Global subprogs in RCU/{preempt,irq}-disabled sections #8584
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Upstream branch: 0b93631 |
The verifier currently does not permit global subprog calls when a lock is held, preemption is disabled, or when IRQs are disabled. This is because we don't know whether the global subprog calls sleepable functions or not. In case of locks, there's an additional reason: functions called by the global subprog may hold additional locks etc. The verifier won't know while verifying the global subprog whether it was called in context where a spin lock is already held by the program. Perform summarization of the sleepable nature of a global subprog just like changes_pkt_data and then allow calls to global subprogs for non-sleepable ones from atomic context. While making this change, I noticed that RCU read sections had no protection against sleepable global subprog calls, include it in the checks and fix this while we're at it. Care needs to be taken to not allow global subprog calls when regular bpf_spin_lock is held. When resilient spin locks is held, we want to potentially have this check relaxed, but not for now. Also make sure extensions freplacing global functions cannot do so in case the target is non-sleepable, but the extension is. The other combination is ok. Tests are included in the next patch to handle all special conditions. Fixes: 9bb00b2 ("bpf: Add kfunc bpf_rcu_read_lock/unlock()") Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>
Add tests for rejecting sleepable and accepting non-sleepable global function calls in atomic contexts. For spin locks, we still reject all global function calls. Once resilient spin locks land, we will carefully lift in cases where we deem it safe. Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>
Add tests for freplace behavior with the combination of sleepable and non-sleepable global subprogs. The changes_pkt_data selftest did all the hardwork, so simply rename it and include new support for more summarization tests for might_sleep bit. Sleepable extensions don't work yet, so add support but disable it for now, allow support to be tested once it's enabled (and ensure we will complain then). Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>
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Upstream branch: 0b93631 |
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Pull request for series with
subject: Global subprogs in RCU/{preempt,irq}-disabled sections
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=939074