Commit 4d6d0a62 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt (Google)
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tracing: Remove redundant config HAVE_FTRACE_MCOUNT_RECORD 

Ftrace is tightly coupled with architecture specific code because it
requires the use of trampolines written in assembly. This means that when
a new feature or optimization is made, it must be done for all
architectures. To simplify the approach, CONFIG_HAVE_FTRACE_* configs are
added to denote which architecture has the new enhancement so that other
architectures can still function until they too have been updated.

The CONFIG_HAVE_FTRACE_MCOUNT was added to help simplify the
DYNAMIC_FTRACE work, but now every architecture that implements
DYNAMIC_FTRACE also has HAVE_FTRACE_MCOUNT set too, making it redundant
with the HAVE_DYNAMIC_FTRACE.

Remove the HAVE_FTRACE_MCOUNT config and use DYNAMIC_FTRACE directly where
applicable.

Link: https://lore.kernel.org/all/20250703154916.48e3ada7@gandalf.local.home/

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/20250704104838.27a18690@gandalf.local.home


Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 9b4d5d33

Documentation/trace/ftrace-design.rst

+4 −8
Original line number Diff line number Diff line
@@ -238,19 +238,15 @@ You need very few things to get the syscalls tracing in an arch. 
  - Tag this arch as HAVE_SYSCALL_TRACEPOINTS.





HAVE_FTRACE_MCOUNT_RECORD

-------------------------

HAVE_DYNAMIC_FTRACE

-------------------



See scripts/recordmcount.pl for more info.  Just fill in the arch-specific

details for how to locate the addresses of mcount call sites via objdump.

This option doesn't make much sense without also implementing dynamic ftrace.





HAVE_DYNAMIC_FTRACE

-------------------



You will first need HAVE_FTRACE_MCOUNT_RECORD and HAVE_FUNCTION_TRACER, so

scroll your reader back up if you got over eager.

You will first need HAVE_FUNCTION_TRACER, so scroll your reader back up if you

got over eager.



Once those are out of the way, you will need to implement:

	- asm/ftrace.h:

arch/arm/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -107,7 +107,6 @@ config ARM 
	select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU

	select HAVE_EXIT_THREAD

	select HAVE_GUP_FAST if ARM_LPAE

	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL

	select HAVE_FUNCTION_ERROR_INJECTION

	select HAVE_FUNCTION_GRAPH_TRACER

	select HAVE_FUNCTION_TRACER if !XIP_KERNEL

arch/arm64/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -223,7 +223,6 @@ config ARM64 
	select HAVE_EFFICIENT_UNALIGNED_ACCESS

	select HAVE_GUP_FAST

	select HAVE_FTRACE_GRAPH_FUNC

	select HAVE_FTRACE_MCOUNT_RECORD

	select HAVE_FUNCTION_TRACER

	select HAVE_FUNCTION_ERROR_INJECTION

	select HAVE_FUNCTION_GRAPH_FREGS

arch/csky/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -80,7 +80,6 @@ config CSKY 
	select HAVE_FUNCTION_TRACER

	select HAVE_FUNCTION_GRAPH_TRACER

	select HAVE_FUNCTION_ERROR_INJECTION

	select HAVE_FTRACE_MCOUNT_RECORD

	select HAVE_KERNEL_GZIP

	select HAVE_KERNEL_LZO

	select HAVE_KERNEL_LZMA

arch/loongarch/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -144,7 +144,6 @@ config LOONGARCH 
	select HAVE_EXIT_THREAD

	select HAVE_GUP_FAST

	select HAVE_FTRACE_GRAPH_FUNC

	select HAVE_FTRACE_MCOUNT_RECORD

	select HAVE_FUNCTION_ARG_ACCESS_API

	select HAVE_FUNCTION_ERROR_INJECTION

	select HAVE_FUNCTION_GRAPH_FREGS