Re: [RFC] ARC: initial ftrace support

[Eugeniy Paltsev]

Hi Claudiu,
ping!

Is is possible to switch between mcount modes (Linux-style <-> baremetal-style) via command-line options for ARC GCC?

>From: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>
>Sent: Thursday, April 2, 2020 17:15
>To: Claudiu Zissulescu Ianculescu
>Cc: linux-kernel@xxxxxxxxxxxxxxx; Steven Rostedt; Ingo Molnar; linux-snps-arc@xxxxxxxxxxxxxxxxxxx; Eugeniy Paltsev; Vineet Gupta
>Subject: RE: [RFC] ARC: initial ftrace support
>
> Hi Claus,
>
>> -----Original Message-----
>> From: linux-snps-arc <linux-snps-arc-bounces@xxxxxxxxxxxxxxxxxxx> On Behalf Of Claudiu Zissulescu
>> Ianculescu
>> Sent: Thursday, April 2, 2020 11:10 AM
>> To: Vineet Gupta <vgupta@xxxxxxxxxxxx>
>> Cc: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; Steven Rostedt
>> <rostedt@xxxxxxxxxxx>; Ingo Molnar <mingo@xxxxxxxxxx>; linux-snps-arc@xxxxxxxxxxxxxxxxxxx; Eugeniy
>> Paltsev <paltsev@xxxxxxxxxxxx>
>> 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