Information for BareMetalArmCortexASingleAngelTrap
This page provides detailed information about the arm.ovpworld.org BareMetalArmCortexASingleAngelTrap Virtual Platform / Virtual Prototype.
Bare Metal Platform for an ARM Cortex-A series Processor (default Cortex-A9UP) that uses the ARM Angel Trap for semihosting. The bare metal platform instantiates a single ARM Cortex-A9UP processor instance. The processor operates using little endian data ordering. It creates contiguous memory from 0x00000000 to 0xFFFFFFFF. The ICM platform can be passed any application compiled to an ARM elf (axf) format, that uses ARM Angel traps for semihosting,. It may also be passed a new variant to be used (default Cortex-A9UP) ./platform.OS.exe application.CROSS.elf [model variant]
Open Source Apache 2.0
BareMetal platform for execution of ARM binary files compiled with Linaro 32-bit CrossCompiler toolchain for Cortex-A.
The BareMetalArmCortexASingleAngelTrap virtual platform is located in an Imperas/OVP installation at the VLNV: arm.ovpworld.org / platform / BareMetalArmCortexASingleAngelTrap / 1.0.
Table 1: Components in platform
Command Line Control of the Platform
Table 2: Platform Built-in Arguments
|allargs||allargs||The Command line parser will accept the complete imperas argument set. Note that this option is ignored in some Imperas products|
For example: myplatform.exe -help
Some command line arguments require a value to be provided.
For example: myplatform.exe -program myimagefile.elf
Platform Specific Command Line Arguments
No platform specific command line arguments have been specified.
Processor [arm.ovpworld.org/processor/arm/1.0] instance: cpu1
Processor model type: 'arm' variant 'Cortex-A9UP' definition
Imperas OVP processor models support multiple variants and details of the variants implemented in this model can be found in:
- the Imperas installation located at ImperasLib/source/arm.ovpworld.org/processor/arm/1.0/doc
- the OVP website: OVP_Model_Specific_Information_arm_Cortex-A9UP.pdf
ARM Processor Model
Usage of binary model under license governing simulator usage.
Note that for models of ARM CPUs the license includes the following terms:
Licensee is granted a non-exclusive, worldwide, non-transferable, revocable licence to:
If no source is being provided to the Licensee: use and copy only (no modifications rights are granted) the model for the sole purpose of designing, developing, analyzing, debugging, testing, verifying, validating and optimizing software which: (a) (i) is for ARM based systems; and (ii) does not incorporate the ARM Models or any part thereof; and (b) such ARM Models may not be used to emulate an ARM based system to run application software in a production or live environment.
If source code is being provided to the Licensee: use, copy and modify the model for the sole purpose of designing, developing, analyzing, debugging, testing, verifying, validating and optimizing software which: (a) (i) is for ARM based systems; and (ii) does not incorporate the ARM Models or any part thereof; and (b) such ARM Models may not be used to emulate an ARM based system to run application software in a production or live environment.
In the case of any Licensee who is either or both an academic or educational institution the purposes shall be limited to internal use.
Except to the extent that such activity is permitted by applicable law, Licensee shall not reverse engineer, decompile, or disassemble this model. If this model was provided to Licensee in Europe, Licensee shall not reverse engineer, decompile or disassemble the Model for the purposes of error correction.
The License agreement does not entitle Licensee to manufacture in silicon any product based on this model.
The License agreement does not entitle Licensee to use this model for evaluating the validity of any ARM patent.
Source of model available under separate Imperas Software License Agreement.
Instruction pipelines are not modeled in any way. All instructions are assumed to complete immediately. This means that instruction barrier instructions (e.g. ISB, CP15ISB) are treated as NOPs, with the exception of any undefined instruction behavior, which is modeled. The model does not implement speculative fetch behavior. The branch cache is not modeled.
Caches and write buffers are not modeled in any way. All loads, fetches and stores complete immediately and in order, and are fully synchronous (as if the memory was of Strongly Ordered or Device-nGnRnE type). Data barrier instructions (e.g. DSB, CP15DSB) are treated as NOPs, with the exception of any undefined instruction behavior, which is modeled. Cache manipulation instructions are implemented as NOPs, with the exception of any undefined instruction behavior, which is modeled.
Real-world timing effects are not modeled: all instructions are assumed to complete in a single cycle.
Performance Monitors are implemented as a register interface only except for the cycle counter, which is implemented assuming one instruction per cycle.
TLBs are architecturally-accurate but not device accurate. This means that all TLB maintenance and address translation operations are fully implemented but the cache is larger than in the real device.
Models have been extensively tested by Imperas. ARM Cortex-A models have been successfully used by customers to simulate SMP Linux, Ubuntu Desktop, VxWorks and ThreadX on Xilinx Zynq virtual platforms.
Thumb-2 instructions are supported.
Trivial Jazelle extension is implemented.
Security extensions are implemented (also known as TrustZone). Non-secure accesses can be made visible externally by connecting the processor to a 41-bit physical bus, in which case bits 39..0 give the true physical address and bit 40 is the NS bit.
VMSA secure and non-secure address translation is implemented.
Advanced SIMD and Floating-Point Features
SIMD and VFP instructions are implemented.
The model implements trapped exceptions if FPTrap is set to 1 in MVFR0 (for AArch32) or MVFR0_EL1 (for AArch64). When floating point exception traps are taken, cumulative exception flags are not updated (in other words, cumulative flag state is always the same as prior to instruction execution, even for SIMD instructions). When multiple enabled exceptions are raised by a single floating point operation, the exception reported is the one in least-significant bit position in FPSCR (for AArch32) or FPCR (for AArch64). When multiple enabled exceptions are raised by different SIMD element computations, the exception reported is selected from the lowest-index-number SIMD operation. Contact Imperas if requirements for exception reporting differ from these.
Trapped exceptions not are implemented in this variant (FPTrap=0)
It is possible to enable model debug messages in various categories. This can be done statically using the "override_debugMask" parameter, or dynamically using the "debugflags" command. Enabled messages are specified using a bitmask value, as follows:
Value 0x004: enable debugging of MMU/MPU mappings
Value 0x080: enable debugging of all system register accesses.
Value 0x100: enable debugging of all traps of system register accesses.
Value 0x200: enable verbose debugging of other miscellaneous behavior (for example, the reason why a particular instruction is undefined).
Value 0x400: enable debugging of Performance Monitor timers
All other bits in the debug bitmask are reserved and must not be set to non-zero values.
AArch32 Unpredictable Behavior
Many AArch32 instruction behaviors are described in the ARM ARM as CONSTRAINED UNPREDICTABLE. This section describes how such situations are handled by this model.
Equal Target Registers
Some instructions allow the specification of two target registers (for example, double-width SMULL, or some VMOV variants), and such instructions are CONSTRAINED UNPREDICTABLE if the same target register is specified in both positions. In this model, such instructions are treated as UNDEFINED.
Floating Point Load/Store Multiple Lists
Instructions that load or store a list of floating point registers (e.g. VSTM, VLDM, VPUSH, VPOP) are CONSTRAINED UNPREDICTABLE if either the uppermost register in the specified range is greater than 32 or (for 64-bit registers) if more than 16 registers are specified. In this model, such instructions are treated as UNDEFINED.
Floating Point VLD[2-4]/VST[2-4] Range Overflow
Instructions that load or store a fixed number of floating point registers (e.g. VST2, VLD2) are CONSTRAINED UNPREDICTABLE if the upper register bound exceeds the number of implemented floating point registers. In this model, these instructions load and store using modulo 32 indexing (consistent with AArch64 instructions with similar behavior).
If-Then (IT) Block Constraints
Where the behavior of an instruction in an if-then (IT) block is described as CONSTRAINED UNPREDICTABLE, this model treats that instruction as UNDEFINED.
Use of R13
In architecture variants before ARMv8, use of R13 was described as CONSTRAINED UNPREDICTABLE in many circumstances. From ARMv8, most of these situations are no longer considered unpredictable. This model allows R13 to be used like any other GPR, consistent with the ARMv8 specification.
Use of R15
Use of R15 is described as CONSTRAINED UNPREDICTABLE in many circumstances. This model allows such use to be configured using the parameter "unpredictable" as follows:
Value "undefined": any reference to R15 in such a situation is treated as UNDEFINED;
Value "nop": any reference to R15 in such a situation causes the instruction to be treated as a NOP;
Value "raz_wi": any reference to R15 in such a situation causes the instruction to be treated as a RAZ/WI (that is, R15 is read as zero and write-ignored);
Value "execute": any reference to R15 in such a situation is executed using the current value of R15 on read, and writes to R15 are allowed (but are not interworking).
Value "assert": any reference to R15 in such a situation causes the simulation to halt with an assertion message (allowing any such unpredictable uses to be easily identified).
In this variant, the default is "undefined".
This model implements a number of non-architectural pseudo-registers and other features to facilitate integration.
Memory Transaction Query
Two registers are intended for use within memory callback functions to provide additional information about the current memory access. Register transactPL indicates the processor execution level of the current access (0-3). Note that for load/store translate instructions (e.g. LDRT, STRT) the reported execution level will be 0, indicating an EL0 access. Register transactAT indicates the type of memory access: 0 for a normal read or write; and 1 for a physical access resulting from a page table walk.
Page Table Walk Query
A banked set of registers provides information about the most recently completed page table walk. There are up to six banks of registers: bank 0 is for stage 1 walks, bank 1 is for stage 2 walks, and banks 2-5 are for stage 2 walks initiated by stage 1 level 0-3 entry lookups, respectively. Banks 1-5 are present only for processors with virtualization extensions. The currently active bank can be set using register PTWBankSelect. Register PTWBankValid is a bitmask indicating which banks contain valid data: for example, the value 0xb indicates that banks 0, 1 and 3 contain valid data.
Within each bank, there are registers that record addresses and values read during that page table walk. Register PTWBase records the table base address. Registers PTWAddressL0-PTWAddressL3 record the addresses of level 0 to level 3 entries read, respectively, and register PTWAddressValid is a bitmask indicating which address registers contain valid data: for example, the value 0xe indicates that PTWAddressL1-PTWAddressL3 are valid but PTWAddressL0 is not. Registers PTWValueL0-PTWValueL3 contain entry values read at level 0 to level 3. Register PTWInput contains the input address that starts a walk and Register PTWOutput contains the result address (valid only if the page table walk completes). Register PTWValueValid is a bitmask indicating which value registers contain valid data: bits 0-3 indicate PTWValueL0-PTWValueL3, respectively, bit 4 indicates PTWBase, bit 5 indicates PTWInput and bit 6 indicates PTWOutput.
Artifact Page Table Walks
Registers are also available to enable a simulation environment to initiate an artifact page table walk (for example, to determine the ultimate PA corresponding to a given VA). Register PTWI_EL1S initiates a secure EL1 table walk for a fetch. Register PTWD_EL1S initiates a secure EL1 table walk for a load or store (note that current ARM processors have unified TLBs, so these registers are synonymous). Registers PTW[ID]_EL1NS initiate walks for non-secure EL1 accesses. Registers PTW[ID]_EL2 initiate EL2 walks. Registers PTW[ID]_S2 initiate stage 2 walks. Registers PTW[ID]_EL3 initiate AArch64 EL3 walks. Finally, registers PTW[ID]_current initiate current-mode walks (useful in a memory callback context). Each walk fills the query registers described above.
MMU and Page Table Walk Events
Two events are available that allow a simulation environment to be notified on MMU and page table walk actions. Event mmuEnable triggers when any MMU is enabled or disabled. Event pageTableWalk triggers on completion of any page table walk (including artifact walks).
Artifact Address Translations
A simulation environment can trigger an artifact address translation operation by writing to the architectural address translation registers (e.g. ATS1CPR). The results of such translations are written to an integration support register artifactPAR, instead of the architectural PAR register. This means that such artifact writes will not perturb architectural state.
Halt Reason Introspection
An artifact register HaltReason can be read to determine the reason or reasons that a processor is halted. This register is a bitfield, with the following encoding: bit 0 indicates the processor has executed a wait-for-event (WFE) instruction; bit 1 indicates the processor has executed a wait-for-interrupt (WFI) instruction; and bit 2 indicates the processor is held in reset.
System Register Access Monitor
If parameter "enableSystemMonitorBus" is True, an artifact 32-bit bus "SystemMonitor" is enabled for each PE. Every system register read or write by that PE is then visible as a read or write on this artifact bus, and can therefore be monitored using callbacks installed in the client environment (use opBusReadMonitorAdd/opBusWriteMonitorAdd or icmAddBusReadCallback/icmAddBusWriteCallback, depending on the client API). The format of the address on the bus is as follows:
bits 31:26 - zero
bit 25 - 1 if AArch64 access, 0 if AArch32 access
bit 24 - 1 if non-secure access, 0 if secure access
bits 23:20 - CRm value
bits 19:16 - CRn value
bits 15:12 - op2 value
bits 11:8 - op1 value
bits 7:4 - op0 value (AArch64) or coprocessor number (AArch32)
bits 3:0 - zero
As an example, to view non-secure writes to writes to CNTFRQ_EL0 in AArch64 state, install a write monitor on address range 0x020e0330:0x020e0333.
System Register Implementation
If parameter "enableSystemBus" is True, an artifact 32-bit bus "System" is enabled for each PE. Slave callbacks installed on this bus can be used to implement modified system register behavior (use opBusSlaveNew or icmMapExternalMemory, depending on the client API). The format of the address on the bus is the same as for the system monitor bus, described above.
Several parameters can be specified when a processor is instanced in a platform. For this processor instance 'cpu1' it has been instanced with the following parameters:
Table 3: Processor Instance 'cpu1' Parameters (Configurations)
|endian||little||Select processor endian (big or little)|
|mips||100||The nominal MIPS for the processor|
|semihostname||armAngel||The VLNV name of a Semihost library|
Table 4: Processor Instance 'cpu1' Parameters (Attributes)
Memory Map for processor 'cpu1' bus: 'bus1'
Processor instance 'cpu1' is connected to bus 'bus1' using master port 'INSTRUCTION'.
Processor instance 'cpu1' is connected to bus 'bus1' using master port 'DATA'.
Table 5: Memory Map ( 'cpu1' / 'bus1' [width: 32] )
|Lo Address||Hi Address||Instance||Component|
Net Connections to processor: 'cpu1'
There are no nets connected to this processor.
Information on the BareMetalArmCortexASingleAngelTrap Virtual Platform can also be found on other web sites :
www.ovpworld.org has the library pages http://www.ovpworld.org/library/wikka.php?wakka=CategoryPlatform
www.imperas.com has more information on the model library
http://www.ovpworld.org: VMI Morph Time (VMI MT) API Reference Guide
http://www.ovpworld.org: Writing C Platforms and Modules using the OVP OP API
Currently available Imperas / OVP Virtual Platforms / Virtual Prototypes.