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From:   Jiri Olsa <jolsa@kernel.org>
To:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>
Cc:     Song Liu <songliubraving@fb.com>,
        Steven Rostedt <rostedt@goodmis.org>, netdev@vger.kernel.org,
        bpf@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>,
        Martin KaFai Lau <kafai@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>,
        Masami Hiramatsu <mhiramat@kernel.org>
Subject: [PATCHv2 bpf 2/3] ftrace: Keep address offset in ftrace_lookup_symbols
Date:   Mon,  6 Jun 2022 20:47:30 +0200
Message-Id: <20220606184731.437300-3-jolsa@kernel.org>
In-Reply-To: <20220606184731.437300-1-jolsa@kernel.org>
References: <20220606184731.437300-1-jolsa@kernel.org>
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We want to store the resolved address on the same index as
the symbol string, because that's the user (bpf kprobe link)
code assumption.

Also making sure we don't store duplicates that might be
present in kallsyms.

Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Fixes: bed0d9a50dac ("ftrace: Add ftrace_lookup_symbols function")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/trace/ftrace.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 674add0aafb3..ee9260ee0b80 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -7984,15 +7984,23 @@ static int kallsyms_callback(void *data, const char *name,
 			     struct module *mod, unsigned long addr)
 {
 	struct kallsyms_data *args = data;
+	const char **sym;
+	int idx;
 
-	if (!bsearch(&name, args->syms, args->cnt, sizeof(*args->syms), symbols_cmp))
+	sym = bsearch(&name, args->syms, args->cnt, sizeof(*args->syms), symbols_cmp);
+	if (!sym)
+		return 0;
+
+	idx = sym - args->syms;
+	if (args->addrs[idx])
 		return 0;
 
 	addr = ftrace_location(addr);
 	if (!addr)
 		return 0;
 
-	args->addrs[args->found++] = addr;
+	args->addrs[idx] = addr;
+	args->found++;
 	return args->found == args->cnt ? 1 : 0;
 }
 
@@ -8017,6 +8025,7 @@ int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *a
 	struct kallsyms_data args;
 	int err;
 
+	memset(addrs, 0, sizeof(*addrs) * cnt);
 	args.addrs = addrs;
 	args.syms = sorted_syms;
 	args.cnt = cnt;
-- 
2.35.3