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SubjectRe: [PATCH v2 bpf-next 1/4] perf: export get/put_chain_entry()
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;
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