Jordan Niethe's on March 23, 2020 7:25 pm: > On Mon, Mar 23, 2020 at 5:22 PM Nicholas Piggin <npig...@gmail.com> wrote: >> >> Jordan Niethe's on March 20, 2020 3:17 pm: >> > A future revision of the ISA will introduce prefixed instructions. A >> > prefixed instruction is composed of a 4-byte prefix followed by a >> > 4-byte suffix. >> > >> > All prefixes have the major opcode 1. A prefix will never be a valid >> > word instruction. A suffix may be an existing word instruction or a >> > new instruction. >> > >> > This series enables prefixed instructions and extends the instruction >> > emulation to support them. Then the places where prefixed instructions >> > might need to be emulated are updated. >> > >> > The series is based on top of: >> > https://patchwork.ozlabs.org/patch/1232619/ as this will effect >> > kprobes. >> > >> > v4 is based on feedback from Nick Piggins, Christophe Leroy and Daniel >> > Axtens. >> > The major changes: >> > - Move xmon breakpoints from data section to text section >> > - Introduce a data type for instructions on powerpc >> >> Thanks for doing this, looks like a lot of work, I hope it works out :) >> > Yes it did end up touching a lot of places. I started thinking that > that maybe it would be simpler to just use a u64 instead of the struct > for instructions. > If we always keep the word instruction / prefix in the lower bytes, > all of the current masking should still work and we can use operators > again instead of ppc_inst_equal(), etc.
Yeah.. I think now that you've done it, I prefer it this way. > It also makes printing easier. We could just #define INST_FMT %llx or > #define INST_FMT %x on powerpc32 and use that for printing out > instructions. Well, not sure about that. Would it make endian concerns more complicated? Print format for prefix might be '%016llx', but we don't want that for all instructions only prefixed ones, and I don't know if that is the way to go either. We'll want to adopt some convention for displaying prefixed instruction bytes, but I don't know what what works best. I wonder if binutils or any userspace tools have a convention. Which reminds me, you might have missed show_instructions()? Although maybe you don't need that until we start using them in the kernel. Thanks, Nick
