ARM: always use ARM_UNWIND for thumb2 kernels

Thumb2 kernels cannot be built with frame pointers, but can use the
ARM_UNWIND feature for unwinding instead. This makes sure that all
features that rely on unwinding includeing CONFIG_LATENCYTOP and
FAULT_INJECTION_STACKTRACE_FILTER do not enable frame pointers
when the unwinder is already selected, and we always build with
the unwinder when we want a thumb2 kernel, to make sure we do not
get the frame pointers instead.

A different option would be to redefine the CONFIG_FRAME_POINTERS
option on ARM to mean builing with either frame pointers or
the unwinder, and then select which one to use based on the
CPU architecture or another user option. That would still allow
building thumb2 kernels without the unwinder but would also be
more confusing.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4e1eee0c2d64..497af51e9176 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1457,6 +1457,7 @@ config THUMB2_KERNEL
         depends on CPU_V7 && !CPU_V6 && !CPU_V6K && EXPERIMENTAL
         select AEABI
         select ARM_ASM_UNIFIED
+        select ARM_UNWIND
         help
           By enabling this option, the kernel will be compiled in
           Thumb-2 mode. A compiler/assembler that understand the unified