debug: gdbstub: add bits to restrict memory read/write

This adds bits for architectures, SoCs or boards to restrict
memory access in GDB stub. This is mainly to make sure
GDB stub only read/write to memory that can be legally accessed
without resulting in memory faults.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>

include/debug/gdbstub.h

@@ -15,6 +15,49 @@
 #define GDB_EXCEPTION_INVALID_MEMORY        11UL
 #define GDB_EXCEPTION_OVERFLOW              16UL
 
+/* Access permissions for memory regions */
+#define GDB_MEM_REGION_NO_ACCESS            0UL
+#define GDB_MEM_REGION_READ                 BIT(0)
+#define GDB_MEM_REGION_WRITE                BIT(1)
+
+#define GDB_MEM_REGION_RO \
+	(GDB_MEM_REGION_READ)
+
+#define GDB_MEM_REGION_RW \
+	(GDB_MEM_REGION_READ | GDB_MEM_REGION_WRITE)
+
+/** Describe one memory region */
+struct gdb_mem_region {
+	/** Start address of a memory region */
+	uintptr_t start;
+
+	/** End address of a memory region */
+	uintptr_t end;
+
+	/** Memory region attributes */
+	uint16_t  attributes;
+
+	/** Read/write alignment, 0 if using default alignment */
+	uint8_t   alignment;
+};
+
+/**
+ * Memory region descriptions used for GDB memory access.
+ *
+ * This array specifies which region of memory GDB can access
+ * with read/write attribites. This is used to restrict
+ * memory read/write in GDB stub to memory that can be
+ * legally accessed without resulting in memory faults.
+ */
+extern const struct gdb_mem_region gdb_mem_region_array[];
+
+/**
+ * Number of Memory Regions.
+ *
+ * Number of elements in gdb_mem_region_array[];
+ */
+extern const size_t gdb_mem_num_regions;
+
 /**
  * @brief Convert a binary array into string representation.
  *
@@ -31,4 +74,31 @@
 size_t gdb_bin2hex(const uint8_t *buf, size_t buflen,
 		   char *hex, size_t hexlen);
 
+
+/**
+ * @brief Check if a memory block can be read.
+ *
+ * This checks if the specified memory block can be read.
+ *
+ * @param[in]  addr  Starting address of the memory block
+ * @param[in]  len   Size of memory block
+ * @param[out] align Read alignment of region
+ *
+ * @return True if memory block can be read, false otherwise.
+ */
+bool gdb_mem_can_read(const uintptr_t addr, const size_t len, uint8_t *align);
+
+/**
+ * @brief Check if a memory block can be written into.
+ *
+ * This checks if the specified memory block can be written into.
+ *
+ * @param[in]  addr  Starting address of the memory block
+ * @param[in]  len   Size of memory block
+ * @param[out] align Write alignment of region
+ *
+ * @return True if GDB stub can write to the block, false otherwise.
+ */
+bool gdb_mem_can_write(const uintptr_t addr, const size_t len, uint8_t *align);
+
 #endif