Re: [Xen-devel] [PATCH 1/3] x86/EFI: don't apply relocations to l{2, 3}_bootmap

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 19/08/16 08:50, Jan Beulich wrote:
> Other than claimed in commit 2ce5963727's ("x86: construct the
> {l2,l3}_bootmap at compile time") the initialization of the two page
> tables doesn't take care of everything without furher adjustment: The
> compile time initialization obviously requires base relocations, and
> those get processed after efi_arch_memory_setup(). Hence without
> additional care the correctly initialized values may then get wrongly
> "adjusted" again. Except the two table from being subject to base
> relocation.

Do you mean Exempt? "Except the two tables" doesn't parse.

>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> --- a/xen/arch/x86/efi/efi-boot.h
> +++ b/xen/arch/x86/efi/efi-boot.h
> @@ -47,11 +47,23 @@ static void __init efi_arch_relocate_ima
>  
>      for ( base_relocs = __base_relocs_start; base_relocs < 
> __base_relocs_end; )
>      {
> -        unsigned int i, n;
> +        unsigned int i = 0, n;
>  
>          n = (base_relocs->size - sizeof(*base_relocs)) /
>              sizeof(*base_relocs->entries);
> -        for ( i = 0; i < n; ++i )
> +
> +        /*
> +         * Relevant l{2,3}_bootmap entries get initialized explicitly in
> +         * efi_arch_memory_setup(), so we must not apply relocations there.
> +         * l2_identmap's first slot, otoh, should be handled normally, as

And l3 surely?

Reviewed-by: Andrew Cooper <andrew.cooper@xxxxxxxxxx>

> +         * efi_arch_memory_setup() won't touch it (xen_phys_start should
> +         * never be zero).
> +         */
> +        if ( xen_phys_start + base_relocs->rva == (unsigned long)l3_bootmap 
> ||
> +             xen_phys_start + base_relocs->rva == (unsigned long)l2_bootmap )
> +            i = n;
> +
> +        for ( ; i < n; ++i )
>          {
>              unsigned long addr = xen_phys_start + base_relocs->rva +
>                                   (base_relocs->entries[i] & 0xfff);
>
>
>


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