On Thu, Jul 09, 2020 at 10:22:04PM +0200, Clement Leger wrote:
> When dtb is provided by the FSBL (first stage bootloader), it might
> end up in the malloc zone initialized by barebox. While the dtb is
> discarded after being unflatten, if the dtb is provided right after
> barebox elf, then the malloc can overwrite it while unflattening it when
> allocating nodes.
> To avoid that, exclude the dtb from the malloc zone by checking if it
> overlaps it. If so, determine the largest zone for the allocation and
> modify the memory area to use that.
>
> Signed-off-by: Clement Leger <cleger@xxxxxxxxx>
> ---
> arch/kvx/lib/board.c | 43 +++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 41 insertions(+), 2 deletions(-)
Applied, thanks
Sascha
>
> diff --git a/arch/kvx/lib/board.c b/arch/kvx/lib/board.c
> index 4d6ca6983..78fa83e02 100644
> --- a/arch/kvx/lib/board.c
> +++ b/arch/kvx/lib/board.c
> @@ -103,15 +103,54 @@ err:
> while (1);
> }
>
> +/**
> + * exclude_dtb_from_alloc - Find best zone to allocate without overwriting dtb
> + *
> + * @fdt: fdt blob
> + * @alloc_start: start of allocation zone
> + * @alloc_end: end of allocation zone
> + */
> +static void exclude_dtb_from_alloc(void *fdt, u64 *alloc_start, u64 *alloc_end)
> +{
> + const struct fdt_header *fdth = fdt;
> + u64 fdt_start = (u64) fdt;
> + u64 fdt_end = fdt_start + be32_to_cpu(fdth->totalsize);
> + u64 start_size = 0, end_size = 0;
> +
> + /*
> + * If the device tree is inside the malloc zone, we must exclude it to
> + * avoid allocating memory over it while unflattening it
> + */
> + if (fdt_end < *alloc_start || fdt_start > (*alloc_end))
> + return;
> +
> + /* Compute the largest remaining chunk when removing the dtb */
> + if (fdt_start >= *alloc_start)
> + start_size = (fdt_start - *alloc_start);
> +
> + if (fdt_end <= *alloc_end)
> + end_size = *alloc_end - fdt_end;
> +
> + /* Modify start/end to reflect the maximum area we found */
> + if (start_size >= end_size)
> + *alloc_end = fdt_start;
> + else
> + *alloc_start = fdt_end;
> +}
> +
> void __noreturn kvx_start_barebox(void)
> {
> u64 memsize = 0, membase = 0;
> u64 barebox_text_end = (u64) &__end;
> + u64 alloc_start, alloc_end;
>
> of_find_mem(boot_dtb, barebox_text_end, &membase, &memsize);
>
> - mem_malloc_init((void *) barebox_text_end,
> - (void *) (membase + memsize));
> + alloc_start = barebox_text_end;
> + alloc_end = (membase + memsize);
> + exclude_dtb_from_alloc(boot_dtb, &alloc_start, &alloc_end);
> +
> + mem_malloc_init((void *) alloc_start, (void *) alloc_end);
>
> start_barebox();
>
> --
> 2.17.1
>
>
--
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