Messages in this thread | | | Date | Mon, 11 Nov 2019 09:47:28 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 00/10] ftrace: Add register_ftrace_direct() |
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On Fri, Nov 08, 2019 at 04:51:00PM -0600, Josh Poimboeuf wrote:
> From: Josh Poimboeuf <jpoimboe@redhat.com> > Subject: [PATCH] ftrace/x86: Tell objtool to ignore nondeterministic ftrace stack layout > > Objtool complains about the new ftrace direct trampoline code: > > arch/x86/kernel/ftrace_64.o: warning: objtool: ftrace_regs_caller()+0x190: stack state mismatch: cfa1=7+16 cfa2=7+24 > > Typically, code has a deterministic stack layout, such that at a given > instruction address, the stack frame size is always the same. > > That's not the case for the new ftrace_regs_caller() code after it > adjusts the stack for the direct case. Just plead ignorance and assume > it's always the non-direct path. Note this creates a tiny window for > ORC to get confused.
How is that not a problem for livepatch?
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