powerpc: implementation for arch_override_mprotect_pkey()

arch independent code calls arch_override_mprotect_pkey()
to return a pkey that best matches the requested protection.

This patch provides the implementation.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 20 insertions, 1 deletions

diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index df372557ec33..24e82260052f 100644
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h
@@ -41,6 +41,13 @@ static inline u64 pkey_to_vmflag_bits(u16 pkey)
 	return (((u64)pkey << VM_PKEY_SHIFT) & ARCH_VM_PKEY_FLAGS);
 }
 
+static inline int vma_pkey(struct vm_area_struct *vma)
+{
+	if (static_branch_likely(&pkey_disabled))
+		return 0;
+	return (vma->vm_flags & ARCH_VM_PKEY_FLAGS) >> VM_PKEY_SHIFT;
+}
+
 #define arch_max_pkey() pkeys_total
 
 #define pkey_alloc_mask(pkey) (0x1 << pkey)
@@ -137,10 +144,22 @@ static inline int execute_only_pkey(struct mm_struct *mm)
 	return __execute_only_pkey(mm);
 }
 
+extern int __arch_override_mprotect_pkey(struct vm_area_struct *vma,
+					 int prot, int pkey);
 static inline int arch_override_mprotect_pkey(struct vm_area_struct *vma,
 					      int prot, int pkey)
 {
-	return 0;
+	if (static_branch_likely(&pkey_disabled))
+		return 0;
+
+	/*
+	 * Is this an mprotect_pkey() call? If so, never override the value that
+	 * came from the user.
+	 */
+	if (pkey != -1)
+		return pkey;
+
+	return __arch_override_mprotect_pkey(vma, prot, pkey);
 }
 
 extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,