linux-kernel - Re: [PATCH v2 10/10] objtool: Support multiple stack

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Date:   Fri, 3 Apr 2020 09:55:15 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Julien Thierry <jthierry@...hat.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        raphael.gault@....com
Subject: Re: [PATCH v2 10/10] objtool: Support multiple stack_op per
 instruction

On Fri, Apr 03, 2020 at 09:01:46AM +0100, Julien Thierry wrote:
> 
> 
> On 4/2/20 6:54 PM, Josh Poimboeuf wrote:
> > On Fri, Mar 27, 2020 at 03:28:47PM +0000, Julien Thierry wrote:
> > > @@ -127,6 +129,10 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
> > >   	if (insn.sib.nbytes)
> > >   		sib = insn.sib.bytes[0];
> > > +	op = calloc(1, sizeof(*op));
> > > +	if (!op)
> > > +		return -1;
> > > +
> > 
> > Why not malloc()?
> > 
> 
> It's just that previsously, stack_op was part of the instruction structure
> and was initialized to all 0 in decode_instructions(). Now that it's created
> here, I assumed it would be better to have the same thing here and
> initialized the new stack_op to all 0.
> 
> Do you prefer to have an explicit malloc() + memset()?

Maybe just add a comment that calloc() is equivalent to malloc() +
memset() zero, for us user-space neophytes :-)

-- 
Josh