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 0xba235efcThis 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 sjg@google.com Reported-by: David Virag virag.david003@gmail.com Closes: https://lists.denx.de/pipermail/u-boot/2023-July/522074.html Signed-off-by: Sam Protsenko semen.protsenko@linaro.org Reviewed-by: Heinrich Schuchardt xypron.glpk@gmx.de
Applied to u-boot/master, thanks!