[v30,04/11] arm64: mm: allow for unmapping memory region from kernel mapping

Message ID 20170124085004.3892-3-takahiro.akashi@linaro.org
State New
Headers show
Series
  • arm64: add kdump support
Related show

Commit Message

AKASHI Takahiro Jan. 24, 2017, 8:49 a.m.
The current implementation of create_mapping_late() is only allowed
to modify permission attributes (read-only or read-write) against
the existing kernel mapping.

In this patch, PAGE_KERNEL_INVALID protection attribute is introduced.
We will now be able to invalidate (or unmap) some part of the existing
kernel mapping by specifying PAGE_KERNEL_INVALID to create_mapping_late().

This feature will be used in a suceeding kdump patch to protect
the memory reserved for crash dump kernel once after loaded.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>

---
 arch/arm64/include/asm/mmu.h           |  2 ++
 arch/arm64/include/asm/pgtable-hwdef.h |  2 ++
 arch/arm64/include/asm/pgtable-prot.h  |  1 +
 arch/arm64/include/asm/pgtable.h       |  4 ++++
 arch/arm64/mm/mmu.c                    | 29 ++++++++++++++++++++---------
 5 files changed, 29 insertions(+), 9 deletions(-)

-- 
2.11.0


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Comments

Pratyush Anand Jan. 24, 2017, 11:32 a.m. | #1
On Tuesday 24 January 2017 02:19 PM, AKASHI Takahiro wrote:
> The current implementation of create_mapping_late() is only allowed

> to modify permission attributes (read-only or read-write) against

> the existing kernel mapping.

>

> In this patch, PAGE_KERNEL_INVALID protection attribute is introduced.

> We will now be able to invalidate (or unmap) some part of the existing

> kernel mapping by specifying PAGE_KERNEL_INVALID to create_mapping_late().

>

> This feature will be used in a suceeding kdump patch to protect

> the memory reserved for crash dump kernel once after loaded.

>

> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>

> ---

>  arch/arm64/include/asm/mmu.h           |  2 ++

>  arch/arm64/include/asm/pgtable-hwdef.h |  2 ++

>  arch/arm64/include/asm/pgtable-prot.h  |  1 +

>  arch/arm64/include/asm/pgtable.h       |  4 ++++

>  arch/arm64/mm/mmu.c                    | 29 ++++++++++++++++++++---------

>  5 files changed, 29 insertions(+), 9 deletions(-)

>

> diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h

> index 47619411f0ff..a6c1367527bc 100644

> --- a/arch/arm64/include/asm/mmu.h

> +++ b/arch/arm64/include/asm/mmu.h

> @@ -36,6 +36,8 @@ extern void init_mem_pgprot(void);

>  extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,

>  			       unsigned long virt, phys_addr_t size,

>  			       pgprot_t prot, bool page_mappings_only);

> +extern void create_mapping_late(phys_addr_t phys, unsigned long virt,

> +				phys_addr_t size, pgprot_t prot);

>  extern void *fixmap_remap_fdt(phys_addr_t dt_phys);

>

>  #endif

> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h

> index eb0c2bd90de9..e66efec31ca9 100644

> --- a/arch/arm64/include/asm/pgtable-hwdef.h

> +++ b/arch/arm64/include/asm/pgtable-hwdef.h

> @@ -119,6 +119,7 @@

>  #define PUD_TABLE_BIT		(_AT(pgdval_t, 1) << 1)

>  #define PUD_TYPE_MASK		(_AT(pgdval_t, 3) << 0)

>  #define PUD_TYPE_SECT		(_AT(pgdval_t, 1) << 0)

> +#define PUD_VALID		PUD_TYPE_SECT

>

>  /*

>   * Level 2 descriptor (PMD).

> @@ -128,6 +129,7 @@

>  #define PMD_TYPE_TABLE		(_AT(pmdval_t, 3) << 0)

>  #define PMD_TYPE_SECT		(_AT(pmdval_t, 1) << 0)

>  #define PMD_TABLE_BIT		(_AT(pmdval_t, 1) << 1)

> +#define PMD_VALID		PMD_TYPE_SECT

>

>  /*

>   * Section

> diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h

> index 2142c7726e76..945d84cd5df7 100644

> --- a/arch/arm64/include/asm/pgtable-prot.h

> +++ b/arch/arm64/include/asm/pgtable-prot.h

> @@ -54,6 +54,7 @@

>  #define PAGE_KERNEL_ROX		__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_RDONLY)

>  #define PAGE_KERNEL_EXEC	__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE)

>  #define PAGE_KERNEL_EXEC_CONT	__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_CONT)

> +#define PAGE_KERNEL_INVALID	__pgprot(0)

>

>  #define PAGE_HYP		__pgprot(_PAGE_DEFAULT | PTE_HYP | PTE_HYP_XN)

>  #define PAGE_HYP_EXEC		__pgprot(_PAGE_DEFAULT | PTE_HYP | PTE_RDONLY)

> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h

> index ffbb9a520563..1904a7c07018 100644

> --- a/arch/arm64/include/asm/pgtable.h

> +++ b/arch/arm64/include/asm/pgtable.h

> @@ -364,6 +364,8 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,

>

>  #define pmd_bad(pmd)		(!(pmd_val(pmd) & PMD_TABLE_BIT))

>

> +#define pmd_valid(pmd)		(!!(pmd_val(pmd) & PMD_VALID))

> +

>  #define pmd_table(pmd)		((pmd_val(pmd) & PMD_TYPE_MASK) == \

>  				 PMD_TYPE_TABLE)

>  #define pmd_sect(pmd)		((pmd_val(pmd) & PMD_TYPE_MASK) == \

> @@ -428,6 +430,7 @@ static inline phys_addr_t pmd_page_paddr(pmd_t pmd)

>

>  #define pud_none(pud)		(!pud_val(pud))

>  #define pud_bad(pud)		(!(pud_val(pud) & PUD_TABLE_BIT))

> +#define pud_valid(pud)		(!!(pud_val(pud) & PUD_VALID))


This will break compilation for CONFIG_PGTABLE_LEVELS <= 2

>  #define pud_present(pud)	(pud_val(pud))

>

>  static inline void set_pud(pud_t *pudp, pud_t pud)

> @@ -481,6 +484,7 @@ static inline phys_addr_t pud_page_paddr(pud_t pud)

>

>  #define pgd_none(pgd)		(!pgd_val(pgd))

>  #define pgd_bad(pgd)		(!(pgd_val(pgd) & 2))

> +#define pgd_valid(pgd)		(!!(pgd_val(pgd) & 1))


This has not been used anywhere.

>  #define pgd_present(pgd)	(pgd_val(pgd))

>

>  static inline void set_pgd(pgd_t *pgdp, pgd_t pgd)

> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c

> index 17243e43184e..9c7adcce8e4e 100644

> --- a/arch/arm64/mm/mmu.c

> +++ b/arch/arm64/mm/mmu.c

> @@ -133,7 +133,8 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,

>  		 * Set the contiguous bit for the subsequent group of PTEs if

>  		 * its size and alignment are appropriate.

>  		 */

> -		if (((addr | PFN_PHYS(pfn)) & ~CONT_PTE_MASK) == 0) {

> +		if ((pgprot_val(prot) & PTE_VALID) &&

> +		    (((addr | PFN_PHYS(pfn)) & ~CONT_PTE_MASK) == 0)) {

>  			if (end - addr >= CONT_PTE_SIZE && !page_mappings_only)

>  				__prot = __pgprot(pgprot_val(prot) | PTE_CONT);

>  			else

> @@ -147,7 +148,8 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,

>  		 * After the PTE entry has been populated once, we

>  		 * only allow updates to the permission attributes.

>  		 */

> -		BUG_ON(!pgattr_change_is_safe(pte_val(old_pte), pte_val(*pte)));

> +		BUG_ON(pte_valid(old_pte) && pte_valid(*pte) &&

> +		       !pgattr_change_is_safe(pte_val(old_pte), pte_val(*pte)));

>

>  	} while (pte++, addr += PAGE_SIZE, addr != end);

>

> @@ -190,7 +192,8 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,

>  			 * Set the contiguous bit for the subsequent group of

>  			 * PMDs if its size and alignment are appropriate.

>  			 */

> -			if (((addr | phys) & ~CONT_PMD_MASK) == 0) {

> +			if ((pgprot_val(prot) | PMD_VALID) &&

> +			    ((addr | phys) & ~CONT_PMD_MASK) == 0) {

>  				if (end - addr >= CONT_PMD_SIZE)

>  					__prot = __pgprot(pgprot_val(prot) |

>  							  PTE_CONT);

> @@ -203,7 +206,8 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,

>  			 * After the PMD entry has been populated once, we

>  			 * only allow updates to the permission attributes.

>  			 */

> -			BUG_ON(!pgattr_change_is_safe(pmd_val(old_pmd),

> +			BUG_ON(pmd_valid(old_pmd) && pmd_valid(*pmd) &&

> +			       !pgattr_change_is_safe(pmd_val(old_pmd),

>  						      pmd_val(*pmd)));

>  		} else {

>  			alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),

> @@ -263,7 +267,8 @@ static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,

>  			 * After the PUD entry has been populated once, we

>  			 * only allow updates to the permission attributes.

>  			 */

> -			BUG_ON(!pgattr_change_is_safe(pud_val(old_pud),

> +			BUG_ON(pud_valid(old_pud) && pud_valid(*pud) &&

> +			       !pgattr_change_is_safe(pud_val(old_pud),

>  						      pud_val(*pud)));

>  		} else {

>  			alloc_init_pmd(pud, addr, next, phys, prot,

> @@ -344,8 +349,8 @@ void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,

>  			     pgd_pgtable_alloc, page_mappings_only);

>  }

>

> -static void create_mapping_late(phys_addr_t phys, unsigned long virt,

> -				  phys_addr_t size, pgprot_t prot)

> +void create_mapping_late(phys_addr_t phys, unsigned long virt,

> +			 phys_addr_t size, pgprot_t prot)

>  {

>  	if (virt < VMALLOC_START) {

>  		pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",

> @@ -791,14 +796,20 @@ int __init arch_ioremap_pmd_supported(void)

>  int pud_set_huge(pud_t *pud, phys_addr_t phys, pgprot_t prot)

>  {

>  	BUG_ON(phys & ~PUD_MASK);

> -	set_pud(pud, __pud(phys | PUD_TYPE_SECT | pgprot_val(mk_sect_prot(prot))));

> +	set_pud(pud, __pud(phys |

> +			   ((pgprot_val(prot) & PUD_VALID) ?

> +					PUD_TYPE_SECT : 0) |

> +			   pgprot_val(mk_sect_prot(prot))));

>  	return 1;

>  }

>

>  int pmd_set_huge(pmd_t *pmd, phys_addr_t phys, pgprot_t prot)

>  {

>  	BUG_ON(phys & ~PMD_MASK);

> -	set_pmd(pmd, __pmd(phys | PMD_TYPE_SECT | pgprot_val(mk_sect_prot(prot))));

> +	set_pmd(pmd, __pmd(phys |

> +			   ((pgprot_val(prot) & PMD_VALID) ?

> +					PMD_TYPE_SECT : 0) |

> +			   pgprot_val(mk_sect_prot(prot))));

>  	return 1;

>  }

>

>



~Pratyush

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AKASHI Takahiro Jan. 25, 2017, 6:37 a.m. | #2
On Tue, Jan 24, 2017 at 05:02:20PM +0530, Pratyush Anand wrote:
> 

> 

> On Tuesday 24 January 2017 02:19 PM, AKASHI Takahiro wrote:

> >The current implementation of create_mapping_late() is only allowed

> >to modify permission attributes (read-only or read-write) against

> >the existing kernel mapping.

> >

> >In this patch, PAGE_KERNEL_INVALID protection attribute is introduced.

> >We will now be able to invalidate (or unmap) some part of the existing

> >kernel mapping by specifying PAGE_KERNEL_INVALID to create_mapping_late().

> >

> >This feature will be used in a suceeding kdump patch to protect

> >the memory reserved for crash dump kernel once after loaded.

> >

> >Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>

> >---

> > arch/arm64/include/asm/mmu.h           |  2 ++

> > arch/arm64/include/asm/pgtable-hwdef.h |  2 ++

> > arch/arm64/include/asm/pgtable-prot.h  |  1 +

> > arch/arm64/include/asm/pgtable.h       |  4 ++++

> > arch/arm64/mm/mmu.c                    | 29 ++++++++++++++++++++---------

> > 5 files changed, 29 insertions(+), 9 deletions(-)

> >

> >diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h

> >index 47619411f0ff..a6c1367527bc 100644

> >--- a/arch/arm64/include/asm/mmu.h

> >+++ b/arch/arm64/include/asm/mmu.h

> >@@ -36,6 +36,8 @@ extern void init_mem_pgprot(void);

> > extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,

> > 			       unsigned long virt, phys_addr_t size,

> > 			       pgprot_t prot, bool page_mappings_only);

> >+extern void create_mapping_late(phys_addr_t phys, unsigned long virt,

> >+				phys_addr_t size, pgprot_t prot);

> > extern void *fixmap_remap_fdt(phys_addr_t dt_phys);

> >

> > #endif

> >diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h

> >index eb0c2bd90de9..e66efec31ca9 100644

> >--- a/arch/arm64/include/asm/pgtable-hwdef.h

> >+++ b/arch/arm64/include/asm/pgtable-hwdef.h

> >@@ -119,6 +119,7 @@

> > #define PUD_TABLE_BIT		(_AT(pgdval_t, 1) << 1)

> > #define PUD_TYPE_MASK		(_AT(pgdval_t, 3) << 0)

> > #define PUD_TYPE_SECT		(_AT(pgdval_t, 1) << 0)

> >+#define PUD_VALID		PUD_TYPE_SECT

> >

> > /*

> >  * Level 2 descriptor (PMD).

> >@@ -128,6 +129,7 @@

> > #define PMD_TYPE_TABLE		(_AT(pmdval_t, 3) << 0)

> > #define PMD_TYPE_SECT		(_AT(pmdval_t, 1) << 0)

> > #define PMD_TABLE_BIT		(_AT(pmdval_t, 1) << 1)

> >+#define PMD_VALID		PMD_TYPE_SECT

> >

> > /*

> >  * Section

> >diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h

> >index 2142c7726e76..945d84cd5df7 100644

> >--- a/arch/arm64/include/asm/pgtable-prot.h

> >+++ b/arch/arm64/include/asm/pgtable-prot.h

> >@@ -54,6 +54,7 @@

> > #define PAGE_KERNEL_ROX		__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_RDONLY)

> > #define PAGE_KERNEL_EXEC	__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE)

> > #define PAGE_KERNEL_EXEC_CONT	__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_CONT)

> >+#define PAGE_KERNEL_INVALID	__pgprot(0)

> >

> > #define PAGE_HYP		__pgprot(_PAGE_DEFAULT | PTE_HYP | PTE_HYP_XN)

> > #define PAGE_HYP_EXEC		__pgprot(_PAGE_DEFAULT | PTE_HYP | PTE_RDONLY)

> >diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h

> >index ffbb9a520563..1904a7c07018 100644

> >--- a/arch/arm64/include/asm/pgtable.h

> >+++ b/arch/arm64/include/asm/pgtable.h

> >@@ -364,6 +364,8 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,

> >

> > #define pmd_bad(pmd)		(!(pmd_val(pmd) & PMD_TABLE_BIT))

> >

> >+#define pmd_valid(pmd)		(!!(pmd_val(pmd) & PMD_VALID))

> >+

> > #define pmd_table(pmd)		((pmd_val(pmd) & PMD_TYPE_MASK) == \

> > 				 PMD_TYPE_TABLE)

> > #define pmd_sect(pmd)		((pmd_val(pmd) & PMD_TYPE_MASK) == \

> >@@ -428,6 +430,7 @@ static inline phys_addr_t pmd_page_paddr(pmd_t pmd)

> >

> > #define pud_none(pud)		(!pud_val(pud))

> > #define pud_bad(pud)		(!(pud_val(pud) & PUD_TABLE_BIT))

> >+#define pud_valid(pud)		(!!(pud_val(pud) & PUD_VALID))

> 

> This will break compilation for CONFIG_PGTABLE_LEVELS <= 2


Ah, yes. A quick fix is as follows:

===>8===

Now I've confirmed that it compiles under the configuration with
    * 4KB page x 39, 48-bit address space
    * 64KB page x 42, 48-bit address space
and also verified a crash dump image for 64KB x 42/48b cases.

> > #define pud_present(pud)	(pud_val(pud))

> >

> > static inline void set_pud(pud_t *pudp, pud_t pud)

> >@@ -481,6 +484,7 @@ static inline phys_addr_t pud_page_paddr(pud_t pud)

> >

> > #define pgd_none(pgd)		(!pgd_val(pgd))

> > #define pgd_bad(pgd)		(!(pgd_val(pgd) & 2))

> >+#define pgd_valid(pgd)		(!!(pgd_val(pgd) & 1))

> 

> This has not been used anywhere.


Well, this patch actually also breaks ptdump (debugfs/kernel_page_tables)
as a descriptor can be non-zero yet invalid after applying this patch.
Once it is accepted, I will post another patch which will fix the issue.
pgd_valid() is used in that patch.

Thanks,
-Takahiro AKASHI

> > #define pgd_present(pgd)	(pgd_val(pgd))

> >

> > static inline void set_pgd(pgd_t *pgdp, pgd_t pgd)

> >diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c

> >index 17243e43184e..9c7adcce8e4e 100644

> >--- a/arch/arm64/mm/mmu.c

> >+++ b/arch/arm64/mm/mmu.c

> >@@ -133,7 +133,8 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,

> > 		 * Set the contiguous bit for the subsequent group of PTEs if

> > 		 * its size and alignment are appropriate.

> > 		 */

> >-		if (((addr | PFN_PHYS(pfn)) & ~CONT_PTE_MASK) == 0) {

> >+		if ((pgprot_val(prot) & PTE_VALID) &&

> >+		    (((addr | PFN_PHYS(pfn)) & ~CONT_PTE_MASK) == 0)) {

> > 			if (end - addr >= CONT_PTE_SIZE && !page_mappings_only)

> > 				__prot = __pgprot(pgprot_val(prot) | PTE_CONT);

> > 			else

> >@@ -147,7 +148,8 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,

> > 		 * After the PTE entry has been populated once, we

> > 		 * only allow updates to the permission attributes.

> > 		 */

> >-		BUG_ON(!pgattr_change_is_safe(pte_val(old_pte), pte_val(*pte)));

> >+		BUG_ON(pte_valid(old_pte) && pte_valid(*pte) &&

> >+		       !pgattr_change_is_safe(pte_val(old_pte), pte_val(*pte)));

> >

> > 	} while (pte++, addr += PAGE_SIZE, addr != end);

> >

> >@@ -190,7 +192,8 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,

> > 			 * Set the contiguous bit for the subsequent group of

> > 			 * PMDs if its size and alignment are appropriate.

> > 			 */

> >-			if (((addr | phys) & ~CONT_PMD_MASK) == 0) {

> >+			if ((pgprot_val(prot) | PMD_VALID) &&

> >+			    ((addr | phys) & ~CONT_PMD_MASK) == 0) {

> > 				if (end - addr >= CONT_PMD_SIZE)

> > 					__prot = __pgprot(pgprot_val(prot) |

> > 							  PTE_CONT);

> >@@ -203,7 +206,8 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,

> > 			 * After the PMD entry has been populated once, we

> > 			 * only allow updates to the permission attributes.

> > 			 */

> >-			BUG_ON(!pgattr_change_is_safe(pmd_val(old_pmd),

> >+			BUG_ON(pmd_valid(old_pmd) && pmd_valid(*pmd) &&

> >+			       !pgattr_change_is_safe(pmd_val(old_pmd),

> > 						      pmd_val(*pmd)));

> > 		} else {

> > 			alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),

> >@@ -263,7 +267,8 @@ static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,

> > 			 * After the PUD entry has been populated once, we

> > 			 * only allow updates to the permission attributes.

> > 			 */

> >-			BUG_ON(!pgattr_change_is_safe(pud_val(old_pud),

> >+			BUG_ON(pud_valid(old_pud) && pud_valid(*pud) &&

> >+			       !pgattr_change_is_safe(pud_val(old_pud),

> > 						      pud_val(*pud)));

> > 		} else {

> > 			alloc_init_pmd(pud, addr, next, phys, prot,

> >@@ -344,8 +349,8 @@ void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,

> > 			     pgd_pgtable_alloc, page_mappings_only);

> > }

> >

> >-static void create_mapping_late(phys_addr_t phys, unsigned long virt,

> >-				  phys_addr_t size, pgprot_t prot)

> >+void create_mapping_late(phys_addr_t phys, unsigned long virt,

> >+			 phys_addr_t size, pgprot_t prot)

> > {

> > 	if (virt < VMALLOC_START) {

> > 		pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",

> >@@ -791,14 +796,20 @@ int __init arch_ioremap_pmd_supported(void)

> > int pud_set_huge(pud_t *pud, phys_addr_t phys, pgprot_t prot)

> > {

> > 	BUG_ON(phys & ~PUD_MASK);

> >-	set_pud(pud, __pud(phys | PUD_TYPE_SECT | pgprot_val(mk_sect_prot(prot))));

> >+	set_pud(pud, __pud(phys |

> >+			   ((pgprot_val(prot) & PUD_VALID) ?

> >+					PUD_TYPE_SECT : 0) |

> >+			   pgprot_val(mk_sect_prot(prot))));

> > 	return 1;

> > }

> >

> > int pmd_set_huge(pmd_t *pmd, phys_addr_t phys, pgprot_t prot)

> > {

> > 	BUG_ON(phys & ~PMD_MASK);

> >-	set_pmd(pmd, __pmd(phys | PMD_TYPE_SECT | pgprot_val(mk_sect_prot(prot))));

> >+	set_pmd(pmd, __pmd(phys |

> >+			   ((pgprot_val(prot) & PMD_VALID) ?

> >+					PMD_TYPE_SECT : 0) |

> >+			   pgprot_val(mk_sect_prot(prot))));

> > 	return 1;

> > }

> >

> >

> 

> 

> ~Pratyush


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diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 1904a7c07018..dc11d4bf332c 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -467,6 +467,8 @@ static inline phys_addr_t pud_page_paddr(pud_t pud)
 
 #else
 
+#define pud_valid(pud)		(1)
+
 #define pud_page_paddr(pud)	({ BUILD_BUG(); 0; })
 
 /* Match pmd_offset folding in <asm/generic/pgtable-nopmd.h> */
@@ -520,6 +522,8 @@ static inline phys_addr_t pgd_page_paddr(pgd_t pgd)
 
 #else
 
+#define pgd_valid(pgd)		(1)
+
 #define pgd_page_paddr(pgd)	({ BUILD_BUG(); 0;})
 
 /* Match pud_offset folding in <asm/generic/pgtable-nopud.h> */

James Morse Jan. 25, 2017, 3:49 p.m. | #3
Hi Akashi,

On 24/01/17 08:49, AKASHI Takahiro wrote:
> The current implementation of create_mapping_late() is only allowed

> to modify permission attributes (read-only or read-write) against

> the existing kernel mapping.

> 

> In this patch, PAGE_KERNEL_INVALID protection attribute is introduced.

> We will now be able to invalidate (or unmap) some part of the existing


Can we stick to calling this 'unmap', otherwise 'invalidate this page range'
becomes ambiguous, cache maintenance or page-table manipulation?!


> kernel mapping by specifying PAGE_KERNEL_INVALID to create_mapping_late().

> 

> This feature will be used in a suceeding kdump patch to protect

> the memory reserved for crash dump kernel once after loaded.


> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c

> index 17243e43184e..9c7adcce8e4e 100644

> --- a/arch/arm64/mm/mmu.c

> +++ b/arch/arm64/mm/mmu.c

> @@ -190,7 +192,8 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,

>  			 * Set the contiguous bit for the subsequent group of

>  			 * PMDs if its size and alignment are appropriate.

>  			 */

> -			if (((addr | phys) & ~CONT_PMD_MASK) == 0) {


> +			if ((pgprot_val(prot) | PMD_VALID) &&


& PMD_VALID?


> +			    ((addr | phys) & ~CONT_PMD_MASK) == 0) {

>  				if (end - addr >= CONT_PMD_SIZE)

>  					__prot = __pgprot(pgprot_val(prot) |

>  							  PTE_CONT);

> @@ -203,7 +206,8 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,

>  			 * After the PMD entry has been populated once, we

>  			 * only allow updates to the permission attributes.

>  			 */

> -			BUG_ON(!pgattr_change_is_safe(pmd_val(old_pmd),

> +			BUG_ON(pmd_valid(old_pmd) && pmd_valid(*pmd) &&

> +			       !pgattr_change_is_safe(pmd_val(old_pmd),

>  						      pmd_val(*pmd)));


Could you add PTE_VALID checks to pgattr_change_is_safe() instead of at every
call? I think (old == 0 || new == 0) is probably doing something similar.


>  		} else {

>  			alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),

> @@ -791,14 +796,20 @@ int __init arch_ioremap_pmd_supported(void)

>  int pud_set_huge(pud_t *pud, phys_addr_t phys, pgprot_t prot)

>  {

>  	BUG_ON(phys & ~PUD_MASK);

> -	set_pud(pud, __pud(phys | PUD_TYPE_SECT | pgprot_val(mk_sect_prot(prot))));

> +	set_pud(pud, __pud(phys |

> +			   ((pgprot_val(prot) & PUD_VALID) ?

> +					PUD_TYPE_SECT : 0) |

> +			   pgprot_val(mk_sect_prot(prot))));


This looks complicated. Is this equivalent?:

>    prot = mk_sect_prot(prot);

>    if (pgprot_val(prot) & PUD_VALID)

>        prot |= PUD_TYPE_SECT;

>

>    set_pud(pud, __pud(phys | pgprot_val(prot)));



Given you defined PUD_VALID as being PUD_TYPE_SECT, I think you can then reduce
it to:
>    set_pud(pud, __pud(phys | pgprot_val(mk_sect_prot(prot))));


It looks like mk_sect_prot() doesn't touch the valid bit so all this is doing is
clearing the table bit making it a section and keeping the valid bit from the
caller.


Thanks,

James


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AKASHI Takahiro Jan. 26, 2017, 8:08 a.m. | #4
On Wed, Jan 25, 2017 at 03:49:56PM +0000, James Morse wrote:
> Hi Akashi,

> 

> On 24/01/17 08:49, AKASHI Takahiro wrote:

> > The current implementation of create_mapping_late() is only allowed

> > to modify permission attributes (read-only or read-write) against

> > the existing kernel mapping.

> > 

> > In this patch, PAGE_KERNEL_INVALID protection attribute is introduced.

> > We will now be able to invalidate (or unmap) some part of the existing

> 

> Can we stick to calling this 'unmap', otherwise 'invalidate this page range'

> becomes ambiguous, cache maintenance or page-table manipulation?!


Sure.
I hesitated to use "unmap" because we don't free any of descriptor table
pages here, but who notice the differences.

> 

> > kernel mapping by specifying PAGE_KERNEL_INVALID to create_mapping_late().

> > 

> > This feature will be used in a suceeding kdump patch to protect

> > the memory reserved for crash dump kernel once after loaded.

> 

> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c

> > index 17243e43184e..9c7adcce8e4e 100644

> > --- a/arch/arm64/mm/mmu.c

> > +++ b/arch/arm64/mm/mmu.c

> > @@ -190,7 +192,8 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,

> >  			 * Set the contiguous bit for the subsequent group of

> >  			 * PMDs if its size and alignment are appropriate.

> >  			 */

> > -			if (((addr | phys) & ~CONT_PMD_MASK) == 0) {

> 

> > +			if ((pgprot_val(prot) | PMD_VALID) &&

> 

> & PMD_VALID?


Shame on me.

> 

> > +			    ((addr | phys) & ~CONT_PMD_MASK) == 0) {

> >  				if (end - addr >= CONT_PMD_SIZE)

> >  					__prot = __pgprot(pgprot_val(prot) |

> >  							  PTE_CONT);

> > @@ -203,7 +206,8 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,

> >  			 * After the PMD entry has been populated once, we

> >  			 * only allow updates to the permission attributes.

> >  			 */

> > -			BUG_ON(!pgattr_change_is_safe(pmd_val(old_pmd),

> > +			BUG_ON(pmd_valid(old_pmd) && pmd_valid(*pmd) &&

> > +			       !pgattr_change_is_safe(pmd_val(old_pmd),

> >  						      pmd_val(*pmd)));

> 

> Could you add PTE_VALID checks to pgattr_change_is_safe() instead of at every

> call? I think (old == 0 || new == 0) is probably doing something similar.


Good catch :)

> 

> >  		} else {

> >  			alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),

> > @@ -791,14 +796,20 @@ int __init arch_ioremap_pmd_supported(void)

> >  int pud_set_huge(pud_t *pud, phys_addr_t phys, pgprot_t prot)

> >  {

> >  	BUG_ON(phys & ~PUD_MASK);

> > -	set_pud(pud, __pud(phys | PUD_TYPE_SECT | pgprot_val(mk_sect_prot(prot))));

> > +	set_pud(pud, __pud(phys |

> > +			   ((pgprot_val(prot) & PUD_VALID) ?

> > +					PUD_TYPE_SECT : 0) |

> > +			   pgprot_val(mk_sect_prot(prot))));

> 

> This looks complicated. Is this equivalent?:

>

> >    prot = mk_sect_prot(prot);

> >    if (pgprot_val(prot) & PUD_VALID)

> >        prot |= PUD_TYPE_SECT;

> >

> >    set_pud(pud, __pud(phys | pgprot_val(prot)));


Yeah, I just wanted to keep it simple,

> 

> Given you defined PUD_VALID as being PUD_TYPE_SECT, I think you can then reduce

> it to:

> >    set_pud(pud, __pud(phys | pgprot_val(mk_sect_prot(prot))));

> 

> It looks like mk_sect_prot() doesn't touch the valid bit so all this is doing is

> clearing the table bit making it a section and keeping the valid bit from the

> caller.


but this seems to be too much optimized because, even without my patch,
this change is applicable. The intention of the original code would be
to make sure the entry be a pud-level descriptor whatever given "prot" is.

-Takahiro AKASHI

> 

> Thanks,

> 

> James

> 


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Patch hide | download patch | download mbox

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 47619411f0ff..a6c1367527bc 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -36,6 +36,8 @@  extern void init_mem_pgprot(void);
 extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
 			       unsigned long virt, phys_addr_t size,
 			       pgprot_t prot, bool page_mappings_only);
+extern void create_mapping_late(phys_addr_t phys, unsigned long virt,
+				phys_addr_t size, pgprot_t prot);
 extern void *fixmap_remap_fdt(phys_addr_t dt_phys);
 
 #endif
diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index eb0c2bd90de9..e66efec31ca9 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -119,6 +119,7 @@ 
 #define PUD_TABLE_BIT		(_AT(pgdval_t, 1) << 1)
 #define PUD_TYPE_MASK		(_AT(pgdval_t, 3) << 0)
 #define PUD_TYPE_SECT		(_AT(pgdval_t, 1) << 0)
+#define PUD_VALID		PUD_TYPE_SECT
 
 /*
  * Level 2 descriptor (PMD).
@@ -128,6 +129,7 @@ 
 #define PMD_TYPE_TABLE		(_AT(pmdval_t, 3) << 0)
 #define PMD_TYPE_SECT		(_AT(pmdval_t, 1) << 0)
 #define PMD_TABLE_BIT		(_AT(pmdval_t, 1) << 1)
+#define PMD_VALID		PMD_TYPE_SECT
 
 /*
  * Section
diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
index 2142c7726e76..945d84cd5df7 100644
--- a/arch/arm64/include/asm/pgtable-prot.h
+++ b/arch/arm64/include/asm/pgtable-prot.h
@@ -54,6 +54,7 @@ 
 #define PAGE_KERNEL_ROX		__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_RDONLY)
 #define PAGE_KERNEL_EXEC	__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE)
 #define PAGE_KERNEL_EXEC_CONT	__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_CONT)
+#define PAGE_KERNEL_INVALID	__pgprot(0)
 
 #define PAGE_HYP		__pgprot(_PAGE_DEFAULT | PTE_HYP | PTE_HYP_XN)
 #define PAGE_HYP_EXEC		__pgprot(_PAGE_DEFAULT | PTE_HYP | PTE_RDONLY)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index ffbb9a520563..1904a7c07018 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -364,6 +364,8 @@  extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 
 #define pmd_bad(pmd)		(!(pmd_val(pmd) & PMD_TABLE_BIT))
 
+#define pmd_valid(pmd)		(!!(pmd_val(pmd) & PMD_VALID))
+
 #define pmd_table(pmd)		((pmd_val(pmd) & PMD_TYPE_MASK) == \
 				 PMD_TYPE_TABLE)
 #define pmd_sect(pmd)		((pmd_val(pmd) & PMD_TYPE_MASK) == \
@@ -428,6 +430,7 @@  static inline phys_addr_t pmd_page_paddr(pmd_t pmd)
 
 #define pud_none(pud)		(!pud_val(pud))
 #define pud_bad(pud)		(!(pud_val(pud) & PUD_TABLE_BIT))
+#define pud_valid(pud)		(!!(pud_val(pud) & PUD_VALID))
 #define pud_present(pud)	(pud_val(pud))
 
 static inline void set_pud(pud_t *pudp, pud_t pud)
@@ -481,6 +484,7 @@  static inline phys_addr_t pud_page_paddr(pud_t pud)
 
 #define pgd_none(pgd)		(!pgd_val(pgd))
 #define pgd_bad(pgd)		(!(pgd_val(pgd) & 2))
+#define pgd_valid(pgd)		(!!(pgd_val(pgd) & 1))
 #define pgd_present(pgd)	(pgd_val(pgd))
 
 static inline void set_pgd(pgd_t *pgdp, pgd_t pgd)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 17243e43184e..9c7adcce8e4e 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -133,7 +133,8 @@  static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
 		 * Set the contiguous bit for the subsequent group of PTEs if
 		 * its size and alignment are appropriate.
 		 */
-		if (((addr | PFN_PHYS(pfn)) & ~CONT_PTE_MASK) == 0) {
+		if ((pgprot_val(prot) & PTE_VALID) &&
+		    (((addr | PFN_PHYS(pfn)) & ~CONT_PTE_MASK) == 0)) {
 			if (end - addr >= CONT_PTE_SIZE && !page_mappings_only)
 				__prot = __pgprot(pgprot_val(prot) | PTE_CONT);
 			else
@@ -147,7 +148,8 @@  static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
 		 * After the PTE entry has been populated once, we
 		 * only allow updates to the permission attributes.
 		 */
-		BUG_ON(!pgattr_change_is_safe(pte_val(old_pte), pte_val(*pte)));
+		BUG_ON(pte_valid(old_pte) && pte_valid(*pte) &&
+		       !pgattr_change_is_safe(pte_val(old_pte), pte_val(*pte)));
 
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 
@@ -190,7 +192,8 @@  static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
 			 * Set the contiguous bit for the subsequent group of
 			 * PMDs if its size and alignment are appropriate.
 			 */
-			if (((addr | phys) & ~CONT_PMD_MASK) == 0) {
+			if ((pgprot_val(prot) | PMD_VALID) &&
+			    ((addr | phys) & ~CONT_PMD_MASK) == 0) {
 				if (end - addr >= CONT_PMD_SIZE)
 					__prot = __pgprot(pgprot_val(prot) |
 							  PTE_CONT);
@@ -203,7 +206,8 @@  static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
 			 * After the PMD entry has been populated once, we
 			 * only allow updates to the permission attributes.
 			 */
-			BUG_ON(!pgattr_change_is_safe(pmd_val(old_pmd),
+			BUG_ON(pmd_valid(old_pmd) && pmd_valid(*pmd) &&
+			       !pgattr_change_is_safe(pmd_val(old_pmd),
 						      pmd_val(*pmd)));
 		} else {
 			alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),
@@ -263,7 +267,8 @@  static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
 			 * After the PUD entry has been populated once, we
 			 * only allow updates to the permission attributes.
 			 */
-			BUG_ON(!pgattr_change_is_safe(pud_val(old_pud),
+			BUG_ON(pud_valid(old_pud) && pud_valid(*pud) &&
+			       !pgattr_change_is_safe(pud_val(old_pud),
 						      pud_val(*pud)));
 		} else {
 			alloc_init_pmd(pud, addr, next, phys, prot,
@@ -344,8 +349,8 @@  void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
 			     pgd_pgtable_alloc, page_mappings_only);
 }
 
-static void create_mapping_late(phys_addr_t phys, unsigned long virt,
-				  phys_addr_t size, pgprot_t prot)
+void create_mapping_late(phys_addr_t phys, unsigned long virt,
+			 phys_addr_t size, pgprot_t prot)
 {
 	if (virt < VMALLOC_START) {
 		pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
@@ -791,14 +796,20 @@  int __init arch_ioremap_pmd_supported(void)
 int pud_set_huge(pud_t *pud, phys_addr_t phys, pgprot_t prot)
 {
 	BUG_ON(phys & ~PUD_MASK);
-	set_pud(pud, __pud(phys | PUD_TYPE_SECT | pgprot_val(mk_sect_prot(prot))));
+	set_pud(pud, __pud(phys |
+			   ((pgprot_val(prot) & PUD_VALID) ?
+					PUD_TYPE_SECT : 0) |
+			   pgprot_val(mk_sect_prot(prot))));
 	return 1;
 }
 
 int pmd_set_huge(pmd_t *pmd, phys_addr_t phys, pgprot_t prot)
 {
 	BUG_ON(phys & ~PMD_MASK);
-	set_pmd(pmd, __pmd(phys | PMD_TYPE_SECT | pgprot_val(mk_sect_prot(prot))));
+	set_pmd(pmd, __pmd(phys |
+			   ((pgprot_val(prot) & PMD_VALID) ?
+					PMD_TYPE_SECT : 0) |
+			   pgprot_val(mk_sect_prot(prot))));
 	return 1;
 }