linux-kernel - RE: [RFC] ARC: initial ftrace support

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Message-ID: <CY4PR1201MB01207268EA87209A55C31D44A1C60@CY4PR1201MB0120.namprd12.prod.outlook.com>
Date:   Thu, 2 Apr 2020 14:15:37 +0000
From:   Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:     Claudiu Zissulescu Ianculescu <claziss@...il.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Steven Rostedt" <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: RE: [RFC] ARC: initial ftrace support

Hi Claus,

> -----Original Message-----
> From: linux-snps-arc <linux-snps-arc-bounces@...ts.infradead.org> On Behalf Of Claudiu Zissulescu
> Ianculescu
> Sent: Thursday, April 2, 2020 11:10 AM
> To: Vineet Gupta <vgupta@...opsys.com>
> Cc: Alexey Brodkin <abrodkin@...opsys.com>; linux-kernel@...r.kernel.org; Steven Rostedt
> <rostedt@...dmis.org>; Ingo Molnar <mingo@...hat.com>; linux-snps-arc@...ts.infradead.org; Eugeniy
> Paltsev <paltsev@...opsys.com>
> Subject: Re: [RFC] ARC: initial ftrace support
> 
> Hi,
> 
> ARC-gcc has two modes to call the mcount routines. When using elf32
> configuration, the toolchain is set to use newlib mcount. When
> configured for linux, gcc toolchain is using a library call to _mcall
> (single underscore)  having blink as input argument.
> So, using the proper linux toolchain, your patch should work.


Is there a chance to switch to Linux-style mcount in Elf32 toolchain with a command-line
option?

Otherwise I guess we'll need to implement some warning which explicitly says why Elf32
toolchain is not usable for building the Linux kernel... at least in case with ftrace enabled.

-Alexey