Re: [PATCH 12/25] powerpc: ability to associate pkey to a vma

On Wed, Oct 18, 2017 at 03:27:33PM +1100, Balbir Singh wrote:

On Fri,  8 Sep 2017 15:45:00 -0700
Ram Pai [off-list ref] wrote:

quoted

arch-independent code expects the arch to  map
a  pkey  into the vma's protection bit setting.
The patch provides that ability.

Signed-off-by: Ram Pai <redacted>
---
 arch/powerpc/include/asm/mman.h  |    8 +++++++-
 arch/powerpc/include/asm/pkeys.h |   18 ++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletions(-)

diff --git a/arch/powerpc/include/asm/mman.h b/arch/powerpc/include/asm/mman.h
index 30922f6..067eec2 100644
--- a/arch/powerpc/include/asm/mman.h
+++ b/arch/powerpc/include/asm/mman.h

@@ -13,6 +13,7 @@
 
 #include <asm/cputable.h>
 #include <linux/mm.h>
+#include <linux/pkeys.h>
 #include <asm/cpu_has_feature.h>
 
 /*

@@ -22,7 +23,12 @@
 static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
 		unsigned long pkey)
 {
-	return (prot & PROT_SAO) ? VM_SAO : 0;
+#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
+	return (((prot & PROT_SAO) ? VM_SAO : 0) |
+			pkey_to_vmflag_bits(pkey));
+#else
+	return ((prot & PROT_SAO) ? VM_SAO : 0);
+#endif
 }
 #define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey)
 

diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index 0cf115f..f13e913 100644
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h

@@ -23,6 +23,24 @@
 #define VM_PKEY_BIT4	VM_HIGH_ARCH_4
 #endif
 
+/* override any generic PKEY Permission defines */
+#define PKEY_DISABLE_EXECUTE   0x4
+#define PKEY_ACCESS_MASK       (PKEY_DISABLE_ACCESS |\
+				PKEY_DISABLE_WRITE  |\
+				PKEY_DISABLE_EXECUTE)
+
+static inline u64 pkey_to_vmflag_bits(u16 pkey)
+{
+	if (!pkey_inited)
+		return 0x0UL;
+
+	return (((pkey & 0x1UL) ? VM_PKEY_BIT0 : 0x0UL) |
+		((pkey & 0x2UL) ? VM_PKEY_BIT1 : 0x0UL) |
+		((pkey & 0x4UL) ? VM_PKEY_BIT2 : 0x0UL) |
+		((pkey & 0x8UL) ? VM_PKEY_BIT3 : 0x0UL) |
+		((pkey & 0x10UL) ? VM_PKEY_BIT4 : 0x0UL));
+}

Assuming that there is a linear order between VM_PKEY_BIT4 to
VM_PKEY_BIT0, the conditional checks can be removed

(pkey & 0x1fUL) << VM_PKEY_BIT0?

yes. currently the are linear. But I am afraid it will break without
notice someday when someone decides to change the values of VM_PKEY_BITx to
be non-contiguous. I can put a BUILD_ASSERTION I suppose.  But thought
this will be safe.

RP

Balbir Singh

-- 
Ram Pai