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Date:   Sun, 28 Apr 2019 16:37:10 +0800
From:   Dave Young <dyoung@redhat.com>
To:     Pingfan Liu <kernelfans@gmail.com>
Cc:     Matthias Brugger <mbrugger@suse.com>,
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Subject: Re: [PATCHv2] kernel/crash: make parse_crashkernel()'s return value
 more indicant
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On 04/25/19 at 04:20pm, Pingfan Liu wrote:
> On Wed, Apr 24, 2019 at 4:31 PM Matthias Brugger <mbrugger@suse.com> wrote:
> >
> >
> [...]
> > > @@ -139,6 +141,8 @@ static int __init parse_crashkernel_simple(char *cmdline,
> > >               pr_warn("crashkernel: unrecognized char: %c\n", *cur);
> > >               return -EINVAL;
> > >       }
> > > +     if (*crash_size == 0)
> > > +             return -EINVAL;
> >
> > This covers the case where I pass an argument like "crashkernel=0M" ?
> > Can't we fix that by using kstrtoull() in memparse and check if the return value
> > is < 0? In that case we could return without updating the retptr and we will be
> > fine.
> >
> It seems that kstrtoull() treats 0M as invalid parameter, while
> simple_strtoull() does not.
> 
> If changed like your suggestion, then all the callers of memparse()
> will treats 0M as invalid parameter. This affects many components
> besides kexec.  Not sure this can be done or not.

simple_strtoull is obsolete, move to kstrtoull is the right way.

$ git grep memparse|wc
    158     950   10479

Except some documentation/tools etc there are still a log of callers
which directly use the return value as the ull number without error
checking.

So it would be good to mark memparse as obsolete as well in
lib/cmdline.c, and introduce a new function eg. kmemparse() to use
kstrtoull,  and return a real error code, and save the size in an
argument like &size.  Then update X86 crashkernel code to use it.

Thanks
Dave