arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS

DYNAMIC_FTRACE_WITH_REGS uses -fpatchable-function-entry, which makes
running recordmcount unnecessary as there are no mcount calls in object
files, and __mcount_loc doesn't need to be generated.

While there's normally no harm in running recordmcount even when it's
not strictly needed, this won't work with LTO as we have LLVM bitcode
instead of ELF objects.

This change selects FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY, which
disables recordmcount when patchable function entries are used instead.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-16-samitolvanen@google.com

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 05e17351e4f334d765744af5172050c843bda79e..d644d975eddbf49899ba25ab6fd88b81adc4cc2b 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -162,6 +162,8 @@ config ARM64
        select HAVE_DYNAMIC_FTRACE
        select HAVE_DYNAMIC_FTRACE_WITH_REGS \
                if $(cc-option,-fpatchable-function-entry=2)
+       select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY \
+               if DYNAMIC_FTRACE_WITH_REGS
        select HAVE_EFFICIENT_UNALIGNED_ACCESS
        select HAVE_FAST_GUP
        select HAVE_FTRACE_MCOUNT_RECORD