Re: [PATCH] Work around for enabling CONFIG_CMDLINE on ppc64le

[Akshay Adiga]

Hi Michael,

Anton found this bug and raised it against gcc v7.0 and a fix is available
 in upstream gcc.

	https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71709

Currently, gcc v5.4.0  and v6.1.1 shipped with Ubuntu 16.04 and 16.10  respectively,
 are hitting this problem.

I have also raised bug against Ubuntu for fixing gcc for 16.04.

https://bugzilla.linux.ibm.com/show_bug.cgi?id=146668


On 09/22/2016 03:51 PM, Michael Ellerman wrote:
> Akshay Adiga <akshay.adiga@xxxxxxxxxxxxxxxxxx> writes:
>
> > Observed that boot arguments (passed as CONFIG_CMDLINE)  are not being
> > picked up by kernel while using gcc-ppc64-linux-gnu v5.4.0 and v6.1.1.
> > While it works as expected with v5.3.1 .
> >
> > Found that in init/main.c in  setup_command_line() the pointers passed to
> > strcpy() is messed up.
> Hi Akshay,
>
> Thanks for debugging this.
>
> > The problem goes away when compiler optimization is restricted to -O1.
> > diff --git a/init/main.c b/init/main.c
> > index a8a58e2..4259c42 100644
> > --- a/init/main.c
> > +++ b/init/main.c
> > @@ -358,7 +358,13 @@ static inline void smp_prepare_cpus(unsigned int maxcpus) { }
> >    * parsing is performed in place, and we should allow a component to
> >    * store reference of name/value for future reference.
> >    */
> > -static void __init setup_command_line(char *command_line)
> > +static void __init
> > +#ifdef CONFIG_PPC64
> > +	#if  GCC_VERSION > 50301
> > +		__attribute__((optimize("-O1")))
> > +	#endif
> > +#endif
> > +		setup_command_line(char *command_line)
> >   {
> >   	saved_command_line =
> >   		memblock_virt_alloc(strlen(boot_command_line) + 1, 0);
> But I can't merge that patch.
>
> Our options are one or both of:
>   - get GCC fixed and backport the fix to the compilers we care about.
>   - blacklist the broken compiler versions.
>
> Is there a GCC bug filed for this?
>
> cheers