diff options
| author | Dan Handley <dan.handley@arm.com> | 2014-02-25 13:28:04 +0000 |
|---|---|---|
| committer | Dan Handley <dan.handley@arm.com> | 2014-02-28 17:51:07 +0000 |
| commit | 247f60bcbc73d809e69f68da68140e3af63407c1 (patch) | |
| tree | a4b6936ceeb2474e4a391a706e8c48e87428678a | |
| parent | 3505c044a22021855222b6ba95b08f6ef4513bab (diff) | |
Separate firmware design out of user-guide.md
Move the firmware design documentation out of user-guide.md
and into a new file - firmware-design.md. Reformat the
section headers.
Change-Id: I664815dd47011c7c1cf2202aa4472a8fd78ebb92
| -rw-r--r-- | docs/firmware-design.md | 798 | ||||
| -rw-r--r-- | docs/user-guide.md | 943 |
2 files changed, 891 insertions, 850 deletions
diff --git a/docs/firmware-design.md b/docs/firmware-design.md new file mode 100644 index 0000000..89dd45f --- /dev/null +++ b/docs/firmware-design.md @@ -0,0 +1,798 @@ +ARM Trusted Firmware Design +=========================== + +Contents : + +1. Introduction +2. Cold Boot +3. Memory layout on FVP platforms +4. Firmware Image Package (FIP) +5. Code Structure +6. References + + +1. Introduction +---------------- + +The ARM Trusted Firmware implements a subset of the Trusted Board Boot +Requirements (TBBR) Platform Design Document (PDD) [1] for ARM reference +platforms. The TBB sequence starts when the platform is powered on and runs up +to the stage where it hands-off control to firmware running in the normal +world in DRAM. This is the cold boot path. + +The ARM Trusted Firmware also implements the Power State Coordination Interface +([PSCI]) PDD [2] as a runtime service. PSCI is the interface from normal world +software to firmware implementing power management use-cases (for example, +secondary CPU boot, hotplug and idle). Normal world software can access ARM +Trusted Firmware runtime services via the ARM SMC (Secure Monitor Call) +instruction. The SMC instruction must be used as mandated by the [SMC Calling +Convention PDD][SMCCC] [3]. + + +2. Cold Boot +------------- + +The cold boot path starts when the platform is physically turned on. One of +the CPUs released from reset is chosen as the primary CPU, and the remaining +CPUs are considered secondary CPUs. The primary CPU is chosen through +platform-specific means. The cold boot path is mainly executed by the primary +CPU, other than essential CPU initialization executed by all CPUs. The +secondary CPUs are kept in a safe platform-specific state until the primary +CPU has performed enough initialization to boot them. + +The cold boot path in this implementation of the ARM Trusted Firmware is divided +into three stages (in order of execution): + +* Boot Loader stage 1 (BL1) +* Boot Loader stage 2 (BL2) +* Boot Loader stage 3 (BL3-1). The '1' distinguishes this from other 3rd level + boot loader stages. + +The ARM Fixed Virtual Platforms (FVPs) provide trusted ROM, trusted SRAM and +trusted DRAM regions. Each boot loader stage uses one or more of these +memories for its code and data. + + +### BL1 + +This stage begins execution from the platform's reset vector in trusted ROM at +EL3. BL1 code starts at `0x00000000` (trusted ROM) in the FVP memory map. The +BL1 data section is placed at the start of trusted SRAM, `0x04000000`. The +functionality implemented by this stage is as follows. + +#### Determination of boot path + +Whenever a CPU is released from reset, BL1 needs to distinguish between a warm +boot and a cold boot. This is done using a platform-specific mechanism. The +ARM FVPs implement a simple power controller at `0x1c100000`. The `PSYS` +register (`0x10`) is used to distinguish between a cold and warm boot. This +information is contained in the `PSYS.WK[25:24]` field. Additionally, a +per-CPU mailbox is maintained in trusted DRAM (`0x00600000`), to which BL1 +writes an entrypoint. Each CPU jumps to this entrypoint upon warm boot. During +cold boot, BL1 places the secondary CPUs in a safe platform-specific state while +the primary CPU executes the remaining cold boot path as described in the +following sections. + +#### Architectural initialization + +BL1 performs minimal architectural initialization as follows. + +* Exception vectors + + BL1 sets up simple exception vectors for both synchronous and asynchronous + exceptions. The default behavior upon receiving an exception is to set a + status code. In the case of the FVP this code is written to the Versatile + Express System LED register in the following format: + + SYS_LED[0] - Security state (Secure=0/Non-Secure=1) + SYS_LED[2:1] - Exception Level (EL3=0x3, EL2=0x2, EL1=0x1, EL0=0x0) + SYS_LED[7:3] - Exception Class (Sync/Async & origin). The values for + each exception class are: + + 0x0 : Synchronous exception from Current EL with SP_EL0 + 0x1 : IRQ exception from Current EL with SP_EL0 + 0x2 : FIQ exception from Current EL with SP_EL0 + 0x3 : System Error exception from Current EL with SP_EL0 + 0x4 : Synchronous exception from Current EL with SP_ELx + 0x5 : IRQ exception from Current EL with SP_ELx + 0x6 : FIQ exception from Current EL with SP_ELx + 0x7 : System Error exception from Current EL with SP_ELx + 0x8 : Synchronous exception from Lower EL using aarch64 + 0x9 : IRQ exception from Lower EL using aarch64 + 0xa : FIQ exception from Lower EL using aarch64 + 0xb : System Error exception from Lower EL using aarch64 + 0xc : Synchronous exception from Lower EL using aarch32 + 0xd : IRQ exception from Lower EL using aarch32 + 0xe : FIQ exception from Lower EL using aarch32 + 0xf : System Error exception from Lower EL using aarch32 + + A write to the LED register reflects in the System LEDs (S6LED0..7) in the + CLCD window of the FVP. This behavior is because this boot loader stage + does not expect to receive any exceptions other than the SMC exception. + For the latter, BL1 installs a simple stub. The stub expects to receive + only a single type of SMC (determined by its function ID in the general + purpose register `X0`). This SMC is raised by BL2 to make BL1 pass control + to BL3-1 (loaded by BL2) at EL3. Any other SMC leads to an assertion + failure. + +* MMU setup + + BL1 sets up EL3 memory translation by creating page tables to cover the + first 4GB of physical address space. This covers all the memories and + peripherals needed by BL1. + +* Control register setup + - `SCTLR_EL3`. Instruction cache is enabled by setting the `SCTLR_EL3.I` + bit. Alignment and stack alignment checking is enabled by setting the + `SCTLR_EL3.A` and `SCTLR_EL3.SA` bits. Exception endianness is set to + little-endian by clearing the `SCTLR_EL3.EE` bit. + + - `CPUECTLR`. When the FVP includes a model of a specific ARM processor + implementation (for example A57 or A53), then intra-cluster coherency is + enabled by setting the `CPUECTLR.SMPEN` bit. The AEMv8 Base FVP is + inherently coherent so does not implement `CPUECTLR`. + + - `SCR`. Use of the HVC instruction from EL1 is enabled by setting the + `SCR.HCE` bit. FIQ exceptions are configured to be taken in EL3 by + setting the `SCR.FIQ` bit. The register width of the next lower + exception level is set to AArch64 by setting the `SCR.RW` bit. External + Aborts and SError Interrupts are configured to be taken in EL3 by + setting the `SCR.EA` bit. + + - `CPTR_EL3`. Accesses to the `CPACR_EL1` register from EL1 or EL2, or the + `CPTR_EL2` register from EL2 are configured to not trap to EL3 by + clearing the `CPTR_EL3.TCPAC` bit. Access to the trace functionality is + configured not to trap to EL3 by clearing the `CPTR_EL3.TTA` bit. + Instructions that access the registers associated with Floating Point + and Advanced SIMD execution are configured to not trap to EL3 by + clearing the `CPTR_EL3.TFP` bit. + + - `CNTFRQ_EL0`. The `CNTFRQ_EL0` register is programmed with the base + frequency of the system counter, which is retrieved from the first entry + in the frequency modes table. + + - Generic Timer. The system level implementation of the generic timer is + enabled through the memory mapped interface. + +#### Platform initialization + +BL1 enables issuing of snoop and DVM (Distributed Virtual Memory) requests from +the CCI-400 slave interface corresponding to the cluster that includes the +primary CPU. BL1 also initializes UART0 (PL011 console), which enables access to +the `printf` family of functions. + +#### BL2 image load and execution + +BL1 execution continues as follows: + +1. BL1 determines the amount of free trusted SRAM memory available by + calculating the extent of its own data section, which also resides in + trusted SRAM. BL1 loads a BL2 raw binary image from platform storage, at a + platform-specific base address. The filename of the BL2 raw binary image + must be `bl2.bin`. If the BL2 image file is not present or if there is not + enough free trusted SRAM the following error message is printed: + + "Failed to load boot loader stage 2 (BL2) firmware." + + If the load is successful, BL1 updates the limits of the remaining free + trusted SRAM. It also populates information about the amount of trusted + SRAM used by the BL2 image. The exact load location of the image is + provided as a base address in the platform header. Further description of + the memory layout can be found later in this document. + +2. BL1 prints the following string from the primary CPU to indicate successful + execution of the BL1 stage: + + "Booting trusted firmware boot loader stage 1" + +3. BL1 passes control to the BL2 image at Secure EL1, starting from its load + address. + +4. BL1 also passes information about the amount of trusted SRAM used and + available for use. This information is populated at a platform-specific + memory address. + + +### BL2 + +BL1 loads and passes control to BL2 at Secure EL1. BL2 is linked against and +loaded at a platform-specific base address (more information can be found later +in this document). The functionality implemented by BL2 is as follows. + +#### Architectural initialization + +BL2 performs minimal architectural initialization required for subsequent +stages of the ARM Trusted Firmware and normal world software. It sets up +Secure EL1 memory translation by creating page tables to address the first 4GB +of the physical address space in a similar way to BL1. EL1 and EL0 are given +access to Floating Point & Advanced SIMD registers by clearing the `CPACR.FPEN` +bits. + +#### Platform initialization + +BL2 does not perform any platform initialization that affects subsequent +stages of the ARM Trusted Firmware or normal world software. It copies the +information regarding the trusted SRAM populated by BL1 using a +platform-specific mechanism. It calculates the limits of DRAM (main memory) +to determine whether there is enough space to load the normal world software +images. A platform defined base address is used to specify the load address for +the BL3-1 image. It also defines the extents of memory available for use by the +BL3-2 image. + +#### Normal world image load + +BL2 loads the normal world firmware image (e.g. UEFI). BL2 relies on BL3-1 to +pass control to the normal world software image it loads. Hence, BL2 populates +a platform-specific area of memory with the entrypoint and Current Program +Status Register (`CPSR`) of the normal world software image. The entrypoint is +the load address of the normal world software image. The `CPSR` is determined as +specified in Section 5.13 of the [PSCI PDD] [PSCI]. This information is passed +to BL3-1. + +#### BL3-2 (Secure Payload) image load + +BL2 loads the optional BL3-2 image. The image executes in the secure world. BL2 +relies on BL3-1 to pass control to the BL3-2 image, if present. Hence, BL2 +populates a platform- specific area of memory with the entrypoint and Current +Program Status Register (`CPSR`) of the BL3-2 image. The entrypoint is the load +address of the BL3-2 image. The `CPSR` is initialized with Secure EL1 and Stack +pointer set to SP_EL1 (EL1h) as the mode, exception bits disabled (DAIF bits) +and AArch64 execution state. This information is passed to BL3-1. + +##### UEFI firmware load + +BL2 loads the BL3-3 (UEFI) image into non-secure memory as defined by the +platform (`0x88000000` for FVPs), and arranges for BL3-1 to pass control to that +location. As mentioned earlier, BL2 populates platform-specific memory with the +entrypoint and `CPSR` of the BL3-3 image. + +#### BL3-1 image load and execution + +BL2 execution continues as follows: + +1. BL2 loads the BL3-1 image into a platform-specific address in trusted SRAM + and the BL3-3 image into a platform specific address in non-secure DRAM. + The images are identified by the files `bl31.bin` and `bl33.bin` in + platform storage. If there is not enough memory to load the images or the + images are missing it leads to an assertion failure. If the BL3-1 image + loads successfully, BL1 updates the amount of trusted SRAM used and + available for use by BL3-1. This information is populated at a + platform-specific memory address. + +2. BL2 passes control back to BL1 by raising an SMC, providing BL1 with the + BL3-1 entrypoint. The exception is handled by the SMC exception handler + installed by BL1. + +3. BL1 turns off the MMU and flushes the caches. It clears the + `SCTLR_EL3.M/I/C` bits, flushes the data cache to the point of coherency + and invalidates the TLBs. + +4. BL1 passes control to BL3-1 at the specified entrypoint at EL3. + + +### BL3-1 + +The image for this stage is loaded by BL2 and BL1 passes control to BL3-1 at +EL3. BL3-1 executes solely in trusted SRAM. BL3-1 is linked against and +loaded at a platform-specific base address (more information can be found later +in this document). The functionality implemented by BL3-1 is as follows. + +#### Architectural initialization + +Currently, BL3-1 performs a similar architectural initialization to BL1 as +far as system register settings are concerned. Since BL1 code resides in ROM, +architectural initialization in BL3-1 allows override of any previous +initialization done by BL1. BL3-1 creates page tables to address the first +4GB of physical address space and initializes the MMU accordingly. It replaces +the exception vectors populated by BL1 with its own. BL3-1 exception vectors +signal error conditions in the same way as BL1 does if an unexpected +exception is raised. They implement more elaborate support for handling SMCs +since this is the only mechanism to access the runtime services implemented by +BL3-1 (PSCI for example). BL3-1 checks each SMC for validity as specified by +the [SMC calling convention PDD][SMCCC] before passing control to the required +SMC handler routine. + +#### Platform initialization + +BL3-1 performs detailed platform initialization, which enables normal world +software to function correctly. It also retrieves entrypoint information for +the normal world software image loaded by BL2 from the platform defined +memory address populated by BL2. + +* GICv2 initialization: + + - Enable group0 interrupts in the GIC CPU interface. + - Configure group0 interrupts to be asserted as FIQs. + - Disable the legacy interrupt bypass mechanism. + - Configure the priority mask register to allow interrupts of all + priorities to be signaled to the CPU interface. + - Mark SGIs 8-15, the secure physical timer interrupt (#29) and the + trusted watchdog interrupt (#56) as group0 (secure). + - Target the trusted watchdog interrupt to CPU0. + - Enable these group0 interrupts in the GIC distributor. + - Configure all other interrupts as group1 (non-secure). + - Enable signaling of group0 interrupts in the GIC distributor. + +* GICv3 initialization: + + If a GICv3 implementation is available in the platform, BL3-1 initializes + the GICv3 in GICv2 emulation mode with settings as described for GICv2 + above. + +* Power management initialization: + + BL3-1 implements a state machine to track CPU and cluster state. The state + can be one of `OFF`, `ON_PENDING`, `SUSPEND` or `ON`. All secondary CPUs are + initially in the `OFF` state. The cluster that the primary CPU belongs to is + `ON`; any other cluster is `OFF`. BL3-1 initializes the data structures that + implement the state machine, including the locks that protect them. BL3-1 + accesses the state of a CPU or cluster immediately after reset and before + the MMU is enabled in the warm boot path. It is not currently possible to + use 'exclusive' based spinlocks, therefore BL3-1 uses locks based on + Lamport's Bakery algorithm instead. BL3-1 allocates these locks in device + memory. They are accessible irrespective of MMU state. + +* Runtime services initialization: + + The only runtime service implemented by BL3-1 is PSCI. The complete PSCI API + is not yet implemented. The following functions are currently implemented: + + - `PSCI_VERSION` + - `CPU_OFF` + - `CPU_ON` + - `CPU_SUSPEND` + - `AFFINITY_INFO` + + The `CPU_ON`, `CPU_OFF` and `CPU_SUSPEND` functions implement the warm boot + path in ARM Trusted Firmware. `CPU_ON` and `CPU_OFF` have undergone testing + on all the supported FVPs. `CPU_SUSPEND` & `AFFINITY_INFO` have undergone + testing only on the AEM v8 Base FVP. Support for `AFFINITY_INFO` is still + experimental. Support for `CPU_SUSPEND` is stable for entry into power down + states. Standby states are currently not supported. `PSCI_VERSION` is + present but completely untested in this version of the software. + + Unsupported PSCI functions can be divided into ones that can return + execution to the caller and ones that cannot. The following functions + return with a error code as documented in the [Power State Coordination + Interface PDD] [PSCI]. + + - `MIGRATE` : -1 (NOT_SUPPORTED) + - `MIGRATE_INFO_TYPE` : 2 (Trusted OS is either not present or does not + require migration) + - `MIGRATE_INFO_UP_CPU` : 0 (Return value is UNDEFINED) + + The following unsupported functions do not return and signal an assertion + failure if invoked. + + - `SYSTEM_OFF` + - `SYSTEM_RESET` + + BL3-1 returns the error code `-1` if an SMC is raised for any other runtime + service. This behavior is mandated by the [SMC calling convention PDD] + [SMCCC]. + + +### BL3-2 (Secure Payload) image initialization + +BL2 is responsible for loading a BL3-2 image in memory specified by the platform. +BL3-1 provides an api that uses the entrypoint and memory layout information for +the BL3-2 image provided by BL2 to initialise BL3-2 in S-EL1. + + +### Normal world software execution + +BL3-1 uses the entrypoint information provided by BL2 to jump to the normal +world software image (BL3-3) at the highest available Exception Level (EL2 if +available, otherwise EL1). + + +3. Memory layout on FVP platforms +---------------------------------- + +On FVP platforms, we use the Trusted ROM and Trusted SRAM to store the trusted +firmware binaries. BL1 is originally sitting in the Trusted ROM. Its read-write +data are relocated at the base of the Trusted SRAM at runtime. BL1 loads BL2 +image near the top of the the trusted SRAM. BL2 loads BL3-1 image between BL1 +and BL2. This memory layout is illustrated by the following diagram. + + Trusted SRAM + +----------+ 0x04040000 + | | + |----------| + | BL2 | + |----------| + | | + |----------| + | BL31 | + |----------| + | | + |----------| + | BL1 (rw) | + +----------+ 0x04000000 + + Trusted ROM + +----------+ 0x04000000 + | BL1 (ro) | + +----------+ 0x00000000 + +Each bootloader stage image layout is described by its own linker script. The +linker scripts export some symbols into the program symbol table. Their values +correspond to particular addresses. The trusted firmware code can refer to these +symbols to figure out the image memory layout. + +Linker symbols follow the following naming convention in the trusted firmware. + +* `__<SECTION>_START__` + + Start address of a given section named `<SECTION>`. + +* `__<SECTION>_END__` + + End address of a given section named `<SECTION>`. If there is an alignment + constraint on the section's end address then `__<SECTION>_END__` corresponds + to the end address of the section's actual contents, rounded up to the right + boundary. Refer to the value of `__<SECTION>_UNALIGNED_END__` to know the + actual end address of the section's contents. + +* `__<SECTION>_UNALIGNED_END__` + + End address of a given section named `<SECTION>` without any padding or + rounding up due to some alignment constraint. + +* `__<SECTION>_SIZE__` + + Size (in bytes) of a given section named `<SECTION>`. If there is an + alignment constraint on the section's end address then `__<SECTION>_SIZE__` + corresponds to the size of the section's actual contents, rounded up to the + right boundary. In other words, `__<SECTION>_SIZE__ = __<SECTION>_END__ - + _<SECTION>_START__`. Refer to the value of `__<SECTION>_UNALIGNED_SIZE__` + to know the actual size of the section's contents. + +* `__<SECTION>_UNALIGNED_SIZE__` + + Size (in bytes) of a given section named `<SECTION>` without any padding or + rounding up due to some alignment constraint. In other words, + `__<SECTION>_UNALIGNED_SIZE__ = __<SECTION>_UNALIGNED_END__ - + __<SECTION>_START__`. + +Some of the linker symbols are mandatory as the trusted firmware code relies on +them to be defined. They are listed in the following subsections. Some of them +must be provided for each bootloader stage and some are specific to a given +bootloader stage. + +The linker scripts define some extra, optional symbols. They are not actually +used by any code but they help in understanding the bootloader images' memory +layout as they are easy to spot in the link map files. + +### Common linker symbols + +Early setup code needs to know the extents of the BSS section to zero-initialise +it before executing any C code. The following linker symbols are defined for +this purpose: + +* `__BSS_START__` This address must be aligned on a 16-byte boundary. +* `__BSS_SIZE__` + +Similarly, the coherent memory section must be zero-initialised. Also, the MMU +setup code needs to know the extents of this section to set the right memory +attributes for it. The following linker symbols are defined for this purpose: + +* `__COHERENT_RAM_START__` This address must be aligned on a page-size boundary. +* `__COHERENT_RAM_END__` This address must be aligned on a page-size boundary. +* `__COHERENT_RAM_UNALIGNED_SIZE__` + +### BL1's linker symbols + +BL1's early setup code needs to know the extents of the .data section to +relocate it from ROM to RAM before executing any C code. The following linker +symbols are defined for this purpose: + +* `__DATA_ROM_START__` This address must be aligned on a 16-byte boundary. +* `__DATA_RAM_START__` This address must be aligned on a 16-byte boundary. +* `__DATA_SIZE__` + +BL1's platform setup code needs to know the extents of its read-write data +region to figure out its memory layout. The following linker symbols are defined +for this purpose: + +* `__BL1_RAM_START__` This is the start address of BL1 RW data. +* `__BL1_RAM_END__` This is the end address of BL1 RW data. + +### BL2's and BL3-1's linker symbols + +Both BL2 and BL3-1 need to know the extents of their read-only section to set +the right memory attributes for this memory region in their MMU setup code. The +following linker symbols are defined for this purpose: + +* `__RO_START__` +* `__RO_END__` + +### How to choose the right base address for each bootloader stage image + +The current implementation of the image loader has some limitations. It is +designed to load images dynamically, at a load address chosen to minimize memory +fragmentation. The chosen image location can be either at the top or the bottom +of free memory. However, until this feature is fully functional, the code also +contains support for loading images at a link-time fixed address. + +BL1 is always loaded at address `0x0`. BL2 and BL3-1 are loaded at specified +locations in Trusted SRAM. The lack of dynamic image loader support means these +load addresses must currently be adjusted as the code grows. The individual +images must be linked against their ultimate runtime locations. + +BL2 is loaded near the top of the Trusted SRAM. BL3-1 is loaded between BL1 +and BL2. All three images are resident concurrently in Trusted RAM during boot +so overlaps are not permitted. + +The image end addresses can be determined from the link map files of the +different images. These are the `build/<platform>/<build-type>/bl<x>/bl<x>.map` +files, with `<x>` the stage bootloader. + +* `bl1.map` link map file provides `__BL1_RAM_END__` address. +* `bl2.map` link map file provides `__BL2_END__` address. +* `bl31.map` link map file provides `__BL31_END__` address. + +To prevent images from overlapping each other, the following constraints must be +enforced: + +1. `__BL1_RAM_END__ <= BL31_BASE` +2. `__BL31_END__ <= BL2_BASE` +3. `__BL2_END__ <= (<Top of Trusted SRAM>)` + +This is illustrated by the following memory layout diagram: + + +----------+ 0x04040000 + | | + |----------| __BL2_END__ + | BL2 | + |----------| BL2_BASE + | | + |----------| __BL31_END__ + | BL31 | + |----------| BL31_BASE + | | + |----------| __BL1_RAM_END__ + | BL1 (rw) | + +----------+ 0x04000000 + +Overlaps are detected during image linking as follows. + +Constraint 1 is enforced by BL1's linker script. If it is violated then the +linker will report an error while building BL1 to indicate that it doesn't +fit: + + aarch64-none-elf-ld: BL31 image overlaps BL1 image. + +This error means that the BL3-1 base address needs to be incremented. Ensure +that the new memory layout still obeys all constraints. + +Constraint 2 is enforced by BL3-1's linker script. If it is violated then the +linker will report an error while building BL3-1 to indicate that it doesn't +fit: + + aarch64-none-elf-ld: BL31 image overlaps BL2 image. + +This error can either mean that the BL3-1 base address needs to be decremented +or that BL2 base address needs to be incremented. Ensure that the new memory +layout still obeys all constraints. + +Constraint 3 is enforced by BL2's linker script. If it is violated then the +linker will report an error while building BL2 to indicate that it doesn't +fit. For example: + + aarch64-none-elf-ld: address 0x40400c8 of bl2.elf section `.bss' is not + within region `RAM' + +This error means that the BL2 base address needs to be decremented. Ensure that +the new memory layout still obeys all constraints. + +Since constraint checks are scattered across linker scripts, it is required to +`make clean` prior to building to ensure that all possible overlapping scenarios +are checked. + +The current implementation of the image loader can result in wasted space +because of the simplified data structure used to represent the extents of free +memory. For example, to load BL2 at address `0x0402D000`, the resulting memory +layout should be as follows: + + ------------ 0x04040000 + | | <- Free space (1) + |----------| + | BL2 | + |----------| BL2_BASE (0x0402D000) + | | <- Free space (2) + |----------| + | BL1 | + ------------ 0x04000000 + +In the current implementation, we need to specify whether BL2 is loaded at the +top or bottom of the free memory. BL2 is top-loaded so in the example above, +the free space (1) above BL2 is hidden, resulting in the following view of +memory: + + ------------ 0x04040000 + | | + | | + | BL2 | + |----------| BL2_BASE (0x0402D000) + | | <- Free space (2) + |----------| + | BL1 | + ------------ 0x04000000 + +BL3-1 is bottom-loaded above BL1. For example, if BL3-1 is bottom-loaded at +`0x0400E000`, the memory layout should look like this: + + ------------ 0x04040000 + | | + | | + | BL2 | + |----------| BL2_BASE (0x0402D000) + | | <- Free space (2) + | | + |----------| + | | + | BL31 | + |----------| BL31_BASE (0x0400E000) + | | <- Free space (3) + |----------| + | BL1 | + ------------ 0x04000000 + +But the free space (3) between BL1 and BL3-1 is wasted, resulting in the +following view: + + ------------ 0x04040000 + | | + | | + | BL2 | + |----------| BL2_BASE (0x0402D000) + | | <- Free space (2) + | | + |----------| + | | + | | + | BL31 | BL31_BASE (0x0400E000) + | | + |----------| + | BL1 | + ------------ 0x04000000 + + +4. Firmware Image Package (FIP) +-------------------------------- + +Using a Firmware Image Package (FIP) allows for packing bootloader images (and +potentially other payloads) into a single archive that can be loaded by the ARM +Trusted Firmware from non-volatile platform storage. A driver to load images +from a FIP has been added to the storage layer and allows a package to be read +from supported platform storage. A tool to create Firmware Image Packages is +also provided and described below. + +### Firmware Image Package layout + +The FIP layout consists of a table of contents (ToC) followed by payload data. +The ToC itself has a header followed by one or more table entries. The ToC is +terminated by an end marker entry. All ToC entries describe some payload data +that has been appended to the end of the binary package. With the information +provided in the ToC entry the corresponding payload data can be retrieved. + + ------------------ + | ToC Header | + |----------------| + | ToC Entry 0 | + |----------------| + | ToC Entry 1 | + |----------------| + | ToC End Marker | + |----------------| + | | + | Data 0 | + | | + |----------------| + | | + | Data 1 | + | | + ------------------ + +The ToC header and entry formats are described in the header file +`include/firmware_image_package.h`. This file is used by both the tool and the +ARM Trusted firmware. + +The ToC header has the following fields: + `name`: The name of the ToC. This is currently used to validate the header. + `serial_number`: A non-zero number provided by the creation tool + `flags`: Flags associated with this data. None are yet defined. + +A ToC entry has the following fields: + `uuid`: All files are referred to by a pre-defined Universally Unique + IDentifier [UUID] . The UUIDs are defined in + `include/firmware_image_package`. The platform translates the requested + image name into the corresponding UUID when accessing the package. + `offset_address`: The offset address at which the corresponding payload data + can be found. The offset is calculated from the ToC base address. + `size`: The size of the corresponding payload data in bytes. + `flags`: Flags associated with this entry. Non are yet defined. + +### Firmware Image Package creation tool + +The FIP creation tool can be used to pack specified images into a binary package +that can be loaded by the ARM Trusted Firmware from platform storage. The tool +currently only supports packing bootloader images. Additional image definitions +can be added to the tool as required. + +The tool can be found in `tools/fip_create`. + +### Loading from a Firmware Image Package (FIP) + +The Firmware Image Package (FIP) driver can load images from a binary package on +non-volatile platform storage. For the FVPs this currently NOR FLASH. For +information on how to load a FIP into FVP NOR FLASH see the "Running the +software" section. + +Bootloader images are loaded according to the platform policy as specified in +`plat/<platform>/plat_io_storage.c`. For the FVPs this means the platform will +attempt to load images from a Firmware Image Package located at the start of NOR +FLASH0. + +Currently the FVPs policy only allows for loading of known images. The platform +policy can be modified to add additional images. + + +5. Code Structure +------------------ + +Trusted Firmware code is logically divided between the three boot loader +stages mentioned in the previous sections. The code is also divided into the +following categories (present as directories in the source code): + +* **Architecture specific.** This could be AArch32 or AArch64. +* **Platform specific.** Choice of architecture specific code depends upon + the platform. +* **Common code.** This is platform and architecture agnostic code. +* **Library code.** This code comprises of functionality commonly used by all + other code. +* **Stage specific.** Code specific to a boot stage. +* **Drivers.** + +Each boot loader stage uses code from one or more of the above mentioned +categories. Based upon the above, the code layout looks like this: + + Directory Used by BL1? Used by BL2? Used by BL3? + bl1 Yes No No + bl2 No Yes No + bl31 No No Yes + arch Yes Yes Yes + plat Yes Yes Yes + drivers Yes No Yes + common Yes Yes Yes + lib Yes Yes Yes + +All assembler files have the `.S` extension. The linker source files for each +boot stage have the extension `.ld.S`. These are processed by GCC to create the +linker scripts which have the extension `.ld`. + +FDTs provide a description of the hardware platform and are used by the Linux +kernel at boot time. These can be found in the `fdts` directory. + + +6. References +-------------- + +1. Trusted Board Boot Requirements CLIENT PDD (ARM DEN 0006B-5). Available + under NDA through your ARM account representative. + +2. [Power State Coordination Interface PDD (ARM DEN 0022B.b)][PSCI]. + +3. [SMC Calling Convention PDD (ARM DEN 0028A)][SMCCC]. + + + +- - - - - - - - - - - - - - - - - - - - - - - - - - + +_Copyright (c) 2013-2014, ARM Limited and Contributors. All rights reserved._ + + +[PSCI]: http://infocenter.arm.com/help/topic/com.arm.doc.den0022b/index.html "Power State Coordination Interface PDD (ARM DEN 0022B.b)" +[SMCCC]: http://infocenter.arm.com/help/topic/com.arm.doc.den0028a/index.html "SMC Calling Convention PDD (ARM DEN 0028A)" +[UUID]: https://tools.ietf.org/rfc/rfc4122.txt "A Universally Unique IDentifier (UUID) URN Namespace" diff --git a/docs/user-guide.md b/docs/user-guide.md index 8c03fcd..01a6d73 100644 --- a/docs/user-guide.md +++ b/docs/user-guide.md @@ -4,45 +4,39 @@ ARM Trusted Firmware User Guide Contents : 1. Introduction -2. Using the Software -3. Firmware Design -4. References +2. Host machine requirements +3. Tools +4. Building the Trusted Firmware +5. Obtaining the normal world software +6. Running the software 1. Introduction ---------------- +This document describes how to build ARM Trusted Firmware and run it with a +tested set of other software components using defined configurations on 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. -The ARM Trusted Firmware implements a subset of the Trusted Board Boot -Requirements (TBBR) Platform Design Document (PDD) [1] for ARM reference -platforms. The TBB sequence starts when the platform is powered on and runs up -to the stage where it hands-off control to firmware running in the normal -world in DRAM. This is the cold boot path. +This document should be used in conjunction with the [Firmware Design]. -The ARM Trusted Firmware also implements the Power State Coordination Interface -([PSCI]) PDD [2] as a runtime service. PSCI is the interface from normal world -software to firmware implementing power management use-cases (for example, -secondary CPU boot, hotplug and idle). Normal world software can access ARM -Trusted Firmware runtime services via the ARM SMC (Secure Monitor Call) -instruction. The SMC instruction must be used as mandated by the [SMC Calling -Convention PDD][SMCCC] [3]. - -2. Using the Software ----------------------- - -### Host machine requirements +2. Host machine requirements +----------------------------- The minimum recommended machine specification for building the software and -running the FVP (Fixed Virtual Platform) model 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. +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 12.04.02 (64-bit). Packages used for building the software were installed from that distribution unless otherwise specified. -### Tools +3. Tools +--------- The following tools are required to use the ARM Trusted Firmware: @@ -69,7 +63,8 @@ The following tools are required to use the ARM Trusted Firmware: * (Optional) For debugging, ARM [Development Studio 5 (DS-5)][DS-5] v5.17. -### Building the Trusted Firmware +4. Building the Trusted Firmware +--------------------------------- To build the software for the FVPs, follow these steps: @@ -108,8 +103,8 @@ To build the software for the FVPs, follow these steps: * `build/<platform>/<build-type>/fip.bin` - For more information on the `fip.bin` image see the "Firmware Image Package" - section below + For more information on FIPs, see the "Firmware Image Package" section in + the [Firmware Design]. 4. Copy the `bl1.bin` and `fip.bin` binary files to the directory from which the FVP will be launched. Symbolic links of the same names may be created @@ -126,7 +121,62 @@ To build the software for the FVPs, follow these steps: make realclean -#### Debugging options +### Creating a Firmware Image Package + +FIPs are automatically created as part of the build instructions described in +the previous section. It is also possible to independently build the FIP +creation tool and FIPs if required. To do this, follow these steps: + +Build the tool: + + make -C tools/fip_create + +It is recommended to remove the build artifacts before rebuilding: + + make -C tools/fip_create clean + +Create a Firmware package that contains existing FVP BL2 and BL3-1 images: + + # fip_create --help to print usage information + # fip_create <fip_name> <images to add> [--dump to show result] + ./tools/fip_create/fip_create fip.bin --dump \ + --bl2 build/fvp/debug/bl2.bin --bl31 build/fvp/debug/bl31.bin + + Firmware Image Package ToC: + --------------------------- + - Trusted Boot Firmware BL2: offset=0x88, size=0x81E8 + file: 'build/fvp/debug/bl2.bin' + - EL3 Runtime Firmware BL3-1: offset=0x8270, size=0xC218 + file: 'build/fvp/debug/bl31.bin' + --------------------------- + Creating "fip.bin" + +View the contents of an existing Firmware package: + + ./tools/fip_create/fip_create fip.bin --dump + + Firmware Image Package ToC: + --------------------------- + - Trusted Boot Firmware BL2: offset=0x88, size=0x81E8 + - EL3 Runtime Firmware BL3-1: offset=0x8270, size=0xC218 + --------------------------- + +Existing package entries can be individially updated: + + # Change the BL2 from Debug to Release version + ./tools/fip_create/fip_create fip.bin --dump \ + --bl2 build/fvp/release/bl2.bin + + Firmware Image Package ToC: + --------------------------- + - Trusted Boot Firmware BL2: offset=0x88, size=0x7240 + file: 'build/fvp/release/bl2.bin' + - EL3 Runtime Firmware BL3-1: offset=0x72C8, size=0xC218 + --------------------------- + Updating "fip.bin" + + +### Debugging options To compile a debug version and make the build more verbose use @@ -157,7 +207,7 @@ Extra debug options can be passed to the build system by setting `CFLAGS`: NOTE: The Foundation FVP does not provide a debugger interface. -#### Checking source code style +### 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 @@ -180,9 +230,10 @@ set the BASE_COMMIT variable to your desired branch. By default, BASE_COMMIT is set to 'origin/master'. -### Obtaining the normal world software +5. Obtaining the normal world software +--------------------------------------- -#### Obtaining EDK2 +### Obtaining EDK2 Potentially any kind of non-trusted firmware may be used with the ARM Trusted Firmware but the software has only been tested with the EFI Development Kit 2 @@ -246,7 +297,7 @@ these steps: instructions in the "Building the Trusted Firmware" section. -#### Obtaining a Linux kernel +### Obtaining a Linux kernel The software has been verified using a Linux kernel based on version 3.13. Patches have been applied in order to enable the CPU idle feature. @@ -283,7 +334,7 @@ be done as follows (GICv2 support only): 3. Copy the Linux image `arch/arm64/boot/Image` to the working directory from where the FVP is launched. Alternatively a symbolic link may be used. -#### Obtaining the Flattened Device Trees +### 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 @@ -322,13 +373,13 @@ and MMC support, and has only one CPU cluster. Copy the chosen FDT blob as `fdt.dtb` to the directory from which the FVP is launched. Alternatively a symbolic link may be used. -#### Obtaining a root file-system +### Obtaining a root file-system To prepare a Linaro LAMP based Open Embedded file-system, the following instructions can be used as a guide. The file-system can be provided to Linux via VirtioBlock or as a RAM-disk. Both methods are described below. -##### Prepare VirtioBlock +#### Prepare VirtioBlock To prepare a VirtioBlock file-system, do the following: @@ -392,7 +443,7 @@ To prepare a VirtioBlock file-system, do the following: correct and that read permission is correctly set on the file-system image file. -##### Prepare RAM-disk +#### Prepare RAM-disk To prepare a RAM-disk root file-system, do the following: @@ -415,7 +466,8 @@ To prepare a RAM-disk root file-system, do the following: launched from. Alternatively a symbolic link may be used. -### Running the software +6. Running the software +------------------------ This version of the ARM Trusted Firmware has been tested on the following ARM FVPs (64-bit versions only). @@ -435,7 +487,7 @@ ARM Trusted Firmware and normal world software behavior is provided below. The Foundation FVP is a cut down version of the AArch64 Base FVP. It can be downloaded for free from [ARM's website][ARM FVP website]. -#### Running on the Foundation FVP +### Running on the Foundation FVP The following `Foundation_v8` parameters should be used to boot Linux with 4 CPUs using the ARM Trusted Firmware. @@ -463,7 +515,7 @@ emulation mode. The memory mapped addresses `0x0` and `0x8000000` correspond to the start of trusted ROM and NOR FLASH0 respectively. -#### Running on the AEMv8 Base FVP +### Running on the AEMv8 Base FVP The following `FVP_Base_AEMv8A-AEMv8A` parameters should be used to boot Linux with 8 CPUs using the ARM Trusted Firmware. @@ -491,7 +543,7 @@ section above). -C bp.flashloader0.fname="<path-to>/<FIP-binary>" \ -C bp.virtioblockdevice.image_path="<path-to>/<file-system-image>" -#### Running on the Cortex-A57-A53 Base FVP +### Running on the Cortex-A57-A53 Base FVP The following `FVP_Base_Cortex-A57x4-A53x4` model parameters should be used to boot Linux with 8 CPUs using the ARM Trusted Firmware. @@ -572,7 +624,6 @@ legacy VE memory map: Explicit configuration of the `SYS_ID` register is not required. - #### Configuring AEMv8 Base FVP GIC for legacy VE memory map The following parameters configure the AEMv8 Base FVP to use GICv2 with the @@ -599,822 +650,14 @@ The `bp.variant` parameter corresponds to the build variant field of the detect the legacy VE memory map while configuring the GIC. -3. Firmware Design -------------------- - -The cold boot path starts when the platform is physically turned on. One of -the CPUs released from reset is chosen as the primary CPU, and the remaining -CPUs are considered secondary CPUs. The primary CPU is chosen through -platform-specific means. The cold boot path is mainly executed by the primary -CPU, other than essential CPU initialization executed by all CPUs. The -secondary CPUs are kept in a safe platform-specific state until the primary -CPU has performed enough initialization to boot them. - -The cold boot path in this implementation of the ARM Trusted Firmware is divided -into three stages (in order of execution): - -* Boot Loader stage 1 (BL1) -* Boot Loader stage 2 (BL2) -* Boot Loader stage 3 (BL3-1). The '1' distinguishes this from other 3rd level - boot loader stages. - -The ARM Fixed Virtual Platforms (FVPs) provide trusted ROM, trusted SRAM and -trusted DRAM regions. Each boot loader stage uses one or more of these -memories for its code and data. - - -### BL1 - -This stage begins execution from the platform's reset vector in trusted ROM at -EL3. BL1 code starts at `0x00000000` (trusted ROM) in the FVP memory map. The -BL1 data section is placed at the start of trusted SRAM, `0x04000000`. The -functionality implemented by this stage is as follows. - -#### Determination of boot path - -Whenever a CPU is released from reset, BL1 needs to distinguish between a warm -boot and a cold boot. This is done using a platform-specific mechanism. The -ARM FVPs implement a simple power controller at `0x1c100000`. The `PSYS` -register (`0x10`) is used to distinguish between a cold and warm boot. This -information is contained in the `PSYS.WK[25:24]` field. Additionally, a -per-CPU mailbox is maintained in trusted DRAM (`0x00600000`), to which BL1 -writes an entrypoint. Each CPU jumps to this entrypoint upon warm boot. During -cold boot, BL1 places the secondary CPUs in a safe platform-specific state while -the primary CPU executes the remaining cold boot path as described in the -following sections. - -#### Architectural initialization - -BL1 performs minimal architectural initialization as follows. - -* Exception vectors - - BL1 sets up simple exception vectors for both synchronous and asynchronous - exceptions. The default behavior upon receiving an exception is to set a - status code. In the case of the FVP this code is written to the Versatile - Express System LED register in the following format: - - SYS_LED[0] - Security state (Secure=0/Non-Secure=1) - SYS_LED[2:1] - Exception Level (EL3=0x3, EL2=0x2, EL1=0x1, EL0=0x0) - SYS_LED[7:3] - Exception Class (Sync/Async & origin). The values for - each exception class are: - - 0x0 : Synchronous exception from Current EL with SP_EL0 - 0x1 : IRQ exception from Current EL with SP_EL0 - 0x2 : FIQ exception from Current EL with SP_EL0 - 0x3 : System Error exception from Current EL with SP_EL0 - 0x4 : Synchronous exception from Current EL with SP_ELx - 0x5 : IRQ exception from Current EL with SP_ELx - 0x6 : FIQ exception from Current EL with SP_ELx - 0x7 : System Error exception from Current EL with SP_ELx - 0x8 : Synchronous exception from Lower EL using aarch64 - 0x9 : IRQ exception from Lower EL using aarch64 - 0xa : FIQ exception from Lower EL using aarch64 - 0xb : System Error exception from Lower EL using aarch64 - 0xc : Synchronous exception from Lower EL using aarch32 - 0xd : IRQ exception from Lower EL using aarch32 - 0xe : FIQ exception from Lower EL using aarch32 - 0xf : System Error exception from Lower EL using aarch32 - - A write to the LED register reflects in the System LEDs (S6LED0..7) in the - CLCD window of the FVP. This behavior is because this boot loader stage - does not expect to receive any exceptions other than the SMC exception. - For the latter, BL1 installs a simple stub. The stub expects to receive - only a single type of SMC (determined by its function ID in the general - purpose register `X0`). This SMC is raised by BL2 to make BL1 pass control - to BL3-1 (loaded by BL2) at EL3. Any other SMC leads to an assertion - failure. - -* MMU setup - - BL1 sets up EL3 memory translation by creating page tables to cover the - first 4GB of physical address space. This covers all the memories and - peripherals needed by BL1. - -* Control register setup - - `SCTLR_EL3`. Instruction cache is enabled by setting the `SCTLR_EL3.I` - bit. Alignment and stack alignment checking is enabled by setting the - `SCTLR_EL3.A` and `SCTLR_EL3.SA` bits. Exception endianness is set to - little-endian by clearing the `SCTLR_EL3.EE` bit. - - - `CPUECTLR`. When the FVP includes a model of a specific ARM processor - implementation (for example A57 or A53), then intra-cluster coherency is - enabled by setting the `CPUECTLR.SMPEN` bit. The AEMv8 Base FVP is - inherently coherent so does not implement `CPUECTLR`. - - - `SCR`. Use of the HVC instruction from EL1 is enabled by setting the - `SCR.HCE` bit. FIQ exceptions are configured to be taken in EL3 by - setting the `SCR.FIQ` bit. The register width of the next lower - exception level is set to AArch64 by setting the `SCR.RW` bit. External - Aborts and SError Interrupts are configured to be taken in EL3 by - setting the `SCR.EA` bit. - - - `CPTR_EL3`. Accesses to the `CPACR_EL1` register from EL1 or EL2, or the - `CPTR_EL2` register from EL2 are configured to not trap to EL3 by - clearing the `CPTR_EL3.TCPAC` bit. Access to the trace functionality is - configured not to trap to EL3 by clearing the `CPTR_EL3.TTA` bit. - Instructions that access the registers associated with Floating Point - and Advanced SIMD execution are configured to not trap to EL3 by - clearing the `CPTR_EL3.TFP` bit. - - - `CNTFRQ_EL0`. The `CNTFRQ_EL0` register is programmed with the base - frequency of the system counter, which is retrieved from the first entry - in the frequency modes table. - - - Generic Timer. The system level implementation of the generic timer is - enabled through the memory mapped interface. - -#### Platform initialization - -BL1 enables issuing of snoop and DVM (Distributed Virtual Memory) requests from -the CCI-400 slave interface corresponding to the cluster that includes the -primary CPU. BL1 also initializes UART0 (PL011 console), which enables access to -the `printf` family of functions. - -#### BL2 image load and execution - -BL1 execution continues as follows: - -1. BL1 determines the amount of free trusted SRAM memory available by - calculating the extent of its own data section, which also resides in - trusted SRAM. BL1 loads a BL2 raw binary image from platform storage, at a - platform-specific base address. The filename of the BL2 raw binary image - must be `bl2.bin`. If the BL2 image file is not present or if there is not - enough free trusted SRAM the following error message is printed: - - "Failed to load boot loader stage 2 (BL2) firmware." - - If the load is successful, BL1 updates the limits of the remaining free - trusted SRAM. It also populates information about the amount of trusted - SRAM used by the BL2 image. The exact load location of the image is - provided as a base address in the platform header. Further description of - the memory layout can be found later in this document. - -2. BL1 prints the following string from the primary CPU to indicate successful - execution of the BL1 stage: - - "Booting trusted firmware boot loader stage 1" - -3. BL1 passes control to the BL2 image at Secure EL1, starting from its load - address. - -4. BL1 also passes information about the amount of trusted SRAM used and - available for use. This information is populated at a platform-specific - memory address. - - -### BL2 - -BL1 loads and passes control to BL2 at Secure EL1. BL2 is linked against and -loaded at a platform-specific base address (more information can be found later -in this document). The functionality implemented by BL2 is as follows. - -#### Architectural initialization - -BL2 performs minimal architectural initialization required for subsequent -stages of the ARM Trusted Firmware and normal world software. It sets up -Secure EL1 memory translation by creating page tables to address the first 4GB -of the physical address space in a similar way to BL1. EL1 and EL0 are given -access to Floating Point & Advanced SIMD registers by clearing the `CPACR.FPEN` -bits. - -#### Platform initialization - -BL2 does not perform any platform initialization that affects subsequent -stages of the ARM Trusted Firmware or normal world software. It copies the -information regarding the trusted SRAM populated by BL1 using a -platform-specific mechanism. It calculates the limits of DRAM (main memory) -to determine whether there is enough space to load the normal world software -images. A platform defined base address is used to specify the load address for -the BL3-1 image. It also defines the extents of memory available for use by the -BL3-2 image. - -#### Normal world image load - -BL2 loads the normal world firmware image (e.g. UEFI). BL2 relies on BL3-1 to -pass control to the normal world software image it loads. Hence, BL2 populates -a platform-specific area of memory with the entrypoint and Current Program -Status Register (`CPSR`) of the normal world software image. The entrypoint is -the load address of the normal world software image. The `CPSR` is determined as -specified in Section 5.13 of the [PSCI PDD] [PSCI]. This information is passed -to BL3-1. - -#### BL3-2 (Secure Payload) image load - -BL2 loads the optional BL3-2 image. The image executes in the secure world. BL2 -relies on BL3-1 to pass control to the BL3-2 image, if present. Hence, BL2 -populates a platform- specific area of memory with the entrypoint and Current -Program Status Register (`CPSR`) of the BL3-2 image. The entrypoint is the load -address of the BL3-2 image. The `CPSR` is initialized with Secure EL1 and Stack -pointer set to SP_EL1 (EL1h) as the mode, exception bits disabled (DAIF bits) -and AArch64 execution state. This information is passed to BL3-1. - -##### UEFI firmware load - -BL2 loads the BL3-3 (UEFI) image into non-secure memory as defined by the -platform (`0x88000000` for FVPs), and arranges for BL3-1 to pass control to that -location. As mentioned earlier, BL2 populates platform-specific memory with the -entrypoint and `CPSR` of the BL3-3 image. - -#### BL3-1 image load and execution - -BL2 execution continues as follows: - -1. BL2 loads the BL3-1 image into a platform-specific address in trusted SRAM - and the BL3-3 image into a platform specific address in non-secure DRAM. - The images are identified by the files `bl31.bin` and `bl33.bin` in - platform storage. If there is not enough memory to load the images or the - images are missing it leads to an assertion failure. If the BL3-1 image - loads successfully, BL1 updates the amount of trusted SRAM used and - available for use by BL3-1. This information is populated at a - platform-specific memory address. - -2. BL2 passes control back to BL1 by raising an SMC, providing BL1 with the - BL3-1 entrypoint. The exception is handled by the SMC exception handler - installed by BL1. - -3. BL1 turns off the MMU and flushes the caches. It clears the - `SCTLR_EL3.M/I/C` bits, flushes the data cache to the point of coherency - and invalidates the TLBs. - -4. BL1 passes control to BL3-1 at the specified entrypoint at EL3. - - -### BL3-1 - -The image for this stage is loaded by BL2 and BL1 passes control to BL3-1 at -EL3. BL3-1 executes solely in trusted SRAM. BL3-1 is linked against and -loaded at a platform-specific base address (more information can be found later -in this document). The functionality implemented by BL3-1 is as follows. - -#### Architectural initialization - -Currently, BL3-1 performs a similar architectural initialization to BL1 as -far as system register settings are concerned. Since BL1 code resides in ROM, -architectural initialization in BL3-1 allows override of any previous -initialization done by BL1. BL3-1 creates page tables to address the first -4GB of physical address space and initializes the MMU accordingly. It replaces -the exception vectors populated by BL1 with its own. BL3-1 exception vectors -signal error conditions in the same way as BL1 does if an unexpected -exception is raised. They implement more elaborate support for handling SMCs -since this is the only mechanism to access the runtime services implemented by -BL3-1 (PSCI for example). BL3-1 checks each SMC for validity as specified by -the [SMC calling convention PDD][SMCCC] before passing control to the required -SMC handler routine. - -#### Platform initialization - -BL3-1 performs detailed platform initialization, which enables normal world -software to function correctly. It also retrieves entrypoint information for -the normal world software image loaded by BL2 from the platform defined -memory address populated by BL2. - -* GICv2 initialization: - - - Enable group0 interrupts in the GIC CPU interface. - - Configure group0 interrupts to be asserted as FIQs. - - Disable the legacy interrupt bypass mechanism. - - Configure the priority mask register to allow interrupts of all - priorities to be signaled to the CPU interface. - - Mark SGIs 8-15, the secure physical timer interrupt (#29) and the - trusted watchdog interrupt (#56) as group0 (secure). - - Target the trusted watchdog interrupt to CPU0. - - Enable these group0 interrupts in the GIC distributor. - - Configure all other interrupts as group1 (non-secure). - - Enable signaling of group0 interrupts in the GIC distributor. - -* GICv3 initialization: - - If a GICv3 implementation is available in the platform, BL3-1 initializes - the GICv3 in GICv2 emulation mode with settings as described for GICv2 - above. - -* Power management initialization: - - BL3-1 implements a state machine to track CPU and cluster state. The state - can be one of `OFF`, `ON_PENDING`, `SUSPEND` or `ON`. All secondary CPUs are - initially in the `OFF` state. The cluster that the primary CPU belongs to is - `ON`; any other cluster is `OFF`. BL3-1 initializes the data structures that - implement the state machine, including the locks that protect them. BL3-1 - accesses the state of a CPU or cluster immediately after reset and before - the MMU is enabled in the warm boot path. It is not currently possible to - use 'exclusive' based spinlocks, therefore BL3-1 uses locks based on - Lamport's Bakery algorithm instead. BL3-1 allocates these locks in device - memory. They are accessible irrespective of MMU state. - -* Runtime services initialization: - - The only runtime service implemented by BL3-1 is PSCI. The complete PSCI API - is not yet implemented. The following functions are currently implemented: - - - `PSCI_VERSION` - - `CPU_OFF` - - `CPU_ON` - - `CPU_SUSPEND` - - `AFFINITY_INFO` - - The `CPU_ON`, `CPU_OFF` and `CPU_SUSPEND` functions implement the warm boot - path in ARM Trusted Firmware. `CPU_ON` and `CPU_OFF` have undergone testing - on all the supported FVPs. `CPU_SUSPEND` & `AFFINITY_INFO` have undergone - testing only on the AEM v8 Base FVP. Support for `AFFINITY_INFO` is still - experimental. Support for `CPU_SUSPEND` is stable for entry into power down - states. Standby states are currently not supported. `PSCI_VERSION` is - present but completely untested in this version of the software. - - Unsupported PSCI functions can be divided into ones that can return - execution to the caller and ones that cannot. The following functions - return with a error code as documented in the [Power State Coordination - Interface PDD] [PSCI]. - - - `MIGRATE` : -1 (NOT_SUPPORTED) - - `MIGRATE_INFO_TYPE` : 2 (Trusted OS is either not present or does not - require migration) - - `MIGRATE_INFO_UP_CPU` : 0 (Return value is UNDEFINED) - - The following unsupported functions do not return and signal an assertion - failure if invoked. - - - `SYSTEM_OFF` - - `SYSTEM_RESET` - - BL3-1 returns the error code `-1` if an SMC is raised for any other runtime - service. This behavior is mandated by the [SMC calling convention PDD] - [SMCCC]. - - -### BL3-2 (Secure Payload) image initialization - -BL2 is responsible for loading a BL3-2 image in memory specified by the platform. -BL3-1 provides an api that uses the entrypoint and memory layout information for -the BL3-2 image provided by BL2 to initialise BL3-2 in S-EL1. - - -### Normal world software execution - -BL3-1 uses the entrypoint information provided by BL2 to jump to the normal -world software image (BL3-3) at the highest available Exception Level (EL2 if -available, otherwise EL1). - - -### Memory layout on FVP platforms - -On FVP platforms, we use the Trusted ROM and Trusted SRAM to store the trusted -firmware binaries. BL1 is originally sitting in the Trusted ROM. Its read-write -data are relocated at the base of the Trusted SRAM at runtime. BL1 loads BL2 -image near the top of the the trusted SRAM. BL2 loads BL3-1 image between BL1 -and BL2. This memory layout is illustrated by the following diagram. - - Trusted SRAM - +----------+ 0x04040000 - | | - |----------| - | BL2 | - |----------| - | | - |----------| - | BL31 | - |----------| - | | - |----------| - | BL1 (rw) | - +----------+ 0x04000000 - - Trusted ROM - +----------+ 0x04000000 - | BL1 (ro) | - +----------+ 0x00000000 - -Each bootloader stage image layout is described by its own linker script. The -linker scripts export some symbols into the program symbol table. Their values -correspond to particular addresses. The trusted firmware code can refer to these -symbols to figure out the image memory layout. - -Linker symbols follow the following naming convention in the trusted firmware. - -* `__<SECTION>_START__` - - Start address of a given section named `<SECTION>`. - -* `__<SECTION>_END__` - - End address of a given section named `<SECTION>`. If there is an alignment - constraint on the section's end address then `__<SECTION>_END__` corresponds - to the end address of the section's actual contents, rounded up to the right - boundary. Refer to the value of `__<SECTION>_UNALIGNED_END__` to know the - actual end address of the section's contents. - -* `__<SECTION>_UNALIGNED_END__` - - End address of a given section named `<SECTION>` without any padding or - rounding up due to some alignment constraint. - -* `__<SECTION>_SIZE__` - - Size (in bytes) of a given section named `<SECTION>`. If there is an - alignment constraint on the section's end address then `__<SECTION>_SIZE__` - corresponds to the size of the section's actual contents, rounded up to the - right boundary. In other words, `__<SECTION>_SIZE__ = __<SECTION>_END__ - - _<SECTION>_START__`. Refer to the value of `__<SECTION>_UNALIGNED_SIZE__` - to know the actual size of the section's contents. - -* `__<SECTION>_UNALIGNED_SIZE__` - - Size (in bytes) of a given section named `<SECTION>` without any padding or - rounding up due to some alignment constraint. In other words, - `__<SECTION>_UNALIGNED_SIZE__ = __<SECTION>_UNALIGNED_END__ - - __<SECTION>_START__`. - -Some of the linker symbols are mandatory as the trusted firmware code relies on -them to be defined. They are listed in the following subsections. Some of them -must be provided for each bootloader stage and some are specific to a given -bootloader stage. - -The linker scripts define some extra, optional symbols. They are not actually -used by any code but they help in understanding the bootloader images' memory -layout as they are easy to spot in the link map files. - -#### Common linker symbols - -Early setup code needs to know the extents of the BSS section to zero-initialise -it before executing any C code. The following linker symbols are defined for -this purpose: - -* `__BSS_START__` This address must be aligned on a 16-byte boundary. -* `__BSS_SIZE__` - -Similarly, the coherent memory section must be zero-initialised. Also, the MMU -setup code needs to know the extents of this section to set the right memory -attributes for it. The following linker symbols are defined for this purpose: - -* `__COHERENT_RAM_START__` This address must be aligned on a page-size boundary. -* `__COHERENT_RAM_END__` This address must be aligned on a page-size boundary. -* `__COHERENT_RAM_UNALIGNED_SIZE__` - -#### BL1's linker symbols - -BL1's early setup code needs to know the extents of the .data section to -relocate it from ROM to RAM before executing any C code. The following linker -symbols are defined for this purpose: - -* `__DATA_ROM_START__` This address must be aligned on a 16-byte boundary. -* `__DATA_RAM_START__` This address must be aligned on a 16-byte boundary. -* `__DATA_SIZE__` - -BL1's platform setup code needs to know the extents of its read-write data -region to figure out its memory layout. The following linker symbols are defined -for this purpose: - -* `__BL1_RAM_START__` This is the start address of BL1 RW data. -* `__BL1_RAM_END__` This is the end address of BL1 RW data. - -#### BL2's and BL3-1's linker symbols - -Both BL2 and BL3-1 need to know the extents of their read-only section to set -the right memory attributes for this memory region in their MMU setup code. The -following linker symbols are defined for this purpose: - -* `__RO_START__` -* `__RO_END__` - -#### How to choose the right base address for each bootloader stage image - -The current implementation of the image loader has some limitations. It is -designed to load images dynamically, at a load address chosen to minimize memory -fragmentation. The chosen image location can be either at the top or the bottom -of free memory. However, until this feature is fully functional, the code also -contains support for loading images at a link-time fixed address. - -BL1 is always loaded at address `0x0`. BL2 and BL3-1 are loaded at specified -locations in Trusted SRAM. The lack of dynamic image loader support means these -load addresses must currently be adjusted as the code grows. The individual -images must be linked against their ultimate runtime locations. - -BL2 is loaded near the top of the Trusted SRAM. BL3-1 is loaded between BL1 -and BL2. All three images are resident concurrently in Trusted RAM during boot -so overlaps are not permitted. - -The image end addresses can be determined from the link map files of the -different images. These are the `build/<platform>/<build-type>/bl<x>/bl<x>.map` -files, with `<x>` the stage bootloader. - -* `bl1.map` link map file provides `__BL1_RAM_END__` address. -* `bl2.map` link map file provides `__BL2_END__` address. -* `bl31.map` link map file provides `__BL31_END__` address. - -To prevent images from overlapping each other, the following constraints must be -enforced: - -1. `__BL1_RAM_END__ <= BL31_BASE` -2. `__BL31_END__ <= BL2_BASE` -3. `__BL2_END__ <= (<Top of Trusted SRAM>)` - -This is illustrated by the following memory layout diagram: - - +----------+ 0x04040000 - | | - |----------| __BL2_END__ - | BL2 | - |----------| BL2_BASE - | | - |----------| __BL31_END__ - | BL31 | - |----------| BL31_BASE - | | - |----------| __BL1_RAM_END__ - | BL1 (rw) | - +----------+ 0x04000000 - -Overlaps are detected during image linking as follows. - -Constraint 1 is enforced by BL1's linker script. If it is violated then the -linker will report an error while building BL1 to indicate that it doesn't -fit: - - aarch64-none-elf-ld: BL31 image overlaps BL1 image. - -This error means that the BL3-1 base address needs to be incremented. Ensure -that the new memory layout still obeys all constraints. - -Constraint 2 is enforced by BL3-1's linker script. If it is violated then the -linker will report an error while building BL3-1 to indicate that it doesn't -fit: - - aarch64-none-elf-ld: BL31 image overlaps BL2 image. - -This error can either mean that the BL3-1 base address needs to be decremented -or that BL2 base address needs to be incremented. Ensure that the new memory -layout still obeys all constraints. - -Constraint 3 is enforced by BL2's linker script. If it is violated then the -linker will report an error while building BL2 to indicate that it doesn't -fit. For example: - - aarch64-none-elf-ld: address 0x40400c8 of bl2.elf section `.bss' is not - within region `RAM' - -This error means that the BL2 base address needs to be decremented. Ensure that -the new memory layout still obeys all constraints. - -Since constraint checks are scattered across linker scripts, it is required to -`make clean` prior to building to ensure that all possible overlapping scenarios -are checked. - -The current implementation of the image loader can result in wasted space -because of the simplified data structure used to represent the extents of free -memory. For example, to load BL2 at address `0x0402D000`, the resulting memory -layout should be as follows: - - ------------ 0x04040000 - | | <- Free space (1) - |----------| - | BL2 | - |----------| BL2_BASE (0x0402D000) - | | <- Free space (2) - |----------| - | BL1 | - ------------ 0x04000000 - -In the current implementation, we need to specify whether BL2 is loaded at the -top or bottom of the free memory. BL2 is top-loaded so in the example above, -the free space (1) above BL2 is hidden, resulting in the following view of -memory: - - ------------ 0x04040000 - | | - | | - | BL2 | - |----------| BL2_BASE (0x0402D000) - | | <- Free space (2) - |----------| - | BL1 | - ------------ 0x04000000 - -BL3-1 is bottom-loaded above BL1. For example, if BL3-1 is bottom-loaded at -`0x0400E000`, the memory layout should look like this: - - ------------ 0x04040000 - | | - | | - | BL2 | - |----------| BL2_BASE (0x0402D000) - | | <- Free space (2) - | | - |----------| - | | - | BL31 | - |----------| BL31_BASE (0x0400E000) - | | <- Free space (3) - |----------| - | BL1 | - ------------ 0x04000000 - -But the free space (3) between BL1 and BL3-1 is wasted, resulting in the -following view: - - ------------ 0x04040000 - | | - | | - | BL2 | - |----------| BL2_BASE (0x0402D000) - | | <- Free space (2) - | | - |----------| - | | - | | - | BL31 | BL31_BASE (0x0400E000) - | | - |----------| - | BL1 | - ------------ 0x04000000 - - -### Firmware Image Package (FIP) - -Using a Firmware Image Package (FIP) allows for packing bootloader images (and -potentially other payloads) into a single archive that can be loaded by the ARM -Trusted Firmware from non-volatile platform storage. A driver to load images -from a FIP has been added to the storage layer and allows a package to be read -from supported platform storage. A tool to create Firmware Image Packages is -also provided and described below. - -#### Firmware Image Package layout - -The FIP layout consists of a table of contents (ToC) followed by payload data. -The ToC itself has a header followed by one or more table entries. The ToC is -terminated by an end marker entry. All ToC entries describe some payload data -that has been appended to the end of the binary package. With the information -provided in the ToC entry the corresponding payload data can be retrieved. - - ------------------ - | ToC Header | - |----------------| - | ToC Entry 0 | - |----------------| - | ToC Entry 1 | - |----------------| - | ToC End Marker | - |----------------| - | | - | Data 0 | - | | - |----------------| - | | - | Data 1 | - | | - ------------------ - -The ToC header and entry formats are described in the header file -`include/firmware_image_package.h`. This file is used by both the tool and the -ARM Trusted firmware. - -The ToC header has the following fields: - `name`: The name of the ToC. This is currently used to validate the header. - `serial_number`: A non-zero number provided by the creation tool - `flags`: Flags associated with this data. None are yet defined. - -A ToC entry has the following fields: - `uuid`: All files are referred to by a pre-defined Universally Unique - IDentifier [UUID] . The UUIDs are defined in - `include/firmware_image_package`. The platform translates the requested - image name into the corresponding UUID when accessing the package. - `offset_address`: The offset address at which the corresponding payload data - can be found. The offset is calculated from the ToC base address. - `size`: The size of the corresponding payload data in bytes. - `flags`: Flags associated with this entry. Non are yet defined. - -#### Creating a Firmware Image Package - -The FIP creation tool can be used to pack specified images into a binary package -that can be loaded by the ARM Trusted Firmware from platform storage. The tool -currently only supports packing bootloader images. Additional image definitions -can be added to the tool as required. - -The tool can be found in `tools/fip_create`. Instructions on how to build and -use the tool follow. - -Build the tool: - - make -C tools/fip_create - -It is recommended to remove the build artifacts before rebuilding: - - make -C tools/fip_create clean - -Create a Firmware package that contains existing FVP BL2 and BL3-1 images: - - # fip_create --help to print usage information - # fip_create <fip_name> <images to add> [--dump to show result] - ./tools/fip_create/fip_create fip.bin --dump \ - --bl2 build/fvp/debug/bl2.bin --bl31 build/fvp/debug/bl31.bin - - Firmware Image Package ToC: - --------------------------- - - Trusted Boot Firmware BL2: offset=0x88, size=0x81E8 - file: 'build/fvp/debug/bl2.bin' - - EL3 Runtime Firmware BL3-1: offset=0x8270, size=0xC218 - file: 'build/fvp/debug/bl31.bin' - --------------------------- - Creating "fip.bin" - -View the contents of an existing Firmware package: - - ./tools/fip_create/fip_create fip.bin --dump - - Firmware Image Package ToC: - --------------------------- - - Trusted Boot Firmware BL2: offset=0x88, size=0x81E8 - - EL3 Runtime Firmware BL3-1: offset=0x8270, size=0xC218 - --------------------------- - -Existing package entries can be individially updated: - - # Change the BL2 from Debug to Release version - ./tools/fip_create/fip_create fip.bin --dump \ - --bl2 build/fvp/release/bl2.bin - - Firmware Image Package ToC: - --------------------------- - - Trusted Boot Firmware BL2: offset=0x88, size=0x7240 - file: 'build/fvp/release/bl2.bin' - - EL3 Runtime Firmware BL3-1: offset=0x72C8, size=0xC218 - --------------------------- - Updating "fip.bin" - - -#### Loading from a Firmware Image Package (FIP) - -The Firmware Image Package (FIP) driver can load images from a binary package on -non-volatile platform storage. For the FVPs this currently NOR FLASH. For -information on how to load a FIP into FVP NOR FLASH see the "Running the -software" section. - -Bootloader images are loaded according to the platform policy as specified in -`plat/<platform>/plat_io_storage.c`. For the FVPs this means the platform will -attempt to load images from a Firmware Image Package located at the start of NOR -FLASH0. - -Currently the FVPs policy only allows for loading of known images. The platform -policy can be modified to add additional images. - - -### Code Structure - -Trusted Firmware code is logically divided between the three boot loader -stages mentioned in the previous sections. The code is also divided into the -following categories (present as directories in the source code): - -* **Architecture specific.** This could be AArch32 or AArch64. -* **Platform specific.** Choice of architecture specific code depends upon - the platform. -* **Common code.** This is platform and architecture agnostic code. -* **Library code.** This code comprises of functionality commonly used by all - other code. -* **Stage specific.** Code specific to a boot stage. -* **Drivers.** - -Each boot loader stage uses code from one or more of the above mentioned -categories. Based upon the above, the code layout looks like this: - - Directory Used by BL1? Used by BL2? Used by BL3? - bl1 Yes No No - bl2 No Yes No - bl31 No No Yes - arch Yes Yes Yes - plat Yes Yes Yes - drivers Yes No Yes - common Yes Yes Yes - lib Yes Yes Yes - -All assembler files have the `.S` extension. The linker source files for each -boot stage have the extension `.ld.S`. These are processed by GCC to create the -linker scripts which have the extension `.ld`. - -FDTs provide a description of the hardware platform and are used by the Linux -kernel at boot time. These can be found in the `fdts` directory. - - -4. References --------------- - -1. Trusted Board Boot Requirements CLIENT PDD (ARM DEN 0006B-5). Available - under NDA through your ARM account representative. - -2. [Power State Coordination Interface PDD (ARM DEN 0022B.b)][PSCI]. - -3. [SMC Calling Convention PDD (ARM DEN 0028A)][SMCCC]. - - - - - - - - - - - - - - - - - - - - - - - - - - - - _Copyright (c) 2013-2014, ARM Limited and Contributors. All rights reserved._ -[Change Log]: change-log.md +[Firmware Design]: ./firmware-design.md [ARM FVP website]: http://www.arm.com/fvp [Linaro Toolchain]: http://releases.linaro.org/13.09/components/toolchain/binaries/ [EDK2]: http://github.com/tianocore/edk2 [DS-5]: http://www.arm.com/products/tools/software-tools/ds-5/index.php -[PSCI]: http://infocenter.arm.com/help/topic/com.arm.doc.den0022b/index.html "Power State Coordination Interface PDD (ARM DEN 0022B.b)" -[SMCCC]: http://infocenter.arm.com/help/topic/com.arm.doc.den0028a/index.html "SMC Calling Convention PDD (ARM DEN 0028A)" -[UUID]: https://tools.ietf.org/rfc/rfc4122.txt "A Universally Unique IDentifier (UUID) URN Namespace" |