Control-flow graph

In some cases, instructions store the destination address in a register known only at runtime, such as Jump to Register (JR) or Jiunp and Link Register (JALR) instructions. When that happens, the code must be further analyzed in order to find the runtime value of the register. When the value is not foimd, the control flow graph can still be partially extracted and used by the techniques, but with vulnerabilities in such points. 

The insertion of new instructions to the program code must take into accoimt the control flow graph. Whenever an instmction is added or removed, all the addresses, relative or absolute, must be checked for consistency. When repheating an instrac-tion using spare registers, such registers must also be accoimted for and removed from the available registers list. 

The fact that each BID is a unique prime number combined with the fact that the CFID is the multiplication of the destination BBs BIDS, gives PODER an interesting characteristic the operation rest of division of the dequeued CFDD by the destination BB s BID always returns zero when the control flow graph is respected by the exeeution flow. When the value is different than zero, some control flow error happened, causing an incorrect transition in the program s execution flow. 

The data/control-flow graphs are large and complex. Moreover, the applications require clock frequencies of 10 20 MHz, whereas the intermediate data throughput and sample frequencies remain far below 1 MHz. As a result of these factors, the hardware-sharing factor (HSF) is much larger than 1, resulting in highly multiplexed architectures. 

Scheduling receives the optimized data/control flow graph, a fixed CBB allocation, and a maximum timing constraint as input. The goal of scheduling... 

Secondly, the checks run by the verifying compilers are usually not based on abstract interpretation. They are mostly realized as abstract syntax tree transformations much in the line with the supporting routines of the compilation process (data and control flow graph analysis, dead code elimination, register allocation, etc.) and the evaluation function is basically the matching of antipatterns of common programming bugs. 

Compilation of the source HDL into an internal representation, usually a data flow graph and/or a control flow graph. This step is very similar to the compilation of a programming language. 

Continuing the previous example, separate data-flow and control-flow graphs are generated, as shown in Figure 3. Nodes are numbered with the labels provided in comments in the VHDL model. Operation nodes in the data-flow and control-flow graphs correspond to each other, and are labeled with the operation they represent, e.g., The reader can easily verify the one-to-one correspondence to the specification of EXAMPLE in Figure 2. 

Reducing the number of levels in the data-flow or control-flow graphs, such as in FLAMEL [63], which may lead to faster hardware. 

We finally review scheduling methods which put more emphasis on conditional branching. The main idea of these algorithms is to schedule mutually exclusive operations to allow sharing of hardware, and possibly a faster schedule for some paths in the control flow graph. 

The CSTEP control step scheduler uses list scheduling on a block-by-block basis, with timing constraint evaluation as the priority function. Operations are scheduled into control steps one basic block at a time, with the blocks scheduled in executidepth-first traversal of the control flow graph. For each basic block, data ready operator are considered for placement into the current control step, using a priority function that reflects whether or not that placement will violate timing constraints. Resource limits may be applied to limit the number of operators of a particular type in any one control step. 

CSTEP schedules operators into control steps one basic block at a time. Basic blocks are scheduled in execution order using an execution-order traversal of the control flow graph. This guarantees that when a timing constraint is expressed on two operators that are in separate basic blocks, the first operator in the constraint is scheduled before the second operator is scheduled. This leaves the second operator to be evaluated for placement in terms of how placement affects the constraint. The ordered scheduling of basic blocks also ensures that inter-basic block data dependencies will be satisfied. 

Another important metric is cyclomatic complexity which aims to measures the total numher of decision points in an application (Thomas, 1976). It is used to give the numher of tests for software and to keep software reliable, testable, and manageable. Cyclomatic complexity is based entirely on the structure of software s control flow graph and is defined as M = E-V + 2P (considering a single exit statement) where E is lire number of edges, V is the number of vertices and P is the number of connected components. 

Next, we show a pseudo-code of a generic forward propagation algorithm that is a specific instance of the algorithms applied to control flow graph described in (Aho, Sethi Ullman, 1985) ... 

Constraint intervals depend on the order of the operations in the control-flow graph. Since data-independent operations may be arbitrarily ordered, any valid ordering is possible. AFAP scheduling just uses the given order, which may be obtained, for example, by using a list scheduler. 

For registers, conflicts are derived from the lifetimes. Lifetimes are computed on the control-flow graph and then projected to the states in the control FSM. 

Computing the transitive closure of the control flow graph in each state. Operation pairs in the transitive closure conflict. 

Hafer and Parker [17] used a mixed-integer linear programming approach to automatically synthesize register-transfer level datapaths, given a data flow/control flow graph description of the hardware. The approach involves... 

Fig. 3 illustrates a sample control flow graph, where the executing frequency of basic blocks and the probability of branch edges are also marked. For example, the executing frequency of B is 5, and the probability of B2 executing after Bi is 0.2. The target register 2 is written in Bi and B2, read in B3 and B5 respectively. If the masking operation is inserted before instruction 4(ij ), the latest accesses of 2 include =lp2 wnte) in B2 and 3(read) in B3. The maskable intervals of 2 are described by the thick arrows in Fig. 3. It should be pointed that the interval between 1 and 3 can not be masked because the errors...

The graphical user interface of StackAnalyzer provides different views of the result, including visualizations of the call graph and control flow graph, and enables the information contained in the executable to be browsed in a user-friendly way. Creating AIS annotations is facilitated by a dedicated annotation wizard. These mechanisms help users to efficiently set up the analysis and evaluate the analysis results. After the configuration of the analysis and the assessment of the results the analysis can be executed in batch mode as a part of continuous verification processes or regression tests. 

The use of enhanced parallel programming models such as this one proposed for Ada, will allow for the compiler (with optional parameters/annotations provided by the programmer) to generate the task graphs (similar to the Parallel Control Flow Graphs [14]) which can be used to perform the required schedulability analysis [15]. 

Bouffard et al. described in [13], two methods to change the control flow graph of a Java Card. The first one is Eman 2, which provides a way to change the return address of the current function. This information is stored in the Java Card stack header. Once the malicious function exits during the correct execution, the program counter returns to the instruction which addresses it. The address of the jpg is also stored in the Java Card Stack header. An overflow attack success to change the return address by the address of the malicious byte code. Since there is no runtime check on the parameter, it allows a standard buffer overflow attack to modify the frame header. 

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