[U-Boot] [RFC] efi_loader: Handle 32-bit memory overflows

[Alexander Graf]

> Am 13.04.2016 um 05:24 schrieb Andreas Färber <afaerber at suse.de>:
> 
> jetson-tk1 has 2 GB of RAM at 0x80000000, causing gd->ram_top to be zero.
> Handle this by replacing it with 0x100000000 in that case.

Nice catch!

> 
> Cc: Alexander Graf <agraf at suse.de>
> Signed-off-by: Andreas Färber <afaerber at suse.de>
> ---
> lib/efi_loader/efi_memory.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
> index 138736f..7b87108 100644
> --- a/lib/efi_loader/efi_memory.c
> +++ b/lib/efi_loader/efi_memory.c
> @@ -225,7 +225,7 @@ efi_status_t efi_allocate_pages(int type, int memory_type,
>    switch (type) {
>    case 0:
>        /* Any page */
> -        addr = efi_find_free_memory(len, gd->ram_top);
> +        addr = efi_find_free_memory(len, gd->ram_top == 0 ? 0x100000000ull : gd->ram_top);

Couldn't we just use gd->ram_top - 1? Then we underflow to 0xffffffff and everything should just work.

>        if (!addr) {
>            r = EFI_NOT_FOUND;
>            break;
> @@ -343,7 +343,7 @@ int efi_memory_init(void)
> 
>    /* Add U-Boot */
>    uboot_start = (gd->start_addr_sp - uboot_stack_size) & ~EFI_PAGE_MASK;
> -    uboot_pages = (gd->ram_top - uboot_start) >> EFI_PAGE_SHIFT;
> +    uboot_pages = ((gd->ram_top == 0 ? 0x100000000ull : gd->ram_top) - uboot_start) >> EFI_PAGE_SHIFT;

Are you sure this hunk is necessary? We should already underflow to the correct value here.

Alex

>    efi_add_memory_map(uboot_start, uboot_pages, EFI_LOADER_DATA, false);
> 
>    /* Add Runtime Services */
> -- 
> 2.6.6
>