diff options
Diffstat (limited to 'plat/arm/board/arm_fpga/kernel_trampoline.S')
| -rw-r--r-- | plat/arm/board/arm_fpga/kernel_trampoline.S | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/plat/arm/board/arm_fpga/kernel_trampoline.S b/plat/arm/board/arm_fpga/kernel_trampoline.S new file mode 100644 index 0000000..f4c08ef --- /dev/null +++ b/plat/arm/board/arm_fpga/kernel_trampoline.S @@ -0,0 +1,35 @@ +/* + * Copyright (c) 2021, ARM Limited. All rights reserved. + * + * SPDX-License-Identifier: BSD-3-Clause + * + * The traditional arm64 Linux kernel load address is 512KiB from the + * beginning of DRAM, caused by this having been the default value of the + * kernel's CONFIG_TEXT_OFFSET Kconfig value. + * However kernel version 5.8 changed the default offset (into a 2MB page) + * to 0, so TF-A's default assumption is no longer true. Fortunately the + * kernel got more relaxed about this offset at the same time, so it + * tolerates the wrong offset, but issues a warning: + * [Firmware Bug]: Kernel image misaligned at boot, please fix your bootloader! + * + * We cannot easily change the load address offset in TF-A to be 2MiB, because + * this would break older kernels - and they are not as forgiving in this + * respect. + * + * But we can allow users to load the kernel at the right offset, and + * offer this trampoline here to transition to this new load address. + * Any older kernels, or newer kernels misloaded, will overwrite this code + * here, so it does no harm in this case. + */ + +#include <asm_macros.S> +#include <common/bl_common.ld.h> + +.text +.global _tramp_start + +_tramp_start: + adr x4, _tramp_start + orr x4, x4, #0x1fffff + add x4, x4, #1 /* align up to 2MB */ + br x4 |