On 10/31/24 23:06, Sam Protsenko wrote:

Usually ARMv8 platforms allow unaligned access for Normal memory. But some chips might not allow it by default, having SCTLR.A bit set to 1 before U-Boot execution. One such example is Exynos850 SoC. As allow_unaligned() is not implemented for ARMv8 at the moment, its __weak implementation is used, which does nothing. That might lead to unaligned access abort, for example when running EFI selftest. Fix that by implementing allow_unaligned() for ARMv8.

The issue was found when running EFI selftest on E850-96 board (Exynos850 based):

 => bootefi selftest $fdtcontroladdr

 ...
 Executing 'HII database protocols'
 "Synchronous Abort" handler, esr 0x96000021, far 0xbaac0991
 ...
 resetting ...

Unaligned abort happens in u16_strnlen(), which is called from efi_hii_sibt_string_ucs2_block_next():

 u16_strlen(blk->string_text)

where 'blk' type is struct efi_hii_sibt_string_ucs2_block. Because this struct is packed, doing "->string_text" makes 'blk' address incremented by 1 byte, which makes it unaligned. Although allow_unaligned() was called in efi_init_early() before EFI selftest execution, it wasn't implemented for ARMv8 CPUs, so data abort happened.

Signed-off-by: Sam Protsenko semen.protsenko@linaro.org

arch/arm/cpu/armv8/cpu.c | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/arch/arm/cpu/armv8/cpu.c b/arch/arm/cpu/armv8/cpu.c index d568efa427ab..82ecf02f4b03 100644 --- a/arch/arm/cpu/armv8/cpu.c +++ b/arch/arm/cpu/armv8/cpu.c @@ -94,3 +94,8 @@ void armv8_setup_psci(void) secure_ram_addr(psci_arch_init)(); } #endif

+void allow_unaligned(void) +{

• set_sctlr(get_sctlr() & ~CR_A);

Looking at the ARM documentation SCTLR_EL2 is a 64bit register.

https://developer.arm.com/documentation/ddi0595/2021-06/AArch64-Registers/SC...

But get_sctlr() is defined as

arch/arm/include/asm/system.h:174: static inline unsigned int get_sctlr(void)

Your code might not work as expected. Should we adjust the definition of get_sctlr() to return a long value?

Best regards

Heinrich

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