Most of ARCHs use empty ftrace_dyn_arch_init(), introduce a weak common
ftrace_dyn_arch_init() to cleanup them.

Link: https://lkml.kernel.org/r/20210909090216.1955240-1-o451686892@gmail.com

Acked-by: Heiko Carstens <hca@linux.ibm.com> (s390)
Acked-by: Helge Deller <deller@gmx.de> (parisc)
Signed-off-by: Weizhao Ouyang <o451686892@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Better describe what these functions do.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

When CONFIG_DYNAMIC_FTRACE is enabled, static ftrace will fail to
boot up and compile. It's a carelessness when developing "dynamic
ftrace" and "ftrace with regs".

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>

If ICACHE_INS is not supported, we use IPI to sync icache on each
core. But ftrace_modify_code is called from stop_machine from default
implementation of arch_ftrace_update_code and stop_machine callback
is irq_disabled. When you call ipi with irq_disabled, a deadlock will
happen.

We couldn't use icache_flush with irq_disabled, but startup make_nop
is specific case and it needn't ipi other cores.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>

This patch implements FTRACE_WITH_REGS for csky, which allows a traced
function's arguments (and some other registers) to be captured into a
struct pt_regs, allowing these to be inspected and/or modified.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>

Support dynamic ftrace including dynamic graph tracer. Gcc-csky with -pg
will produce call site in every function prologue and we can use these
call site to hook trace function.

gcc with -pg origin call site:
	push	lr
	jbsr	_mcount
	nop32
	nop32

If the (callee - caller)'s offset is in range of bsr instruction, we'll
modify code with:
	push	lr
	bsr	_mcount
	nop32
	nop32
Else if the (callee - caller)'s offset is out of bsr instrunction, we'll
modify code with:
	push	lr
	movih	r26, ...
	ori	r26, ...
	jsr	r26

(r26 is reserved for jsr link reg in csky abiv2 spec.)

Signed-off-by: Guo Ren <ren_guo@c-sky.com>

With csky-gcc -pg -mbacktrace, ftrace call graph supported.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>

When gcc with -pg, it'll add _mcount stub in every function. We need
implement the _mcount in kernel and ftrace depends on stackstrace.

To do: call-graph, dynamic ftrace

Signed-off-by: Guo Ren <ren_guo@c-sky.com>