linux-kernel - Re: [PATCHv2] x86/boot/KASLR: skip the specified crashkernel reserved region

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Date:   Fri, 22 Mar 2019 15:52:59 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Pingfan Liu <kernelfans@...il.com>
Cc:     x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Will Deacon <will.deacon@....com>,
        Nicolas Pitre <nico@...aro.org>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2] x86/boot/KASLR: skip the specified crashkernel
 reserved region

On 03/22/19 at 03:43pm, Pingfan Liu wrote:
> > > +/* parse crashkernel=x@y option */
> > > +static void mem_avoid_crashkernel_simple(char *option)
> >
> > Chao ever mentioned this, I want to ask again, why does it has to be
> > xxx_simple()?
> >
> Seems that I had replied Chao's question in another email. The naming
> follows the function parse_crashkernel_simple(), as the notes above
                       ~~~~~~~~~~~~~~~~~~~~~~~~

Sorry, I don't get.  typo?

> the definition
> /*
>  * That function parses "simple" (old) crashkernel command lines like
>  *
>  * crashkernel=size[@offset]

Hmm, should only crashkernel=size@...set be cared? crashkernel=size will
auto finding a place to reserve, and that is after KASLR.

>  *
>  * It returns 0 on success and -EINVAL on failure.
>  */
> static int __init parse_crashkernel_simple(char *cmdline,
> 
> Do you have alternative suggestion?
> 
> > Except of these, patch looks good to me. It's a nice catch, and only
> > need a simple fix based on the current code.
> >
> Thank you for the kindly review.
> 
> Regards,
> Pingfan
> 
> > Thanks
> > Baoquan
> >
> > > +{
> > > +     unsigned long long crash_size, crash_base;
> > > +     char *cur = option;
> > > +
> > > +     crash_size = memparse(option, &cur);
> > > +     if (option == cur)
> > > +             return;
> > > +
> > > +     if (*cur == '@') {
> > > +             option = cur + 1;
> > > +             crash_base = memparse(option, &cur);
> > > +             if (option == cur)
> > > +                     return;
> > > +             mem_avoid[MEM_AVOID_CRASHKERNEL].start = crash_base;
> > > +             mem_avoid[MEM_AVOID_CRASHKERNEL].size = crash_size;
> > > +     }
> > > +}
> > >
> > >  static void handle_mem_options(void)
> > >  {
> > > @@ -250,7 +270,7 @@ static void handle_mem_options(void)
> > >       u64 mem_size;
> > >
> > >       if (!strstr(args, "memmap=") && !strstr(args, "mem=") &&
> > > -             !strstr(args, "hugepages"))
> > > +             !strstr(args, "hugepages") && !strstr(args, "crashkernel="))
> > >               return;
> > >
> > >       tmp_cmdline = malloc(len + 1);
> > > @@ -286,6 +306,8 @@ static void handle_mem_options(void)
> > >                               goto out;
> > >
> > >                       mem_limit = mem_size;
> > > +             } else if (strstr(param, "crashkernel")) {
> > > +                     mem_avoid_crashkernel_simple(val);
> > >               }
> > >       }
> > >
> > > @@ -414,7 +436,7 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
> > >
> > >       /* We don't need to set a mapping for setup_data. */
> > >
> > > -     /* Mark the memmap regions we need to avoid */
> > > +     /* Mark the regions we need to avoid */
> > >       handle_mem_options();
> > >
> > >  #ifdef CONFIG_X86_VERBOSE_BOOTUP
> > > --
> > > 2.7.4
> > >