Re: [Xen-devel] [PATCH RFC 6/7] xen/x86/efi: Verify dom0 kernel with SHIM_LOCK protocol in efi_multiboot2()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.07.17 at 23:53, <daniel.kiper@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/boot/head.S
> +++ b/xen/arch/x86/boot/head.S
> @@ -383,9 +383,13 @@ __efi64_mb2_start:
>          jmp     x86_32_switch
>  
>  .Lefi_multiboot2_proto:
> -        /* Zero EFI SystemTable and EFI ImageHandle addresses. */
> +        /*
> +         * Zero EFI SystemTable, EFI ImageHandle and
> +         * dom0 kernel module struct addresses.
> +         */
>          xor     %esi,%esi
>          xor     %edi,%edi
> +        xor     %r14d,%r14d
>  
>          /* Skip Multiboot2 information fixed part. */
>          lea     (MB2_fixed_sizeof+MULTIBOOT2_TAG_ALIGN-1)(%rbx),%ecx
> @@ -423,6 +427,15 @@ __efi64_mb2_start:
>          cmove   MB2_efi64_ih(%rcx),%rdi
>          je      .Lefi_mb2_next_tag
>  
> +        /* Get dom0 kernel module struct address from Multiboot2 
> information. */
> +        cmpl    $MULTIBOOT2_TAG_TYPE_MODULE,MB2_tag_type(%rcx)
> +        jne     .Lefi_mb2_end
> +
> +        test    %r14d,%r14d
> +        cmovz   %ecx,%r14d
> +        jmp     .Lefi_mb2_next_tag
> +
> +.Lefi_mb2_end:
>          /* Is it the end of Multiboot2 information? */
>          cmpl    $MULTIBOOT2_TAG_TYPE_END,MB2_tag_type(%rcx)
>          je      .Lrun_bs
> @@ -484,9 +497,12 @@ __efi64_mb2_start:
>          /* Keep the stack aligned. Do not pop a single item off it. */
>          mov     (%rsp),%rdi
>  
> +        mov     %r14d,%edx
> +
>          /*
>           * efi_multiboot2() is called according to System V AMD64 ABI:
> -         *   - IN:  %rdi - EFI ImageHandle, %rsi - EFI SystemTable.
> +         *   - IN: %rdi - EFI ImageHandle, %rsi - EFI SystemTable,
> +         *         %rdx - dom0 kernel module struct address.

How come everything further up treats this as a 32-bit quantity only?

> @@ -47,6 +49,7 @@ extern const struct pe_base_relocs {
>  
>  static void __init efi_arch_relocate_image(unsigned long delta)
>  {
> +#if 0
>      const struct pe_base_relocs *base_relocs;
>  
>      for ( base_relocs = __base_relocs_start; base_relocs < 
> __base_relocs_end; )
> @@ -95,6 +98,7 @@ static void __init efi_arch_relocate_image(unsigned long 
> delta)
>          }
>          base_relocs = (const void *)(base_relocs->entries + i + (i & 1));
>      }
> +#endif
>  }

???

> @@ -669,7 +673,9 @@ static bool __init 
> efi_arch_use_config_file(EFI_SYSTEM_TABLE *SystemTable)
>  
>  static void efi_arch_flush_dcache_area(const void *vaddr, UINTN size) { }
>  
> -void __init efi_multiboot2(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE 
> *SystemTable)
> +void __init efi_multiboot2(EFI_HANDLE ImageHandle,
> +                           EFI_SYSTEM_TABLE *SystemTable,
> +                           multiboot2_tag_module_t *dom0_kernel)

const?

Jan



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