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

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Message-ID: <CAFgQCTuu1j64QUHfXp3MJYOD2U9zhrcNCNkWA=6KVy6_cwYyNw@mail.gmail.com>
Date:   Mon, 25 Mar 2019 13:56:37 +0800
From:   Pingfan Liu <kernelfans@...il.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     Dave Young <dyoung@...hat.com>, 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 Fri, Mar 22, 2019 at 4:34 PM Baoquan He <bhe@...hat.com> wrote:
>
> On 03/22/19 at 03:52pm, Baoquan He wrote:
> > 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?
>
> OK, I misunderstood it. We do have parse_crashkernel_simple() to handle
> crashkernel=size[@offset] case, to differente with other complicated
> cases, like crashkernel=size,[high|low],
>
> Then I am fine with this naming. Soryy about the noise.
>
> By the way, do you think if we should take care of this case:
> crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
>
> It can also specify @offset. Not sure if it's too complicated, you may
> have a investigation.
>
OK, I will try it.
> These two cases have dependency on your crashkernel=X bug fix patch.
No, crashkernel=x@y should have no dependcy on crashkernel=X, the
later one relies on memblock searching.
> The current code only allow crashkernel= to reserve under 896MB. I
> noticed Boris has agreed on the solution. Maybe you can repost a new
> version based on the discussion.
I will sync with Dave to see whether he will post the new version.

Thank you for kindly review.

Regards,
Pingfan
>
> http://lkml.kernel.org/r/1548047768-7656-1-git-send-email-kernelfans@gmail.com
> [PATCHv7] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr
>
> Thanks
> Baoquan
>
> >
> > > 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
> > > > >