powerpc: Implement set_memory_rox()

Same as x86 and s390, add set_memory_rox() to avoid doing
one pass with set_memory_ro() and a second pass with set_memory_x().

See commit 60463628 ("x86/mm: Implement native set_memory_rox()")
and commit 22e99fa5 ("s390/mm: implement set_memory_rox()") for
more information.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/dc9a794f82ab62572d7d0be5cb4b8b27920a4f78.1708078316.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/set_memory.h

@@ -8,6 +8,7 @@
 #define SET_MEMORY_X	3
 #define SET_MEMORY_NP	4	/* Set memory non present */
 #define SET_MEMORY_P	5	/* Set memory present */
+#define SET_MEMORY_ROX	6
 
 int change_memory_attr(unsigned long addr, int numpages, long action);
 
@@ -41,4 +42,10 @@ static inline int set_memory_p(unsigned long addr, int numpages)
 	return change_memory_attr(addr, numpages, SET_MEMORY_P);
 }
 
+static inline int set_memory_rox(unsigned long addr, int numpages)
+{
+	return change_memory_attr(addr, numpages, SET_MEMORY_ROX);
+}
+#define set_memory_rox set_memory_rox
+
 #endif

arch/powerpc/mm/pageattr.c

@@ -38,6 +38,10 @@ static int change_page_attr(pte_t *ptep, unsigned long addr, void *data)
 		/* Don't clear DIRTY bit */
 		pte_update_delta(ptep, addr, _PAGE_KERNEL_RW & ~_PAGE_DIRTY, _PAGE_KERNEL_RO);
 		break;
+	case SET_MEMORY_ROX:
+		/* Don't clear DIRTY bit */
+		pte_update_delta(ptep, addr, _PAGE_KERNEL_RW & ~_PAGE_DIRTY, _PAGE_KERNEL_ROX);
+		break;
 	case SET_MEMORY_RW:
 		pte_update_delta(ptep, addr, _PAGE_KERNEL_RO, _PAGE_KERNEL_RW);
 		break;