[U-Boot] [PATCH 1/1] efi_loader: fix bug in efi_add_known_memory

[Alexander Graf]

On 18.09.17 12:56, Heinrich Schuchardt wrote:
> In efi_add_known_memory the start address is correctly rounded
> up to a mulitple of EFI_PAGE_SIZE.
> By this rounding we may loose up to EFI_PAGE_MASK bytes.
> The current code does not take this loss of available memory
> into account when calculating the number of pages.
> 
> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
> ---
>   lib/efi_loader/efi_memory.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
> index c1a080e2e9..38b0e1d808 100644
> --- a/lib/efi_loader/efi_memory.c
> +++ b/lib/efi_loader/efi_memory.c
> @@ -444,8 +444,14 @@ __weak void efi_add_known_memory(void)
>   		u64 ram_start = gd->bd->bi_dram[i].start;
>   		u64 ram_size = gd->bd->bi_dram[i].size;
>   		u64 start = (ram_start + EFI_PAGE_MASK) & ~EFI_PAGE_MASK;
> -		u64 pages = (ram_size + EFI_PAGE_MASK) >> EFI_PAGE_SHIFT;
> +		u64 pages;
>   
> +		if (ram_size <= EFI_PAGE_MASK)
> +			continue;

Why? The old code accounted that as 1 page in use.

> +		pages = (ram_start + ram_size - start + EFI_PAGE_MASK) >>
> +			EFI_PAGE_SHIFT;

Hmm, looking at that code it seems quite bogus to me. Imagine we pass in 
a start address of 0x1001. Then the code will move start to 0x2000. 
That's just plain wrong - the region should start at 0x1000, no?

> +		if (pages == 0)
> +			continue;

Is this necessary? efi_add_memory_map() already checks for pages == 0.


Alex


>   		efi_add_memory_map(start, pages, EFI_CONVENTIONAL_MEMORY,
>   				   false);
>   	}
>