arch: arm: Define & implement API for test target (Non-Secure)

This commit defines and implements an internal ARMv8-M API
that allows the user to evaluate access permissions of memory
locations, based on the ARMv8-M Test Target (TT) instruction
support.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>

arch/arm/core/CMakeLists.txt

@@ -23,3 +23,4 @@ zephyr_library_sources_ifdef(CONFIG_USERSPACE userspace.S)
 
 add_subdirectory_ifdef(CONFIG_CPU_CORTEX_M cortex_m)
 add_subdirectory_ifdef(CONFIG_CPU_HAS_MPU  cortex_m/mpu)
+add_subdirectory_ifdef(CONFIG_CPU_CORTEX_M_HAS_CMSE cortex_m/cmse)

arch/arm/core/cortex_m/Kconfig

@@ -166,6 +166,12 @@ config CPU_CORTEX_M0_HAS_VECTOR_TABLE_REMAP
 	  This option signifies the Cortex-M0 has some mechanisms that can map
 	  the vector table to SRAM
 
+config CPU_CORTEX_M_HAS_CMSE
+	bool
+	default n
+	help
+	  This option signifies the Cortex-M CPU has the CMSE intrinsics.
+
 config ARMV6_M_ARMV8_M_BASELINE
 	bool
 	# Omit prompt to signify "hidden" option

arch/arm/core/cortex_m/cmse/CMakeLists.txt

@@ -0,0 +1 @@
+zephyr_sources(arm_core_cmse.c)

arch/arm/core/cortex_m/cmse/arm_core_cmse.c

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2018 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+#include <cortex_m/cmse.h>
+
+int arm_cmse_mpu_region_get(u32_t addr, u8_t *p_region)
+{
+	cmse_address_info_t addr_info =	cmse_TT((void *)addr);
+
+	if (addr_info.flags.mpu_region_valid) {
+		*p_region = addr_info.flags.mpu_region;
+	}
+
+	return addr_info.flags.mpu_region_valid;
+}
+
+static int arm_cmse_addr_read_write_ok(u32_t addr, int force_npriv, int rw)
+{
+	cmse_address_info_t addr_info;
+	if (force_npriv) {
+		addr_info = cmse_TTT((void *)addr);
+	} else {
+		addr_info = cmse_TT((void *)addr);
+	}
+
+	return rw ? addr_info.flags.readwrite_ok : addr_info.flags.read_ok;
+}
+
+int arm_cmse_addr_read_ok(u32_t addr, int force_npriv)
+{
+	return arm_cmse_addr_read_write_ok(addr, force_npriv, 0);
+}
+
+int arm_cmse_addr_readwrite_ok(u32_t addr, int force_npriv)
+{
+	return arm_cmse_addr_read_write_ok(addr, force_npriv, 1);
+}

arch/arm/include/cortex_m/cmse.h

@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2018 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @file
+ * @brief ARM Core CMSE API
+ *
+ * CMSE API for Cortex-M23/M33 CPUs.
+ */
+
+#ifndef _ARM_CORTEXM_CMSE__H_
+#define _ARM_CORTEXM_CMSE__H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef _ASMLANGUAGE
+
+/* nothing */
+
+#else
+
+#include <arm_cmse.h>
+#include <stdint.h>
+
+/*
+ * Address information retrieval based on the TT instructions.
+ *
+ * The TT instructions are used to check the access permissions that different
+ * security states and privilege levels have on memory at a specified address
+ */
+
+/**
+ * @brief Get the MPU region number of an address
+ *
+ * Get the MPU region that the address maps to. Return non-zero
+ * to indicate that a valid MPU region was retrieved, and store the
+ * MPU region information in the supplied location.
+ *
+ * Note:
+ * Obtained region is valid only if:
+ * - the function is called from privileged mode
+ * - the MPU is implemented and enabled
+ * - the given address matches a single, enabled MPU region
+ *
+ * @param addr The address for which the MPU region is requested
+ * @param p_region Output pointer to the location to store the MPU region
+ *
+ * @return non-zero if @ref region contains a valid MPU region, otherwise 0.
+  */
+int arm_cmse_mpu_region_get(u32_t addr, u8_t *p_region);
+
+/**
+ * @brief Read accessibility of an address
+ *
+ * Evaluates whether a specified memory location can be read according to the
+ * permissions of the current state MPU and the specified operation mode.
+ *
+ * This function shall always return zero:
+ * - if executed from an unprivileged mode,
+ * - if the address matches multiple MPU regions.
+ *
+ * @param addr The address for which the readability is requested
+ * @param force_npriv Instruct to return the readability of the address
+ *                    for unprivileged access, regardless of whether the current
+ *                    mode is privileged or unprivileged.
+ *
+ * @return 1 if address is readable, 0 otherwise.
+ */
+int arm_cmse_addr_read_ok(u32_t addr, int force_npriv);
+
+/**
+ * @brief Read and Write accessibility of an address
+ *
+ * Evaluates whether a specified memory location can be read/written according
+ * to the permissions of the current state MPU and the specified operation
+ * mode.
+ *
+ * This function shall always return zero:
+ * - if executed from an unprivileged mode,
+ * - if the address matches multiple MPU regions.
+ *
+ * @param addr The address for which the RW ability is requested
+ * @param force_npriv Instruct to return the RW ability of the address
+ *                    for unprivileged access, regardless of whether the current
+ *                    mode is privileged or unprivileged.
+ *
+ * @return 1 if address is Read and Writable, 0 otherwise.
+ */
+int arm_cmse_addr_readwrite_ok(u32_t addr, int force_npriv);
+
+#endif /* _ASMLANGUAGE */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _ARM_CORTEXM_CMSE__H_ */