[PATCH 1/2] Enable storage keys for radix - user mode execution

[Balbir Singh <bsingharora@gmail.com>]

ISA 3 defines new encoded access authority that allows instruction
access prevention in privileged mode and allows normal access
to problem state. This patch just enables IAMR (Instruction Authority
Mask Register), enabling AMR would require more work.

I've tested this with a buggy driver and a simple payload. The payload
is specific to the build I've tested.

Signed-off-by: Balbir Singh <bsingharora@gmail.com>
---
 arch/powerpc/mm/pgtable-radix.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c
index af897d9..9e25663 100644
--- a/arch/powerpc/mm/pgtable-radix.c
+++ b/arch/powerpc/mm/pgtable-radix.c
@@ -294,6 +294,27 @@ found:
 	return;
 }
 
+/*
+ * For radix page tables we setup, the IAMR values as follows
+ * IMAR = 0100...00 (key 0 is set to 1)
+ * AMOR = 1100....00 (Mask for key 0 is 11)
+ * AMR, UAMR, UAMOR are not affected
+ */
+static void __init radix_init_iamr(void)
+{
+	unsigned long iamr_mask = 0x4000000000000000;
+	unsigned long iamr = mfspr(SPRN_IAMR);
+
+	unsigned long amor_mask = 0xc000000000000000;
+	unsigned long amor = mfspr(SPRN_AMOR);
+
+	iamr |= iamr_mask;
+	amor |= amor_mask;
+
+	mtspr(SPRN_AMOR, amor);
+	mtspr(SPRN_IAMR, iamr);
+}
+
 void __init radix__early_init_mmu(void)
 {
 	unsigned long lpcr;
@@ -350,6 +371,7 @@ void __init radix__early_init_mmu(void)
 		radix_init_partition_table();
 	}
 
+	radix_init_iamr();
 	radix_init_pgtable();
 }
 
-- 
2.5.5