[RFC PATCH v2 4/8] arm/mem_access: Add short-descriptor pte typedefs

[Sergej Proskurin <proskurin@sec.in.tum.de>]

The current implementation does not provide appropriate types for
short-descriptor translation table entries. As such, this commit adds new
types, which simplify managing the respective translation table entries.

Signed-off-by: Sergej Proskurin <proskurin@sec.in.tum.de>
---
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Julien Grall <julien.grall@arm.com>
---
 xen/include/asm-arm/page.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/xen/include/asm-arm/page.h b/xen/include/asm-arm/page.h
index 6222b1d4a2..5ea97ba95b 100644
--- a/xen/include/asm-arm/page.h
+++ b/xen/include/asm-arm/page.h
@@ -205,6 +205,25 @@ typedef union {
     lpae_walk_t walk;
 } lpae_t;
 
+/*
+ * Comprises the bits required to walk page tables adhering to the
+ * short-descriptor translation table format.
+ */
+typedef struct __packed {
+    unsigned int dt:2;          /* Descriptor type */
+    unsigned int pad1:8;
+    unsigned int base:22;       /* Base address of block or next table */
+} pte_sd_walk_t;
+
+/*
+ * Represents page table entries adhering to the short-descriptor translation
+ * table format.
+ */
+typedef union {
+    uint32_t bits;
+    pte_sd_walk_t walk;
+} pte_sd_t;
+
 /* Standard entry type that we'll use to build Xen's own pagetables.
  * We put the same permissions at every level, because they're ignored
  * by the walker in non-leaf entries. */
-- 
2.12.2


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