linux-kernel - [PATCH v4 6/8] livepatch: Use kallsyms_on_each_match

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Message-ID: <20220920071317.1787-7-thunder.leizhen@huawei.com>
Date:   Tue, 20 Sep 2022 15:13:15 +0800
From:   Zhen Lei <thunder.leizhen@...wei.com>
To:     Josh Poimboeuf <jpoimboe@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        <live-patching@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Luis Chamberlain" <mcgrof@...nel.org>,
        <linux-modules@...r.kernel.org>
CC:     Zhen Lei <thunder.leizhen@...wei.com>
Subject: [PATCH v4 6/8] livepatch: Use kallsyms_on_each_match_symbol() to improve performance

Based on the test results of kallsyms_on_each_match_symbol() and
kallsyms_on_each_symbol(), the average performance can be improved by 20
to 30 times.

Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
---
 kernel/livepatch/core.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 42f7e716d56bf72..31b57ccf908017e 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -153,6 +153,24 @@ static int klp_find_callback(void *data, const char *name,
 	return 0;
 }
 
+static int klp_match_callback(void *data, unsigned long addr)
+{
+	struct klp_find_arg *args = data;
+
+	args->addr = addr;
+	args->count++;
+
+	/*
+	 * Finish the search when the symbol is found for the desired position
+	 * or the position is not defined for a non-unique symbol.
+	 */
+	if ((args->pos && (args->count == args->pos)) ||
+	    (!args->pos && (args->count > 1)))
+		return 1;
+
+	return 0;
+}
+
 static int klp_find_object_symbol(const char *objname, const char *name,
 				  unsigned long sympos, unsigned long *addr)
 {
@@ -167,7 +185,7 @@ static int klp_find_object_symbol(const char *objname, const char *name,
 	if (objname)
 		module_kallsyms_on_each_symbol(klp_find_callback, &args);
 	else
-		kallsyms_on_each_symbol(klp_find_callback, &args);
+		kallsyms_on_each_match_symbol(klp_match_callback, name, &args);
 
 	/*
 	 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
-- 
2.25.1