linux-kernel - [PATCH 3/3] tracing/kprobes: Use APIs that matches symbols with .llvm.<hash> suffix

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Message-ID: <20240730005433.3559731-4-song@kernel.org>
Date: Mon, 29 Jul 2024 17:54:33 -0700
From: Song Liu <song@...nel.org>
To: live-patching@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Cc: jpoimboe@...nel.org,
	jikos@...nel.org,
	mbenes@...e.cz,
	pmladek@...e.com,
	joe.lawrence@...hat.com,
	nathan@...nel.org,
	morbo@...gle.com,
	justinstitt@...gle.com,
	mcgrof@...nel.org,
	thunder.leizhen@...wei.com,
	kees@...nel.org,
	kernel-team@...a.com,
	song@...nel.org,
	mmaurer@...gle.com,
	samitolvanen@...gle.com,
	mhiramat@...nel.org,
	rostedt@...dmis.org
Subject: [PATCH 3/3] tracing/kprobes: Use APIs that matches symbols with .llvm.<hash> suffix

Use the new kallsyms APIs that matches symbols name with .llvm.<hash>
suffix. This allows userspace tools to get kprobes on the expected
function name, while the actual symbol has a .llvm.<hash> suffix.

This only effects kernel compared with CONFIG_LTO_CLANG.

Signed-off-by: Song Liu <song@...nel.org>
---
 kernel/trace/trace_kprobe.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 61a6da808203..c319382c1a09 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -202,7 +202,8 @@ unsigned long trace_kprobe_address(struct trace_kprobe *tk)
 
 	if (tk->symbol) {
 		addr = (unsigned long)
-			kallsyms_lookup_name(trace_kprobe_symbol(tk));
+			kallsyms_lookup_name_or_prefix(trace_kprobe_symbol(tk));
+
 		if (addr)
 			addr += tk->rp.kp.offset;
 	} else {
@@ -766,8 +767,13 @@ static unsigned int number_of_same_symbols(const char *mod, const char *func_nam
 {
 	struct sym_count_ctx ctx = { .count = 0, .name = func_name };
 
-	if (!mod)
+	if (!mod) {
 		kallsyms_on_each_match_symbol(count_symbols, func_name, &ctx.count);
+		if (IS_ENABLED(CONFIG_LTO_CLANG) && !ctx.count) {
+			kallsyms_on_each_match_symbol_or_prefix(
+				count_symbols, func_name, &ctx.count);
+		}
+	}
 
 	module_kallsyms_on_each_symbol(mod, count_mod_symbols, &ctx);
 
-- 
2.43.0