xlat: Introduce API to change memory attributes of a region

This patch introduces a new API in the translation tables library
(v2), that allows to change the memory attributes of a memory
region. It may be used to change its execution permissions and
data access permissions.

As a prerequisite, the memory must be already mapped. Moreover, it
must be mapped at the finest granularity (currently 4 KB).

Change-Id: I242a8c6f0f3ef2b0a81a61e28706540462faca3c
Co-authored-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Co-authored-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/include/lib/xlat_tables/xlat_tables_v2.h b/include/lib/xlat_tables/xlat_tables_v2.h
index bdad1332..73a9c533 100644
--- a/include/lib/xlat_tables/xlat_tables_v2.h
+++ b/include/lib/xlat_tables/xlat_tables_v2.h
@@ -252,6 +252,49 @@ int mmap_remove_dynamic_region_ctx(xlat_ctx_t *ctx,
 #endif /* PLAT_XLAT_TABLES_DYNAMIC */
 
 /*
+ * Change the memory attributes of the memory region starting from a given
+ * virtual address in a set of translation tables.
+ *
+ * This function can only be used after the translation tables have been
+ * initialized.
+ *
+ * The base address of the memory region must be aligned on a page boundary.
+ * The size of this memory region must be a multiple of a page size.
+ * The memory region must be already mapped by the given translation tables
+ * and it must be mapped at the granularity of a page.
+ *
+ * Return 0 on success, a negative value on error.
+ *
+ * In case of error, the memory attributes remain unchanged and this function
+ * has no effect.
+ *
+ * ctx
+ *   Translation context to work on.
+ * base_va:
+ *   Virtual address of the 1st page to change the attributes of.
+ * size:
+ *   Size in bytes of the memory region.
+ * attr:
+ *   New attributes of the page tables. The attributes that can be changed are
+ *   data access (MT_RO/MT_RW), instruction access (MT_EXECUTE_NEVER/MT_EXECUTE)
+ *   and user/privileged access (MT_USER/MT_PRIVILEGED) in the case of contexts
+ *   that are used in the EL1&0 translation regime. Also, note that this
+ *   function doesn't allow to remap a region as RW and executable, or to remap
+ *   device memory as executable.
+ *
+ * NOTE: The caller of this function must be able to write to the translation
+ * tables, i.e. the memory where they are stored must be mapped with read-write
+ * access permissions. This function assumes it is the case. If this is not
+ * the case then this function might trigger a data abort exception.
+ *
+ * NOTE2: The caller is responsible for making sure that the targeted
+ * translation tables are not modified by any other code while this function is
+ * executing.
+ */
+int change_mem_attributes(xlat_ctx_t *ctx, uintptr_t base_va, size_t size,
+			mmap_attr_t attr);
+
+/*
  * Query the memory attributes of a memory page in a set of translation tables.
  *
  * Return 0 on success, a negative error code on error.