arm64: log vm_fault error for data_abort

[bz]

Summary

Log the vm_fault() error in the data_abort panic so it is easier to
find the reason vm_fault() failed (e.g., invalid address).

Reviewed by: ..
MFC After: 2 weeks
Differential Revision: ...

[andrew]

We could drop printing frame->tf_elr as we already do so in print_registers

[bz]

In D30362#683175, @andrew wrote:

We could drip printing frame->tf_elr as we already do so in print_registers

That brings me to a different question: print_registers and a "show reg" in ddb right after the panic result in two different outputs. Is that intentional?

[andrew]

They are printing different trap frames. print_registers will print the fault frame while show reg will print a frame from a breakpoint within panic. The registers seen when debugger_on_trap is true should be identical to the version printed by print_registers.

[bz]

In D30362#683320, @andrew wrote:

They are printing different trap frames. print_registers will print the fault frame while show reg will print a frame from a breakpoint within panic. The registers seen when debugger_on_trap is true should be identical to the version printed by print_registers.

Thank you; Let's keep the ELR in the panicstr then.