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[$] Verifier-state pruning in BPF
The BPF verifier works, on a theoretical level, by considering every possible
path that a BPF program could take. As a practical matter, however, it needs to
do that in a reasonable amount of time. At the
2025 Linux Plumbers Conference, Mahé Tardy and Paul Chaignon
gave a detailed explanation
(slides;
video) of
the main mechanism that it uses to accomplish that: state pruning. They focused
on two optimizations that help reduce the number of paths the verifier needs to
check, and discussed some of the complications the optimizations introduced to the verifier's
code.
path that a BPF program could take. As a practical matter, however, it needs to
do that in a reasonable amount of time. At the
2025 Linux Plumbers Conference, Mahé Tardy and Paul Chaignon
gave a detailed explanation
(slides;
video) of
the main mechanism that it uses to accomplish that: state pruning. They focused
on two optimizations that help reduce the number of paths the verifier needs to
check, and discussed some of the complications the optimizations introduced to the verifier's
code.
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