1 files changed, 51 insertions, 1 deletions

diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index e61bea4a3606..91ec6c467074 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -12,6 +12,8 @@ DEFINE_STATIC_KEY_TRUE(pkey_disabled);
 bool pkey_execute_disable_supported;
 int  pkeys_total;		/* Total pkeys as per device tree */
 u32  initial_allocation_mask;	/* Bits set for reserved keys */
+u64  pkey_amr_uamor_mask;	/* Bits in AMR/UMOR not to be touched */
+u64  pkey_iamr_mask;		/* Bits in AMR not to be touched */
 
 #define AMR_BITS_PER_PKEY 2
 #define AMR_RD_BIT 0x1UL
@@ -70,8 +72,16 @@ int pkey_initialize(void)
 	 * programming note.
 	 */
 	initial_allocation_mask = ~0x0;
-	for (i = 2; i < (pkeys_total - os_reserved); i++)
+
+	/* register mask is in BE format */
+	pkey_amr_uamor_mask = ~0x0ul;
+	pkey_iamr_mask = ~0x0ul;
+
+	for (i = 2; i < (pkeys_total - os_reserved); i++) {
 		initial_allocation_mask &= ~(0x1 << i);
+		pkey_amr_uamor_mask &= ~(0x3ul << pkeyshift(i));
+		pkey_iamr_mask &= ~(0x1ul << pkeyshift(i));
+	}
 	return 0;
 }
 
@@ -206,3 +216,43 @@ int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 	init_amr(pkey, new_amr_bits);
 	return 0;
 }
+
+void thread_pkey_regs_save(struct thread_struct *thread)
+{
+	if (static_branch_likely(&pkey_disabled))
+		return;
+
+	/*
+	 * TODO: Skip saving registers if @thread hasn't used any keys yet.
+	 */
+	thread->amr = read_amr();
+	thread->iamr = read_iamr();
+	thread->uamor = read_uamor();
+}
+
+void thread_pkey_regs_restore(struct thread_struct *new_thread,
+			      struct thread_struct *old_thread)
+{
+	if (static_branch_likely(&pkey_disabled))
+		return;
+
+	/*
+	 * TODO: Just set UAMOR to zero if @new_thread hasn't used any keys yet.
+	 */
+	if (old_thread->amr != new_thread->amr)
+		write_amr(new_thread->amr);
+	if (old_thread->iamr != new_thread->iamr)
+		write_iamr(new_thread->iamr);
+	if (old_thread->uamor != new_thread->uamor)
+		write_uamor(new_thread->uamor);
+}
+
+void thread_pkey_regs_init(struct thread_struct *thread)
+{
+	if (static_branch_likely(&pkey_disabled))
+		return;
+
+	write_amr(read_amr() & pkey_amr_uamor_mask);
+	write_iamr(read_iamr() & pkey_iamr_mask);
+	write_uamor(read_uamor() & pkey_amr_uamor_mask);
+}