64 bits alignment problem on device tree parsing

[xvisor]

64 bits alignment problem on device tree parsing

[avpatel]

Good catch.

Yes, the LIBFDT_DATA64() needs to be fixed. Basically, we should be joining two u32 for forming u64 in LIBFDT_DATA64()

Regards,
Anup

[llabadie]

The MMU was not enabled and setup properly in my previous explanation. Causing the A bit in SCTRL_EL2 register to be ignored. This is why wrong alignment triggered an exception.

Wrong alignment exception were triggered in libs/common/libfdt.c, arch/arm/cpu/arm64/cpu_memcpy.S and arch/arm/cpu/arm64/cpu_memset.S

Now that the MMU is correctly enabled, Xvisor is not stuck anymore. The fact that the alignment is wrong still stands but triggers no exception.

Before fixing MMU, I tried manually fixing LIBFDT_DATA64 alignment. This is not very elegant but does not seem to break anything else:

xvisor/libs/common/libfdt.c

Line 32 in 6fea5d2

#define LIBFDT_DATA64(ptr) vmm_be64_to_cpu(*((u64*)ptr))

#define LIBFDT_DATA64(ptr)	lifdt_data64_alignement(((u64*)ptr))

static u64 lifdt_data64_alignement(u64* ptr)
{
	u64 tmp_val;
	if(((u64) ptr % 8) == 0)
	{
		tmp_val = *ptr;
	}
	else
	{
		u64 d1 = *((u32*) ptr);
		u64 d2 = *(((u32*)ptr)+1);

		d2 = d2 << 32;
		tmp_val = d1 | d2;
	}
	tmp_val = vmm_be64_to_cpu(tmp_val);
	return tmp_val;
}

Do you think this would be interesting? If yes, I can send a pull request.