/*
 * Get the target pfn from the original entry:
@@ -930,18 +926,7 @@ static void populate_pte(struct cpa_data
 
pte = pte_offset_kernel(pmd, start);
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is
-* set otherwise pte_present will return true even on
-* a non present pte. The canon_pgprot will clear
-* _PAGE_GLOBAL for the ancient hardware that doesn't
-* support it.
-*/
-   if (pgprot_val(pgprot) & _PAGE_PRESENT)
-   pgprot_val(pgprot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(pgprot) &= ~_PAGE_GLOBAL;
-
+   pgprot = pgprot_set_on_present(pgprot, _PAGE_GLOBAL);
pgprot = canon_pgprot(pgprot);
 
while (num_pages-- && start < end) {
@@ -1234,17 +1219,7 @@ repeat:
 
new_prot = static_protections(new_prot, address, pfn);
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is
-* set otherwise pte_present will return true even on
-* a non present pte. The canon_pgprot will clear
-* _PAGE_GLOBAL for the ancient hardware that doesn't
-* support it.
-*/
-   if (pgprot_val(new_prot) & _PAGE_PRESENT)
-   pgprot_val(new_prot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(new_prot) &= ~_PAGE_GLOBAL;
+   new_prot = pgprot_set_on_present(new_prot, _PAGE_GLOBAL);
 
/*
 * We need to keep the pfn from the existing PTE,
_

[PATCH 1/3] x86/mm: factor out conditional pageattr PTE bit setting code

[Dave Hansen]

From: Dave Hansen 

The pageattr code has a pattern repeated where it sets a PTE bit
for present PTEs but clears it for non-present PTEs.  This helps
to keep pte_none() from getting messed up.  _PAGE_GLOBAL is the
most frequent target of this pattern.

This pattern also includes a nice, copy-and-pasted comment.

I want to do some special stuff with _PAGE_GLOBAL in a moment,
so refactor this a _bit_ to centralize the comment and the
bit operations.

Signed-off-by: Dave Hansen 
Cc: Andy Lutomirski 
Cc: Linus Torvalds 
Cc: Kees Cook 
Cc: Hugh Dickins 
Cc: Juergen Gross 
Cc: x...@kernel.org
---

 b/arch/x86/mm/pageattr.c |   65 ++-
 1 file changed, 20 insertions(+), 45 deletions(-)

diff -puN arch/x86/mm/pageattr.c~kpti-centralize-global-setting 
arch/x86/mm/pageattr.c
--- a/arch/x86/mm/pageattr.c~kpti-centralize-global-setting 2018-02-13 
15:17:55.602210062 -0800
+++ b/arch/x86/mm/pageattr.c2018-02-13 15:17:55.606210062 -0800
@@ -512,6 +512,22 @@ static void __set_pmd_pte(pte_t *kpte, u
 #endif
 }
 
+static pgprot_t pgprot_set_on_present(pgprot_t prot, pteval_t flags)
+{
+   /*
+* Set 'flags' only if PRESENT.  Ensures that we do not
+* set flags in an otherwise empty PTE breaking pte_none().
+* A later function (such as canon_pgprot()) must clear
+* possibly unsupported flags (like _PAGE_GLOBAL).
+*/
+   if (pgprot_val(prot) & _PAGE_PRESENT)
+   pgprot_val(prot) |= flags;
+   else
+   pgprot_val(prot) &= ~flags;
+
+   return prot;
+}
+
 static int
 try_preserve_large_page(pte_t *kpte, unsigned long address,
struct cpa_data *cpa)
@@ -577,18 +593,7 @@ try_preserve_large_page(pte_t *kpte, uns
 * different bit positions in the two formats.
 */
req_prot = pgprot_4k_2_large(req_prot);
-
-   /*
-* Set the PSE and GLOBAL flags only if the PRESENT flag is
-* set otherwise pmd_present/pmd_huge will return true even on
-* a non present pmd. The canon_pgprot will clear _PAGE_GLOBAL
-* for the ancient hardware that doesn't support it.
-*/
-   if (pgprot_val(req_prot) & _PAGE_PRESENT)
-   pgprot_val(req_prot) |= _PAGE_PSE | _PAGE_GLOBAL;
-   else
-   pgprot_val(req_prot) &= ~(_PAGE_PSE | _PAGE_GLOBAL);
-
+   req_prot = pgprot_set_on_present(req_prot, _PAGE_GLOBAL | _PAGE_PSE);
req_prot = canon_pgprot(req_prot);
 
/*
@@ -698,16 +703,7 @@ __split_large_page(struct cpa_data *cpa,
return 1;
}
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is set
-* otherwise pmd/pte_present will return true even on a non
-* present pmd/pte. The canon_pgprot will clear _PAGE_GLOBAL
-* for the ancient hardware that doesn't support it.
-*/
-   if (pgprot_val(ref_prot) & _PAGE_PRESENT)
-   pgprot_val(ref_prot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(ref_prot) &= ~_PAGE_GLOBAL;
+   ref_prot = pgprot_set_on_present(ref_prot, _PAGE_GLOBAL);
 
/*
 * Get the target pfn from the original entry:
@@ -930,18 +926,7 @@ static void populate_pte(struct cpa_data
 
pte = pte_offset_kernel(pmd, start);
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is
-* set otherwise pte_present will return true even on
-* a non present pte. The canon_pgprot will clear
-* _PAGE_GLOBAL for the ancient hardware that doesn't
-* support it.
-*/
-   if (pgprot_val(pgprot) & _PAGE_PRESENT)
-   pgprot_val(pgprot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(pgprot) &= ~_PAGE_GLOBAL;
-
+   pgprot = pgprot_set_on_present(pgprot, _PAGE_GLOBAL);
pgprot = canon_pgprot(pgprot);
 
while (num_pages-- && start < end) {
@@ -1234,17 +1219,7 @@ repeat:
 
new_prot = static_protections(new_prot, address, pfn);
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is
-* set otherwise pte_present will return true even on
-* a non present pte. The canon_pgprot will clear
-* _PAGE_GLOBAL for the ancient hardware that doesn't
-* support it.
-*/
-   if (pgprot_val(new_prot) & _PAGE_PRESENT)
-   pgprot_val(new_prot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(new_prot) &= ~_PAGE_GLOBAL;
+   new_prot = pgprot_set_on_present(new_prot, _PAGE_GLOBAL);
 
/*
 * We need to keep the pfn from the existing PTE,
_

[PATCH 1/3] x86/mm: factor out conditional pageattr PTE bit setting code

[Dave Hansen]

From: Dave Hansen 

The pageattr code has a pattern repeated where it sets a PTE bit
for present PTEs but clears it for non-present PTEs.  This helps
to keep pte_none() from getting messed up.  _PAGE_GLOBAL is the
most frequent target of this pattern.

This pattern also includes a nice, copy-and-pasted comment.

I want to do some special stuff with _PAGE_GLOBAL in a moment,
so refactor this a _bit_ to centralize the comment and the
bit operations.

Signed-off-by: Dave Hansen 
Cc: Andy Lutomirski 
Cc: Linus Torvalds 
Cc: Kees Cook 
Cc: Hugh Dickins 
Cc: Juergen Gross 
Cc: x...@kernel.org
---

 b/arch/x86/mm/pageattr.c |   65 ++-
 1 file changed, 20 insertions(+), 45 deletions(-)

diff -puN arch/x86/mm/pageattr.c~kpti-centralize-global-setting 
arch/x86/mm/pageattr.c
--- a/arch/x86/mm/pageattr.c~kpti-centralize-global-setting 2018-02-13 
15:17:55.602210062 -0800
+++ b/arch/x86/mm/pageattr.c2018-02-13 15:17:55.606210062 -0800
@@ -512,6 +512,22 @@ static void __set_pmd_pte(pte_t *kpte, u
 #endif
 }
 
+static pgprot_t pgprot_set_on_present(pgprot_t prot, pteval_t flags)
+{
+   /*
+* Set 'flags' only if PRESENT.  Ensures that we do not
+* set flags in an otherwise empty PTE breaking pte_none().
+* A later function (such as canon_pgprot()) must clear
+* possibly unsupported flags (like _PAGE_GLOBAL).
+*/
+   if (pgprot_val(prot) & _PAGE_PRESENT)
+   pgprot_val(prot) |= flags;
+   else
+   pgprot_val(prot) &= ~flags;
+
+   return prot;
+}
+
 static int
 try_preserve_large_page(pte_t *kpte, unsigned long address,
struct cpa_data *cpa)
@@ -577,18 +593,7 @@ try_preserve_large_page(pte_t *kpte, uns
 * different bit positions in the two formats.
 */
req_prot = pgprot_4k_2_large(req_prot);
-
-   /*
-* Set the PSE and GLOBAL flags only if the PRESENT flag is
-* set otherwise pmd_present/pmd_huge will return true even on
-* a non present pmd. The canon_pgprot will clear _PAGE_GLOBAL
-* for the ancient hardware that doesn't support it.
-*/
-   if (pgprot_val(req_prot) & _PAGE_PRESENT)
-   pgprot_val(req_prot) |= _PAGE_PSE | _PAGE_GLOBAL;
-   else
-   pgprot_val(req_prot) &= ~(_PAGE_PSE | _PAGE_GLOBAL);
-
+   req_prot = pgprot_set_on_present(req_prot, _PAGE_GLOBAL | _PAGE_PSE);
req_prot = canon_pgprot(req_prot);
 
/*
@@ -698,16 +703,7 @@ __split_large_page(struct cpa_data *cpa,
return 1;
}
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is set
-* otherwise pmd/pte_present will return true even on a non
-* present pmd/pte. The canon_pgprot will clear _PAGE_GLOBAL
-* for the ancient hardware that doesn't support it.
-*/
-   if (pgprot_val(ref_prot) & _PAGE_PRESENT)
-   pgprot_val(ref_prot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(ref_prot) &= ~_PAGE_GLOBAL;
+   ref_prot = pgprot_set_on_present(ref_prot, _PAGE_GLOBAL);
 
/*
 * Get the target pfn from the original entry:
@@ -930,18 +926,7 @@ static void populate_pte(struct cpa_data
 
pte = pte_offset_kernel(pmd, start);
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is
-* set otherwise pte_present will return true even on
-* a non present pte. The canon_pgprot will clear
-* _PAGE_GLOBAL for the ancient hardware that doesn't
-* support it.
-*/
-   if (pgprot_val(pgprot) & _PAGE_PRESENT)
-   pgprot_val(pgprot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(pgprot) &= ~_PAGE_GLOBAL;
-
+   pgprot = pgprot_set_on_present(pgprot, _PAGE_GLOBAL);
pgprot = canon_pgprot(pgprot);
 
while (num_pages-- && start < end) {
@@ -1234,17 +1219,7 @@ repeat:
 
new_prot = static_protections(new_prot, address, pfn);
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is
-* set otherwise pte_present will return true even on
-* a non present pte. The canon_pgprot will clear
-* _PAGE_GLOBAL for the ancient hardware that doesn't
-* support it.
-*/
-   if (pgprot_val(new_prot) & _PAGE_PRESENT)
-   pgprot_val(new_prot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(new_prot) &= ~_PAGE_GLOBAL;
+   new_prot = pgprot_set_on_present(new_prot, _PAGE_GLOBAL);
 
/*
 * We need to keep the pfn from the existing PTE,
_