[Xen-devel] [PATCH v4 08/10] xen/arm: mm: Embed permission in the flags

[Julien Grall <julien.grall@xxxxxxx>]

Currently, it is not possible to specify the permission of a new
mapping. It would be necessary to use the function modify_xen_mappings
with a different set of flags.

Introduce a couple of new flags for the permissions (Non-eXecutable,
Read-Only) and also provides definition that combine the memory attribute
and permission for common combinations.

PAGE_HYPERVISOR is now an alias to PAGE_HYPERVISOR_RW (read-write,
non-executable mappings). This does not affect the current mapping using
PAGE_HYPERVISOR because Xen is currently forcing all the mapping to be
non-executable by default (see mfn_to_xen_entry).

A follow-up patch will change modify_xen_mappings to use the new flags.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

---

    Changes in v3:
        - Add a comment about _PAGE_DEVICE and _PAGE_NORMAL

    Changes in v2:
        - Update the commit message
---
 xen/include/asm-arm/page.h | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/xen/include/asm-arm/page.h b/xen/include/asm-arm/page.h
index aa3e83f5b4..e2b3e402d0 100644
--- a/xen/include/asm-arm/page.h
+++ b/xen/include/asm-arm/page.h
@@ -69,12 +69,31 @@
  * Layout of the flags used for updating the hypervisor page tables
  *
  * [0:2] Memory Attribute Index
+ * [3:4] Permission flags
  */
 #define PAGE_AI_MASK(x) ((x) & 0x7U)
 
-#define PAGE_HYPERVISOR         (MT_NORMAL)
-#define PAGE_HYPERVISOR_NOCACHE (MT_DEVICE_nGnRE)
-#define PAGE_HYPERVISOR_WC      (MT_NORMAL_NC)
+#define _PAGE_XN_BIT    3
+#define _PAGE_RO_BIT    4
+#define _PAGE_XN    (1U << _PAGE_XN_BIT)
+#define _PAGE_RO    (1U << _PAGE_RO_BIT)
+#define PAGE_XN_MASK(x) (((x) >> _PAGE_XN_BIT) & 0x1U)
+#define PAGE_RO_MASK(x) (((x) >> _PAGE_RO_BIT) & 0x1U)
+
+/*
+ * _PAGE_DEVICE and _PAGE_NORMAL are conveniences defines. They are not
+ * meant to be used outside of the headers.
+ */
+#define _PAGE_DEVICE    _PAGE_XN
+#define _PAGE_NORMAL    MT_NORMAL
+
+#define PAGE_HYPERVISOR_RO      (_PAGE_NORMAL|_PAGE_RO|_PAGE_XN)
+#define PAGE_HYPERVISOR_RX      (_PAGE_NORMAL|_PAGE_RO)
+#define PAGE_HYPERVISOR_RW      (_PAGE_NORMAL|_PAGE_XN)
+
+#define PAGE_HYPERVISOR         PAGE_HYPERVISOR_RW
+#define PAGE_HYPERVISOR_NOCACHE (_PAGE_DEVICE|MT_DEVICE_nGnRE)
+#define PAGE_HYPERVISOR_WC      (_PAGE_DEVICE|MT_NORMAL_NC)
 
 /*
  * Defines for changing the hypervisor PTE .ro and .nx bits. This is only to be
-- 
2.11.0


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