[RFC v6 17/62] powerpc: implementation for arch_set_user_pkey_access()

[Ram Pai]

This patch provides the detailed implementation for
a user to allocate a key and enable it in the hardware.

It provides the plumbing, but it cannot be used till
the system call is implemented. The next patch  will
do so.

Signed-off-by: Ram Pai <linux...@us.ibm.com>
---
 arch/powerpc/include/asm/pkeys.h |   10 +++++++++-
 arch/powerpc/mm/pkeys.c          |   27 +++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletions(-)

diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index 7f5c21d..1943e6b 100644
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h
@@ -3,6 +3,10 @@
 
 extern bool pkey_inited;
 #define arch_max_pkey()  32
+#define AMR_RD_BIT 0x1UL
+#define AMR_WR_BIT 0x2UL
+#define IAMR_EX_BIT 0x1UL
+#define AMR_BITS_PER_PKEY 2
 #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
@@ -113,10 +117,14 @@ static inline int arch_override_mprotect_pkey(struct 
vm_area_struct *vma,
        return 0;
 }
 
+extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
+               unsigned long init_val);
 static inline int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
                unsigned long init_val)
 {
-       return 0;
+       if (!pkey_inited)
+               return -1;
+       return __arch_set_user_pkey_access(tsk, pkey, init_val);
 }
 
 static inline void pkey_mm_init(struct mm_struct *mm)
diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index 04ee361..98d0391 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -17,6 +17,10 @@
 
 bool pkey_inited;
 #define pkeyshift(pkey) ((arch_max_pkey()-pkey-1) * AMR_BITS_PER_PKEY)
+static bool is_pkey_enabled(int pkey)
+{
+       return !!(read_uamor() & (0x3ul << pkeyshift(pkey)));
+}
 
 static inline void init_amr(int pkey, u8 init_bits)
 {
@@ -60,3 +64,26 @@ void __arch_deactivate_pkey(int pkey)
 {
        pkey_status_change(pkey, false);
 }
+
+/*
+ * set the access right in AMR IAMR and UAMOR register
+ * for @pkey to that specified in @init_val.
+ */
+int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
+               unsigned long init_val)
+{
+       u64 new_amr_bits = 0x0ul;
+
+       if (!is_pkey_enabled(pkey))
+               return -1;
+
+       /* Set the bits we need in AMR:  */
+       if (init_val & PKEY_DISABLE_ACCESS)
+               new_amr_bits |= AMR_RD_BIT | AMR_WR_BIT;
+       else if (init_val & PKEY_DISABLE_WRITE)
+               new_amr_bits |= AMR_WR_BIT;
+
+       init_amr(pkey, new_amr_bits);
+
+       return 0;
+}
-- 
1.7.1