From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, joao@overdrivepizza.com, hjl.tools@gmail.com,
andrew.cooper3@citrix.com, linux-kernel@vger.kernel.org,
ndesaulniers@google.com, keescook@chromium.org,
samitolvanen@google.com, mark.rutland@arm.com,
alyssa.milburn@intel.com, mbenes@suse.cz, rostedt@goodmis.org,
mhiramat@kernel.org, alexei.starovoitov@gmail.com
Subject: Re: [PATCH v3 18/39] x86/ibt,ftrace: Make function-graph play nice
Date: Fri, 4 Mar 2022 14:05:19 -0800 [thread overview]
Message-ID: <20220304220519.o6mel7h6qx4ucesm@treble> (raw)
In-Reply-To: <20220304214454.GT11184@worktop.programming.kicks-ass.net>
On Fri, Mar 04, 2022 at 10:44:54PM +0100, Peter Zijlstra wrote:
> On Fri, Mar 04, 2022 at 01:03:34PM -0800, Josh Poimboeuf wrote:
> > On Fri, Mar 04, 2022 at 08:48:53PM +0100, Peter Zijlstra wrote:
> > > On Fri, Mar 04, 2022 at 09:51:54AM -0800, Josh Poimboeuf wrote:
> > > > On Thu, Mar 03, 2022 at 12:23:39PM +0100, Peter Zijlstra wrote:
> > > > > +
> > > > > + addq $16, %rsp
> > > > > + ANNOTATE_INTRA_FUNCTION_CALL
> > > > > + call .Ldo_rop
> > > > > + int3
> > > > > +.Ldo_rop:
> > > > > + mov %rdi, (%rsp)
> > > > > + UNWIND_HINT_FUNC
> > > > > + RET
> > > >
> > > > Why the int3?
> > >
> > > Speculation trap :-) Either I'm too paranoid or not paranoid enough; but
> > > without it it's just too close to a retpoline and it doesn't feel right.
> >
> > Um, it *is* a retpoline :-)
> >
> > Can you just use the RETPOLINE macro? Along with a comment stating why
> > it can't just do a JMP_NOSPEC?
>
> There is no RETPOLINE macro; or rather it is completely contained in
> lib/retpoline.S and I'd sorta like to keep it that way.
>
> That said, I can stick a comment on.
The only reason it's in retpoline.S is because nobody else needed it.
It just seems weird to reinvent the wheel, especially with a slightly
different method of stopping speculation.
And I could envision other cases where we might want an unconditional
retpoline.
Your call though...
--
Josh
next prev parent reply other threads:[~2022-03-04 22:05 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-03 11:23 [PATCH v3 00/39] x86: Kernel IBT Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 01/39] static_call: Avoid building empty .static_call_sites Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 02/39] x86/module: Fix the paravirt vs alternative order Peter Zijlstra
2022-03-08 13:58 ` [tip: x86/urgent] " tip-bot2 for Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 03/39] objtool: Add --dry-run Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 04/39] x86/ibt: Base IBT bits Peter Zijlstra
2022-03-07 11:17 ` Peter Zijlstra
2022-03-07 12:25 ` Joao Moreira
2022-03-07 18:19 ` Nick Desaulniers
2022-03-03 11:23 ` [PATCH v3 05/39] x86/ibt: Add ANNOTATE_NOENDBR Peter Zijlstra
2022-03-04 18:59 ` Josh Poimboeuf
2022-03-04 20:22 ` Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 06/39] x86/text-patching: Make text_gen_insn() play nice with ANNOTATE_NOENDBR Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 07/39] x86/ibt,paravirt: Use text_gen_insn() for paravirt_patch() Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 08/39] x86/entry: Cleanup PARAVIRT Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 09/39] x86/entry,xen: Early rewrite of restore_regs_and_return_to_kernel() Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 10/39] x86/ibt,xen: Sprinkle the ENDBR Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 11/39] x86/ibt,entry: Sprinkle ENDBR dust Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 12/39] x86/linkage: Add ENDBR to SYM_FUNC_START*() Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 13/39] x86/ibt,paravirt: Sprinkle ENDBR Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 14/39] x86/ibt,crypto: Add ENDBR for the jump-table entries Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 15/39] x86/ibt,kvm: Add ENDBR to fastops Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 16/39] x86/ibt,ftrace: Search for __fentry__ location Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 17/39] x86/livepatch: Validate " Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 18/39] x86/ibt,ftrace: Make function-graph play nice Peter Zijlstra
2022-03-04 17:51 ` Josh Poimboeuf
2022-03-04 19:48 ` Peter Zijlstra
2022-03-04 21:03 ` Josh Poimboeuf
2022-03-04 21:44 ` Peter Zijlstra
2022-03-04 22:05 ` Josh Poimboeuf [this message]
2022-03-04 23:08 ` David Laight
2022-03-03 11:23 ` [PATCH v3 19/39] x86/ibt,kprobes: Cure sym+0 equals fentry woes Peter Zijlstra
2022-03-07 9:44 ` Masami Hiramatsu
2022-03-03 11:23 ` [PATCH v3 20/39] x86/ibt,bpf: Add ENDBR instructions to prologue and trampoline Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 21/39] x86/ibt,ftrace: Add ENDBR to samples/ftrace Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 22/39] x86/ibt: Add IBT feature, MSR and #CP handling Peter Zijlstra
2022-03-04 17:57 ` Josh Poimboeuf
2022-03-04 20:38 ` Peter Zijlstra
2022-03-04 18:07 ` Josh Poimboeuf
2022-03-04 20:39 ` Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 23/39] x86/alternative: Simplify int3_selftest_ip Peter Zijlstra
2022-03-04 18:02 ` Josh Poimboeuf
2022-03-04 18:09 ` Josh Poimboeuf
2022-03-03 11:23 ` [PATCH v3 24/39] x86/ibt: Disable IBT around firmware Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 25/39] x86/bugs: Disable Retpoline when IBT Peter Zijlstra
2022-03-04 17:39 ` Josh Poimboeuf
2022-03-03 11:23 ` [PATCH v3 26/39] x86/ibt: Annotate text references Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 27/39] x86/ibt,ftrace: Annotate ftrace code patching Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 28/39] x86/ibt,sev: Annotations Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 29/39] x86/ibt: Dont generate ENDBR in .discard.text Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 30/39] x86/ibt: Ensure module init/exit points have references Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 31/39] objtool: Rename --duplicate to --lto Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 32/39] Kbuild: Allow whole module objtool runs Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 33/39] objtool: Read the NOENDBR annotation Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 34/39] objtool: Have WARN_FUNC fall back to sym+off Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 35/39] objtool: Add IBT/ENDBR decoding Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 36/39] objtool: Validate IBT assumptions Peter Zijlstra
2022-03-03 11:23 ` [PATCH v3 37/39] objtool: Optionally WARN about unused ANNOTATE_NOENDBR Peter Zijlstra
2022-03-04 18:27 ` Josh Poimboeuf
2022-03-03 11:23 ` [PATCH v3 38/39] objtool: Find unused ENDBR instructions Peter Zijlstra
2022-03-03 11:24 ` [PATCH v3 39/39] x86/alternative: Use .ibt_endbr_seal to seal indirect calls Peter Zijlstra
2022-03-04 19:09 ` [PATCH v3 00/39] x86: Kernel IBT Josh Poimboeuf
2022-03-04 20:22 ` Peter Zijlstra
2022-03-04 21:39 ` Peter Zijlstra
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