bpf: Introduce file dynptr #6188
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Remove unnecessary kfunc prototypes from test programs, these are provided by vmlinux.h Signed-off-by: Mykyta Yatsenko <[email protected]> Acked-by: Eduard Zingerman <[email protected]>
Dynptr currently caps size and offset at 24 bits, which isn’t sufficient for file-backed use cases; even 32 bits can be limiting. Refactor dynptr helpers/kfuncs to use 64-bit size and offset, ensuring consistency across the APIs. This change does not affect internals of xdp, skb or other dynptrs, which continue to behave as before, and does not break binary compatibility. The widening enables large-file access support via dynptr, implemented in the next patches. Signed-off-by: Mykyta Yatsenko <[email protected]>
Move struct freader and prototypes of the functions operating on it into the buildid.h. This allows reusing freader outside buildid, e.g. for file dynptr support added later. Signed-off-by: Mykyta Yatsenko <[email protected]>
freader_fetch currently reads from at most two folios. When a read spans into a third folio, the overflow bytes are copied adjacent to the second folio’s data instead of being handled as a separate folio. This patch modifies fetch algorithm to support reading from many folios. Signed-off-by: Mykyta Yatsenko <[email protected]> Reviewed-by: Andrii Nakryiko <[email protected]>
…nptr() Move the const dynptr check into unmark_stack_slots_dynptr() so callers don’t have to duplicate it. This puts the validation next to the code that manipulates dynptr stack slots and allows upcoming changes to reuse it directly. Signed-off-by: Mykyta Yatsenko <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Acked-by: Eduard Zingerman <[email protected]>
Add the necessary verifier plumbing for the new file-backed dynptr type. Introduce two kfuncs for its lifecycle management: * bpf_dynptr_from_file() for initialization * bpf_dynptr_file_discard() for destruction Currently there is no mechanism for kfunc to release dynptr, this patch add one: * Dynptr release function sets meta->release_regno * Call unmark_stack_slots_dynptr() if meta->release_regno is set and dynptr ref_obj_id is set as well. Signed-off-by: Mykyta Yatsenko <[email protected]> Acked-by: Eduard Zingerman <[email protected]>
Add support for file dynptr. Introduce struct bpf_dynptr_file_impl to hold internal state for file dynptrs, with 64-bit size and offset support. Introduce lifecycle management kfuncs: - bpf_dynptr_from_file() for initialization - bpf_dynptr_file_discard() for destruction Extend existing helpers to support file dynptrs in: - bpf_dynptr_read() - bpf_dynptr_slice() Write helpers (bpf_dynptr_write() and bpf_dynptr_data()) are not modified, as file dynptr is read-only. Signed-off-by: Mykyta Yatsenko <[email protected]> Acked-by: Eduard Zingerman <[email protected]>
Move kfunc specialization (function address substitution) to later stage of verification to support a new use case, where we need to take into consideration whether kfunc is called in sleepable context. Minor refactoring in add_kfunc_call(), making sure that if function fails, kfunc desc is not added to tab->descs (previously it could be added or not, depending on what failed). Signed-off-by: Mykyta Yatsenko <[email protected]>
File dynptr reads may sleep when the requested folios are not in the page cache. To avoid sleeping in non-sleepable contexts while still supporting valid sleepable use, given that dynptrs are non-sleepable by default, enable sleeping only when bpf_dynptr_from_file() is invoked from a sleepable context. This change: * Introduces a sleepable constructor: bpf_dynptr_from_file_sleepable() * Override non-sleepable constructor with sleepable if it's always called in sleepable context Signed-off-by: Mykyta Yatsenko <[email protected]> Acked-by: Eduard Zingerman <[email protected]>
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Introducing selftests for validating file-backed dynptr works as expected. * validate implementation supports dynptr slice and read operations * validate destructors should be paired with initializers * validate sleepable progs can page in. Signed-off-by: Mykyta Yatsenko <[email protected]>
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Pull request for series with
subject: bpf: Introduce file dynptr
version: 3
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1013778