[PATCH v2] kallsyms: strip ThinLTO postfix ".cfi_jt"

From: Padmanabha Srinivasaiah <treasure4paddy@gmail.com>
To: jeyu@kernel.org, keescook@chromium.org
Cc: samitolvanen@google.com, treasure4paddy@gmail.com,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Miroslav Benes <mbenes@suse.cz>, Petr Mladek <pmladek@suse.com>,
	Miguel Ojeda <ojeda@kernel.org>, Joe Perches <joe@perches.com>,
	Stephen Boyd <swboyd@chromium.org>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: [PATCH v2] kallsyms: strip ThinLTO postfix ".cfi_jt"
Date: Tue, 27 Jul 2021 16:06:15 +0200	[thread overview]
Message-ID: <20210727140618.19130-1-treasure4paddy@gmail.com> (raw)
In-Reply-To: <20210727131853.GA18032@pswork>

Clang ThinLTO adds a postfix ".cfi_jt" to a symbols of extern functions.
For example this breaks syscall tracer that doesn't expect such postfix,
so strip out the postfix from the output.

Signed-off-by: Padmanabha Srinivasaiah <treasure4paddy@gmail.com>
---
Change in v2:
  - Use existing routine in kallsyms to strip postfix ".cfi_jt" from
    extern function name.
  - Modified the commit message accordingly

 kernel/kallsyms.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 0ba87982d017..e9148626ae6c 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -166,16 +166,20 @@ static unsigned long kallsyms_sym_address(int idx)
 
 #if defined(CONFIG_CFI_CLANG) && defined(CONFIG_LTO_CLANG_THIN)
 /*
- * LLVM appends a hash to static function names when ThinLTO and CFI are
- * both enabled, i.e. foo() becomes foo$707af9a22804d33c81801f27dcfe489b.
- * This causes confusion and potentially breaks user space tools, so we
- * strip the suffix from expanded symbol names.
+ * LLVM appends a hash to static function names and just ".cfi_jt" postfix
+ * for non-static functions when both ThinLTO and CFI are enabled,
+ * i.e. for example foo() becomes foo$707af9a22804d33c81801f27dcfe489b.
+ * This causes confusion and potentially breaks user space tools and
+ * built-in components, so we strip the suffix from expanded symbol names.
  */
 static inline bool cleanup_symbol_name(char *s)
 {
 	char *res;
 
 	res = strrchr(s, '$');
+	if (!res)
+		res = strstr(s, ".cfi_jt");
+
 	if (res)
 		*res = '\0';
 
-- 
2.17.1

