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Trusted Firmware-A User Guide

Contents

This document describes how to build Trusted Firmware-A (TF-A) and run it with a tested set of other software components using defined configurations on the Juno Arm development platform and Arm Fixed Virtual Platform (FVP) models. It is possible to use other software components, configurations and platforms but that is outside the scope of this document.

This document assumes that the reader has previous experience running a fully bootable Linux software stack on Juno or FVP using the prebuilt binaries and filesystems provided by Linaro. Further information may be found in the Linaro instructions. It also assumes that the user understands the role of the different software components required to boot a Linux system:

  • Specific firmware images required by the platform (e.g. SCP firmware on Juno)
  • Normal world bootloader (e.g. UEFI or U-Boot)
  • Device tree
  • Linux kernel image
  • Root filesystem

This document also assumes that the user is familiar with the FVP models and the different command line options available to launch the model.

This document should be used in conjunction with the Firmware Design.

1.   Host machine requirements

The minimum recommended machine specification for building the software and running the FVP models is a dual-core processor running at 2GHz with 12GB of RAM. For best performance, use a machine with a quad-core processor running at 2.6GHz with 16GB of RAM.

The software has been tested on Ubuntu 16.04 LTS (64-bit). Packages used for building the software were installed from that distribution unless otherwise specified.

The software has also been built on Windows 7 Enterprise SP1, using CMD.EXE, Cygwin, and Msys (MinGW) shells, using version 5.3.1 of the GNU toolchain.

2.   Tools

Install the required packages to build TF-A with the following command:

sudo apt-get install build-essential gcc make git libssl-dev

TF-A has been tested with Linaro Release 17.10.

Download and install the AArch32 or AArch64 little-endian GCC cross compiler. The Linaro Release Notes documents which version of the compiler to use for a given Linaro Release. Also, these Linaro instructions provide further guidance and a script, which can be used to download Linaro deliverables automatically.

Optionally, TF-A can be built using clang or Arm Compiler 6. See instructions below on how to switch the default compiler.

In addition, the following optional packages and tools may be needed:

  • device-tree-compiler package if you need to rebuild the Flattened Device Tree (FDT) source files (.dts files) provided with this software.
  • For debugging, Arm Development Studio 5 (DS-5).
  • To create and modify the diagram files included in the documentation, Dia. This tool can be found in most Linux distributions. Inkscape is needed to generate the actual *.png files.

3.   Getting the TF-A source code

Download the TF-A source code from Github:

git clone https://github.com/ARM-software/arm-trusted-firmware.git

4.   Building TF-A

  • Before building TF-A, the environment variable CROSS_COMPILE must point to the Linaro cross compiler.

    For AArch64:

    export CROSS_COMPILE=<path-to-aarch64-gcc>/bin/aarch64-linux-gnu-

    For AArch32:

    export CROSS_COMPILE=<path-to-aarch32-gcc>/bin/arm-linux-gnueabihf-

    It is possible to build TF-A using clang or Arm Compiler 6. To do so CC needs to point to the clang or armclang binary. Only the compiler is switched; the assembler and linker need to be provided by the GNU toolchain, thus CROSS_COMPILE should be set as described above.

    Arm Compiler 6 will be selected when the base name of the path assigned to CC matches the string 'armclang'.

    For AArch64 using Arm Compiler 6:

    export CROSS_COMPILE=<path-to-aarch64-gcc>/bin/aarch64-linux-gnu-
make CC=<path-to-armclang>/bin/armclang PLAT=<platform> all

    Clang will be selected when the base name of the path assigned to CC contains the string 'clang'. This is to allow both clang and clang-X.Y to work.

    For AArch64 using clang:

    export CROSS_COMPILE=<path-to-aarch64-gcc>/bin/aarch64-linux-gnu-
make CC=<path-to-clang>/bin/clang PLAT=<platform> all

  • Change to the root directory of the TF-A source tree and build.

    For AArch64:

    make PLAT=<platform> all

    For AArch32:

    make PLAT=<platform> ARCH=aarch32 AARCH32_SP=sp_min all

    Notes:

    • If PLAT is not specified, fvp is assumed by default. See the Summary of build options for more information on available build options.

    • (AArch32 only) Currently only PLAT=fvp is supported.

    • (AArch32 only) AARCH32_SP is the AArch32 EL3 Runtime Software and it corresponds to the BL32 image. A minimal AARCH32_SP, sp_min, is provided by TF-A to demonstrate how PSCI Library can be integrated with an AArch32 EL3 Runtime Software. Some AArch32 EL3 Runtime Software may include other runtime services, for example Trusted OS services. A guide to integrate PSCI library with AArch32 EL3 Runtime Software can be found here.

    • (AArch64 only) The TSP (Test Secure Payload), corresponding to the BL32 image, is not compiled in by default. Refer to the Building the Test Secure Payload section below.

    • By default this produces a release version of the build. To produce a debug version instead, refer to the "Debugging options" section below.

    • The build process creates products in a build directory tree, building the objects and binaries for each boot loader stage in separate sub-directories. The following boot loader binary files are created from the corresponding ELF files:

      • build/<platform>/<build-type>/bl1.bin
      • build/<platform>/<build-type>/bl2.bin
      • build/<platform>/<build-type>/bl31.bin (AArch64 only)
      • build/<platform>/<build-type>/bl32.bin (mandatory for AArch32)

      where <platform> is the name of the chosen platform and <build-type> is either debug or release. The actual number of images might differ depending on the platform.

  • Build products for a specific build variant can be removed using:

    make DEBUG=<D> PLAT=<platform> clean

    ... where <D> is 0 or 1, as specified when building.

    The build tree can be removed completely using:

    make realclean

4.1.   Summary of build options

The TF-A build system supports the following build options. Unless mentioned otherwise, these options are expected to be specified at the build command line and are not to be modified in any component makefiles. Note that the build system doesn't track dependency for build options. Therefore, if any of the build options are changed from a previous build, a clean build must be performed.

4.1.1.   Common build options

  • AARCH32_SP : Choose the AArch32 Secure Payload component to be built as as the BL32 image when ARCH=aarch32. The value should be the path to the directory containing the SP source, relative to the bl32/; the directory is expected to contain a makefile called <aarch32_sp-value>.mk.

  • ARCH : Choose the target build architecture for TF-A. It can take either aarch64 or aarch32 as values. By default, it is defined to aarch64.

  • ARM_ARCH_MAJOR: The major version of Arm Architecture to target when compiling TF-A. Its value must be numeric, and defaults to 8 . See also, Armv8 Architecture Extensions and Armv7 Architecture Extensions in Firmware Design.

  • ARM_ARCH_MINOR: The minor version of Arm Architecture to target when compiling TF-A. Its value must be a numeric, and defaults to 0. See also, Armv8 Architecture Extensions in Firmware Design.

  • ARM_GIC_ARCH: Choice of Arm GIC architecture version used by the Arm Legacy GIC driver for implementing the platform GIC API. This API is used by the interrupt management framework. Default is 2 (that is, version 2.0). This build option is deprecated.

  • ARM_PLAT_MT: This flag determines whether the Arm platform layer has to cater for the multi-threading MT bit when accessing MPIDR. When this flag is set, the functions which deal with MPIDR assume that the MT bit in MPIDR is set and access the bit-fields in MPIDR accordingly. Default value of this flag is 0. Note that this option is not used on FVP platforms.

  • BL2: This is an optional build option which specifies the path to BL2 image for the fip target. In this case, the BL2 in the TF-A will not be built.

  • BL2U: This is an optional build option which specifies the path to BL2U image. In this case, the BL2U in TF-A will not be built.

  • BL2_AT_EL3: This is an optional build option that enables the use of

    BL2 at EL3 execution level.

  • BL2_IN_XIP_MEM: In some use-cases BL2 will be stored in eXecute In Place

    (XIP) memory, like BL1. In these use-cases, it is necessary to initialize the RW sections in RAM, while leaving the RO sections in place. This option enable this use-case. For now, this option is only supported when BL2_AT_EL3 is set to '1'.

  • BL31: This is an optional build option which specifies the path to BL31 image for the fip target. In this case, the BL31 in TF-A will not be built.

  • BL31_KEY: This option is used when GENERATE_COT=1. It specifies the file that contains the BL31 private key in PEM format. If SAVE_KEYS=1, this file name will be used to save the key.

  • BL32: This is an optional build option which specifies the path to BL32 image for the fip target. In this case, the BL32 in TF-A will not be built.

  • BL32_EXTRA1: This is an optional build option which specifies the path to

    Trusted OS Extra1 image for the fip target.

  • BL32_EXTRA2: This is an optional build option which specifies the path to

    Trusted OS Extra2 image for the fip target.

  • BL32_KEY: This option is used when GENERATE_COT=1. It specifies the file that contains the BL32 private key in PEM format. If SAVE_KEYS=1, this file name will be used to save the key.

  • BL33: Path to BL33 image in the host file system. This is mandatory for fip target in case TF-A BL2 is used.

  • BL33_KEY: This option is used when GENERATE_COT=1. It specifies the file that contains the BL33 private key in PEM format. If SAVE_KEYS=1, this file name will be used to save the key.

  • BUILD_MESSAGE_TIMESTAMP: String used to identify the time and date of the compilation of each build. It must be set to a C string (including quotes where applicable). Defaults to a string that contains the time and date of the compilation.

  • BUILD_STRING: Input string for VERSION_STRING, which allows the TF-A build to be uniquely identified. Defaults to the current git commit id.

  • CFLAGS: Extra user options appended on the compiler's command line in addition to the options set by the build system.

  • COLD_BOOT_SINGLE_CPU: This option indicates whether the platform may release several CPUs out of reset. It can take either 0 (several CPUs may be brought up) or 1 (only one CPU will ever be brought up during cold reset). Default is 0. If the platform always brings up a single CPU, there is no need to distinguish between primary and secondary CPUs and the boot path can be optimised. The plat_is_my_cpu_primary() and plat_secondary_cold_boot_setup() platform porting interfaces do not need to be implemented in this case.

  • CRASH_REPORTING: A non-zero value enables a console dump of processor register state when an unexpected exception occurs during execution of BL31. This option defaults to the value of DEBUG - i.e. by default this is only enabled for a debug build of the firmware.

  • CREATE_KEYS: This option is used when GENERATE_COT=1. It tells the certificate generation tool to create new keys in case no valid keys are present or specified. Allowed options are '0' or '1'. Default is '1'.

  • CTX_INCLUDE_AARCH32_REGS : Boolean option that, when set to 1, will cause the AArch32 system registers to be included when saving and restoring the CPU context. The option must be set to 0 for AArch64-only platforms (that is on hardware that does not implement AArch32, or at least not at EL1 and higher ELs). Default value is 1.

  • CTX_INCLUDE_FPREGS: Boolean option that, when set to 1, will cause the FP registers to be included when saving and restoring the CPU context. Default is 0.

  • DEBUG: Chooses between a debug and release build. It can take either 0 (release) or 1 (debug) as values. 0 is the default.

  • EL3_PAYLOAD_BASE: This option enables booting an EL3 payload instead of the normal boot flow. It must specify the entry point address of the EL3 payload. Please refer to the "Booting an EL3 payload" section for more details.

  • ENABLE_AMU: Boolean option to enable Activity Monitor Unit extensions. This is an optional architectural feature available on v8.4 onwards. Some v8.2 implementations also implement an AMU and this option can be used to enable this feature on those systems as well. Default is 0.

  • ENABLE_ASSERTIONS: This option controls whether or not calls to assert() are compiled out. For debug builds, this option defaults to 1, and calls to assert() are left in place. For release builds, this option defaults to 0 and calls to assert() function are compiled out. This option can be set independently of DEBUG. It can also be used to hide any auxiliary code that is only required for the assertion and does not fit in the assertion itself.

  • ENABLE_PMF: Boolean option to enable support for optional Performance Measurement Framework(PMF). Default is 0.

  • ENABLE_PSCI_STAT: Boolean option to enable support for optional PSCI functions PSCI_STAT_RESIDENCY and PSCI_STAT_COUNT. Default is 0. In the absence of an alternate stat collection backend, ENABLE_PMF must be enabled. If ENABLE_PMF is set, the residency statistics are tracked in software.

  • ENABLE_RUNTIME_INSTRUMENTATION: Boolean option to enable runtime instrumentation which injects timestamp collection points into TF-A to allow runtime performance to be measured. Currently, only PSCI is instrumented. Enabling this option enables the ENABLE_PMF build option as well. Default is 0.

  • ENABLE_SPE_FOR_LOWER_ELS : Boolean option to enable Statistical Profiling extensions. This is an optional architectural feature for AArch64. The default is 1 but is automatically disabled when the target architecture is AArch32.

  • ENABLE_SVE_FOR_NS: Boolean option to enable Scalable Vector Extension (SVE) for the Non-secure world only. SVE is an optional architectural feature for AArch64. Note that when SVE is enabled for the Non-secure world, access to SIMD and floating-point functionality from the Secure world is disabled. This is to avoid corruption of the Non-secure world data in the Z-registers which are aliased by the SIMD and FP registers. The build option is not compatible with the CTX_INCLUDE_FPREGS build option, and will raise an assert on platforms where SVE is implemented and ENABLE_SVE_FOR_NS set to 1. The default is 1 but is automatically disabled when the target architecture is AArch32.

  • ENABLE_STACK_PROTECTOR: String option to enable the stack protection checks in GCC. Allowed values are "all", "strong" and "0" (default). "strong" is the recommended stack protection level if this feature is desired. 0 disables the stack protection. For all values other than 0, the plat_get_stack_protector_canary() platform hook needs to be implemented. The value is passed as the last component of the option -fstack-protector-$ENABLE_STACK_PROTECTOR.

  • ERROR_DEPRECATED: This option decides whether to treat the usage of deprecated platform APIs, helper functions or drivers within Trusted Firmware as error. It can take the value 1 (flag the use of deprecated APIs as error) or 0. The default is 0.

  • EL3_EXCEPTION_HANDLING: When set to 1, enable handling of exceptions targeted at EL3. When set 0 (default), no exceptions are expected or handled at EL3, and a panic will result. This is supported only for AArch64 builds.

  • FIP_NAME: This is an optional build option which specifies the FIP filename for the fip target. Default is fip.bin.

  • FWU_FIP_NAME: This is an optional build option which specifies the FWU FIP filename for the fwu_fip target. Default is fwu_fip.bin.

  • GENERATE_COT: Boolean flag used to build and execute the cert_create tool to create certificates as per the Chain of Trust described in Trusted Board Boot. The build system then calls fiptool to include the certificates in the FIP and FWU_FIP. Default value is '0'.

    Specify both TRUSTED_BOARD_BOOT=1 and GENERATE_COT=1 to include support for the Trusted Board Boot feature in the BL1 and BL2 images, to generate the corresponding certificates, and to include those certificates in the FIP and FWU_FIP.

    Note that if TRUSTED_BOARD_BOOT=0 and GENERATE_COT=1, the BL1 and BL2 images will not include support for Trusted Board Boot. The FIP will still include the corresponding certificates. This FIP can be used to verify the Chain of Trust on the host machine through other mechanisms.

    Note that if TRUSTED_BOARD_BOOT=1 and GENERATE_COT=0, the BL1 and BL2 images will include support for Trusted Board Boot, but the FIP and FWU_FIP will not include the corresponding certificates, causing a boot failure.

  • GICV2_G0_FOR_EL3: Unlike GICv3, the GICv2 architecture doesn't have inherent support for specific EL3 type interrupts. Setting this build option to 1 assumes GICv2 Group 0 interrupts are expected to target EL3, both by platform abstraction layer and Interrupt Management Framework. This allows GICv2 platforms to enable features requiring EL3 interrupt type. This also means that all GICv2 Group 0 interrupts are delivered to EL3, and the Secure Payload interrupts needs to be synchronously handed over to Secure EL1 for handling. The default value of this option is 0, which means the Group 0 interrupts are assumed to be handled by Secure EL1.

  • HANDLE_EA_EL3_FIRST: When defined External Aborts and SError Interrupts will be always trapped in EL3 i.e. in BL31 at runtime.

  • HW_ASSISTED_COHERENCY: On most Arm systems to-date, platform-specific software operations are required for CPUs to enter and exit coherency. However, there exists newer systems where CPUs' entry to and exit from coherency is managed in hardware. Such systems require software to only initiate the operations, and the rest is managed in hardware, minimizing active software management. In such systems, this boolean option enables TF-A to carry out build and run-time optimizations during boot and power management operations. This option defaults to 0 and if it is enabled, then it implies WARMBOOT_ENABLE_DCACHE_EARLY is also enabled.

  • JUNO_AARCH32_EL3_RUNTIME: This build flag enables you to execute EL3 runtime software in AArch32 mode, which is required to run AArch32 on Juno. By default this flag is set to '0'. Enabling this flag builds BL1 and BL2 in AArch64 and facilitates the loading of SP_MIN and BL33 as AArch32 executable images.

  • KEY_ALG: This build flag enables the user to select the algorithm to be used for generating the PKCS keys and subsequent signing of the certificate. It accepts 3 values viz. rsa, rsa_1_5, ecdsa. The rsa_1_5 is the legacy PKCS#1 RSA 1.5 algorithm which is not TBBR compliant and is retained only for compatibility. The default value of this flag is rsa which is the TBBR compliant PKCS#1 RSA 2.1 scheme.

  • HASH_ALG: This build flag enables the user to select the secure hash algorithm. It accepts 3 values viz. sha256, sha384, sha512. The default value of this flag is sha256.

  • LDFLAGS: Extra user options appended to the linkers' command line in addition to the one set by the build system.

  • LOAD_IMAGE_V2: Boolean option to enable support for new version (v2) of image loading, which provides more flexibility and scalability around what images are loaded and executed during boot. Default is 0. Note: TRUSTED_BOARD_BOOT is currently only supported for AArch64 when LOAD_IMAGE_V2 is enabled.

  • LOG_LEVEL: Chooses the log level, which controls the amount of console log output compiled into the build. This should be one of the following:

    0  (LOG_LEVEL_NONE)
10 (LOG_LEVEL_NOTICE)
20 (LOG_LEVEL_ERROR)
30 (LOG_LEVEL_WARNING)
40 (LOG_LEVEL_INFO)
50 (LOG_LEVEL_VERBOSE)

    All log output up to and including the log level is compiled into the build. The default value is 40 in debug builds and 20 in release builds.

  • NON_TRUSTED_WORLD_KEY: This option is used when GENERATE_COT=1. It specifies the file that contains the Non-Trusted World private key in PEM format. If SAVE_KEYS=1, this file name will be used to save the key.

  • NS_BL2U: Path to NS_BL2U image in the host file system. This image is optional. It is only needed if the platform makefile specifies that it is required in order to build the fwu_fip target.

  • NS_TIMER_SWITCH: Enable save and restore for non-secure timer register contents upon world switch. It can take either 0 (don't save and restore) or 1 (do save and restore). 0 is the default. An SPD may set this to 1 if it wants the timer registers to be saved and restored.

  • PL011_GENERIC_UART: Boolean option to indicate the PL011 driver that the underlying hardware is not a full PL011 UART but a minimally compliant generic UART, which is a subset of the PL011. The driver will not access any register that is not part of the SBSA generic UART specification. Default value is 0 (a full PL011 compliant UART is present).

  • PLAT: Choose a platform to build TF-A for. The chosen platform name must be subdirectory of any depth under plat/, and must contain a platform makefile named platform.mk. For example, to build TF-A for the Arm Juno board, select PLAT=juno.

  • PRELOADED_BL33_BASE: This option enables booting a preloaded BL33 image instead of the normal boot flow. When defined, it must specify the entry point address for the preloaded BL33 image. This option is incompatible with EL3_PAYLOAD_BASE. If both are defined, EL3_PAYLOAD_BASE has priority over PRELOADED_BL33_BASE.

  • PROGRAMMABLE_RESET_ADDRESS: This option indicates whether the reset vector address can be programmed or is fixed on the platform. It can take either 0 (fixed) or 1 (programmable). Default is 0. If the platform has a programmable reset address, it is expected that a CPU will start executing code directly at the right address, both on a cold and warm reset. In this case, there is no need to identify the entrypoint on boot and the boot path can be optimised. The plat_get_my_entrypoint() platform porting interface does not need to be implemented in this case.

  • PSCI_EXTENDED_STATE_ID: As per PSCI1.0 Specification, there are 2 formats possible for the PSCI power-state parameter viz original and extended State-ID formats. This flag if set to 1, configures the generic PSCI layer to use the extended format. The default value of this flag is 0, which means by default the original power-state format is used by the PSCI implementation. This flag should be specified by the platform makefile and it governs the return value of PSCI_FEATURES API for CPU_SUSPEND smc function id. When this option is enabled on Arm platforms, the option ARM_RECOM_STATE_ID_ENC needs to be set to 1 as well.

  • RESET_TO_BL31: Enable BL31 entrypoint as the CPU reset vector instead of the BL1 entrypoint. It can take the value 0 (CPU reset to BL1 entrypoint) or 1 (CPU reset to BL31 entrypoint). The default value is 0.

  • RESET_TO_SP_MIN: SP_MIN is the minimal AArch32 Secure Payload provided in TF-A. This flag configures SP_MIN entrypoint as the CPU reset vector instead of the BL1 entrypoint. It can take the value 0 (CPU reset to BL1 entrypoint) or 1 (CPU reset to SP_MIN entrypoint). The default value is 0.

  • ROT_KEY: This option is used when GENERATE_COT=1. It specifies the file that contains the ROT private key in PEM format. If SAVE_KEYS=1, this file name will be used to save the key.

  • SAVE_KEYS: This option is used when GENERATE_COT=1. It tells the certificate generation tool to save the keys used to establish the Chain of Trust. Allowed options are '0' or '1'. Default is '0' (do not save).

  • SCP_BL2: Path to SCP_BL2 image in the host file system. This image is optional. If a SCP_BL2 image is present then this option must be passed for the fip target.

  • SCP_BL2_KEY: This option is used when GENERATE_COT=1. It specifies the file that contains the SCP_BL2 private key in PEM format. If SAVE_KEYS=1, this file name will be used to save the key.

  • SCP_BL2U: Path to SCP_BL2U image in the host file system. This image is optional. It is only needed if the platform makefile specifies that it is required in order to build the fwu_fip target.

  • SDEI_SUPPORT: Setting this to 1 enables support for Software Delegated Exception Interface to BL31 image. This defaults to 0.

    When set to 1, the build option EL3_EXCEPTION_HANDLING must also be set to 1.

  • SEPARATE_CODE_AND_RODATA: Whether code and read-only data should be isolated on separate memory pages. This is a trade-off between security and memory usage. See "Isolating code and read-only data on separate memory pages" section in Firmware Design. This flag is disabled by default and affects all BL images.

  • SPD: Choose a Secure Payload Dispatcher component to be built into TF-A. This build option is only valid if ARCH=aarch64. The value should be the path to the directory containing the SPD source, relative to services/spd/; the directory is expected to contain a makefile called <spd-value>.mk.

  • SPIN_ON_BL1_EXIT: This option introduces an infinite loop in BL1. It can take either 0 (no loop) or 1 (add a loop). 0 is the default. This loop stops execution in BL1 just before handing over to BL31. At this point, all firmware images have been loaded in memory, and the MMU and caches are turned off. Refer to the "Debugging options" section for more details.

  • SP_MIN_WITH_SECURE_FIQ: Boolean flag to indicate the SP_MIN handles

    secure interrupts (caught through the FIQ line). Platforms can enable this directive if they need to handle such interruption. When enabled, the FIQ are handled in monitor mode and non secure world is not allowed to mask these events. Platforms that enable FIQ handling in SP_MIN shall implement the api sp_min_plat_fiq_handler(). The default value is 0.

  • TRUSTED_BOARD_BOOT: Boolean flag to include support for the Trusted Board Boot feature. When set to '1', BL1 and BL2 images include support to load and verify the certificates and images in a FIP, and BL1 includes support for the Firmware Update. The default value is '0'. Generation and inclusion of certificates in the FIP and FWU_FIP depends upon the value of the GENERATE_COT option.

    Note: This option depends on CREATE_KEYS to be enabled. If the keys already exist in disk, they will be overwritten without further notice.

  • TRUSTED_WORLD_KEY: This option is used when GENERATE_COT=1. It specifies the file that contains the Trusted World private key in PEM format. If SAVE_KEYS=1, this file name will be used to save the key.

  • TSP_INIT_ASYNC: Choose BL32 initialization method as asynchronous or synchronous, (see "Initializing a BL32 Image" section in Firmware Design). It can take the value 0 (BL32 is initialized using synchronous method) or 1 (BL32 is initialized using asynchronous method). Default is 0.

  • TSP_NS_INTR_ASYNC_PREEMPT: A non zero value enables the interrupt routing model which routes non-secure interrupts asynchronously from TSP to EL3 causing immediate preemption of TSP. The EL3 is responsible for saving and restoring the TSP context in this routing model. The default routing model (when the value is 0) is to route non-secure interrupts to TSP allowing it to save its context and hand over synchronously to EL3 via an SMC.

    Note: when EL3_EXCEPTION_HANDLING is 1, TSP_NS_INTR_ASYNC_PREEMPT must also be set to 1.

  • USE_COHERENT_MEM: This flag determines whether to include the coherent memory region in the BL memory map or not (see "Use of Coherent memory in TF-A" section in Firmware Design). It can take the value 1 (Coherent memory region is included) or 0 (Coherent memory region is excluded). Default is 1.

  • V: Verbose build. If assigned anything other than 0, the build commands are printed. Default is 0.

  • VERSION_STRING: String used in the log output for each TF-A image. Defaults to a string formed by concatenating the version number, build type and build string.

  • WARMBOOT_ENABLE_DCACHE_EARLY : Boolean option to enable D-cache early on the CPU after warm boot. This is applicable for platforms which do not require interconnect programming to enable cache coherency (eg: single cluster platforms). If this option is enabled, then warm boot path enables D-caches immediately after enabling MMU. This option defaults to 0.

4.1.2.   Arm development platform specific build options

  • ARM_BL31_IN_DRAM: Boolean option to select loading of BL31 in TZC secured DRAM. By default, BL31 is in the secure SRAM. Set this flag to 1 to load BL31 in TZC secured DRAM. If TSP is present, then setting this option also sets the TSP location to DRAM and ignores the ARM_TSP_RAM_LOCATION build flag.
  • ARM_BOARD_OPTIMISE_MEM: Boolean option to enable or disable optimisation of the memory reserved for each image. This affects the maximum size of each BL image as well as the number of allocated memory regions and translation tables. By default this flag is 0, which means it uses the default unoptimised values for these macros. Arm development platforms that wish to optimise memory usage need to set this flag to 1 and must override the related macros.
  • ARM_CONFIG_CNTACR: boolean option to unlock access to the CNTBase<N> frame registers by setting the CNTCTLBase.CNTACR<N> register bits. The frame number <N> is defined by PLAT_ARM_NSTIMER_FRAME_ID, which should match the frame used by the Non-Secure image (normally the Linux kernel). Default is true (access to the frame is allowed).
  • ARM_DISABLE_TRUSTED_WDOG: boolean option to disable the Trusted Watchdog. By default, Arm platforms use a watchdog to trigger a system reset in case an error is encountered during the boot process (for example, when an image could not be loaded or authenticated). The watchdog is enabled in the early platform setup hook at BL1 and disabled in the BL1 prepare exit hook. The Trusted Watchdog may be disabled at build time for testing or development purposes.
  • ARM_RECOM_STATE_ID_ENC: The PSCI1.0 specification recommends an encoding for the construction of composite state-ID in the power-state parameter. The existing PSCI clients currently do not support this encoding of State-ID yet. Hence this flag is used to configure whether to use the recommended State-ID encoding or not. The default value of this flag is 0, in which case the platform is configured to expect NULL in the State-ID field of power-state parameter.
  • ARM_ROTPK_LOCATION: used when TRUSTED_BOARD_BOOT=1. It specifies the location of the ROTPK hash returned by the function plat_get_rotpk_info() for Arm platforms. Depending on the selected option, the proper private key must be specified using the ROT_KEY option when building the Trusted Firmware. This private key will be used by the certificate generation tool to sign the BL2 and Trusted Key certificates. Available options for ARM_ROTPK_LOCATION are:
    • regs : return the ROTPK hash stored in the Trusted root-key storage registers. The private key corresponding to this ROTPK hash is not currently available.
    • devel_rsa : return a development public key hash embedded in the BL1 and BL2 binaries. This hash has been obtained from the RSA public key arm_rotpk_rsa.der, located in plat/arm/board/common/rotpk. To use this option, arm_rotprivk_rsa.pem must be specified as ROT_KEY when creating the certificates.
    • devel_ecdsa : return a development public key hash embedded in the BL1 and BL2 binaries. This hash has been obtained from the ECDSA public key arm_rotpk_ecdsa.der, located in plat/arm/board/common/rotpk. To use this option, arm_rotprivk_ecdsa.pem must be specified as ROT_KEY when creating the certificates.
  • ARM_TSP_RAM_LOCATION: location of the TSP binary. Options:
    • tsram : Trusted SRAM (default option when TBB is not enabled)
    • tdram : Trusted DRAM (if available)
    • dram : Secure region in DRAM (default option when TBB is enabled,
      configured by the TrustZone controller)
  • ARM_XLAT_TABLES_LIB_V1: boolean option to compile TF-A with version 1 of the translation tables library instead of version 2. It is set to 0 by default, which selects version 2.
  • ARM_CRYPTOCELL_INTEG : bool option to enable TF-A to invoke Arm® TrustZone® CryptoCell functionality for Trusted Board Boot on capable Arm platforms. If this option is specified, then the path to the CryptoCell SBROM library must be specified via CCSBROM_LIB_PATH flag.

For a better understanding of these options, the Arm development platform memory map is explained in the Firmware Design.

4.1.3.   Arm CSS platform specific build options

  • CSS_DETECT_PRE_1_7_0_SCP: Boolean flag to detect SCP version incompatibility. Version 1.7.0 of the SCP firmware made a non-backwards compatible change to the MTL protocol, used for AP/SCP communication. TF-A no longer supports earlier SCP versions. If this option is set to 1 then TF-A will detect if an earlier version is in use. Default is 1.
  • CSS_LOAD_SCP_IMAGES: Boolean flag, which when set, adds SCP_BL2 and SCP_BL2U to the FIP and FWU_FIP respectively, and enables them to be loaded during boot. Default is 1.
  • CSS_USE_SCMI_SDS_DRIVER: Boolean flag which selects SCMI/SDS drivers instead of SCPI/BOM driver for communicating with the SCP during power management operations and for SCP RAM Firmware transfer. If this option is set to 1, then SCMI/SDS drivers will be used. Default is 0.

4.1.4.   Arm FVP platform specific build options

  • FVP_CLUSTER_COUNT : Configures the cluster count to be used to build the topology tree within TF-A. By default TF-A is configured for dual cluster topology and this option can be used to override the default value.
  • FVP_INTERCONNECT_DRIVER: Selects the interconnect driver to be built. The default interconnect driver depends on the value of FVP_CLUSTER_COUNT as explained in the options below:
    • FVP_CCI : The CCI driver is selected. This is the default if 0 < FVP_CLUSTER_COUNT <= 2.
    • FVP_CCN : The CCN driver is selected. This is the default if FVP_CLUSTER_COUNT > 2.
  • FVP_MAX_CPUS_PER_CLUSTER: Sets the maximum number of CPUs implemented in a single cluster. This option defaults to 4.
  • FVP_MAX_PE_PER_CPU: Sets the maximum number of PEs implemented on any CPU in the system. This option defaults to 1. Note that the build option ARM_PLAT_MT doesn't have any effect on FVP platforms.
  • FVP_USE_GIC_DRIVER : Selects the GIC driver to be built. Options:
    • FVP_GIC600 : The GIC600 implementation of GICv3 is selected
    • FVP_GICV2 : The GICv2 only driver is selected
    • FVP_GICV3 : The GICv3 only driver is selected (default option)
    • FVP_GICV3_LEGACY: The Legacy GICv3 driver is selected (deprecated) Note: If TF-A is compiled with this option on FVPs with GICv3 hardware, then it configures the hardware to run in GICv2 emulation mode
  • FVP_USE_SP804_TIMER : Use the SP804 timer instead of the Generic Timer for functions that wait for an arbitrary time length (udelay and mdelay). The default value is 0.
  • FVP_HW_CONFIG_DTS : Specify the path to the DTS file to be compiled to DTB and packaged in FIP as the HW_CONFIG. See Firmware Design for details on HW_CONFIG. By default, this is initialized to a sensible DTS file in fdts/ folder depending on other build options. But some cases, like shifted affinity format for MPIDR, cannot be detected at build time and this option is needed to specify the appropriate DTS file.
  • FVP_HW_CONFIG : Specify the path to the HW_CONFIG blob to be packaged in FIP. See Firmware Design for details on HW_CONFIG. This option is similar to the FVP_HW_CONFIG_DTS option, but it directly specifies the HW_CONFIG blob instead of the DTS file. This option is useful to override the default HW_CONFIG selected by the build system.

4.1.5.   ARM JUNO platform specific build options

  • JUNO_TZMP1 : Boolean option to configure Juno to be used for TrustZone Media Protection (TZ-MP1). Default value of this flag is 0.

4.2.   Debugging options

To compile a debug version and make the build more verbose use

make PLAT=<platform> DEBUG=1 V=1 all

AArch64 GCC uses DWARF version 4 debugging symbols by default. Some tools (for example DS-5) might not support this and may need an older version of DWARF symbols to be emitted by GCC. This can be achieved by using the -gdwarf-<version> flag, with the version being set to 2 or 3. Setting the version to 2 is recommended for DS-5 versions older than 5.16.

When debugging logic problems it might also be useful to disable all compiler optimizations by using -O0.

NOTE: Using -O0 could cause output images to be larger and base addresses might need to be recalculated (see the Memory layout on Arm development platforms section in the Firmware Design).

Extra debug options can be passed to the build system by setting CFLAGS or LDFLAGS:

CFLAGS='-O0 -gdwarf-2'                                     \
make PLAT=<platform> DEBUG=1 V=1 all

Note that using -Wl, style compilation driver options in CFLAGS will be ignored as the linker is called directly.

It is also possible to introduce an infinite loop to help in debugging the post-BL2 phase of TF-A. This can be done by rebuilding BL1 with the SPIN_ON_BL1_EXIT=1 build flag. Refer to the Summary of build options section. In this case, the developer may take control of the target using a debugger when indicated by the console output. When using DS-5, the following commands can be used:

# Stop target execution
interrupt

#
# Prepare your debugging environment, e.g. set breakpoints
#

# Jump over the debug loop
set var $AARCH64::$Core::$PC = $AARCH64::$Core::$PC + 4

# Resume execution
continue

4.3.   Building the Test Secure Payload

The TSP is coupled with a companion runtime service in the BL31 firmware, called the TSPD. Therefore, if you intend to use the TSP, the BL31 image must be recompiled as well. For more information on SPs and SPDs, see the Secure-EL1 Payloads and Dispatchers section in the Firmware Design.

First clean the TF-A build directory to get rid of any previous BL31 binary. Then to build the TSP image use:

make PLAT=<platform> SPD=tspd all

An additional boot loader binary file is created in the build directory:

build/<platform>/<build-type>/bl32.bin

4.4.   Checking source code style

When making changes to the source for submission to the project, the source must be in compliance with the Linux style guide, and to assist with this check the project Makefile contains two targets, which both utilise the checkpatch.pl script that ships with the Linux source tree.

To check the entire source tree, you must first download copies of checkpatch.pl, spelling.txt and const_structs.checkpatch available in the Linux master tree scripts directory, then set the CHECKPATCH environment variable to point to checkpatch.pl (with the other 2 files in the same directory) and build the target checkcodebase:

make CHECKPATCH=<path-to-linux>/linux/scripts/checkpatch.pl checkcodebase

To just check the style on the files that differ between your local branch and the remote master, use:

make CHECKPATCH=<path-to-linux>/linux/scripts/checkpatch.pl checkpatch

If you wish to check your patch against something other than the remote master, set the BASE_COMMIT variable to your desired branch. By default, BASE_COMMIT is set to origin/master.

4.5.   Building and using the FIP tool

Firmware Image Package (FIP) is a packaging format used by TF-A to package firmware images in a single binary. The number and type of images that should be packed in a FIP is platform specific and may include TF-A images and other firmware images required by the platform. For example, most platforms require a BL33 image which corresponds to the normal world bootloader (e.g. UEFI or U-Boot).

The TF-A build system provides the make target fip to create a FIP file for the specified platform using the FIP creation tool included in the TF-A project. Examples below show how to build a FIP file for FVP, packaging TF-A and BL33 images.

For AArch64:

make PLAT=fvp BL33=<path/to/bl33.bin> fip

For AArch32:

make PLAT=fvp ARCH=aarch32 AARCH32_SP=sp_min BL33=<path/to/bl33.bin> fip

Note that AArch32 support for Normal world boot loader (BL33), like U-boot or UEFI, on FVP is not available upstream. Hence custom solutions are required to allow Linux boot on FVP. These instructions assume such a custom boot loader (BL33) is available.

The resulting FIP may be found in:

build/fvp/<build-type>/fip.bin

For advanced operations on FIP files, it is also possible to independently build the tool and create or modify FIPs using this tool. To do this, follow these steps:

It is recommended to remove old artifacts before building the tool:

make -C tools/fiptool clean

Build the tool:

make [DEBUG=1] [V=1] fiptool

The tool binary can be located in:

./tools/fiptool/fiptool

Invoking the tool with --help will print a help message with all available options.

Example 1: create a new Firmware package fip.bin that contains BL2 and BL31:

./tools/fiptool/fiptool create \
    --tb-fw build/<platform>/<build-type>/bl2.bin \
    --soc-fw build/<platform>/<build-type>/bl31.bin \
    fip.bin

Example 2: view the contents of an existing Firmware package:

./tools/fiptool/fiptool info <path-to>/fip.bin

Example 3: update the entries of an existing Firmware package:

# Change the BL2 from Debug to Release version
./tools/fiptool/fiptool update \
    --tb-fw build/<platform>/release/bl2.bin \
    build/<platform>/debug/fip.bin

Example 4: unpack all entries from an existing Firmware package:

# Images will be unpacked to the working directory
./tools/fiptool/fiptool unpack <path-to>/fip.bin

Example 5: remove an entry from an existing Firmware package:

./tools/fiptool/fiptool remove \
    --tb-fw build/<platform>/debug/fip.bin

Note that if the destination FIP file exists, the create, update and remove operations will automatically overwrite it.

The unpack operation will fail if the images already exist at the destination. In that case, use -f or --force to continue.

More information about FIP can be found in the Firmware Design document.

4.5.1.   Migrating from fip_create to fiptool

The previous version of fiptool was called fip_create. A compatibility script that emulates the basic functionality of the previous fip_create is provided. However, users are strongly encouraged to migrate to fiptool.

  • To create a new FIP file, replace "fip_create" with "fiptool create".
  • To update a FIP file, replace "fip_create" with "fiptool update".
  • To dump the contents of a FIP file, replace "fip_create --dump" with "fiptool info".

4.6.   Building FIP images with support for Trusted Board Boot

Trusted Board Boot primarily consists of the following two features:

The following steps should be followed to build FIP and (optionally) FWU_FIP images with support for these features:

  1. Fulfill the dependencies of the mbedtls cryptographic and image parser modules by checking out a recent version of the mbed TLS Repository. It is important to use a version that is compatible with TF-A and fixes any known security vulnerabilities. See mbed TLS Security Center for more information. The latest version of TF-A is tested with tag mbedtls-2.6.0.

    The drivers/auth/mbedtls/mbedtls_*.mk files contain the list of mbed TLS source files the modules depend upon. include/drivers/auth/mbedtls/mbedtls_config.h contains the configuration options required to build the mbed TLS sources.

    Note that the mbed TLS library is licensed under the Apache version 2.0 license. Using mbed TLS source code will affect the licensing of TF-A binaries that are built using this library.

  2. To build the FIP image, ensure the following command line variables are set while invoking make to build TF-A:

    • MBEDTLS_DIR=<path of the directory containing mbed TLS sources>
    • TRUSTED_BOARD_BOOT=1
    • GENERATE_COT=1

    In the case of Arm platforms, the location of the ROTPK hash must also be specified at build time. Two locations are currently supported (see ARM_ROTPK_LOCATION build option):

    • ARM_ROTPK_LOCATION=regs: the ROTPK hash is obtained from the Trusted root-key storage registers present in the platform. On Juno, this registers are read-only. On FVP Base and Cortex models, the registers are read-only, but the value can be specified using the command line option bp.trusted_key_storage.public_key when launching the model. On both Juno and FVP models, the default value corresponds to an ECDSA-SECP256R1 public key hash, whose private part is not currently available.
    • ARM_ROTPK_LOCATION=devel_rsa: use the ROTPK hash that is hardcoded in the Arm platform port. The private/public RSA key pair may be found in plat/arm/board/common/rotpk.
    • ARM_ROTPK_LOCATION=devel_ecdsa: use the ROTPK hash that is hardcoded in the Arm platform port. The private/public ECDSA key pair may be found in plat/arm/board/common/rotpk.

    Example of command line using RSA development keys:

    MBEDTLS_DIR=<path of the directory containing mbed TLS sources> \
make PLAT=<platform> TRUSTED_BOARD_BOOT=1 GENERATE_COT=1        \
ARM_ROTPK_LOCATION=devel_rsa                                    \
ROT_KEY=plat/arm/board/common/rotpk/arm_rotprivk_rsa.pem        \
BL33=<path-to>/<bl33_image>                                     \
all fip

    The result of this build will be the bl1.bin and the fip.bin binaries. This FIP will include the certificates corresponding to the Chain of Trust described in the TBBR-client document. These certificates can also be found in the output build directory.

  3. The optional FWU_FIP contains any additional images to be loaded from Non-Volatile storage during the Firmware Update process. To build the FWU_FIP, any FWU images required by the platform must be specified on the command line. On Arm development platforms like Juno, these are:

    • NS_BL2U. The AP non-secure Firmware Updater image.
    • SCP_BL2U. The SCP Firmware Update Configuration image.

    Example of Juno command line for generating both fwu and fwu_fip targets using RSA development:

    MBEDTLS_DIR=<path of the directory containing mbed TLS sources> \
make PLAT=juno TRUSTED_BOARD_BOOT=1 GENERATE_COT=1              \
ARM_ROTPK_LOCATION=devel_rsa                                    \
ROT_KEY=plat/arm/board/common/rotpk/arm_rotprivk_rsa.pem        \
BL33=<path-to>/<bl33_image>                                     \
SCP_BL2=<path-to>/<scp_bl2_image>                               \
SCP_BL2U=<path-to>/<scp_bl2u_image>                             \
NS_BL2U=<path-to>/<ns_bl2u_image>                               \
all fip fwu_fip

    Note: The BL2U image will be built by default and added to the FWU_FIP. The user may override this by adding BL2U=<path-to>/<bl2u_image> to the command line above.

    Note: Building and installing the non-secure and SCP FWU images (NS_BL1U, NS_BL2U and SCP_BL2U) is outside the scope of this document.

    The result of this build will be bl1.bin, fip.bin and fwu_fip.bin binaries. Both the FIP and FWU_FIP will include the certificates corresponding to the Chain of Trust described in the TBBR-client document. These certificates can also be found in the output build directory.

4.7.   Building the Certificate Generation Tool

The cert_create tool is built as part of the TF-A build process when the fip make target is specified and TBB is enabled (as described in the previous section), but it can also be built separately with the following command:

make PLAT=<platform> [DEBUG=1] [V=1] certtool

For platforms that do not require their own IDs in certificate files, the generic 'cert_create' tool can be built with the following command:

make USE_TBBR_DEFS=1 [DEBUG=1] [V=1] certtool

DEBUG=1 builds the tool in debug mode. V=1 makes the build process more verbose. The following command should be used to obtain help about the tool:

./tools/cert_create/cert_create -h

5.   Building a FIP for Juno and FVP

This section provides Juno and FVP specific instructions to build Trusted Firmware, obtain the additional required firmware, and pack it all together in a single FIP binary. It assumes that a Linaro Release has been installed.

Note: Pre-built binaries for AArch32 are available from Linaro Release 16.12 onwards. Before that release, pre-built binaries are only available for AArch64.

Note: Follow the full instructions for one platform before switching to a different one. Mixing instructions for different platforms may result in corrupted binaries.

Note: The uboot image downloaded by the Linaro workspace script does not always match the uboot image packaged as BL33 in the corresponding fip file. It is recommended to use the version that is packaged in the fip file using the instructions below.

  1. Clean the working directory

    make realclean

  2. Obtain SCP_BL2 (Juno) and BL33 (all platforms)

    Use the fiptool to extract the SCP_BL2 and BL33 images from the FIP package included in the Linaro release:

    # Build the fiptool
make [DEBUG=1] [V=1] fiptool

# Unpack firmware images from Linaro FIP
./tools/fiptool/fiptool unpack \
     <path/to/linaro/release>/fip.bin

    The unpack operation will result in a set of binary images extracted to the current working directory. The SCP_BL2 image corresponds to scp-fw.bin and BL33 corresponds to nt-fw.bin.

    Note: The fiptool will complain if the images to be unpacked already exist in the current directory. If that is the case, either delete those files or use the --force option to overwrite.

    Note: For AArch32, the instructions below assume that nt-fw.bin is a custom Normal world boot loader that supports AArch32.

  3. Build TF-A images and create a new FIP for FVP

    # AArch64
make PLAT=fvp BL33=nt-fw.bin all fip

# AArch32
make PLAT=fvp ARCH=aarch32 AARCH32_SP=sp_min BL33=nt-fw.bin all fip

  4. Build TF-A images and create a new FIP for Juno

    For AArch64:

    Building for AArch64 on Juno simply requires the addition of SCP_BL2 as a build parameter.

    make PLAT=juno all fip \
BL33=<path-to-juno-oe-uboot>/SOFTWARE/bl33-uboot.bin \
SCP_BL2=<path-to-juno-busybox-uboot>/SOFTWARE/scp_bl2.bin

    For AArch32:

    Hardware restrictions on Juno prevent cold reset into AArch32 execution mode, therefore BL1 and BL2 must be compiled for AArch64, and BL32 is compiled separately for AArch32.

    • Before building BL32, the environment variable CROSS_COMPILE must point to the AArch32 Linaro cross compiler.

      export CROSS_COMPILE=<path-to-aarch32-gcc>/bin/arm-linux-gnueabihf-

    • Build BL32 in AArch32.

      make ARCH=aarch32 PLAT=juno AARCH32_SP=sp_min \
RESET_TO_SP_MIN=1 JUNO_AARCH32_EL3_RUNTIME=1 bl32

    • Before building BL1 and BL2, the environment variable CROSS_COMPILE must point to the AArch64 Linaro cross compiler.

      export CROSS_COMPILE=<path-to-aarch64-gcc>/bin/aarch64-linux-gnu-

    • The following parameters should be used to build BL1 and BL2 in AArch64 and point to the BL32 file.

      make ARCH=aarch64 PLAT=juno LOAD_IMAGE_V2=1 JUNO_AARCH32_EL3_RUNTIME=1 \
BL33=<path-to-juno32-oe-uboot>/SOFTWARE/bl33-uboot.bin \
SCP_BL2=<path-to-juno32-oe-uboot>/SOFTWARE/scp_bl2.bin \
BL32=<path-to-bl32>/bl32.bin all fip

The resulting BL1 and FIP images may be found in:

# Juno
./build/juno/release/bl1.bin
./build/juno/release/fip.bin

# FVP
./build/fvp/release/bl1.bin
./build/fvp/release/fip.bin

6.   Booting Firmware Update images

When Firmware Update (FWU) is enabled there are at least 2 new images that have to be loaded, the Non-Secure FWU ROM (NS-BL1U), and the FWU FIP.

6.1.   Juno

The new images must be programmed in flash memory by adding an entry in the SITE1/HBI0262x/images.txt configuration file on the Juno SD card (where x depends on the revision of the Juno board). Refer to the Juno Getting Started Guide, section 2.3 "Flash memory programming" for more information. User should ensure these do not overlap with any other entries in the file.

NOR10UPDATE: AUTO                       ;Image Update:NONE/AUTO/FORCE
NOR10ADDRESS: 0x00400000                ;Image Flash Address [ns_bl2u_base_address]
NOR10FILE: \SOFTWARE\fwu_fip.bin        ;Image File Name
NOR10LOAD: 00000000                     ;Image Load Address
NOR10ENTRY: 00000000                    ;Image Entry Point

NOR11UPDATE: AUTO                       ;Image Update:NONE/AUTO/FORCE
NOR11ADDRESS: 0x03EB8000                ;Image Flash Address [ns_bl1u_base_address]
NOR11FILE: \SOFTWARE\ns_bl1u.bin        ;Image File Name
NOR11LOAD: 00000000                     ;Image Load Address

The address ns_bl1u_base_address is the value of NS_BL1U_BASE - 0x8000000. In the same way, the address ns_bl2u_base_address is the value of NS_BL2U_BASE - 0x8000000.

6.2.   FVP

The additional fip images must be loaded with:

--data cluster0.cpu0="<path_to>/ns_bl1u.bin"@0x0beb8000     [ns_bl1u_base_address]
--data cluster0.cpu0="<path_to>/fwu_fip.bin"@0x08400000     [ns_bl2u_base_address]

The address ns_bl1u_base_address is the value of NS_BL1U_BASE. In the same way, the address ns_bl2u_base_address is the value of NS_BL2U_BASE.

7.   EL3 payloads alternative boot flow

On a pre-production system, the ability to execute arbitrary, bare-metal code at the highest exception level is required. It allows full, direct access to the hardware, for example to run silicon soak tests.

Although it is possible to implement some baremetal secure firmware from scratch, this is a complex task on some platforms, depending on the level of configuration required to put the system in the expected state.

Rather than booting a baremetal application, a possible compromise is to boot EL3 payloads through TF-A instead. This is implemented as an alternative boot flow, where a modified BL2 boots an EL3 payload, instead of loading the other BL images and passing control to BL31. It reduces the complexity of developing EL3 baremetal code by:

  • putting the system into a known architectural state;
  • taking care of platform secure world initialization;
  • loading the SCP_BL2 image if required by the platform.

When booting an EL3 payload on Arm standard platforms, the configuration of the TrustZone controller is simplified such that only region 0 is enabled and is configured to permit secure access only. This gives full access to the whole DRAM to the EL3 payload.

The system is left in the same state as when entering BL31 in the default boot flow. In particular:

  • Running in EL3;
  • Current state is AArch64;
  • Little-endian data access;
  • All exceptions disabled;
  • MMU disabled;
  • Caches disabled.

7.1.   Booting an EL3 payload

The EL3 payload image is a standalone image and is not part of the FIP. It is not loaded by TF-A. Therefore, there are 2 possible scenarios:

  • The EL3 payload may reside in non-volatile memory (NVM) and execute in place. In this case, booting it is just a matter of specifying the right address in NVM through EL3_PAYLOAD_BASE when building TF-A.
  • The EL3 payload needs to be loaded in volatile memory (e.g. DRAM) at run-time.

To help in the latter scenario, the SPIN_ON_BL1_EXIT=1 build option can be used. The infinite loop that it introduces in BL1 stops execution at the right moment for a debugger to take control of the target and load the payload (for example, over JTAG).

It is expected that this loading method will work in most cases, as a debugger connection is usually available in a pre-production system. The user is free to use any other platform-specific mechanism to load the EL3 payload, though.

7.1.1.   Booting an EL3 payload on FVP

The EL3 payloads boot flow requires the CPU's mailbox to be cleared at reset for the secondary CPUs holding pen to work properly. Unfortunately, its reset value is undefined on the FVP platform and the FVP platform code doesn't clear it. Therefore, one must modify the way the model is normally invoked in order to clear the mailbox at start-up.

One way to do that is to create an 8-byte file containing all zero bytes using the following command:

dd if=/dev/zero of=mailbox.dat bs=1 count=8

and pre-load it into the FVP memory at the mailbox address (i.e. 0x04000000) using the following model parameters:

--data cluster0.cpu0=mailbox.dat@0x04000000   [Base FVPs]
--data=mailbox.dat@0x04000000                 [Foundation FVP]

To provide the model with the EL3 payload image, the following methods may be used:

  1. If the EL3 payload is able to execute in place, it may be programmed into flash memory. On Base Cortex and AEM FVPs, the following model parameter loads it at the base address of the NOR FLASH1 (the NOR FLASH0 is already used for the FIP):

    -C bp.flashloader1.fname="/path/to/el3-payload"

    On Foundation FVP, there is no flash loader component and the EL3 payload may be programmed anywhere in flash using method 3 below.

  2. When using the SPIN_ON_BL1_EXIT=1 loading method, the following DS-5 command may be used to load the EL3 payload ELF image over JTAG:

    load /path/to/el3-payload.elf

  3. The EL3 payload may be pre-loaded in volatile memory using the following model parameters:

    --data cluster0.cpu0="/path/to/el3-payload"@address  [Base FVPs]
--data="/path/to/el3-payload"@address                [Foundation FVP]

    The address provided to the FVP must match the EL3_PAYLOAD_BASE address used when building TF-A.

7.1.2.   Booting an EL3 payload on Juno

If the EL3 payload is able to execute in place, it may be programmed in flash memory by adding an entry in the SITE1/HBI0262x/images.txt configuration file on the Juno SD card (where x depends on the revision of the Juno board). Refer to the Juno Getting Started Guide, section 2.3 "Flash memory programming" for more information.

Alternatively, the same DS-5 command mentioned in the FVP section above can be used to load the EL3 payload's ELF file over JTAG on Juno.

8.   Preloaded BL33 alternative boot flow

Some platforms have the ability to preload BL33 into memory instead of relying on TF-A to load it. This may simplify packaging of the normal world code and improve performance in a development environment. When secure world cold boot is complete, TF-A simply jumps to a BL33 base address provided at build time.

For this option to be used, the PRELOADED_BL33_BASE build option has to be used when compiling TF-A. For example, the following command will create a FIP without a BL33 and prepare to jump to a BL33 image loaded at address 0x80000000:

make PRELOADED_BL33_BASE=0x80000000 PLAT=fvp all fip

8.1.   Boot of a preloaded bootwrapped kernel image on Base FVP

The following example uses the AArch64 boot wrapper. This simplifies normal world booting while also making use of TF-A features. It can be obtained from its repository with:

git clone git://git.kernel.org/pub/scm/linux/kernel/git/mark/boot-wrapper-aarch64.git

After compiling it, an ELF file is generated. It can be loaded with the following command:

<path-to>/FVP_Base_AEMv8A-AEMv8A              \
    -C bp.secureflashloader.fname=bl1.bin     \
    -C bp.flashloader0.fname=fip.bin          \
    -a cluster0.cpu0=<bootwrapped-kernel.elf> \
    --start cluster0.cpu0=0x0

The -a cluster0.cpu0=<bootwrapped-kernel.elf> option loads the ELF file. It also sets the PC register to the ELF entry point address, which is not the desired behaviour, so the --start cluster0.cpu0=0x0 option forces the PC back to 0x0 (the BL1 entry point address) on CPU #0. The PRELOADED_BL33_BASE define used when compiling the FIP must match the ELF entry point.

8.2.   Boot of a preloaded bootwrapped kernel image on Juno

The procedure to obtain and compile the boot wrapper is very similar to the case of the FVP. The execution must be stopped at the end of bl2_main(), and the loading method explained above in the EL3 payload boot flow section may be used to load the ELF file over JTAG on Juno.

9.   Running the software on FVP

The latest version of the AArch64 build of TF-A has been tested on the following Arm FVPs without shifted affinities, and that do not support threaded CPU cores (64-bit host machine only).

NOTE: Unless otherwise stated, the model version is Version 11.2 Build 11.2.33.

  • Foundation_Platform
  • FVP_Base_AEMv8A-AEMv8A (and also Version 9.0, Build 0.8.9005)
  • FVP_Base_Cortex-A35x4
  • FVP_Base_Cortex-A53x4
  • FVP_Base_Cortex-A57x4-A53x4
  • FVP_Base_Cortex-A57x4
  • FVP_Base_Cortex-A72x4-A53x4
  • FVP_Base_Cortex-A72x4
  • FVP_Base_Cortex-A73x4-A53x4
  • FVP_Base_Cortex-A73x4

Additionally, the AArch64 build was tested on the following Arm FVPs with shifted affinities, supporting threaded CPU cores (64-bit host machine only).

  • FVP_Base_Cortex-A55x4-A75x4 (Version 0.0, build 0.0.4395)
  • FVP_Base_Cortex-A55x4 (Version 0.0, build 0.0.4395)
  • FVP_Base_Cortex-A75x4 (Version 0.0, build 0.0.4395)
  • FVP_Base_RevC-2xAEMv8A

The latest version of the AArch32 build of TF-A has been tested on the following Arm FVPs without shifted affinities, and that do not support threaded CPU cores (64-bit host machine only).

  • FVP_Base_AEMv8A-AEMv8A
  • FVP_Base_Cortex-A32x4

NOTE: The FVP_Base_RevC-2xAEMv8A FVP only supports shifted affinities, which is not compatible with legacy GIC configurations. Therefore this FVP does not support these legacy GIC configurations.

NOTE: The build numbers quoted above are those reported by launching the FVP with the --version parameter.

NOTE: Linaro provides a ramdisk image in prebuilt FVP configurations and full file systems that can be downloaded separately. To run an FVP with a virtio file system image an additional FVP configuration option -C bp.virtioblockdevice.image_path="<path-to>/<file-system-image> can be used.

NOTE: The software will not work on Version 1.0 of the Foundation FVP. The commands below would report an unhandled argument error in this case.

NOTE: FVPs can be launched with --cadi-server option such that a CADI-compliant debugger (for example, Arm DS-5) can connect to and control its execution.

NOTE: Since FVP model Version 11.0 Build 11.0.34 and Version 8.5 Build 0.8.5202 the internal synchronisation timings changed compared to older versions of the models. The models can be launched with -Q 100 option if they are required to match the run time characteristics of the older versions.

The Foundation FVP is a cut down version of the AArch64 Base FVP. It can be downloaded for free from Arm's website.

The Cortex-A models listed above are also available to download from Arm's website.

Please refer to the FVP documentation for a detailed description of the model parameter options. A brief description of the important ones that affect TF-A and normal world software behavior is provided below.

9.1.   Obtaining the Flattened Device Trees

Depending on the FVP configuration and Linux configuration used, different FDT files are required. FDTs for the Foundation and Base FVPs can be found in the TF-A source directory under fdts/. The Foundation FVP has a subset of the Base FVP components. For example, the Foundation FVP lacks CLCD and MMC support, and has only one CPU cluster.

Note: It is not recommended to use the FDTs built along the kernel because not all FDTs are available from there.

  • fvp-base-gicv2-psci.dtb

    For use with models such as the Cortex-A57-A53 Base FVPs without shifted affinities and with Base memory map configuration.

  • fvp-base-gicv2-psci-aarch32.dtb

    For use with models such as the Cortex-A32 Base FVPs without shifted affinities and running Linux in AArch32 state with Base memory map configuration.

  • fvp-base-gicv3-psci.dtb

    For use with models such as the Cortex-A57-A53 Base FVPs without shifted affinities and with Base memory map configuration and Linux GICv3 support.

  • fvp-base-gicv3-psci-1t.dtb

    For use with models such as the AEMv8-RevC Base FVP with shifted affinities, single threaded CPUs, Base memory map configuration and Linux GICv3 support.

  • fvp-base-gicv3-psci-dynamiq.dtb

    For use with models as the Cortex-A55-A75 Base FVPs with shifted affinities, single cluster, single threaded CPUs, Base memory map configuration and Linux GICv3 support.

  • fvp-base-gicv3-psci-aarch32.dtb

    For use with models such as the Cortex-A32 Base FVPs without shifted affinities and running Linux in AArch32 state with Base memory map configuration and Linux GICv3 support.

  • fvp-foundation-gicv2-psci.dtb

    For use with Foundation FVP with Base memory map configuration.

  • fvp-foundation-gicv3-psci.dtb

    (Default) For use with Foundation FVP with Base memory map configuration and Linux GICv3 support.

9.2.   Running on the Foundation FVP with reset to BL1 entrypoint

The following Foundation_Platform parameters should be used to boot Linux with 4 CPUs using the AArch64 build of TF-A.

<path-to>/Foundation_Platform                   \
--cores=4                                       \
--arm-v8.0                                      \
--secure-memory                                 \
--visualization                                 \
--gicv3                                         \
--data="<path-to>/<bl1-binary>"@0x0             \
--data="<path-to>/<FIP-binary>"@0x08000000      \
--data="<path-to>/<fdt>"@0x82000000             \
--data="<path-to>/<kernel-binary>"@0x80080000   \
--data="<path-to>/<ramdisk-binary>"@0x84000000

Notes:

  • BL1 is loaded at the start of the Trusted ROM.
  • The Firmware Image Package is loaded at the start of NOR FLASH0.
  • The Linux kernel image and device tree are loaded in DRAM.
  • The default use-case for the Foundation FVP is to use the --gicv3 option and enable the GICv3 device in the model. Note that without this option, the Foundation FVP defaults to legacy (Versatile Express) memory map which is not supported by TF-A.
  • In order for TF-A to run correctly on the Foundation FVP, the architecture versions must match. The Foundation FVP defaults to the highest v8.x version it supports but the default build for TF-A is for v8.0. To avoid issues either start the Foundation FVP to use v8.0 architecture using the --arm-v8.0 option, or build TF-A with an appropriate value for ARM_ARCH_MINOR.

9.3.   Running on the AEMv8 Base FVP with reset to BL1 entrypoint

The following FVP_Base_RevC-2xAEMv8A parameters should be used to boot Linux with 8 CPUs using the AArch64 build of TF-A.

<path-to>/FVP_Base_RevC-2xAEMv8A                            \
-C pctl.startup=0.0.0.0                                     \
-C bp.secure_memory=1                                       \
-C bp.tzc_400.diagnostics=1                                 \
-C cluster0.NUM_CORES=4                                     \
-C cluster1.NUM_CORES=4                                     \
-C cache_state_modelled=1                                   \
-C bp.secureflashloader.fname="<path-to>/<bl1-binary>"      \
-C bp.flashloader0.fname="<path-to>/<FIP-binary>"           \
--data cluster0.cpu0="<path-to>/<fdt>"@0x82000000           \
--data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000 \
--data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000

9.4.   Running on the AEMv8 Base FVP (AArch32) with reset to BL1 entrypoint

The following FVP_Base_AEMv8A-AEMv8A parameters should be used to boot Linux with 8 CPUs using the AArch32 build of TF-A.

<path-to>/FVP_Base_AEMv8A-AEMv8A                            \
-C pctl.startup=0.0.0.0                                     \
-C bp.secure_memory=1                                       \
-C bp.tzc_400.diagnostics=1                                 \
-C cluster0.NUM_CORES=4                                     \
-C cluster1.NUM_CORES=4                                     \
-C cache_state_modelled=1                                   \
-C cluster0.cpu0.CONFIG64=0                                 \
-C cluster0.cpu1.CONFIG64=0                                 \
-C cluster0.cpu2.CONFIG64=0                                 \
-C cluster0.cpu3.CONFIG64=0                                 \
-C cluster1.cpu0.CONFIG64=0                                 \
-C cluster1.cpu1.CONFIG64=0                                 \
-C cluster1.cpu2.CONFIG64=0                                 \
-C cluster1.cpu3.CONFIG64=0                                 \
-C bp.secureflashloader.fname="<path-to>/<bl1-binary>"      \
-C bp.flashloader0.fname="<path-to>/<FIP-binary>"           \
--data cluster0.cpu0="<path-to>/<fdt>"@0x82000000           \
--data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000 \
--data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000

9.5.   Running on the Cortex-A57-A53 Base FVP with reset to BL1 entrypoint

The following FVP_Base_Cortex-A57x4-A53x4 model parameters should be used to boot Linux with 8 CPUs using the AArch64 build of TF-A.

<path-to>/FVP_Base_Cortex-A57x4-A53x4                       \
-C pctl.startup=0.0.0.0                                     \
-C bp.secure_memory=1                                       \
-C bp.tzc_400.diagnostics=1                                 \
-C cache_state_modelled=1                                   \
-C bp.secureflashloader.fname="<path-to>/<bl1-binary>"      \
-C bp.flashloader0.fname="<path-to>/<FIP-binary>"           \
--data cluster0.cpu0="<path-to>/<fdt>"@0x82000000           \
--data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000 \
--data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000

9.6.   Running on the Cortex-A32 Base FVP (AArch32) with reset to BL1 entrypoint

The following FVP_Base_Cortex-A32x4 model parameters should be used to boot Linux with 4 CPUs using the AArch32 build of TF-A.

<path-to>/FVP_Base_Cortex-A32x4                             \
-C pctl.startup=0.0.0.0                                     \
-C bp.secure_memory=1                                       \
-C bp.tzc_400.diagnostics=1                                 \
-C cache_state_modelled=1                                   \
-C bp.secureflashloader.fname="<path-to>/<bl1-binary>"      \
-C bp.flashloader0.fname="<path-to>/<FIP-binary>"           \
--data cluster0.cpu0="<path-to>/<fdt>"@0x82000000           \
--data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000 \
--data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000

9.7.   Running on the AEMv8 Base FVP with reset to BL31 entrypoint

The following FVP_Base_RevC-2xAEMv8A parameters should be used to boot Linux with 8 CPUs using the AArch64 build of TF-A.

<path-to>/FVP_Base_RevC-2xAEMv8A                             \
-C pctl.startup=0.0.0.0                                      \
-C bp.secure_memory=1                                        \
-C bp.tzc_400.diagnostics=1                                  \
-C cluster0.NUM_CORES=4                                      \
-C cluster1.NUM_CORES=4                                      \
-C cache_state_modelled=1                                    \
-C cluster0.cpu0.RVBAR=0x04020000                            \
-C cluster0.cpu1.RVBAR=0x04020000                            \
-C cluster0.cpu2.RVBAR=0x04020000                            \
-C cluster0.cpu3.RVBAR=0x04020000                            \
-C cluster1.cpu0.RVBAR=0x04020000                            \
-C cluster1.cpu1.RVBAR=0x04020000                            \
-C cluster1.cpu2.RVBAR=0x04020000                            \
-C cluster1.cpu3.RVBAR=0x04020000                            \
--data cluster0.cpu0="<path-to>/<bl31-binary>"@0x04020000    \
--data cluster0.cpu0="<path-to>/<bl32-binary>"@0x04001000    \
--data cluster0.cpu0="<path-to>/<bl33-binary>"@0x88000000    \
--data cluster0.cpu0="<path-to>/<fdt>"@0x82000000            \
--data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000  \
--data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000

Notes:

  • Since a FIP is not loaded when using BL31 as reset entrypoint, the --data="<path-to><bl31|bl32|bl33-binary>"@<base-address-of-binary> parameter is needed to load the individual bootloader images in memory. BL32 image is only needed if BL31 has been built to expect a Secure-EL1 Payload.
  • The -C cluster<X>.cpu<Y>.RVBAR=@<base-address-of-bl31> parameter, where X and Y are the cluster and CPU numbers respectively, is used to set the reset vector for each core.
  • Changing the default value of ARM_TSP_RAM_LOCATION will also require changing the value of --data="<path-to><bl32-binary>"@<base-address-of-bl32> to the new value of BL32_BASE.

9.8.   Running on the AEMv8 Base FVP (AArch32) with reset to SP_MIN entrypoint

The following FVP_Base_AEMv8A-AEMv8A parameters should be used to boot Linux with 8 CPUs using the AArch32 build of TF-A.

<path-to>/FVP_Base_AEMv8A-AEMv8A                             \
-C pctl.startup=0.0.0.0                                      \
-C bp.secure_memory=1                                        \
-C bp.tzc_400.diagnostics=1                                  \
-C cluster0.NUM_CORES=4                                      \
-C cluster1.NUM_CORES=4                                      \
-C cache_state_modelled=1                                    \
-C cluster0.cpu0.CONFIG64=0                                  \
-C cluster0.cpu1.CONFIG64=0                                  \
-C cluster0.cpu2.CONFIG64=0                                  \
-C cluster0.cpu3.CONFIG64=0                                  \
-C cluster1.cpu0.CONFIG64=0                                  \
-C cluster1.cpu1.CONFIG64=0                                  \
-C cluster1.cpu2.CONFIG64=0                                  \
-C cluster1.cpu3.CONFIG64=0                                  \
-C cluster0.cpu0.RVBAR=0x04001000                            \
-C cluster0.cpu1.RVBAR=0x04001000                            \
-C cluster0.cpu2.RVBAR=0x04001000                            \
-C cluster0.cpu3.RVBAR=0x04001000                            \
-C cluster1.cpu0.RVBAR=0x04001000                            \
-C cluster1.cpu1.RVBAR=0x04001000                            \
-C cluster1.cpu2.RVBAR=0x04001000                            \
-C cluster1.cpu3.RVBAR=0x04001000                            \
--data cluster0.cpu0="<path-to>/<bl32-binary>"@0x04001000    \
--data cluster0.cpu0="<path-to>/<bl33-binary>"@0x88000000    \
--data cluster0.cpu0="<path-to>/<fdt>"@0x82000000            \
--data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000  \
--data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000

Note: The load address of <bl32-binary> depends on the value BL32_BASE. It should match the address programmed into the RVBAR register as well.

9.9.   Running on the Cortex-A57-A53 Base FVP with reset to BL31 entrypoint

The following FVP_Base_Cortex-A57x4-A53x4 model parameters should be used to boot Linux with 8 CPUs using the AArch64 build of TF-A.

<path-to>/FVP_Base_Cortex-A57x4-A53x4                        \
-C pctl.startup=0.0.0.0                                      \
-C bp.secure_memory=1                                        \
-C bp.tzc_400.diagnostics=1                                  \
-C cache_state_modelled=1                                    \
-C cluster0.cpu0.RVBARADDR=0x04020000                        \
-C cluster0.cpu1.RVBARADDR=0x04020000                        \
-C cluster0.cpu2.RVBARADDR=0x04020000                        \
-C cluster0.cpu3.RVBARADDR=0x04020000                        \
-C cluster1.cpu0.RVBARADDR=0x04020000                        \
-C cluster1.cpu1.RVBARADDR=0x04020000                        \
-C cluster1.cpu2.RVBARADDR=0x04020000                        \
-C cluster1.cpu3.RVBARADDR=0x04020000                        \
--data cluster0.cpu0="<path-to>/<bl31-binary>"@0x04020000    \
--data cluster0.cpu0="<path-to>/<bl32-binary>"@0x04001000    \
--data cluster0.cpu0="<path-to>/<bl33-binary>"@0x88000000    \
--data cluster0.cpu0="<path-to>/<fdt>"@0x82000000            \
--data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000  \
--data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000

9.10.   Running on the Cortex-A32 Base FVP (AArch32) with reset to SP_MIN entrypoint

The following FVP_Base_Cortex-A32x4 model parameters should be used to boot Linux with 4 CPUs using the AArch32 build of TF-A.

<path-to>/FVP_Base_Cortex-A32x4                             \
-C pctl.startup=0.0.0.0                                     \
-C bp.secure_memory=1                                       \
-C bp.tzc_400.diagnostics=1                                 \
-C cache_state_modelled=1                                   \
-C cluster0.cpu0.RVBARADDR=0x04001000                       \
-C cluster0.cpu1.RVBARADDR=0x04001000                       \
-C cluster0.cpu2.RVBARADDR=0x04001000                       \
-C cluster0.cpu3.RVBARADDR=0x04001000                       \
--data cluster0.cpu0="<path-to>/<bl32-binary>"@0x04001000   \
--data cluster0.cpu0="<path-to>/<bl33-binary>"@0x88000000   \
--data cluster0.cpu0="<path-to>/<fdt>"@0x82000000           \
--data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000 \
--data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000

10.   Running the software on Juno

This version of TF-A has been tested on variants r0, r1 and r2 of Juno.

To execute the software stack on Juno, the version of the Juno board recovery image indicated in the Linaro Release Notes must be installed. If you have an earlier version installed or are unsure which version is installed, please re-install the recovery image by following the Instructions for using Linaro's deliverables on Juno.

10.1.   Preparing TF-A images

After building TF-A, the files bl1.bin and fip.bin need copying to the SOFTWARE/ directory of the Juno SD card.

10.2.   Other Juno software information

Please visit the Arm Platforms Portal to get support and obtain any other Juno software information. Please also refer to the Juno Getting Started Guide to get more detailed information about the Juno Arm development platform and how to configure it.

10.3.   Testing SYSTEM SUSPEND on Juno

The SYSTEM SUSPEND is a PSCI API which can be used to implement system suspend to RAM. For more details refer to section 5.16 of PSCI. To test system suspend on Juno, at the linux shell prompt, issue the following command:

echo +10 > /sys/class/rtc/rtc0/wakealarm
echo -n mem > /sys/power/state

The Juno board should suspend to RAM and then wakeup after 10 seconds due to wakeup interrupt from RTC.

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