On Mon, Jul 10, 2023 at 01:45:46PM -0600, Simon Glass wrote:
Hi David,
On Sun, 9 Jul 2023 at 19:11, David Virag virag.david003@gmail.com wrote:
Hi,
I'm trying to port U-Boot to a new board (Samsung JACKPOTLTE, ARMv8, Exynos7885) but when CONFIG_ARCH_FIXUP_FDT_MEMORY is enabled, the bootm command leads to an unaligned memory access, which results in a synchronous abort.
After a long debugging session, I concluded that fdt_pack_reg in common/fdt_support.c writes to unaligned addresses in its for loop. In the case of address_cells being 2, and size_cells being 1, the buffer pointer gets incremented by 12 in each loop, making the second iteration (i=1) write a 64bit value to a non 64bit aligned address.
Turning the alignment check enable bit (A) off in SCTLR makes the function work as intended. I couldn't find code that touches this bit, but I may have missed something. I don't think writing in two parts should be the fix, but something should be done about this. As far as I understand, any arm64 board that has this bit turned on, either from previous code or just the initial status of the bit after power on, could crash here.
This is on top of the latest commit as of now (0beb649053b86b2cfd5cf55a0fc68bc2fe91a430)
What should be done here?
+Tom Rini
... I was hoping you had an idea Simon. Is this part of the code we share with libfdt itself, or one of the helpers we made?