From: Pingfan Liu <kernelfans@gmail.com>
To: Baoquan He <bhe@redhat.com>
Cc: x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Will Deacon <will.deacon@arm.com>,
Nicolas Pitre <nico@linaro.org>,
Chao Fan <fanc.fnst@cn.fujitsu.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCHv3] x86/boot/KASLR: skip the specified crashkernel region
Date: Thu, 4 Apr 2019 17:40:26 +0800 [thread overview]
Message-ID: <CAFgQCTs0YTFOePmv6R+j41BTsixE0HdED8kHHVY6+GaZzq4TMg@mail.gmail.com> (raw)
In-Reply-To: <20190403031049.GP7627@MiWiFi-R3L-srv>
On Wed, Apr 3, 2019 at 11:10 AM Baoquan He <bhe@redhat.com> wrote:
>
> On 04/03/19 at 10:58am, Pingfan Liu wrote:
> > On Tue, Apr 2, 2019 at 4:08 PM Baoquan He <bhe@redhat.com> wrote:
> > >
> > > > +/* handle crashkernel=x@y or =range1:size1[,range2:size2,...]@offset options */
> > > > +static void mem_avoid_specified_crashkernel_region(char *option)
> > > > +{
> > > > + unsigned long long crash_size, crash_base = 0;
> > > > + char *first_colon, *first_space, *cur = option;
> > > > +
> > >
> > > Another thing which need be noticed is that you may only need to handle
> > > when '@' is found. Otherwise just let it go. Right?
> > >
> > According to kernel's behavior, only the last "crashkernel=" option
> > takes effect. Hence if no '@', then clearing mem_avoid
>
> Here I mean that you can search '@' at the beginning if crashkernel is
> found. Maybe no need to clear mem_avoid since it's global data, has been
> initialized to 0 during loading. It's in BSS, right?
>
Consider the following cmdline crashkernel=256M@1G crashkernel=512M.
These two options are handled independently by handle_mem_options(),
and the later one should overwrite the previous one. This is the
behavior of current kernel's code, referring to
get_last_crashkernel().
> You don't have to search first colon or first space, then parse size of
> crashkernel, and finally find out that it's only crashkernel=512M-2G:64M,2G-:128M
> style, no '@' specified. What do you think?
>
Yes, that will be better. But I plan to reuse parse_crashkernel_mem/simple().
Thanks,
Pingfan
> >
> > > > + first_colon = strchr(option, ':');
> > > > + first_space = strchr(option, ' ');
> > > > + /* if contain ":" */
> > > > + if (first_colon && (!first_space || first_colon < first_space)) {
> > > > + int i;
> > > > + u64 total_sz = 0;
> > > > + struct boot_e820_entry *entry;
> > > > +
> > > > + for (i = 0; i < boot_params->e820_entries; i++) {
> > > > + entry = &boot_params->e820_table[i];
> > > > + /* Skip non-RAM entries. */
> > > > + if (entry->type != E820_TYPE_RAM)
> > > > + continue;
> > > > + total_sz += entry->size;
> > > > + }
> > > > + handle_crashkernel_mem(option, total_sz, &crash_size,
> > > > + &crash_base);
> > > > + } else {
> > > > + crash_size = memparse(option, &cur);
> > > > + if (option == cur)
> > > > + return;
> > > > + while (*cur && *cur != ' ' && *cur != '@')
> > > > + cur++;
> > > > + if (*cur == '@') {
> > > > + option = cur + 1;
> > > > + crash_base = memparse(option, &cur);
> > > > + }
> > > > + }
> > > > + if (crash_base) {
> > > > + mem_avoid[MEM_AVOID_CRASHKERNEL].start = crash_base;
> > > > + mem_avoid[MEM_AVOID_CRASHKERNEL].size = crash_size;
> > > > + } else {
> > > > + /*
> > > > + * Clearing mem_avoid if no offset is given. This is consistent
> > > > + * with kernel, which uses the last crashkernel= option.
> > > > + */
> > > > + mem_avoid[MEM_AVOID_CRASHKERNEL].start = 0;
> > > > + mem_avoid[MEM_AVOID_CRASHKERNEL].size = 0;
> > > > + }
> > > > +}
prev parent reply other threads:[~2019-04-04 9:40 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-02 4:10 [PATCHv3] x86/boot/KASLR: skip the specified crashkernel region Pingfan Liu
2019-04-02 6:19 ` Chao Fan
2019-04-02 6:52 ` Baoquan He
2019-04-02 6:58 ` Pingfan Liu
2019-04-02 7:59 ` Chao Fan
2019-04-02 6:46 ` Baoquan He
2019-04-03 2:59 ` Pingfan Liu
2019-04-02 8:08 ` Baoquan He
2019-04-03 2:58 ` Pingfan Liu
2019-04-03 3:10 ` Baoquan He
2019-04-04 9:40 ` Pingfan Liu [this message]
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