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| author |   Alexei Starovoitov <ast@kernel.org> | 2022-06-16 19:27:30 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2022-06-16 19:27:37 -0700 |
| commit | 88bf18581375aa9b891e390aaf134b30d94232b3 (patch) | |
| tree | bc5e33450d2453b1449a83b0fe21ce943145f4d3 /kernel/trace | |
| parent | libbpf: Fix internal USDT address translation logic for shared libraries (diff) | |
| parent | selftests/bpf: add tests for sleepable (uk)probes (diff) | |
Merge branch 'sleepable uprobe support'
Delyan Kratunov says:
====================
This series implements support for sleepable uprobe programs.
Key work is in patches 2 and 3, the rest is plumbing and tests.
The main observation is that the only obstacle in the way of sleepable uprobe
programs is not the uprobe infrastructure, which already runs in a user-like
context, but the rcu usage around bpf_prog_array.
Details are in patch 2 but the tl;dr is that we chain trace_tasks and normal rcu
grace periods when releasing to array to accommodate users of either rcu type.
This introduces latency for non-sleepable users (kprobe, tp) but that's deemed
acceptable, given recent benchmarks by Andrii [1]. We're a couple of orders of
magnitude under the rate of bpf_prog_array churn that would raise flags (~1MM/s per Paul).
[1]: https://lore.kernel.org/bpf/CAEf4BzbpjN6ca7D9KOTiFPOoBYkciYvTz0UJNp5c-_3ptm=Mrg@mail.gmail.com/
v3 -> v4:
* Fix kdoc and inline issues
* Rebase
v2 -> v3:
* Inline uprobe_call_bpf into trace_uprobe.c, it's just a bpf_prog_run_array_sleepable call now.
* Do not disable preemption for uprobe non-sleepable programs.
* Add acks.
v1 -> v2:
* Fix lockdep annotations in bpf_prog_run_array_sleepable
* Chain rcu grace periods only for perf_event-attached programs. This limits
the additional latency on the free path to use cases where we know it won't
be a problem.
* Add tests calling helpers only available in sleepable programs.
* Remove kprobe.s support from libbpf.
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/trace')
| -rw-r--r-- | kernel/trace/bpf_trace.c | 4 | ||||
| -rw-r--r-- | kernel/trace/trace_uprobe.c | 5 |
2 files changed, 4 insertions, 5 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 10b157a6d73e..d1c22594dbf9 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1936,7 +1936,7 @@ int perf_event_attach_bpf_prog(struct perf_event *event, event->prog = prog; event->bpf_cookie = bpf_cookie; rcu_assign_pointer(event->tp_event->prog_array, new_array); - bpf_prog_array_free(old_array); + bpf_prog_array_free_sleepable(old_array); unlock: mutex_unlock(&bpf_event_mutex); @@ -1962,7 +1962,7 @@ void perf_event_detach_bpf_prog(struct perf_event *event) bpf_prog_array_delete_safe(old_array, event->prog); } else { rcu_assign_pointer(event->tp_event->prog_array, new_array); - bpf_prog_array_free(old_array); + bpf_prog_array_free_sleepable(old_array); } bpf_prog_put(event->prog); diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 9711589273cd..0282c119b1b2 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -16,6 +16,7 @@ #include <linux/namei.h> #include <linux/string.h> #include <linux/rculist.h> +#include <linux/filter.h> #include "trace_dynevent.h" #include "trace_probe.h" @@ -1346,9 +1347,7 @@ static void __uprobe_perf_func(struct trace_uprobe *tu, if (bpf_prog_array_valid(call)) { u32 ret; - preempt_disable(); - ret = trace_call_bpf(call, regs); - preempt_enable(); + ret = bpf_prog_run_array_sleepable(call->prog_array, regs, bpf_prog_run); if (!ret) return; } |