From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Julien Thierry <jthierry@redhat.com>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de
Subject: Re: [PATCH 4/7] objtool: Add support for return trampoline call
Date: Sat, 4 Apr 2020 17:51:26 +0200 [thread overview]
Message-ID: <20200404155126.GF20730@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200404142232.wpn7estahnabfy3z@treble>
On Sat, Apr 04, 2020 at 09:22:32AM -0500, Josh Poimboeuf wrote:
> On Sat, Apr 04, 2020 at 03:32:18PM +0200, Peter Zijlstra wrote:
> > On Fri, Apr 03, 2020 at 05:46:20PM +0200, Peter Zijlstra wrote:
> > > On Fri, Apr 03, 2020 at 10:17:57AM -0500, Josh Poimboeuf wrote:
> > > > Peter, I think my previous idea for UNWIND_HINT_ADJUST stack_add=8 would
> > > > work here?
> > >
> > > Yes, it would.
> >
> > Sorry, I have reconsidered. While it will shut up objtool, it will not
> > 'work'. That is, the ORC data generated will not correctly unwind.
> >
> > I'll try and write a longer email tonight.
>
> Right, that's what I've been trying to say. The ORC data will be
> non-deterministic unless we unroll the loop. Or did you mean something
> else?
The below should result in deterministic code.
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 07e95dcb40ad..109ee65f4a11 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -59,8 +59,8 @@
jmp 775b; \
774: \
dec reg; \
- jnz 771b; \
- add $(BITS_PER_LONG/8) * nr, sp;
+ add $(BITS_PER_LONG/8) * $2, sp; \
+ jnz 771b;
#ifdef __ASSEMBLY__
next prev parent reply other threads:[~2020-04-04 15:51 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-02 8:22 [PATCH 0/7] objtool changes to remove most ANNOTATE_NOSPEC_ALTERNATIVE Alexandre Chartre
2020-04-02 8:22 ` [PATCH 1/7] objtool: is_fentry_call() crashes if call has no destination Alexandre Chartre
2020-04-02 8:22 ` [PATCH 2/7] objtool: Allow branches within the same alternative Alexandre Chartre
2020-04-02 12:03 ` Julien Thierry
2020-04-02 12:38 ` Alexandre Chartre
2020-04-02 8:22 ` [PATCH 3/7] objtool: Add support for intra-function calls Alexandre Chartre
2020-04-02 12:53 ` Julien Thierry
2020-04-02 13:24 ` Alexandre Chartre
2020-04-02 13:38 ` Julien Thierry
2020-04-02 14:56 ` Alexandre Chartre
2020-04-02 15:04 ` Peter Zijlstra
2020-04-02 15:54 ` Josh Poimboeuf
2020-04-03 7:06 ` Alexandre Chartre
2020-04-02 15:49 ` Josh Poimboeuf
2020-04-02 17:27 ` Josh Poimboeuf
2020-04-03 8:01 ` Julien Thierry
2020-04-03 12:41 ` Peter Zijlstra
2020-04-03 12:49 ` Julien Thierry
2020-04-03 14:37 ` Peter Zijlstra
2020-04-03 14:44 ` Josh Poimboeuf
2020-04-02 8:22 ` [PATCH 4/7] objtool: Add support for return trampoline call Alexandre Chartre
2020-04-02 13:26 ` Julien Thierry
2020-04-02 14:46 ` Alexandre Chartre
2020-04-02 15:31 ` Julien Thierry
2020-04-02 15:40 ` Peter Zijlstra
2020-04-03 8:11 ` Julien Thierry
2020-04-03 15:17 ` Josh Poimboeuf
2020-04-03 15:22 ` Josh Poimboeuf
2020-04-03 15:32 ` Josh Poimboeuf
2020-04-03 15:46 ` Peter Zijlstra
2020-04-03 15:55 ` Josh Poimboeuf
2020-04-04 13:32 ` Peter Zijlstra
2020-04-04 14:22 ` Josh Poimboeuf
2020-04-04 15:51 ` Peter Zijlstra [this message]
2020-04-06 8:19 ` Alexandre Chartre
2020-04-06 9:31 ` Peter Zijlstra
2020-04-06 11:03 ` Alexandre Chartre
2020-04-06 14:16 ` Josh Poimboeuf
2020-04-02 15:27 ` Peter Zijlstra
2020-04-03 7:19 ` Alexandre Chartre
2020-04-06 14:34 ` Alexandre Chartre
2020-04-06 14:55 ` Alexandre Chartre
2020-04-02 8:22 ` [PATCH 5/7] x86/speculation: Annotate intra-function calls Alexandre Chartre
2020-04-03 16:05 ` Josh Poimboeuf
2020-04-03 16:16 ` Josh Poimboeuf
2020-04-03 17:14 ` Alexandre Chartre
2020-04-03 17:18 ` Peter Zijlstra
2020-04-03 17:24 ` Josh Poimboeuf
2020-04-03 18:20 ` Peter Zijlstra
2020-04-02 8:22 ` [PATCH 6/7] x86/speculation: Annotate retpoline return instructions Alexandre Chartre
2020-04-02 8:22 ` [PATCH 7/7] x86/speculation: Remove most ANNOTATE_NOSPEC_ALTERNATIVE Alexandre Chartre
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