Re: [PATCH v2 bpf-next 1/4] perf: export get/put_chain_entry()
From: Peter Zijlstra <peterz@infradead.org>
Date: 2020-06-26 11:01:16
Also in:
bpf, lkml
Subsystem:
performance events subsystem, the rest · Maintainers:
Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, Linus Torvalds
On Thu, Jun 25, 2020 at 05:13:29PM -0700, Song Liu wrote:
This would be used by bpf stack mapo.
Would it make sense to sanitize the API a little before exposing it?
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index 334d48b16c36..016894b0d2c2 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c@@ -159,8 +159,10 @@ static struct perf_callchain_entry *get_callchain_entry(int *rctx) return NULL; entries = rcu_dereference(callchain_cpus_entries); - if (!entries) + if (!entries) { + put_recursion_context(this_cpu_ptr(callchain_recursion), rctx); return NULL; + } cpu = smp_processor_id();
@@ -183,12 +185,9 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user, int rctx; entry = get_callchain_entry(&rctx); - if (rctx == -1) + if (!entry || rctx == -1) return NULL; - if (!entry) - goto exit_put; - ctx.entry = entry; ctx.max_stack = max_stack; ctx.nr = entry->nr = init_nr;