powerpc: implementation for arch_set_user_pkey_access()

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.

Reviewed-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index 5ed52ac..bf8e706 100644 (file)
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h
@@ -128,10 +128,14 @@ 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 (static_branch_likely(&pkey_disabled))
+               return -EINVAL;
+       return __arch_set_user_pkey_access(tsk, pkey, init_val);
 }
 
 extern void pkey_mm_init(struct mm_struct *mm);

diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index 0cfe901..b01238b 100644 (file)
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -5,6 +5,7 @@
  * Copyright 2017, Ram Pai, IBM Corporation.
  */
 
+#include <asm/mman.h>
 #include <linux/pkeys.h>
 
 DEFINE_STATIC_KEY_TRUE(pkey_disabled);
@@ -13,6 +14,9 @@ int  pkeys_total;             /* Total pkeys as per device tree */
 u32  initial_allocation_mask;  /* Bits set for reserved keys */
 
 #define AMR_BITS_PER_PKEY 2
+#define AMR_RD_BIT 0x1UL
+#define AMR_WR_BIT 0x2UL
+#define IAMR_EX_BIT 0x1UL
 #define PKEY_REG_BITS (sizeof(u64)*8)
 #define pkeyshift(pkey) (PKEY_REG_BITS - ((pkey+1) * AMR_BITS_PER_PKEY))
 
@@ -108,6 +112,20 @@ static inline void write_uamor(u64 value)
        mtspr(SPRN_UAMOR, value);
 }
 
+static bool is_pkey_enabled(int pkey)
+{
+       u64 uamor = read_uamor();
+       u64 pkey_bits = 0x3ul << pkeyshift(pkey);
+       u64 uamor_pkey_bits = (uamor & pkey_bits);
+
+       /*
+        * Both the bits in UAMOR corresponding to the key should be set or
+        * reset.
+        */
+       WARN_ON(uamor_pkey_bits && (uamor_pkey_bits != pkey_bits));
+       return !!(uamor_pkey_bits);
+}
+
 static inline void init_amr(int pkey, u8 init_bits)
 {
        u64 new_amr_bits = (((u64)init_bits & 0x3UL) << pkeyshift(pkey));
@@ -150,3 +168,25 @@ void __arch_deactivate_pkey(int pkey)
 {
        pkey_status_change(pkey, false);
 }
+
+/*
+ * Set the access rights in AMR IAMR and UAMOR registers 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 -EINVAL;
+
+       /* 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;
+}