Re: [PATCH 7/7 v4] sh: mcount.S: fix build error when PRINTK is not enabled

Hi Geert!

On Mon, 2023-03-20 at 13:42 +0100, Geert Uytterhoeven wrote:

Oops, obviously all of that happened before my morning coffee ;-)

Makefile has:

ifdef CONFIG_FRAME_POINTER
KBUILD_CFLAGS   += -fno-omit-frame-pointer -fno-optimize-sibling-calls
KBUILD_RUSTFLAGS += -Cforce-frame-pointers=y
else
# Some targets (ARM with Thumb2, for example), can't be built with frame
# pointers.  For those, we don't have FUNCTION_TRACER automatically
# select FRAME_POINTER.  However, FUNCTION_TRACER adds -pg, and this is
# incompatible with -fomit-frame-pointer with current GCC, so we don't use
# -fomit-frame-pointer with FUNCTION_TRACER.
# In the Rust target specification, "frame-pointer" is set explicitly
# to "may-omit".
ifndef CONFIG_FUNCTION_TRACER
KBUILD_CFLAGS   += -fomit-frame-pointer
endif
endif

Your config probably has CONFIG_FRAME_POINTER set?

arch/sh/Kconfig.debug=config DWARF_UNWINDER
arch/sh/Kconfig.debug-  bool "Enable the DWARF unwinder for stacktraces"
arch/sh/Kconfig.debug-  depends on DEBUG_KERNEL
arch/sh/Kconfig.debug:  select FRAME_POINTER

You should make sure that cannot happen when CONFIG_FUNCTION_TRACER is enabled. I.e. make DWARF_UNWINDER depend on !FUNCTION_TRACER?

Other architectures do something similar:

arch/sparc/Kconfig.debug:config FRAME_POINTER
arch/sparc/Kconfig.debug-       bool
arch/sparc/Kconfig.debug-       depends on MCOUNT

arch/x86/Kconfig.debug:config FRAME_POINTER
arch/x86/Kconfig.debug- depends on !UNWINDER_ORC && !UNWINDER_GUESS
arch/x86/Kconfig.debug- bool

Probably you need to adjust the following, too:

lib/Kconfig.debug:config FRAME_POINTER
lib/Kconfig.debug-      bool "Compile the kernel with frame pointers"
lib/Kconfig.debug-      depends on DEBUG_KERNEL && (M68K || UML ||

SUPERH) || ARCH_WANT_FRAME_POINTERS lib/Kconfig.debug- default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS

i.e. drop SUPERH from the list above, and select ARCH_WANT_FRAME_POINTERS if !FUNCTION_TRACER.

Do you think you can send a patch for this change? I can then review and apply it together with Randy's series in case everything works as expected.

Adrian