Messages in this thread | | | Date | Tue, 19 Jul 2022 11:06:40 -0700 | From | Sami Tolvanen <> | Subject | Re: [patch 00/38] x86/retbleed: Call depth tracking mitigation |
| |
On Tue, Jul 19, 2022 at 10:27:00AM -0700, Linus Torvalds wrote: > On Tue, Jul 19, 2022 at 10:23 AM Sami Tolvanen <samitolvanen@google.com> wrote: > > > > The preamble hash is encoded into an instruction just to avoid special > > casing objtool, which would otherwise get confused about the random > > bytes. On arm64, we just emit a bare constant before the function. > > Ahh. > > I think objtool would want to understand about kCFI anyway, so I think > in the long run that hack isn't a goog idea. > > But I get why you'd do it as a "do this as just a compiler thing and > hide it from objtool" as a development strategy.
I believe it was actually Peter's idea to use an instruction. :) In earlier revisions of KCFI, I did teach objtool about the preambles, but that was just so it can ignore them.
Sami
| |