linux-kernel - [PATCH v2 3/3] tracing/kprobes: Use APIs that matches symbols without .XXX suffix

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Message-ID: <20240802210836.2210140-4-song@kernel.org>
Date: Fri,  2 Aug 2024 14:08:35 -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 v2 3/3] tracing/kprobes: Use APIs that matches symbols without .XXX suffix

Use the new kallsyms APIs that matches symbols name with .XXX
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 compile with CONFIG_LTO_CLANG.

Signed-off-by: Song Liu <song@...nel.org>
---
 kernel/kprobes.c            |  6 +++++-
 kernel/trace/trace_kprobe.c | 11 ++++++++++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index e85de37d9e1e..99102283b076 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -70,7 +70,11 @@ static DEFINE_PER_CPU(struct kprobe *, kprobe_instance);
 kprobe_opcode_t * __weak kprobe_lookup_name(const char *name,
 					unsigned int __unused)
 {
-	return ((kprobe_opcode_t *)(kallsyms_lookup_name(name)));
+	unsigned long addr = kallsyms_lookup_name(name);
+
+	if (IS_ENABLED(CONFIG_LTO_CLANG) && !addr)
+		addr = kallsyms_lookup_name_without_suffix(name);
+	return ((kprobe_opcode_t *)(addr));
 }
 
 /*
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 61a6da808203..d2ad0c561c83 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -203,6 +203,10 @@ unsigned long trace_kprobe_address(struct trace_kprobe *tk)
 	if (tk->symbol) {
 		addr = (unsigned long)
 			kallsyms_lookup_name(trace_kprobe_symbol(tk));
+
+		if (IS_ENABLED(CONFIG_LTO_CLANG) && !addr)
+			addr = kallsyms_lookup_name_without_suffix(trace_kprobe_symbol(tk));
+
 		if (addr)
 			addr += tk->rp.kp.offset;
 	} else {
@@ -766,8 +770,13 @@ 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_without_suffix(
+				count_symbols, func_name, &ctx.count);
+		}
+	}
 
 	module_kallsyms_on_each_symbol(mod, count_mod_symbols, &ctx);
 
-- 
2.43.0