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>

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 4d69223..3ba571d 100644 (file)
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -198,6 +198,11 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
 #define thread_pkey_regs_save(thread)
 #define thread_pkey_regs_restore(new_thread, old_thread)
 #define thread_pkey_regs_init(thread)
+
+static inline int vma_pkey(struct vm_area_struct *vma)
+{
+       return 0;
+}
 #endif /* CONFIG_PPC_MEM_KEYS */
 
 #endif /* __KERNEL__ */

diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index df37255..24e8226 100644 (file)
--- 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,

diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index a4aac75..010c90c 100644 (file)
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -322,3 +322,39 @@ int __execute_only_pkey(struct mm_struct *mm)
                mm->context.execute_only_pkey = execute_only_pkey;
        return execute_only_pkey;
 }
+
+static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
+{
+       /* Do this check first since the vm_flags should be hot */
+       if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
+               return false;
+
+       return (vma_pkey(vma) == vma->vm_mm->context.execute_only_pkey);
+}
+
+/*
+ * This should only be called for *plain* mprotect calls.
+ */
+int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot,
+                                 int pkey)
+{
+       /*
+        * If the currently associated pkey is execute-only, but the requested
+        * protection requires read or write, move it back to the default pkey.
+        */
+       if (vma_is_pkey_exec_only(vma) && (prot & (PROT_READ | PROT_WRITE)))
+               return 0;
+
+       /*
+        * The requested protection is execute-only. Hence let's use an
+        * execute-only pkey.
+        */
+       if (prot == PROT_EXEC) {
+               pkey = execute_only_pkey(vma->vm_mm);
+               if (pkey > 0)
+                       return pkey;
+       }
+
+       /* Nothing to override. */
+       return vma_pkey(vma);
+}