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SubjectRe: [PATCH] x86, efi: Only print warning when desc_size is smaller than defined one.
On Tue, 26 Apr 2011 15:42:24 -0700
Yinghai Lu <yinghai@kernel.org> wrote:

>
> One system get warning:
> Kernel-defined memdesc doesn't match the one from EFI!
>
> UEFI spec allows GetMemoryMap() return bigger desc_size and desc_ver for future
> extension.
> And desc_size is already used to get offset of next memory entry.
>
> Only need to check if desc_size is smaller than defined struct.
>
> Also print the size in warning if it happens.
>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
>
> ---
> arch/x86/platform/efi/efi.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/arch/x86/platform/efi/efi.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/platform/efi/efi.c
> +++ linux-2.6/arch/x86/platform/efi/efi.c
> @@ -448,9 +448,10 @@ void __init efi_init(void)
> printk(KERN_ERR "Could not map the EFI memory map!\n");
> memmap.map_end = memmap.map + (memmap.nr_map * memmap.desc_size);
>
> - if (memmap.desc_size != sizeof(efi_memory_desc_t))
> + if (memmap.desc_size < sizeof(efi_memory_desc_t))
> printk(KERN_WARNING
> - "Kernel-defined memdesc doesn't match the one from EFI!\n");
> + "Kernel-defined memdesc size is bigger than the one from EFI! %ld > %ld\n",
> + sizeof(efi_memory_desc_t), memmap.desc_size);

Does it make sense for this to just be a warning? If
sizeof(efi_memory_desec_t) > sizeof(memmap.desc_size) aren't we going
to run into some pretty serious problems when we start accessing
memory descriptors?

Would it not make more sense for this to be a BUG_ON()? In the unlikely
event that the kernel's efi_memory_desc_t is too large I really don't
see how we can recover from that.

--
Matt Fleming, Intel Open Source Technology Center


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