Resolving Conflicts Between RTOS Timekeeping and Uninterruptable Trusted Computing
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arXiv
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| Main Authors: | , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866918470601408512 |
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| author | Neto, Antonio Joia Laohajirapan, Amarin Rattanavipanon, Norrathep Nunes, Ivan De Oliveira |
| author_facet | Neto, Antonio Joia Laohajirapan, Amarin Rattanavipanon, Norrathep Nunes, Ivan De Oliveira |
| contents | Trusted Execution Environments (TEEs) on low-power microcontrollers (e.g., ARM TrustZone-M) enable isolation of Secure and Non-Secure software but still require both worlds to share resources, including interrupt controllers. In this model, real-time applications and real-time operating systems (RTOS-s) are executed in the Non-Secure sub-system, whereas the Secure sub-system is typically reserved for a small set of pre-defined security (e.g., cryptographic) operations referred to as trusted computing services. However, many RTOS-s rely on periodic interrupts (SysTicks) to advance their own notion of time (time-keeping), and the delivery of this interrupt is essential for preserving real-time behavior. On the other hand, the security of many trusted computing services requires atomicity vis-a-vis the Non-Secure sub-system (where the RTOS resides), precluding SysTick handling.
This paper first characterizes this conflict and then introduces a Secure-driven time synchronization mechanism in which the Secure World measures elapsed time and compensates the Non-Secure RTOS by unobtrusively updating the RTOS time-keeping data structures with the appropriate number of missed ticks before re-enabling interrupts and resuming the execution of the Non-Secure system. This approach restores a consistent, monotonic notion of time across worlds and enables secure coexistence of trusted computing services and RTOS-s on microcontrollers. Importantly, the proposed approach requires no modifications to the underlying RTOS and yields no significant run-time overhead. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_24277 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Resolving Conflicts Between RTOS Timekeeping and Uninterruptable Trusted Computing Neto, Antonio Joia Laohajirapan, Amarin Rattanavipanon, Norrathep Nunes, Ivan De Oliveira Cryptography and Security Trusted Execution Environments (TEEs) on low-power microcontrollers (e.g., ARM TrustZone-M) enable isolation of Secure and Non-Secure software but still require both worlds to share resources, including interrupt controllers. In this model, real-time applications and real-time operating systems (RTOS-s) are executed in the Non-Secure sub-system, whereas the Secure sub-system is typically reserved for a small set of pre-defined security (e.g., cryptographic) operations referred to as trusted computing services. However, many RTOS-s rely on periodic interrupts (SysTicks) to advance their own notion of time (time-keeping), and the delivery of this interrupt is essential for preserving real-time behavior. On the other hand, the security of many trusted computing services requires atomicity vis-a-vis the Non-Secure sub-system (where the RTOS resides), precluding SysTick handling. This paper first characterizes this conflict and then introduces a Secure-driven time synchronization mechanism in which the Secure World measures elapsed time and compensates the Non-Secure RTOS by unobtrusively updating the RTOS time-keeping data structures with the appropriate number of missed ticks before re-enabling interrupts and resuming the execution of the Non-Secure system. This approach restores a consistent, monotonic notion of time across worlds and enables secure coexistence of trusted computing services and RTOS-s on microcontrollers. Importantly, the proposed approach requires no modifications to the underlying RTOS and yields no significant run-time overhead. |
| title | Resolving Conflicts Between RTOS Timekeeping and Uninterruptable Trusted Computing |
| topic | Cryptography and Security |
| url | https://arxiv.org/abs/2604.24277 |