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Date:   Fri, 16 Apr 2021 13:38:36 -0700
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Subject: [PATCH 07/15] x86/ftrace: Use function_nocfi in MCOUNT_ADDR
From:   Sami Tolvanen <samitolvanen@google.com>
To:     x86@kernel.org
Cc:     Kees Cook <keescook@chromium.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org,
        clang-built-linux@googlegroups.com,
        Sami Tolvanen <samitolvanen@google.com>
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With CONFIG_CFI_CLANG, the compiler replaces the __fentry__ address in
MCOUNT_ADDR with the address of a CFI jump table. Use function_nocfi()
to get the actual function address.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 arch/x86/include/asm/ftrace.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index 9f3130f40807..0b7567994f4a 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -6,7 +6,7 @@
 #ifndef CC_USING_FENTRY
 # error Compiler does not support fentry?
 #endif
-# define MCOUNT_ADDR		((unsigned long)(__fentry__))
+# define MCOUNT_ADDR		((unsigned long)(function_nocfi(__fentry__)))
 #define MCOUNT_INSN_SIZE	5 /* sizeof mcount call */
 
 #ifdef CONFIG_DYNAMIC_FTRACE
-- 
2.31.1.368.gbe11c130af-goog