On Fri, Mar 29, 2024 at 07:55:53PM -0500, Sam Protsenko wrote:
> When "memory" node is being processed in fdt_pack_reg() on ARM64
> platforms, an unaligned bus access might happen, which leads to
> "synchronous abort" CPU exception. Consider next dts example:
>
> / {
> #address-cells = <2>;
> #size-cells = <1>;
>
> memory@80000000 {
> device_type = "memory";
> reg = <0x0 0x80000000 0x3ab00000>,
> <0x0 0xc0000000 0x40000000>,
> <0x8 0x80000000 0x80000000>;
> };
> };
>
> After fdt_pack_reg() reads the first addr/size entry from such memory
> node, the "p" pointer becomes 12 bytes shifted from its original value
> (8 bytes for two address cells + 4 bytes for one size cell). So now it's
> not 64-bit aligned, and an attempt to do 64-bit bus access to that
> address will cause an abort like this:
>
> "Synchronous Abort" handler, esr 0x96000021, far 0xba235efc
>
> This issue was originally reported by David Virag [1] who observed it
> happening on Samsung Exynos7885 SoC (ARM64), and later the same issue
> was observed on Samsung Exynos850 (ARM64).
>
> Fix the issue by using put_unaligned_be64() helper, which takes care of
> possible unaligned 64-bit accesses. That solution was proposed by Simon
> Glass in the original thread [1].
>
> [1] https://lists.denx.de/pipermail/u-boot/2023-July/522074.html
>
> Fixes: 739a01ed8e02 ("fdt_support: fix an endian bug of
> fdt_fixup_memory_banks")
> Suggested-by: Simon Glass <s...@google.com>
> Reported-by: David Virag <virag.david...@gmail.com>
> Closes: https://lists.denx.de/pipermail/u-boot/2023-July/522074.html
> Signed-off-by: Sam Protsenko <semen.protse...@linaro.org>
> Reviewed-by: Heinrich Schuchardt <xypron.g...@gmx.de>Applied to u-boot/master, thanks! -- Tom
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