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xlat lib: Introduce MT_EXECUTE/MT_EXECUTE_NEVER attributes 

This patch introduces the MT_EXECUTE/MT_EXECUTE_NEVER memory mapping
attributes in the translation table library to specify the
access permissions for instruction execution of a memory region.
These new attributes should be used only for normal, read-only
memory regions. For other types of memory, the translation table
library still enforces the following rules, regardless of the
MT_EXECUTE/MT_EXECUTE_NEVER attribute:

 - Device memory is always marked as execute-never.
 - Read-write normal memory is always marked as execute-never.

Change-Id: I8bd27800a8c1d8ac1559910caf4a4840cf25b8b0
This commit is contained in:
Sandrine Bailleux 2016-06-14 16:31:09 +01:00
parent bcbe19afaa
commit b9161469fa
2 changed files with 20 additions and 2 deletions
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15
include/lib/xlat_tables.h
View File

@ -134,6 +134,8 @@
#define MT_PERM_SHIFT 3
/* Security state (SECURE/NS) */
#define MT_SEC_SHIFT 4
/* Access permissions for instruction execution (EXECUTE/EXECUTE_NEVER) */
#define MT_EXECUTE_SHIFT 5
/*
* Memory mapping attributes
@ -155,8 +157,21 @@ typedef enum {
MT_SECURE = 0 << MT_SEC_SHIFT,
MT_NS = 1 << MT_SEC_SHIFT,
/*
* Access permissions for instruction execution are only relevant for
* normal read-only memory, i.e. MT_MEMORY | MT_RO. They are ignored
* (and potentially overridden) otherwise:
* - Device memory is always marked as execute-never.
* - Read-write normal memory is always marked as execute-never.
*/
MT_EXECUTE = 0 << MT_EXECUTE_SHIFT,
MT_EXECUTE_NEVER = 1 << MT_EXECUTE_SHIFT,
} mmap_attr_t;
#define MT_CODE (MT_MEMORY | MT_RO | MT_EXECUTE)
#define MT_RO_DATA (MT_MEMORY | MT_RO | MT_EXECUTE_NEVER)
/*
* Structure for specifying a single region of memory.
*/

7
lib/xlat_tables/xlat_tables_common.c
View File

@ -234,8 +234,11 @@ static uint64_t mmap_desc(unsigned attr, unsigned long long addr_pa,
* which makes any writable memory region to be treated as
* execute-never, regardless of the value of the XN bit in the
* translation table.
*
* For read-only memory, rely on the MT_EXECUTE/MT_EXECUTE_NEVER
* attribute to figure out the value of the XN bit.
*/
if (attr & MT_RW)
if ((attr & MT_RW) || (attr & MT_EXECUTE_NEVER))
desc |= UPPER_ATTRS(XN);
if (mem_type == MT_MEMORY) {
@ -250,7 +253,7 @@ static uint64_t mmap_desc(unsigned attr, unsigned long long addr_pa,
((mem_type == MT_NON_CACHEABLE) ? "NC" : "DEV"));
debug_print(attr & MT_RW ? "-RW" : "-RO");
debug_print(attr & MT_NS ? "-NS" : "-S");
debug_print(attr & MT_EXECUTE_NEVER ? "-XN" : "-EXEC");
return desc;
}