Re: [PATCH] ARM: boot: Fix ATAGs with appended DTB

Marek Szyprowski
2020-02-26T06:35:51Z

Hi Geert,

On 25.02.2020 15:47, Geert Uytterhoeven wrote:
> At early boot, register r8 may contain an ATAGs or DTB pointer.
> When an appended DTB is found, its address is stored in r8, for
> extraction of the RAM base address later.
>
> However, if r8 contained an ATAGs pointer before, that pointer will be
> lost, and the provided ATAGs is no longer folded into the provided DTB.
>
> Fix this by leaving r8 untouched.
>
> Fixes: 137e522593918be2 ("ARM: 8960/1: boot: Obtain start of physical memory from DTB")
> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> Not tested with ATAGs, only with [uz]Image + DTB, and zImage with
> appended DTB.

Works fine with zImage + appended DTB + cmdline/memory info passed via ATAGs

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---
> arch/arm/boot/compressed/head.S | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
> index 339d4b4cfbbeed15..a351ed2bc195ed8d 100644
> --- a/arch/arm/boot/compressed/head.S
> +++ b/arch/arm/boot/compressed/head.S
> @@ -267,16 +267,18 @@ not_angel:
> cmp r0, r1 @ do we have a DTB there?
> bne 1f
>
> - mov r8, r6 @ use it if so
> /* preserve 64-bit alignment */
> add r5, r5, #7
> bic r5, r5, #7
> - add sp, sp, r5 @ and move stack above it
> + add sp, sp, r5 @ if so, move stack above DTB
> + mov r0, r6 @ and extract memory start from DTB
> + b 2f
>
> 1:
> #endif /* CONFIG_ARM_APPENDED_DTB */
>
> mov r0, r8
> +2:
> bl fdt_get_mem_start
> mov r4, r0
> cmp r0, #-1

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland