powerpc: implementation for arch_vma_access_permitted()

This patch provides the implementation for
arch_vma_access_permitted(). Returns true if the
requested access is allowed by pkey associated with the
vma.

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

1 files changed, 34 insertions, 0 deletions

diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index 5071778fdd20..4a885cc165e5 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -386,3 +386,37 @@ bool arch_pte_access_permitted(u64 pte, bool write, bool execute)
 
 	return pkey_access_permitted(pte_to_pkey_bits(pte), write, execute);
 }
+
+/*
+ * We only want to enforce protection keys on the current thread because we
+ * effectively have no access to AMR/IAMR for other threads or any way to tell
+ * which AMR/IAMR in a threaded process we could use.
+ *
+ * So do not enforce things if the VMA is not from the current mm, or if we are
+ * in a kernel thread.
+ */
+static inline bool vma_is_foreign(struct vm_area_struct *vma)
+{
+	if (!current->mm)
+		return true;
+
+	/* if it is not our ->mm, it has to be foreign */
+	if (current->mm != vma->vm_mm)
+		return true;
+
+	return false;
+}
+
+bool arch_vma_access_permitted(struct vm_area_struct *vma, bool write,
+			       bool execute, bool foreign)
+{
+	if (static_branch_likely(&pkey_disabled))
+		return true;
+	/*
+	 * Do not enforce our key-permissions on a foreign vma.
+	 */
+	if (foreign || vma_is_foreign(vma))
+		return true;
+
+	return pkey_access_permitted(vma_pkey(vma), write, execute);
+}