linux-kernel - [PATCH] ARM: use ARM unwinder for gcov

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Date:   Tue,  5 May 2020 16:11:56 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Russell King <linux@...linux.org.uk>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Nathan Huckleberry <nhuck15@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH] ARM: use ARM unwinder for gcov

Using gcov on ARM fails when the frame pointer unwinder is used:

arm-linux-gnueabi-ld: kernel/softirq.o:(.ARM.exidx+0x120): undefined reference to `__aeabi_unwind_cpp_pr0'
arm-linux-gnueabi-ld: init/main.o:(.ARM.exidx+0x98): undefined reference to `__aeabi_unwind_cpp_pr0'
arm-linux-gnueabi-ld: init/version.o:(.ARM.exidx+0x0): undefined reference to `__aeabi_unwind_cpp_pr0'
arm-linux-gnueabi-ld: init/do_mounts.o:(.ARM.exidx+0x28): undefined reference to `__aeabi_unwind_cpp_pr0'
arm-linux-gnueabi-ld: init/do_mounts_initrd.o:(.ARM.exidx+0x0): undefined reference to `__aeabi_unwind_cpp_pr0'
arm-linux-gnueabi-ld: init/initramfs.o:(.ARM.exidx+0x8): more undefined references to `__aeabi_unwind_cpp_pr0' follow

This is likely a bug in clang that should be fixed in the compiler.
Forcing the use of the ARM unwinder in this configuration however
works around the problem.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/arm/Kconfig.debug | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index a1dfb04231fd..41ef58acabf7 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -56,7 +56,7 @@ choice
 
 config UNWINDER_FRAME_POINTER
 	bool "Frame pointer unwinder"
-	depends on !THUMB2_KERNEL
+	depends on !THUMB2_KERNEL && !(CC_IS_CLANG && GCOV_KERNEL)
 	select ARCH_WANT_FRAME_POINTERS
 	select FRAME_POINTER
 	help
-- 
2.26.0