linux-kernel - Re: [PATCH v8 0/3] ARM: Implement MODULE

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Message-ID: <20210412110810.t7pqkwawn5zmqbca@e107158-lin.cambridge.arm.com>
Date:   Mon, 12 Apr 2021 12:08:10 +0100
From:   Qais Yousef <qais.yousef@....com>
To:     Alexander Sverdlin <alexander.sverdlin@...ia.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Florian Fainelli <f.fainelli@...il.com>,
        linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v8 0/3] ARM: Implement MODULE_PLT support in FTRACE

Hi Alexander

Fixing Ard's email as the Linaro one keeps bouncing back. Please fix that in
your future postings.

On 04/12/21 08:28, Alexander Sverdlin wrote:
> Hi!
> 
> On 09/04/2021 17:33, Qais Yousef wrote:
> > I still think the ifdefery in patch 3 is ugly. Any reason my suggestion didn't
> > work out for you? I struggle to see how this is better and why it was hard to
> > incorporate my suggestion.
> > 
> > For example
> > 
> > 	-       old = ftrace_call_replace(ip, adjust_address(rec, addr));
> > 	+#ifdef CONFIG_ARM_MODULE_PLTS
> > 	+       /* mod is only supplied during module loading */
> > 	+       if (!mod)
> > 	+               mod = rec->arch.mod;
> > 	+       else
> > 	+               rec->arch.mod = mod;
> > 	+#endif
> > 	+
> > 	+       old = ftrace_call_replace(ip, aaddr,
> > 	+                                 !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
> > 	+#ifdef CONFIG_ARM_MODULE_PLTS
> > 	+       if (!old && mod) {
> > 	+               aaddr = get_module_plt(mod, ip, aaddr);
> > 	+               old = ftrace_call_replace(ip, aaddr, true);
> > 	+       }
> > 	+#endif
> > 	+
> > 
> > There's an ifdef, followed by a code that embeds
> > !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) followed by another ifdef :-/
> 
> No, it's actually two small ifdefed blocks added before and after an original call,
> which parameters have been modified as well. The issue with arch.mod was explained
> by Steven Rostedt, maybe you've missed his email.

If you're referring to arch.mod having to be protected by the ifdef I did
address that. Please look at my patch.

My comment here refers to the ugliness of this ifdefery. Introducing 2 simple
wrapper functions would address that as I've demonstrated in my
suggestion/patch.

Thanks

--
Qais Yousef