Messages in this thread | | | Date | Fri, 24 Jul 2020 14:34:57 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH v2 2/2] kernel/trace: Remove function callback casts |
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On Fri, 24 Jul 2020 19:55:00 +0200 Oscar Carter <oscar.carter@gmx.com> wrote:
> > Which one of the above is this patch set for? > > This patch is the result of a warning obtained with the following: > > make allmodconfig ARCH=powerpc > make ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu- -j4 > > And with the -Wcast-function-type enabled in the top level makefile.
Looking into powerpc I found this:
arch/powerpc/include/asm/ftrace.h:
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS #define ARCH_SUPPORTS_FTRACE_OPS 1 #endif
arch/powerpc/Kconfig:
select HAVE_DYNAMIC_FTRACE_WITH_REGS if MPROFILE_KERNEL [..]
config MPROFILE_KERNEL depends on PPC64 && CPU_LITTLE_ENDIAN && FUNCTION_TRACER def_bool $(success,$(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC) -I$(srctree)/include -D__KERNEL__)
So, it looks like you need to be 64bit PowerPC, Little Endian, and gcc needs to support -mprofile.
Otherwise, it falls back to the old way that does the type casting.
If you are really concerned about this, I would recommend adding support to the architecture you care about, and then this will no longer be an issue.
The funny part is, you can still add support for ftrace_ops, without adding support for DYNAMIC_FTRACE_WITH_REGS, if you only care about not having to do that typecast.
My NAK still stands. I wont let an intrusive patch be added to the ftrace core code to deal with an unsupported feature in an architecture.
I would be will to add that linker trick to remove the warning. Or we just use that warning as incentive to get architecture developers to implement this feature ;-)
-- Steve
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