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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>,
        Masami Hiramatsu <mhiramat@kernel.org>
Cc:     netdev@vger.kernel.org, bpf@vger.kernel.org,
        lkml <linux-kernel@vger.kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: [PATCHv4 bpf-next 3/5] fprobe: Resolve symbols with ftrace_lookup_symbols
Date:   Thu, 28 Apr 2022 22:12:05 +0200
Message-Id: <20220428201207.954552-4-jolsa@kernel.org>
In-Reply-To: <20220428201207.954552-1-jolsa@kernel.org>
References: <20220428201207.954552-1-jolsa@kernel.org>
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Using ftrace_lookup_symbols to speed up symbols lookup
in register_fprobe_syms API.

This requires syms array to be alphabetically sorted.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/trace/fprobe.c | 32 ++++++++++++--------------------
 1 file changed, 12 insertions(+), 20 deletions(-)

diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 89d9f994ebb0..aac63ca9c3d1 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -85,39 +85,31 @@ static void fprobe_exit_handler(struct rethook_node *rh, void *data,
 }
 NOKPROBE_SYMBOL(fprobe_exit_handler);
 
+static int symbols_cmp(const void *a, const void *b)
+{
+	const char **str_a = (const char **) a;
+	const char **str_b = (const char **) b;
+
+	return strcmp(*str_a, *str_b);
+}
+
 /* Convert ftrace location address from symbols */
 static unsigned long *get_ftrace_locations(const char **syms, int num)
 {
-	unsigned long addr, size;
 	unsigned long *addrs;
-	int i;
 
 	/* Convert symbols to symbol address */
 	addrs = kcalloc(num, sizeof(*addrs), GFP_KERNEL);
 	if (!addrs)
 		return ERR_PTR(-ENOMEM);
 
-	for (i = 0; i < num; i++) {
-		addr = kallsyms_lookup_name(syms[i]);
-		if (!addr)	/* Maybe wrong symbol */
-			goto error;
-
-		/* Convert symbol address to ftrace location. */
-		if (!kallsyms_lookup_size_offset(addr, &size, NULL) || !size)
-			goto error;
+	/* ftrace_lookup_symbols expects sorted symbols */
+	sort(syms, num, sizeof(*syms), symbols_cmp, NULL);
 
-		addr = ftrace_location_range(addr, addr + size - 1);
-		if (!addr) /* No dynamic ftrace there. */
-			goto error;
+	if (!ftrace_lookup_symbols(syms, num, addrs))
+		return addrs;
 
-		addrs[i] = addr;
-	}
-
-	return addrs;
-
-error:
 	kfree(addrs);
-
 	return ERR_PTR(-ENOENT);
 }
 
-- 
2.35.1