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Date:   Thu,  8 Apr 2021 11:28:41 -0700
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Subject: [PATCH v6 16/18] arm64: ftrace: use function_nocfi for ftrace_call
From:   Sami Tolvanen <samitolvanen@google.com>
To:     Kees Cook <keescook@chromium.org>
Cc:     Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Will Deacon <will@kernel.org>, Jessica Yu <jeyu@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Tejun Heo <tj@kernel.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>, bpf@vger.kernel.org,
        linux-hardening@vger.kernel.org, linux-arch@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org,
        linux-pci@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 function pointers with
jump table addresses, which breaks dynamic ftrace as the address of
ftrace_call is replaced with the address of ftrace_call.cfi_jt. Use
function_nocfi() to get the address of the actual function instead.

Suggested-by: Ben Dai <ben.dai@unisoc.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
---
 arch/arm64/kernel/ftrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index 86a5cf9bc19a..b5d3ddaf69d9 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -55,7 +55,7 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 	unsigned long pc;
 	u32 new;
 
-	pc = (unsigned long)&ftrace_call;
+	pc = (unsigned long)function_nocfi(ftrace_call);
 	new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func,
 					  AARCH64_INSN_BRANCH_LINK);
 
-- 
2.31.1.295.g9ea45b61b8-goog