[PATCH] kallsyms: let kallsyms_on_each_match_symbol match symbols exactly

[Song Liu <song@xxxxxxxxxx>]

With CONFIG_LTO_CLANG, kallsyms.c:cleanup_symbol_name() removes symbols
suffixes during comparison. This is problematic for livepatch, as
kallsyms_on_each_match_symbol may find multiple matches for the same
symbol, and fail with:

  livepatch: unresolvable ambiguity for symbol 'xxx' in object 'yyy'

Make kallsyms_on_each_match_symbol() to match symbols exactly. Since
livepatch is the only user of kallsyms_on_each_match_symbol(), this
change is safe.

Signed-off-by: Song Liu <song@xxxxxxxxxx>
---
 kernel/kallsyms.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 77747391f49b..2ab459b43084 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -187,7 +187,7 @@ static bool cleanup_symbol_name(char *s)
 	return false;
 }
 
-static int compare_symbol_name(const char *name, char *namebuf)
+static int compare_symbol_name(const char *name, char *namebuf, bool match_exactly)
 {
 	int ret;
 
@@ -195,7 +195,7 @@ static int compare_symbol_name(const char *name, char *namebuf)
 	if (!ret)
 		return ret;
 
-	if (cleanup_symbol_name(namebuf) && !strcmp(name, namebuf))
+	if (!match_exactly && cleanup_symbol_name(namebuf) && !strcmp(name, namebuf))
 		return 0;
 
 	return ret;
@@ -213,7 +213,8 @@ static unsigned int get_symbol_seq(int index)
 
 static int kallsyms_lookup_names(const char *name,
 				 unsigned int *start,
-				 unsigned int *end)
+				 unsigned int *end,
+				 bool match_exactly)
 {
 	int ret;
 	int low, mid, high;
@@ -228,7 +229,7 @@ static int kallsyms_lookup_names(const char *name,
 		seq = get_symbol_seq(mid);
 		off = get_symbol_offset(seq);
 		kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
-		ret = compare_symbol_name(name, namebuf);
+		ret = compare_symbol_name(name, namebuf, match_exactly);
 		if (ret > 0)
 			low = mid + 1;
 		else if (ret < 0)
@@ -245,7 +246,7 @@ static int kallsyms_lookup_names(const char *name,
 		seq = get_symbol_seq(low - 1);
 		off = get_symbol_offset(seq);
 		kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
-		if (compare_symbol_name(name, namebuf))
+		if (compare_symbol_name(name, namebuf, match_exactly))
 			break;
 		low--;
 	}
@@ -257,7 +258,7 @@ static int kallsyms_lookup_names(const char *name,
 			seq = get_symbol_seq(high + 1);
 			off = get_symbol_offset(seq);
 			kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
-			if (compare_symbol_name(name, namebuf))
+			if (compare_symbol_name(name, namebuf, match_exactly))
 				break;
 			high++;
 		}
@@ -277,7 +278,7 @@ unsigned long kallsyms_lookup_name(const char *name)
 	if (!*name)
 		return 0;
 
-	ret = kallsyms_lookup_names(name, &i, NULL);
+	ret = kallsyms_lookup_names(name, &i, NULL, false);
 	if (!ret)
 		return kallsyms_sym_address(get_symbol_seq(i));
 
@@ -312,7 +313,7 @@ int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long),
 	int ret;
 	unsigned int i, start, end;
 
-	ret = kallsyms_lookup_names(name, &start, &end);
+	ret = kallsyms_lookup_names(name, &start, &end, true);
 	if (ret)
 		return 0;
 
-- 
2.34.1