linux-kernel - Re: [PATCHv2 4/8] arm64: module/ftrace: intialize PLT at load time

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Date:   Mon, 4 Nov 2019 13:55:40 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Amit Daniel Kachhap <amit.kachhap@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        catalin.marinas@....com, deller@....de, duwe@...e.de,
        James.Bottomley@...senPartnership.com, james.morse@....com,
        jeyu@...nel.org, jpoimboe@...hat.com, jthierry@...hat.com,
        linux-parisc@...r.kernel.org, mingo@...hat.com,
        peterz@...radead.org, rostedt@...dmis.org, svens@...ckframe.org,
        takahiro.akashi@...aro.org, will@...nel.org
Subject: Re: [PATCHv2 4/8] arm64: module/ftrace: intialize PLT at load time

On Sat, Nov 02, 2019 at 05:50:02PM +0530, Amit Daniel Kachhap wrote:
> On 10/29/19 10:28 PM, Mark Rutland wrote:
> > @@ -485,24 +486,33 @@ static const Elf_Shdr *find_section(const Elf_Ehdr *hdr,
> >   	return NULL;
> >   }
> > +int module_init_ftrace_plt(const Elf_Ehdr *hdr,
> > +			   const Elf_Shdr *sechdrs,
> > +			   struct module *mod)
> I think this function can be made static as it is not used anywhere.

It's only called by module_finalize() below, so making it static makese
sense; done.

Thanks
Mark.

> > +{
> > +#if defined(CONFIG_ARM64_MODULE_PLTS) && defined(CONFIG_DYNAMIC_FTRACE)
> > +	const Elf_Shdr *s;
> > +	struct plt_entry *plt;
> > +
> > +	s = find_section(hdr, sechdrs, ".text.ftrace_trampoline");
> > +	if (!s)
> > +		return -ENOEXEC;
> > +
> > +	plt = (void *)s->sh_addr;
> > +	*plt = get_plt_entry(FTRACE_ADDR, plt);
> > +	mod->arch.ftrace_trampoline = plt;
> > +#endif
> > +	return 0;
> > +}
> > +
> >   int module_finalize(const Elf_Ehdr *hdr,
> >   		    const Elf_Shdr *sechdrs,
> >   		    struct module *me)
> >   {
> >   	const Elf_Shdr *s;
> > -
> >   	s = find_section(hdr, sechdrs, ".altinstructions");
> >   	if (s)
> >   		apply_alternatives_module((void *)s->sh_addr, s->sh_size);
> > -#ifdef CONFIG_ARM64_MODULE_PLTS
> > -	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE)) {
> > -		s = find_section(hdr, sechdrs, ".text.ftrace_trampoline");
> > -		if (!s)
> > -			return -ENOEXEC;
> > -		me->arch.ftrace_trampoline = (void *)s->sh_addr;
> > -	}
> > -#endif
> > -
> > -	return 0;
> > +	return module_init_ftrace_plt(hdr, sechdrs, me);
> >   }
> >