Ram Pai [off-list ref] writes:

On Thu, Jul 20, 2017 at 12:12:47PM +0530, Aneesh Kumar K.V wrote:

quoted

Ram Pai [off-list ref] writes:

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                      |   33 ++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 30d7f55..0056e58 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h

@@ -472,6 +472,10 @@ 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 bbb5d85..7a9aade 100644
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h

@@ -53,6 +53,18 @@ 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;

Do we really need that above check ? We should always find it
peky_inited to be set. 

Yes. there are cases where pkey_inited is not enabled. 
a) if the MMU is radix.

That should be be a feature check

b) if the PAGE size is 4k.

That is a kernel config change

c) if the device tree says the feature is not available
d) if the CPU is of a older generation. P6 and older.

Both feature check.

how about doing something like

static inline u16 pte_to_pkey_bits(u64 pteflags)
{
	if (!(pteflags & H_PAGE_KEY_MASK))
		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));
}

We still have to look at the code generated to see it is really saving
something.

-aneesh