scholarly journals Scenario-Aware Program Specialization for Timing Predictability

2021 ◽  
Vol 18 (4) ◽  
pp. 1-26
Author(s):  
Joscha Benz ◽  
Oliver Bringmann
Keyword(s):  
Program Analysis ◽  
Control Flow ◽  
Wcet Analysis ◽  
Specific System ◽  
Worst Case ◽  
Program Specialization ◽  
Operating Modes ◽  
Source Level ◽  
Dependent Flow ◽  
Timing Simulation

The successful application of static program analysis strongly depends on flow facts of a program such as loop bounds, control-flow constraints, and operating modes. This problem heavily affects the design of real-time systems, since static program analyses are a prerequisite to determine the timing behavior of a program. For example, this becomes obvious in worst-case execution time (WCET) analysis, which is often infeasible without user-annotated flow facts. Moreover, many timing simulation approaches use statically derived timings of partial program paths to reduce simulation overhead. Annotating flow facts on binary or source level is either error-prone and tedious, or requires specialized compilers that can transform source-level annotations along with the program during optimization. To overcome these obstacles, so-called scenarios can be used. Scenarios are a design-time methodology that describe a set of possible system parameters, such as image resolutions, operating modes, or application-dependent flow facts. The information described by a scenario is unknown in general but known and constant for a specific system. In this article, 1 we present a methodology for scenario-aware program specialization to improve timing predictability. Moreover, we provide an implementation of this methodology for embedded software written in C/C++. We show the effectiveness of our approach by evaluating its impact on WCET analysis using almost all of TACLeBench–achieving an average reduction of WCET of 31%. In addition, we provide a thorough qualitative and evaluation-based comparison to closely related work, as well as two case studies.

Interactive WCET Prediction with Warning for Timeout Risk

2017 ◽  
Vol 31 (05) ◽  
pp. 1750012 ◽  
Author(s):  
Fanqi Meng ◽  
Xiaohong Su ◽  
Zhaoyang Qu
Keyword(s):  
Execution Time ◽  
Control Flow ◽  
Real Time Systems ◽  
Wcet Analysis ◽  
Running Speed ◽  
Worst Case ◽  
Worst Case Execution Time ◽  
Level Model ◽  
Hard Real Time ◽  
Time Systems

Worst case execution time (WCET) analysis is essential for exposing timeliness defects when developing hard real-time systems. However, it is too late to fix timeliness defects cheaply since developers generally perform WCET analysis in a final verification phase. To help developers quickly identify real timeliness defects in an early programming phase, a novel interactive WCET prediction with warning for timeout risk is proposed. The novelty is that the approach not only fast estimates WCET based on a control flow tree (CFT), but also assesses the estimated WCET with a trusted level by a lightweight false path analysis. According to the trusted levels, corresponding warnings will be triggered once the estimated WCET exceeds a preset safe threshold. Hence developers can identify real timeliness defects more timely and efficiently. To this end, we first analyze the reasons of the overestimation of CFT-based WCET calculation; then we propose a trusted level model of timeout risks; for recognizing the structural patterns of timeout risks, we develop a risk data counting algorithm; and we also give some tactics for applying our approach more effectively. Experimental results show that our approach has almost the same running speed compared with the fast and interactive WCET analysis, but it saves more time in identifying real timeliness defects.

scholarly journals Reconciling optimization with secure compilation

2021 ◽  
Vol 5 (OOPSLA) ◽  
pp. 1-30
Author(s):  
Son Tuan Vu ◽  
Albert Cohen ◽  
Arnaud De Grandmaison ◽  
Christophe Guillon ◽  
Karine Heydemann
Keyword(s):  
Side Effects ◽  
Control Flow ◽  
Partial Ordering ◽  
Input Output ◽  
Machine Code ◽  
Fine Grained ◽  
Control Flow Integrity ◽  
Correct Execution ◽  
Source Level ◽  
And Performance

Software protections against side-channel and physical attacks are essential to the development of secure applications. Such protections are meaningful at machine code or micro-architectural level, but they typically do not carry observable semantics at source level. This renders them susceptible to miscompilation, and security engineers embed input/output side-effects to prevent optimizing compilers from altering them. Yet these side-effects are error-prone and compiler-dependent. The current practice involves analyzing the generated machine code to make sure security or privacy properties are still enforced. These side-effects may also be too expensive in fine-grained protections such as control-flow integrity. We introduce observations of the program state that are intrinsic to the correct execution of security protections, along with means to specify and preserve observations across the compilation flow. Such observations complement the input/output semantics-preservation contract of compilers. We introduce an opacification mechanism to preserve and enforce a partial ordering of observations. This approach is compatible with a production compiler and does not incur any modification to its optimization passes. We validate the effectiveness and performance of our approach on a range of benchmarks, expressing the secure compilation of these applications in terms of observations to be made at specific program points.

scholarly journals Syntactic Accidents in Program Analysis: On the Impact of the CPS Transformation

2001 ◽  
Vol 8 (54) ◽  
Author(s):  
Daniel Damian ◽  
Olivier Danvy
Keyword(s):  
Program Analysis ◽  
Partial Evaluation ◽  
Flow Analysis ◽  
Control Flow ◽  
Time Analysis ◽  
Binding Time ◽  
The Impact ◽  
Positive Effect ◽  
Binding Time Analysis ◽  
Control Flow Analysis

We show that a non-duplicating transformation into continuation-passing style (CPS) has no effect on control-flow analysis, a positive effect on binding-time analysis for traditional partial evaluation, and no effect on binding-time analysis for continuation-based partial evaluation: a monovariant control-flow analysis yields equivalent results on a direct-style program and on its CPS counterpart, a monovariant binding-time analysis yields less precise results on a direct-style program than on its CPS counterpart, and an enhanced monovariant binding-time analysis yields equivalent results on a direct-style program and on its CPS counterpart. Our proof technique amounts to constructing the CPS counterpart of flow information and of binding times.<br /> <br />Our results formalize and confirm a folklore theorem about traditional binding-time analysis, namely that CPS has a positive effect on binding times. What may be more surprising is that the benefit does not arise from a standard refinement of program analysis, as, for instance, duplicating continuations.<br /> <br />The present study is symptomatic of an unsettling property of program analyses: their quality is unpredictably vulnerable to syntactic accidents in source programs, i.e., to the way these programs are written. More reliable program analyses require a better understanding of the effect of syntactic change.

Layered Region Based Flow-Sensitive Demand-Driven Alias Analysis

2014 ◽  
Vol 577 ◽  
pp. 917-920
Author(s):  
Long Pang ◽  
Xiao Hong Su ◽  
Pei Jun Ma ◽  
Ling Ling Zhao
Keyword(s):  
Program Analysis ◽  
Control Flow ◽  
Alias Analysis ◽  
Reachability Problem ◽  
Analysis Algorithm ◽  
Context Free Language ◽  
Context Free ◽  
Free Language ◽  
Demand Driven Analysis

The pointer alias is indispensable for program analysis. Comparing to point-to set, it’s more efficient to formulate the alias as the context free language (CFL) reachability problem. However, the precision is limited to flow-insensitivity. To solve this problem, we propose a flow sensitive, demand-driven analysis algorithm for answering may-alias queries. First the partial single static assignment is used to discriminate the address-taken pointers. Then the order of control flow is encoded in the level linearization code to ease comparison. Finally, the query of alias in demand driven is converted into the search of CFL reachability with feasible flows. The experiments demonstrate the effectiveness of the proposed approach.

A trajectories' guide to the state space - learning missing terms in bifurcating ecological systems

2021 ◽  
Author(s):  
Rahel Vortmeyer-Kley ◽  
Pascal Nieters ◽  
Gordon Pipa
Keyword(s):  
Machine Learning ◽  
Differential Equations ◽  
Algal Blooms ◽  
Ecological Systems ◽  
Short Term ◽  
Specific System ◽  
Worst Case ◽  
System Components ◽  
Full Knowledge

&lt;p&gt;Ecological systems typically can exhibit various states ranging from extinction to coexistence of different species in oscillatory states. The switch from one state to another is called bifurcation. All these behaviours of a specific system are hidden in a set of describing differential equations (DE) depending on different parametrisations. To model such a system as DE requires full knowledge of all possible interactions of the system components. In practise, modellers can end up with terms in the DE that do not fully describe the interactions or in the worst case with missing terms.&lt;/p&gt;&lt;p&gt;The framework of universal differential equations (UDE) for scientific machine learning (SciML) [1] allows to reconstruct the incomplete or missing term from an idea of the DE and a short term timeseries of the system and make long term predictions of the system&amp;#8217;s behaviour. However, the approach in [1] has difficulties to reconstruct the incomplete or missing term in systems with bifurcations. We developed a trajectory-based loss metric for UDE and SciML to tackle the problem and tested it successfully on a system mimicking algal blooms in the ocean.&lt;/p&gt;&lt;p&gt;[1] Rackauckas, Christopher, et al. &quot;Universal differential equations for scientific machine learning.&quot; arXiv preprint arXiv:2001.04385 (2020).&lt;/p&gt;

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