Messages in this thread | | | Date | Wed, 25 May 2022 18:12:27 +0100 | From | Mark Rutland <> | Subject | Re: [RFC PATCH -next v2 3/4] arm64/ftrace: support dynamically allocated trampolines |
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On Wed, May 25, 2022 at 09:43:07AM -0400, Steven Rostedt wrote: > On Wed, 25 May 2022 13:17:30 +0100 > Mark Rutland <mark.rutland@arm.com> wrote: > > > For arm64 I'd like to make this static, and have ftrace *always* capture a > > minimal set of ftrace_regs, which would be: > > > > X0 to X8 inclusive > > SP > > PC > > LR > > FP > > > > Since X0 to X8 + SP is all that we need for arguments and return values (per > > the calling convention we use), and PC+LR+FP gives us everything we need for > > unwinding and live patching. > > > > I *might* want to add x18 to that when SCS is enabled, but I'm not immediately > > sure. > > Does arm64 have HAVE_DYNAMIC_FTRACE_WITH_ARGS enabled?
Not yet. I'd like to implement it, but always only saving the values above and never saving a full pt_regs (since as mentioned elsewhere we can't do that correctly anyway).
> If so, then having the normal ftrace call back save the above so that all > functions have it available would be useful.
I think that's what I'm saying: I'd want to have one trampoline which always saved the above, so all functions would get that.
Thanks, Mark.
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