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From: Sergey Shtylyov <>
To: Steven Rostedt <>, <>
Cc: Ingo Molnar <>,
	Andrew Morton <>,
	Yoshinori Sato <>,
	Rich Felker <>, <>
Subject: Re: [for-next][PATCH 10/12] ftrace/sh: Add arch_ftrace_ops_list_func stub to have compressed image still link
Date: Wed, 27 Oct 2021 11:58:31 +0300	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 26.10.2021 19:23, Steven Rostedt wrote:

> From: "" <>

    Collective author, really? :-)

> Using the linker script to fix an issue where some archs call the
> function tracer with just the ip (instruction pointer) and pip (parent
> instruction pointer) where as more up to date archs also pass in the
> associated ftrace_ops and the ftrace_regs pointer, the generic code
> will be called either with two parameters or four. To avoid any C
> undefined behavior of calling two parameters to four or four to two
> parameter function, two functions are created, where a preprocessor
> macro uses the one that matches the architecture. As the function
> pointers for them may be different, a typecast is used. But this
> triggers issues with newer compilers that will fail due to -Werror.
> A linker trick is now used to map the generic function to the function
> that is used (note the generic function is only used to set the default
> function callback). The linker trick defines ftrace_ops_list_func (the
> generic function) to arch_ftrace_ops_list_func (the arch defined one).
> Link:
> But this fails sh arch because their linker script is included in their
> compressed image that does not define arch_ftrace_ops_list_func at all
>    sh4-linux-ld:arch/sh/boot/compressed/../../kernel/ undefined symbol `arch_ftrace_ops_list_func' referenced in expression
> Included a stub by that name in the misc.c to allow the code to
> compile and link, even though it's not used.
> This is similar to what was done for ftrace_stub:
>    b83b43ffc6e4b ("fgraph: Fix function type mismatches of
>    ftrace_graph_return using ftrace_stub")
> Link:
> Cc: Yoshinori Sato <>
> Cc: Rich Felker <>
> Cc:
> Signed-off-by: Steven Rostedt (VMware) <>

MBR, Sergey

  reply	other threads:[~2021-10-27  8:58 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <>
2021-10-26 16:23 ` Steven Rostedt
2021-10-27  8:58   ` Sergey Shtylyov [this message]
2021-10-27 12:01     ` Steven Rostedt

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