Sorry Guys,
On Tue, Sep 3, 2019 at 11:36 PM Donald Buczek <buczek@xxxxxxxxxxxxx> wrote:
>
> Dear Simon,
>
> On 03.09.19 16:41, Simon Horman wrote:
> > On Fri, Aug 30, 2019 at 11:12:58AM +0200, Donald Buczek wrote:
> >> Linux kernel commit d52888aa2753 ("x86/mm: Move LDT remap out of KASLR
> >> region on 5-level paging") changed the base of the direct mapping
> >> from 0xffff880000000000 to 0xffff888000000000. This was merged
> >> into v4.20-rc2.
> >>
> >> Update to new address accordingly.
> >
> > Thanks, applied for inclusion in v2.0.20.
>
> I must admit, that I overlooked that d52888aa2753 ("x86/mm: Move LDT remap out of KASLR region on 5-level paging") was backported to 4.19.5 as 4074ca7d8a18 ("x86/mm: Move LDT remap out of KASLR region on 5-level paging").
>
> Bhupesh Sharma wanted to look into a a dynamic solution, which, of course, would be better. But if you still want to include this (e.g. as the fallback for the dynamic solution), you might want to replace the patch with the following one, which selects the new PAGE_OFFSET starting from kernel version 4.19.5 instead of 4.20.0.
I was in a conference last week and was not able to connect to my test
machine(s) to develop and test a more generic fix, as I suggested in
my earlier message.
I will try to work on and send a generic fix in a couple of days.
Thanks.
Bhupesh
> Donald
>
> >8------------------------------------------------------8<
>
> x86: Fix PAGE_OFFSET for kernels since 4.19.5
>
> Linux kernel commit d52888aa2753 ("x86/mm: Move LDT remap out of KASLR
> region on 5-level paging") changed the base of the direct mapping
> from 0xffff880000000000 to 0xffff888000000000. This was merged
> into v4.20-rc2.
>
> The patch was backported to 4.19.5 as 4074ca7d8a18 ("x86/mm: Move LDT
> remap out of KASLR region on 5-level paging").
>
> Update to new address accordingly.
>
> diff --git a/kexec/arch/i386/crashdump-x86.c b/kexec/arch/i386/crashdump-x86.c
> index a2aea31..f9d1998 100644
> --- a/kexec/arch/i386/crashdump-x86.c
> +++ b/kexec/arch/i386/crashdump-x86.c
> @@ -61,6 +61,8 @@ static int get_kernel_page_offset(struct kexec_info *UNUSED(info),
>
> if (kv < KERNEL_VERSION(2, 6, 27))
> elf_info->page_offset = X86_64_PAGE_OFFSET_PRE_2_6_27;
> + else if (kv < KERNEL_VERSION(4, 19, 5))
> + elf_info->page_offset = X86_64_PAGE_OFFSET_PRE_4_19_5;
> else
> elf_info->page_offset = X86_64_PAGE_OFFSET;
> }
> diff --git a/kexec/arch/i386/crashdump-x86.h b/kexec/arch/i386/crashdump-x86.h
> index ddee19f..6cd8826 100644
> --- a/kexec/arch/i386/crashdump-x86.h
> +++ b/kexec/arch/i386/crashdump-x86.h
> @@ -13,7 +13,8 @@ int load_crashdump_segments(struct kexec_info *info, char *mod_cmdline,
>
> #define X86_64__START_KERNEL_map 0xffffffff80000000ULL
> #define X86_64_PAGE_OFFSET_PRE_2_6_27 0xffff810000000000ULL
> -#define X86_64_PAGE_OFFSET 0xffff880000000000ULL
> +#define X86_64_PAGE_OFFSET_PRE_4_19_5 0xffff880000000000ULL
> +#define X86_64_PAGE_OFFSET 0xffff888000000000ULL
>
> #define X86_64_MAXMEM 0x3fffffffffffUL
>
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