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

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Message-ID: <CAFgQCTt3-9oZ6yi_MGYFOZhn5+cSdJLGf3OQRMJ1CJr0eXiE5w@mail.gmail.com>
Date:   Fri, 22 Mar 2019 15:43:35 +0800
From:   Pingfan Liu <kernelfans@...il.com>
To:     Baoquan He <bhe@...hat.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 Wed, Mar 20, 2019 at 8:25 AM Baoquan He <bhe@...hat.com> wrote:
>
> Please change subject as:
>
> "x86/boot/KASLR: skip the specified crashkernel region"
>
OK.

> Don't see why reserved is needed here.
>
> On 03/13/19 at 12:19pm, Pingfan Liu wrote:
> > crashkernel=x@y option may fail to reserve the required memory region if
> > KASLR puts kernel into the region. To avoid this uncertainty, making KASLR
> > skip the required region.
> >
> > Signed-off-by: Pingfan Liu <kernelfans@...il.com>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Ingo Molnar <mingo@...hat.com>
> > Cc: Borislav Petkov <bp@...en8.de>
> > Cc: "H. Peter Anvin" <hpa@...or.com>
> > Cc: Baoquan He <bhe@...hat.com>
> > Cc: Will Deacon <will.deacon@....com>
> > Cc: Nicolas Pitre <nico@...aro.org>
> > Cc: Pingfan Liu <kernelfans@...il.com>
> > Cc: Chao Fan <fanc.fnst@...fujitsu.com>
> > Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> > Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> > Cc: linux-kernel@...r.kernel.org
> > ---
> > v1 -> v2: fix some trival format
> >
> >  arch/x86/boot/compressed/kaslr.c | 26 ++++++++++++++++++++++++--
> >  1 file changed, 24 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> > index 9ed9709..e185318 100644
> > --- a/arch/x86/boot/compressed/kaslr.c
> > +++ b/arch/x86/boot/compressed/kaslr.c
> > @@ -109,6 +109,7 @@ enum mem_avoid_index {
> >       MEM_AVOID_BOOTPARAMS,
> >       MEM_AVOID_MEMMAP_BEGIN,
> >       MEM_AVOID_MEMMAP_END = MEM_AVOID_MEMMAP_BEGIN + MAX_MEMMAP_REGIONS - 1,
> > +     MEM_AVOID_CRASHKERNEL,
> >       MEM_AVOID_MAX,
> >  };
> >
> > @@ -240,6 +241,25 @@ static void parse_gb_huge_pages(char *param, char *val)
> >       }
> >  }
> >
> > +/* 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
the definition
/*
 * That function parses "simple" (old) crashkernel command lines like
 *
 * crashkernel=size[@offset]
 *
 * 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
> >