Messages in this thread | | | Date | Wed, 4 Oct 2017 09:04:22 -0500 | From | Josh Poimboeuf <> | Subject | Re: [RFC 1/1] orc: mark it as reliable |
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On Wed, Oct 04, 2017 at 11:23:15AM +0200, Jiri Slaby wrote: > We need a reliable stack unwinder for kernel live patching, but we do > not want to enable frame pointers for performance reasons. So let ORC be > a reliable stack unwinder on x86 as it performs nicely wrt reliability > of traces. > > Signed-off-by: Jiri Slaby <jslaby@suse.cz> > Cc: Josh Poimboeuf <jpoimboe@redhat.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: x86@kernel.org > --- > > I am sending this as an RFC. Do you still consider ORC to be not-enough > reliable?
Off the top of my head, at least the following is missing:
- save_stack_trace_reliable() assumes that kernel mode pt_regs on the stack make the stack trace unreliable. This is an FP-specific assumption which no longer applies for ORC.
- The ORC unwinder needs to set unwind_state.error if it doesn't reach all the way to the end (user pt_regs).
-- Josh
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