CBMC: Use instrumented malloc/free for MLD_ALLOC/MLD_FREE #814
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Thanks @hanno-becker. The changes itself look good to me, but CBMC fails due to timeouts. Marking as draft until we can resolve that.
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This commit replaces multiple successive allocations from MLD_ALLOC by a single allocation of a suitable 'workspace' structure. This reduces the number of allocations as well as the number of exit paths, thereby reducing the complexity of CBMC proofs. It also unifies the zeroization at the end of each function. Signed-off-by: Hanno Becker <[email protected]>
The default implementation of MLD_ALLOC and MLD_FREE uses stack allocation, which the compiler can assume not to fail. This means that CBMC does not exercise the cleanup paths which handle fallible dynamic allocation -- a significant proof gap. This commit changes the configuration uses for the CBMC proofs to use the (instrumented) calls to malloc/free for MLD_ALLOC/MLD_FREE. Importantly, we set --malloc-may-fail to model allocation as fallible, and --malloc-fail-null to return NULL in case of allocation failure. Signed-off-by: Hanno Becker <[email protected]>
Signed-off-by: Hanno Becker <[email protected]>
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The default implementation of MLD_ALLOC and MLD_FREE uses stack
allocation, which the compiler can assume not to fail. This means
that CBMC does not exercise the cleanup paths which handle fallible
dynamic allocation -- a significant proof gap.
This commit changes the configuration uses for the CBMC proofs
to use the (instrumented) calls to malloc/free for MLD_ALLOC/MLD_FREE.
Importantly, we set --malloc-may-fail to model allocation as fallible,
and --malloc-fail-null to return NULL in case of allocation failure.