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codeql-workshop-dataflow-c/graphs/cfg.ql
2025-03-17 19:13:24 -07:00

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/**
* @name Print part of the CFG
* @description Outputs a subset of the control flow graph
* @id cpp/print-cfg
* @kind graph
*/
// The CFG is large. Just show the part for
// int copy_mem(unsigned int unused, dyn_input_t *input,
// unsigned int input_types)
import cpp
predicate allSuccessors3(int distance, ControlFlowNode n1, ControlFlowNode n2) {
// n1.getASuccessor*() = n2 and
distance = 0 and n1 = n2
or
distance = 1 and n1 = n2.getAPredecessor()
or
distance = 2 and n1 = n2.getAPredecessor().getAPredecessor()
or
// allSuccessors3(distance-1, n2.getAPredecessor(), n2)
// or
exists(ControlFlowNode mid |
// // n1 -> mid
// n1 = mid.getAPredecessor() and
// // mid -> n2
// allSuccessors3(distance-1, mid, n2)
// --- right-to-left recursion
// n1 -> mid
distance < 12 and
allSuccessors3(distance - 1, n1, mid) and
// mid -> n2
mid = n2.getAPredecessor()
)
}
predicate allSuccessors1(ControlFlowNode n1, ControlFlowNode n2) {
// n1.getASuccessor*() = n2 and
n1 = n2
or
// n2 = n1.getASuccessor()
exists(ControlFlowNode mid |
allSuccessors1(n1, mid) and
n2 = mid.getASuccessor()
)
}
query predicate nodes(ControlFlowNode n1, string key, string value) {
exists(ControlFlowNode startFrom |
(edges(n1, _) or edges(_, n1)) and
(
if startFrom.getASuccessor*() = n1
then (
key = "color" and value = "red"
or
key = "line" and value = n1.getLocation().getStartLine().toString()
) else (
key = "color" and value = "black"
or
key = "line" and value = n1.getLocation().getStartLine().toString()
)
)
)
}
// query predicate edgesDist(ControlFlowNode n1, ControlFlowNode n2, int distance) {
// distance = 12 and
// // allSuccessors3(distance, n1, n2) and
// n1.(Function).hasName("copy_mem") and
// n2 = n1.getASuccessor+()
// }
query predicate edges(ControlFlowNode n1, ControlFlowNode n2) {
exists(ControlFlowNode t1, ControlFlowNode t2 |
t1.(Function).hasName("copy_mem") and
t2 = t1.(Function).getEntryPoint() and
n1 = t2.getASuccessor*() and
n1 = n2.getAPredecessor()
)
}