libbpf-tools: Allow biostacks to run on old kernels #4550
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michael-chuh
requested review from
drzaeus77,
goldshtn,
yonghong-song,
4ast,
brendangregg and
davemarchevsky
as code owners
| SEC("fentry/blk_account_io_start") | ||
| int BPF_PROG(blk_account_io_start, struct request *rq) | ||
| { | ||
| return trace_start(ctx, rq, false); |
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Missing the true case. fentry progs should have as many as the kprobe ones.
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blk_account_io_{start, done} were renamed to _blk_account_io{start, done} from v5.16, see commit a184f09(libbpf-tools: Fix bio tools).
bpf_program__set_attach_target() can be used for that, fentry progs are not always same as kprobe
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I mean blk_account_io_merge_bio is missing.
libbpf-tools/biostacks.c
Outdated
| "blk_account_io_start"); | ||
| bpf_program__set_attach_target(obj->progs.blk_account_io_done, 0, | ||
| "blk_account_io_done"); | ||
| if (kprobe_exists("blk_account_io_start")) { |
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The userspace part looks way to complicated, could you please simplify that ?
Let's first check if fentry is supported:
- if yes, disable all kprobe progs, and do auto-attach
- if no, disable all fentry progs, and do auto-attach
You may need to disable some progs if symbols not exist
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Hi @chenhengqi
I did some simplification follow you suggestion, do you have some more advice?
And there is a failure in #455, but I cann't see the cause of that request?
Fallback to use kprobes if kernel lacks support for fentry/fexit. Signed-off-by: mickey_zhu <[email protected]>
Fallback to use kprobes if kernel lacks support for fentry/fexit.