[PATCH v6 1/4] tracing: Avoid BTF lookup in atomic context

[Donglin Peng]

From: pengdonglin <pengdonglin@xxxxxxxxxx>

The function graph trace formatter can be called from ftrace_dump_one()
with interrupts disabled. When ftrace_dump_on_oops is enabled, the trace
panic notifier can reach ftrace_dump() from the panic path, including the
nmi_panic() path used by the hard lockup detector.

btf_find_func_proto() calls bpf_find_btf_id(), which may initialize vmlinux
BTF under a mutex. Skip the BTF lookup when running in an atomic context
or with interrupts disabled, and fall back to the existing return value
formatting.

Fixes: ebeed8d4a555 ("tracing/probes: Move finding func-proto API and getting func-param API to trace_btf")
Signed-off-by: pengdonglin <pengdonglin@xxxxxxxxxx>
---
 kernel/trace/trace_btf.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/trace/trace_btf.c b/kernel/trace/trace_btf.c
index 00172f301f25..ae562192b619 100644
--- a/kernel/trace/trace_btf.c
+++ b/kernel/trace/trace_btf.c
@@ -15,6 +15,9 @@ const struct btf_type *btf_find_func_proto(const char *func_name, struct btf **b
 	const struct btf_type *t;
 	s32 id;
 
+	if (unlikely(in_atomic() || irqs_disabled()))
+		return NULL;
+
 	id = bpf_find_btf_id(func_name, BTF_KIND_FUNC, btf_p);
 	if (id < 0)
 		return NULL;
-- 
2.34.1