On Wed, Oct 18, 2017 at 03:48:31PM +1100, Balbir Singh wrote:

On Fri,  8 Sep 2017 15:45:05 -0700
Ram Pai [off-list ref] wrote:

quoted

helper function that checks if the read/write/execute is allowed
on the pte.

Signed-off-by: Ram Pai <redacted>
---
 arch/powerpc/include/asm/book3s/64/pgtable.h |    4 +++
 arch/powerpc/include/asm/pkeys.h             |   12 +++++++++++
 arch/powerpc/mm/pkeys.c                      |   28 ++++++++++++++++++++++++++
 3 files changed, 44 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 5935d4e..bd244b3 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h

@@ -492,6 +492,10 @@ static inline void write_uamor(u64 value)
 	mtspr(SPRN_UAMOR, value);
 }
 
+#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
+extern bool arch_pte_access_permitted(u64 pte, bool write, bool execute);
+#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
+
 #define __HAVE_ARCH_PTEP_GET_AND_CLEAR
 static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
 				       unsigned long addr, pte_t *ptep)

diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index cd3924c..50522a0 100644
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h

@@ -80,6 +80,18 @@ static inline u64 pte_to_hpte_pkey_bits(u64 pteflags)
 		((pteflags & H_PAGE_PKEY_BIT4) ? HPTE_R_KEY_BIT4 : 0x0UL));
 }
 
+static inline u16 pte_to_pkey_bits(u64 pteflags)
+{
+	if (!pkey_inited)
+		return 0x0UL;
+
+	return (((pteflags & H_PAGE_PKEY_BIT0) ? 0x10 : 0x0UL) |
+		((pteflags & H_PAGE_PKEY_BIT1) ? 0x8 : 0x0UL) |
+		((pteflags & H_PAGE_PKEY_BIT2) ? 0x4 : 0x0UL) |
+		((pteflags & H_PAGE_PKEY_BIT3) ? 0x2 : 0x0UL) |
+		((pteflags & H_PAGE_PKEY_BIT4) ? 0x1 : 0x0UL));
+}
+
 #define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | \
 				VM_PKEY_BIT3 | VM_PKEY_BIT4)
 #define AMR_BITS_PER_PKEY 2

diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index fb1a76a..24589d9 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c

@@ -292,3 +292,31 @@ int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot,
 	 */
 	return vma_pkey(vma);
 }
+
+static bool pkey_access_permitted(int pkey, bool write, bool execute)
+{
+	int pkey_shift;
+	u64 amr;
+
+	if (!pkey)
+		return true;

Why would we have pkey set to 0, it's reserved. Why do we return true?

pkey 0 is reserved in some weird sense. it is the default key which is
omnipresent, which cannot be allocated or freed, but can be used any time and
allows read/write/execute at all times.

quoted

+
+	pkey_shift = pkeyshift(pkey);
+	if (!(read_uamor() & (0x3UL << pkey_shift)))
+		return true;
+
+	if (execute && !(read_iamr() & (IAMR_EX_BIT << pkey_shift)))
+		return true;
+
+	amr = read_amr(); /* delay reading amr uptil absolutely needed*/
+	return ((!write && !(amr & (AMR_RD_BIT << pkey_shift))) ||
+		(write &&  !(amr & (AMR_WR_BIT << pkey_shift))));
+}
+
+bool arch_pte_access_permitted(u64 pte, bool write, bool execute)
+{
+	if (!pkey_inited)
+		return true;

Again, don't like the pkey_inited bits :)

suggest something. :) running out of ideas ;)

quoted

+	return pkey_access_permitted(pte_to_pkey_bits(pte),
+			write, execute);
+}

Balbir Singh

-- 
Ram Pai