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[PATCH v3 0/5] powerpc/mm: Fix kernel protection and implement STRICT_KERNEL_RWX on PPC32

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  [PATCH v3 0/5] powerpc/mm: Fix kernel protection and implement STRICT_KERNEL_RWX on PPC32 Christophe Leroy <christophe.leroy@c-s.fr> - 2017-08-02 16:00 +0200
    [PATCH v3 3/5] powerpc/mm: Implement STRICT_KERNEL_RWX on PPC32 Christophe Leroy <christophe.leroy@c-s.fr> - 2017-08-02 16:00 +0200
    [PATCH v3 4/5] powerpc/mm: declare some local functions static Christophe Leroy <christophe.leroy@c-s.fr> - 2017-08-02 16:00 +0200
    [PATCH v3 1/5] powerpc/mm: Ensure change_page_attr() doesn't invalidate  pinned TLBs Christophe Leroy <christophe.leroy@c-s.fr> - 2017-08-02 16:00 +0200
    Re: [PATCH v3 0/5] powerpc/mm: Fix kernel protection and implement  STRICT_KERNEL_RWX on PPC32 Balbir Singh <bsingharora@gmail.com> - 2017-08-03 09:30 +0200

#1702134 — [PATCH v3 0/5] powerpc/mm: Fix kernel protection and implement STRICT_KERNEL_RWX on PPC32

This patch set implements STRICT_KERNEL_RWX on Powerpc32
after fixing a few issues related to kernel code page protection.

At the end we take the opportunity to get rid of some unneccessary/outdated
fixmap stuff.

Changes from v2 to v3:
* Rebased on latest linux-powerpc/merge branch
* Function remap_init_ram() renamed mark_initmem_nx() to match new
  PPC64 implementation

Changes from v1 to v2:
* Rebased on latest linux-next following including of STRICT_KERNEL_RWX for PPC64
* Removed from the serie the two patches already applied.

Christophe Leroy (5):
  powerpc/mm: Ensure change_page_attr() doesn't invalidate pinned TLBs
  powerpc/mm: Fix kernel RAM protection after freeing unused memory on
    PPC32
  powerpc/mm: Implement STRICT_KERNEL_RWX on PPC32
  powerpc/mm: declare some local functions static
  powerpc/mm: Simplify __set_fixmap()

 arch/powerpc/Kconfig                         |  2 +-
 arch/powerpc/include/asm/book3s/32/pgtable.h |  3 --
 arch/powerpc/include/asm/fixmap.h            | 10 +++--
 arch/powerpc/include/asm/nohash/32/pgtable.h |  3 --
 arch/powerpc/include/asm/pgtable.h           |  2 +-
 arch/powerpc/kernel/vmlinux.lds.S            |  2 +-
 arch/powerpc/mm/init_32.c                    |  6 +++
 arch/powerpc/mm/pgtable_32.c                 | 66 ++++++++++++++++++----------
 8 files changed, 58 insertions(+), 36 deletions(-)

-- 
2.13.3

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#1702137 — [PATCH v3 3/5] powerpc/mm: Implement STRICT_KERNEL_RWX on PPC32

This patch implements STRICT_KERNEL_RWX on PPC32.

As for CONFIG_DEBUG_PAGEALLOC, it deactivates BAT and LTLB mappings
in order to allow page protection setup at the level of each page.

As BAT/LTLB mappings are deactivated, there might be a performance
impact.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 v3: no change

 arch/powerpc/Kconfig              |  2 +-
 arch/powerpc/kernel/vmlinux.lds.S |  2 +-
 arch/powerpc/mm/init_32.c         |  6 ++++++
 arch/powerpc/mm/pgtable_32.c      | 24 ++++++++++++++++++++++++
 4 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 5e9de178b557..02d91ee1b601 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -165,7 +165,7 @@ config PPC
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS	if COMPAT
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
-	select ARCH_HAS_STRICT_KERNEL_RWX	if (PPC_BOOK3S_64 && !RELOCATABLE && !HIBERNATION)
+	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
 	select ARCH_OPTIONAL_KERNEL_RWX		if ARCH_HAS_STRICT_KERNEL_RWX
 	select HAVE_CBPF_JIT			if !PPC64
 	select HAVE_CONTEXT_TRACKING		if PPC64
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index b1a250560198..882628fa6987 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -8,7 +8,7 @@
 #include <asm/cache.h>
 #include <asm/thread_info.h>
 
-#ifdef CONFIG_STRICT_KERNEL_RWX
+#if defined(CONFIG_STRICT_KERNEL_RWX) && !defined(CONFIG_PPC32)
 #define STRICT_ALIGN_SIZE	(1 << 24)
 #else
 #define STRICT_ALIGN_SIZE	PAGE_SIZE
diff --git a/arch/powerpc/mm/init_32.c b/arch/powerpc/mm/init_32.c
index 8a7c38b8d335..7d5fee1bb116 100644
--- a/arch/powerpc/mm/init_32.c
+++ b/arch/powerpc/mm/init_32.c
@@ -113,6 +113,12 @@ void __init MMU_setup(void)
 		__map_without_bats = 1;
 		__map_without_ltlbs = 1;
 	}
+#ifdef CONFIG_STRICT_KERNEL_RWX
+	if (rodata_enabled) {
+		__map_without_bats = 1;
+		__map_without_ltlbs = 1;
+	}
+#endif
 }
 
 /*
diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 85e8f0e0efe6..4a3dd9fc6989 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -34,6 +34,7 @@
 #include <asm/fixmap.h>
 #include <asm/io.h>
 #include <asm/setup.h>
+#include <asm/sections.h>
 
 #include "mmu_decl.h"
 
@@ -375,6 +376,29 @@ void mark_initmem_nx(void)
 	change_page_attr(page, numpages, PAGE_KERNEL);
 }
 
+#ifdef CONFIG_STRICT_KERNEL_RWX
+void mark_rodata_ro(void)
+{
+	struct page *page;
+	unsigned long numpages;
+
+	page = virt_to_page(_stext);
+	numpages = PFN_UP((unsigned long)_etext) -
+		   PFN_DOWN((unsigned long)_stext);
+
+	change_page_attr(page, numpages, PAGE_KERNEL_ROX);
+	/*
+	 * mark .rodata as read only. Use __init_begin rather than __end_rodata
+	 * to cover NOTES and EXCEPTION_TABLE.
+	 */
+	page = virt_to_page(__start_rodata);
+	numpages = PFN_UP((unsigned long)__init_begin) -
+		   PFN_DOWN((unsigned long)__start_rodata);
+
+	change_page_attr(page, numpages, PAGE_KERNEL_RO);
+}
+#endif
+
 #ifdef CONFIG_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
-- 
2.13.3

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#1702138 — [PATCH v3 4/5] powerpc/mm: declare some local functions static

get_pteptr() and __mapin_ram_chunk() are only used locally,
so define them static

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 v3: no change

 arch/powerpc/include/asm/book3s/32/pgtable.h | 3 ---
 arch/powerpc/include/asm/nohash/32/pgtable.h | 3 ---
 arch/powerpc/mm/pgtable_32.c                 | 4 ++--
 3 files changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
index 7fb755880409..17c8766777f1 100644
--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -294,9 +294,6 @@ static inline void __ptep_set_access_flags(struct mm_struct *mm,
 #define __pte_to_swp_entry(pte)		((swp_entry_t) { pte_val(pte) >> 3 })
 #define __swp_entry_to_pte(x)		((pte_t) { (x).val << 3 })
 
-extern int get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep,
-		      pmd_t **pmdp);
-
 int map_kernel_page(unsigned long va, phys_addr_t pa, int flags);
 
 /* Generic accessors to PTE bits */
diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
index 91314268f04f..589206bf0358 100644
--- a/arch/powerpc/include/asm/nohash/32/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/32/pgtable.h
@@ -337,9 +337,6 @@ static inline void __ptep_set_access_flags(struct mm_struct *mm,
 #define __pte_to_swp_entry(pte)		((swp_entry_t) { pte_val(pte) >> 3 })
 #define __swp_entry_to_pte(x)		((pte_t) { (x).val << 3 })
 
-extern int get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep,
-		      pmd_t **pmdp);
-
 int map_kernel_page(unsigned long va, phys_addr_t pa, int flags);
 
 #endif /* !__ASSEMBLY__ */
diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 4a3dd9fc6989..57f89cd88568 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -243,7 +243,7 @@ int map_kernel_page(unsigned long va, phys_addr_t pa, int flags)
 /*
  * Map in a chunk of physical memory starting at start.
  */
-void __init __mapin_ram_chunk(unsigned long offset, unsigned long top)
+static void __init __mapin_ram_chunk(unsigned long offset, unsigned long top)
 {
 	unsigned long v, s, f;
 	phys_addr_t p;
@@ -295,7 +295,7 @@ void __init mapin_ram(void)
  * Returns true (1) if PTE was found, zero otherwise.  The pointer to
  * the PTE pointer is unmodified if PTE is not found.
  */
-int
+static int
 get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
 {
         pgd_t	*pgd;
-- 
2.13.3

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#1702140 — [PATCH v3 1/5] powerpc/mm: Ensure change_page_attr() doesn't invalidate pinned TLBs

__change_page_attr() uses flush_tlb_page().
flush_tlb_page() uses tlbie instruction, which also invalidates
pinned TLBs, which is not what we expect.

This patch modifies the implementation to use flush_tlb_kernel_range()
instead. This will make use of tlbia which will preserve pinned TLBs.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 v3: no change

 arch/powerpc/mm/pgtable_32.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index a9e4bfc025bc..991036f818bb 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -325,7 +325,7 @@ get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
 
 #ifdef CONFIG_DEBUG_PAGEALLOC
 
-static int __change_page_attr(struct page *page, pgprot_t prot)
+static int __change_page_attr_noflush(struct page *page, pgprot_t prot)
 {
 	pte_t *kpte;
 	pmd_t *kpmd;
@@ -339,8 +339,6 @@ static int __change_page_attr(struct page *page, pgprot_t prot)
 	if (!get_pteptr(&init_mm, address, &kpte, &kpmd))
 		return -EINVAL;
 	__set_pte_at(&init_mm, address, kpte, mk_pte(page, prot), 0);
-	wmb();
-	flush_tlb_page(NULL, address);
 	pte_unmap(kpte);
 
 	return 0;
@@ -355,13 +353,17 @@ static int change_page_attr(struct page *page, int numpages, pgprot_t prot)
 {
 	int i, err = 0;
 	unsigned long flags;
+	struct page *start = page;
 
 	local_irq_save(flags);
 	for (i = 0; i < numpages; i++, page++) {
-		err = __change_page_attr(page, prot);
+		err = __change_page_attr_noflush(page, prot);
 		if (err)
 			break;
 	}
+	wmb();
+	flush_tlb_kernel_range((unsigned long)page_address(start),
+			       (unsigned long)page_address(page));
 	local_irq_restore(flags);
 	return err;
 }
-- 
2.13.3

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#1702724 — Re: [PATCH v3 0/5] powerpc/mm: Fix kernel protection and implement STRICT_KERNEL_RWX on PPC32

On Wed, Aug 2, 2017 at 11:50 PM, Christophe Leroy
<christophe.leroy@c-s.fr> wrote:
> This patch set implements STRICT_KERNEL_RWX on Powerpc32
> after fixing a few issues related to kernel code page protection.
>
> At the end we take the opportunity to get rid of some unneccessary/outdated
> fixmap stuff.

I looked at it, looks good overall, I've reviewed the previous series. Have you
checked the series against CONFIG_RELOCATABLE?

Balbir Singh.

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