Re: [PATCH] kvx: exclude dtb from malloc zone

[Sascha Hauer <s.hauer@pengutronix.de>]

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@kalray.eu>
> ---
>  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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