| Date | Tue, 9 Jan 2018 23:58:06 -0600 | From | Josh Poimboeuf <> | Subject | Re: [PATCH v7 02/11] x86/retpoline: Temporarily disable objtool when CONFIG_RETPOLINE=y |
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On Tue, Jan 09, 2018 at 02:43:08PM +0000, David Woodhouse wrote: > From: Andi Kleen <ak@linux.intel.com> > > objtool's assembler currently cannot deal with the code generated by the > retpoline compiler and throws hundreds of warnings, mostly because it sees > calls that don't have a symbolic target. > > Exclude all the options that rely on objtool when RETPOLINE is active. > > This mainly means that the kernel has to fallback to use the frame pointer > unwinder and livepatch is not supported. > > Josh is looking into resolving the issue.
I have a fix brewing for this, in two parts:
- Part 1 will allow objtool to understand the flow *around* the retpolines (but not *inside* them). Which basically means that ORC will still get confused if it tries to unwind from inside a retpoline, but otherwise it should work fine. This code is pretty much done, just need to do some testing with it first. This should allow us to re-enable objtool and friends: ORC, reliable stacks, livepatch consistency model.
- Part 2 will add ORC annotations for inside the retpolines. This will be a little harder, but I have my fingers crossed that it's do-able within a week or so.
-- Josh
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