linux-kernel - [PATCH v2 5/7] bpf: do not create bpf_non_sleepable_error

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Message-Id: <20240620-fault-injection-statickeys-v2-5-e23947d3d84b@suse.cz>
Date: Thu, 20 Jun 2024 00:48:59 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Akinobu Mita <akinobu.mita@...il.com>, Christoph Lameter <cl@...ux.com>, 
 David Rientjes <rientjes@...gle.com>, Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
 "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>, 
 Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>, 
 "David S. Miller" <davem@...emloft.net>, 
 Masami Hiramatsu <mhiramat@...nel.org>, 
 Steven Rostedt <rostedt@...dmis.org>, Mark Rutland <mark.rutland@....com>
Cc: Jiri Olsa <jolsa@...nel.org>, Roman Gushchin <roman.gushchin@...ux.dev>, 
 Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-kernel@...r.kernel.org, 
 linux-mm@...ck.org, bpf@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
 Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH v2 5/7] bpf: do not create bpf_non_sleepable_error_inject
 list when unnecessary

When CONFIG_FUNCTION_ERROR_INJECTION is disabled,
within_error_injection_list() will return false for any address and the
result of check_non_sleepable_error_inject() denylist is thus redundant.
The bpf_non_sleepable_error_inject list thus does not need to be
constructed at all, so #ifdef it out.

This will allow to inline functions on the list when
CONFIG_FUNCTION_ERROR_INJECTION is disabled as there will be no BTF_ID()
reference for them.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 kernel/bpf/verifier.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 77da1f438bec..5cd93de37d68 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -21044,6 +21044,8 @@ static int check_attach_modify_return(unsigned long addr, const char *func_name)
 	return -EINVAL;
 }

+#ifdef CONFIG_FUNCTION_ERROR_INJECTION
+
 /* list of non-sleepable functions that are otherwise on
  * ALLOW_ERROR_INJECTION list
  */
@@ -21061,6 +21063,19 @@ static int check_non_sleepable_error_inject(u32 btf_id)
 	return btf_id_set_contains(&btf_non_sleepable_error_inject, btf_id);
 }

+#else /* CONFIG_FUNCTION_ERROR_INJECTION */
+
+/*
+ * Pretend the denylist is empty, within_error_injection_list() will return
+ * false anyway.
+ */
+static int check_non_sleepable_error_inject(u32 btf_id)
+{
+	return 0;
+}
+
+#endif
+
 int bpf_check_attach_target(struct bpf_verifier_log *log,
 			    const struct bpf_prog *prog,
 			    const struct bpf_prog *tgt_prog,

-- 
2.45.2