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Date: Mon, 24 Feb 2025 17:25:42 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Sathvika Vasireddy <sv@linux.ibm.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>, christophe.leroy@csgroup.eu,
	npiggin@gmail.com, maddy@linux.ibm.com,
	linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	llvm@lists.linux.dev
Subject: Re: [RFC PATCH] objtool: Skip unannotated intra-function call
 warning for bl+mflr pattern
Message-ID: <20250224162542.GE11590@noisy.programming.kicks-ass.net>
References: <20250219162014.10334-1-sv@linux.ibm.com>
 <20250220195940.ely2l2fpsozd2tuv@jpoimboe>
 <4bea75bc-d3f6-4972-b644-f9b5a4e8bb77@linux.ibm.com>
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In-Reply-To: <4bea75bc-d3f6-4972-b644-f9b5a4e8bb77@linux.ibm.com>

On Fri, Feb 21, 2025 at 02:20:41PM +0530, Sathvika Vasireddy wrote:

> > > @@ -1625,6 +1626,11 @@ static int add_call_destinations(struct objtool_file *file)
> > >   		reloc = insn_reloc(file, insn);
> > >   		if (!reloc) {
> > >   			dest_off = arch_jump_destination(insn);
> > > +
> > > +			next_insn = next_insn_same_func(file, insn);
> > > +			if (next_insn && dest_off == next_insn->offset)
> > > +				continue;
> > > +
> > This won't work on x86, where an intra-function call is converted to a
> > stack-modifying JUMP.  So this should probably be checked in an
> > arch-specific function.
> 
> Thanks for letting me know, I'll introduce arch_skip_call_warning() to
> handle architecture specific cases in the next patch I send.

Can't you detect this pattern in decode and simpy not emit the call
instruction?