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Date:   Mon, 28 Mar 2022 12:23:42 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Christophe Leroy <christophe.leroy@csgroup.eu>
Cc:     Josh Poimboeuf <jpoimboe@redhat.com>,
        Jiri Kosina <jikos@kernel.org>,
        Miroslav Benes <mbenes@suse.cz>,
        Petr Mladek <pmladek@suse.com>,
        Joe Lawrence <joe.lawrence@redhat.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
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        Vasily Gorbik <gor@linux.ibm.com>,
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        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
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        live-patching@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-s390@vger.kernel.org, x86@kernel.org,
        Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH] livepatch: Remove klp_arch_set_pc() and asm/livepatch.h
Message-ID: <20220328102342.GW8939@worktop.programming.kicks-ass.net>
References: <e029c7cfde436f6bbf99148ab14dc2da99add503.1648447981.git.christophe.leroy@csgroup.eu>
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On Mon, Mar 28, 2022 at 08:26:48AM +0200, Christophe Leroy wrote:
> All three versions of klp_arch_set_pc() do exactly the same: they
> call ftrace_instruction_pointer_set().
> 
> Call ftrace_instruction_pointer_set() directly and remove
> klp_arch_set_pc().
> 
> As klp_arch_set_pc() was the only thing remaining in asm/livepatch.h
> on x86 and s390, remove asm/livepatch.h
> 
> livepatch.h remains on powerpc but its content is exclusively used
> by powerpc specific code.

The only remaining thing seems to be a klp_init_thread_info() for ppc64,
but yeah..

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

> diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c
> index c172bf92b576..4c4f5a776d80 100644
> --- a/kernel/livepatch/patch.c
> +++ b/kernel/livepatch/patch.c
> @@ -118,7 +118,7 @@ static void notrace klp_ftrace_handler(unsigned long ip,
>  	if (func->nop)
>  		goto unlock;
>  
> -	klp_arch_set_pc(fregs, (unsigned long)func->new_func);
> +	ftrace_instruction_pointer_set(fregs, (unsigned long)func->new_func);
>  
>  unlock:
>  	ftrace_test_recursion_unlock(bit);

So ptrace has instruction_pointer_set(), I'm not sure why we have yet
another variant in the ftrace_ namespace. Perhaps also delete that?