netdev - [PATCH 04/10] bpf: Add support to inline bpf_get_func

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Date:   Tue, 22 Feb 2022 18:05:54 +0100
From:   Jiri Olsa <jolsa@...nel.org>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH 04/10] bpf: Add support to inline bpf_get_func_ip helper on x86

Adding support to inline it on x86, because it's single
load instruction.

Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 kernel/bpf/verifier.c    | 21 ++++++++++++++++++++-
 kernel/trace/bpf_trace.c |  1 +
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d7473fee247c..f125c33a37c9 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -13635,7 +13635,7 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 			continue;
 		}
 
-		/* Implement bpf_get_func_ip inline. */
+		/* Implement tracing bpf_get_func_ip inline. */
 		if (prog_type == BPF_PROG_TYPE_TRACING &&
 		    insn->imm == BPF_FUNC_get_func_ip) {
 			/* Load IP address from ctx - 16 */
@@ -13650,6 +13650,25 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 			continue;
 		}
 
+#ifdef CONFIG_X86
+		/* Implement kprobe_multi bpf_get_func_ip inline. */
+		if (prog_type == BPF_PROG_TYPE_KPROBE &&
+		    eatype == BPF_TRACE_KPROBE_MULTI &&
+		    insn->imm == BPF_FUNC_get_func_ip) {
+			/* Load IP address from ctx (struct pt_regs) ip */
+			insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1,
+						  offsetof(struct pt_regs, ip));
+
+			new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, 1);
+			if (!new_prog)
+				return -ENOMEM;
+
+			env->prog = prog = new_prog;
+			insn      = new_prog->insnsi + i + delta;
+			continue;
+		}
+#endif
+
 patch_call_imm:
 		fn = env->ops->get_func_proto(insn->imm, env->prog);
 		/* all functions that have prototype and verifier allowed
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 64891b7b0885..c1998b9d5531 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1039,6 +1039,7 @@ static const struct bpf_func_proto bpf_get_func_ip_proto_kprobe = {
 
 BPF_CALL_1(bpf_get_func_ip_kprobe_multi, struct pt_regs *, regs)
 {
+	/* This helper call is inlined by verifier on x86. */
 	return instruction_pointer(regs);
 }
 
-- 
2.35.1