Suppressing SIGBUS signals

I don't think that's really true. At the assembly level, the outcome of the MOV instruction is that it either loads a value into the register *or* triggers an exception. E.g. if you look in the ARMv8-A Architecture Reference Manual, it explicitly defines the LDR instruction in terms of the "AArch64.MemSingle" operation which can call the "AArch64.TakeException" operation, which sets up the exception state then calls "EndOfInstruction" to stop any further processing of the LDR instruction, so it won't write anything to the destination register.

Once the exception is triggered, the kernel is free to do whatever it wants - update the page tables then jump back to the MOV instruction to retry it, manually update the register state then jump back to the instruction after the MOV, call a signal handler, etc. Anyone writing user-space assembly code has to be aware of that, e.g. there are often ABI rules about stack pointers that are specifically there to allow the kernel to interrupt your thread at any point and run a signal handler on its current stack. So that's not something you can safely ignore when working at assembly level.