DFA (Dependent Failure Analysis)

Persistency DFA		status: valid security: NO safety: ASIL_B
tags: persistency realizes: wp__feature_dfa
doc__persistency_dfa		Generic Document

The DFA for the feature Persistency is performed. To show evidence that all failure initiators are considered, the applicability has to be filled out in the following tables. For all applicable failure initiators, the DFA has to be performed.

Dependent Failure Initiators

Shared resources

The dependent failure initiators related to shared resources are not applicable for the features. The shared resources will be considered in the platform DFA.

Communication between the two elements

Receiving function is affected by information that is false, lost, sent multiple times, or in the wrong order etc. from the sender.

Table 21 DFA communication between elements

ID	Violation cause communication between elements	Applicability	Rationale
CO_01_01	Information passed via argument through a function call, or via writing/reading a variable being global to the two software functions (data flow)	no	Failure initiator not applicable at persistency, so no mitigation is needed.
CO_01_02	Data or message corruption / repetition / loss / delay / masquerading or incorrect addressing of information	no	Persistency is developed fully deterministic. So no corruption, repetition, loss, delay, masquerading or incorrect addressing of information is expected.
CO_01_03	Insertion / sequence of information	no	Subset of CO_01_02.
CO_01_04	Corruption of information, inconsistent data	no	Subset of CO_01_02.
CO_01_05	Asymmetric information sent from a sender to multiple receivers, so that not all defined receivers have the same information	no	Failure initiator not applicable at persistency, so no mitigation is needed.
CO_01_06	Information from a sender received by only a subset of the receivers	no	Failure initiator not applicable at persistency, so no mitigation is needed.
CO_01_07	Blocking access to a communication channel	no	Failure initiator not applicable at persistency, so no mitigation is needed.

Shared information inputs

Same information input used by multiple functions.

Table 22 DFA shared information inputs

ID	Violation cause shared information inputs	Applicability	Rationale
SI_01_02	Configuration data	no	Failure initiator not applicable at persistency, so no mitigation is needed.
SI_01_03	Constants, or variables, being global to the two software functions	no	Failure initiator not applicable at persistency, so no mitigation is needed.
SI_01_04	Basic software passes data (read from hardware register and converted into logical information) to two applications software functions	no	Failure initiator not applicable at persistency, so no mitigation is needed.
SI_01_05	Data / function parameter arguments / messages delivered by software function to more than one other function	no	Failure initiator not applicable at persistency, so no mitigation is needed.

Unintended impact

Unintended impacts to function due to various failures.

Table 23 DFA unintended impact

ID	Violation cause unintended impact	Applicability	Rationale
UI_01_01	Memory miss-allocation and leaks	no	Will be considered at the platform DFA.
UI_01_02	Read/Write access to memory allocated to another software element	no	Will be considered at the platform DFA.
UI_01_03	Stack/Buffer under-/overflow	no	Might happens but very unlikely in RUST. Will be considered at the platform DFA.
UI_01_04	Deadlocks	no	Deadlocks are not caused by the KVS, but by the application.
UI_01_05	Livelocks	no	Same consideration as done in UI_01_04.
UI_01_06	Blocking of execution	no	Failure initiator not applicable at persistency, so no mitigation is needed.
UI_01_07	Incorrect allocation of execution time	no	Failure initiator not applicable at persistency, so no mitigation is needed.
UI_01_08	Incorrect execution flow	no	Failure initiator not applicable at persistency, so no mitigation is needed.
UI_01_09	Incorrect synchronization between software elements	no	Failure initiator not applicable at persistency, so no mitigation is needed.
UI_01_10	CPU time depletion	no	Failure initiator not applicable at persistency, so no mitigation is needed. Will be anylysed at the platform DFA.
UI_01_11	Memory depletion	no	Failure initiator not applicable at persistency, so no mitigation is needed. Will be anylysed at the platform DFA.
UI_01_12	Other HW unavailability	no	Failure initiator not applicable at persistency, so no mitigation is needed.

DFA

For all identified applicable failure initiators, the DFA is performed in the following section.

• Execution blocking will make persistency not available.

Persistency execution blocking		status: valid
failure_effect: Blocking of execution. This will lead to a unavailability of the persistency feature. failure_id: UI_01_06 sufficient: yes mitigated_by: aou_req__persistency__appl_exec violates: feat_arc_sta__persistency__static
Execution blocking will make persistency not available.
feat_saf_dfa__persistency__execution_blocking		Feature DFA (Dependent Failure Analysis)