From: Peter Zijlstra <peterz@infradead.org>
To: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
jpoimboe@redhat.com, jthierry@redhat.com, tglx@linutronix.de
Subject: Re: [PATCH V2 9/9] x86/speculation: Remove all ANNOTATE_NOSPEC_ALTERNATIVE directives
Date: Tue, 7 Apr 2020 15:28:37 +0200 [thread overview]
Message-ID: <20200407132837.GA20730@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200407073142.20659-10-alexandre.chartre@oracle.com>
On Tue, Apr 07, 2020 at 09:31:42AM +0200, Alexandre Chartre wrote:
> Now that intra-function calls have been annotated and are supported
> by objtool, that retpoline return instructions have been annotated,
> and that __FILL_RETURN_BUFFER code is compatible with objtool, then
> all ANNOTATE_NOSPEC_ALTERNATIVE directives can be removed.
Like Josh said in the previous thread, this isn't going to work right.
> - ANNOTATE_NOSPEC_ALTERNATIVE
> ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *\reg), \
> __stringify(RETPOLINE_JMP \reg), X86_FEATURE_RETPOLINE, \
> __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *\reg), X86_FEATURE_RETPOLINE_AMD
The problem is that while objtool can now understand the code flow and
the corresponding stack layout, we only have a single ORC table, one
that must be valid for all alternatives.
Effectively this means there should not be any orc entries in an
alternative range.
In practise it _might_ work when the instruction of the various
alternatives have unique offsets in the range. But I'm not entirely sure
of that.
Josh, we should probably have objtool verify it doesn't emit ORC entries
in alternative ranges.
next prev parent reply other threads:[~2020-04-07 13:28 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-07 7:31 [PATCH V2 0/9] objtool changes to remove all ANNOTATE_NOSPEC_ALTERNATIVE Alexandre Chartre
2020-04-07 7:31 ` [PATCH V2 1/9] objtool: Introduce HINT_RET_OFFSET Alexandre Chartre
2020-04-07 12:53 ` Peter Zijlstra
2020-04-07 13:17 ` Alexandre Chartre
2020-04-07 7:31 ` [PATCH V2 2/9] objtool: UNWIND_HINT_RET_OFFSET should not check registers Alexandre Chartre
2020-05-01 18:22 ` [tip: objtool/core] " tip-bot2 for Alexandre Chartre
2020-04-07 7:31 ` [PATCH V2 3/9] objtool: is_fentry_call() crashes if call has no destination Alexandre Chartre
2020-04-07 7:31 ` [PATCH V2 4/9] objtool: Allow branches within the same alternative Alexandre Chartre
2020-04-07 7:31 ` [PATCH V2 5/9] objtool: Add support for intra-function calls Alexandre Chartre
2020-04-07 13:07 ` Peter Zijlstra
2020-04-07 13:28 ` Alexandre Chartre
2020-04-08 14:06 ` Alexandre Chartre
2020-04-08 14:19 ` Julien Thierry
2020-04-08 16:03 ` Alexandre Chartre
2020-04-08 16:04 ` Julien Thierry
2020-04-08 17:06 ` Alexandre Chartre
2020-04-08 17:07 ` Julien Thierry
2020-04-07 7:31 ` [PATCH V2 6/9] x86/speculation: Change __FILL_RETURN_BUFFER to work with objtool Alexandre Chartre
2020-04-07 13:27 ` Josh Poimboeuf
2020-04-07 7:31 ` [PATCH V2 7/9] x86/speculation: Annotate intra-function calls Alexandre Chartre
2020-04-07 7:31 ` [PATCH V2 8/9] x86/speculation: Add unwind hint to trampoline return Alexandre Chartre
2020-04-07 7:31 ` [PATCH V2 9/9] x86/speculation: Remove all ANNOTATE_NOSPEC_ALTERNATIVE directives Alexandre Chartre
2020-04-07 13:28 ` Peter Zijlstra [this message]
2020-04-07 13:34 ` Josh Poimboeuf
2020-04-07 14:32 ` Alexandre Chartre
2020-04-07 16:18 ` Alexandre Chartre
2020-04-07 16:28 ` Josh Poimboeuf
2020-04-07 17:01 ` Alexandre Chartre
2020-04-07 17:26 ` Peter Zijlstra
2020-04-07 17:27 ` Peter Zijlstra
2020-04-08 21:35 ` Peter Zijlstra
2020-04-09 8:18 ` Alexandre Chartre
2020-04-09 10:34 ` Peter Zijlstra
2020-04-09 10:40 ` Peter Zijlstra
2020-04-07 16:41 ` Peter Zijlstra
2020-04-07 17:04 ` Alexandre Chartre
2020-04-07 13:52 ` Peter Zijlstra
2020-04-07 13:59 ` Peter Zijlstra
2020-04-07 13:35 ` [PATCH V2 0/9] objtool changes to remove all ANNOTATE_NOSPEC_ALTERNATIVE Josh Poimboeuf
2020-04-07 14:02 ` Alexandre Chartre
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