From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: alexandre.chartre@oracle.com, linux-kernel@vger.kernel.org,
jthierry@redhat.com, tglx@linutronix.de, x86@kernel.org,
mbenes@suse.cz
Subject: Re: [PATCH 5/8] x86/speculation: Change FILL_RETURN_BUFFER to work with objtool
Date: Fri, 24 Apr 2020 14:04:27 -0500 [thread overview]
Message-ID: <20200424190427.3p7oxloliov72fwu@treble> (raw)
In-Reply-To: <20200423125042.876058319@infradead.org>
On Thu, Apr 23, 2020 at 02:47:22PM +0200, Peter Zijlstra wrote:
> #define __FILL_RETURN_BUFFER(reg, nr, sp) \
> mov $(nr/2), reg; \
> 771: \
> + ANNOTATE_INTRA_FUNCTION_CALL \
> call 772f; \
> 773: /* speculation trap */ \
> + UNWIND_HINT_EMPTY; \
> pause; \
> lfence; \
> jmp 773b; \
> 772: \
> + ANNOTATE_INTRA_FUNCTION_CALL \
> call 774f; \
> 775: /* speculation trap */ \
> + UNWIND_HINT_EMPTY; \
> pause; \
> lfence; \
> jmp 775b; \
> 774: \
> + add $(BITS_PER_LONG/8) * 2, sp; \
> dec reg; \
> - jnz 771b; \
> - add $(BITS_PER_LONG/8) * nr, sp;
> + jnz 771b;
Looks weird having semicolons for one annotation but not the other...
>
> #ifdef __ASSEMBLY__
>
> @@ -137,10 +143,8 @@
> */
> .macro FILL_RETURN_BUFFER reg:req nr:req ftr:req
> #ifdef CONFIG_RETPOLINE
> - ANNOTATE_NOSPEC_ALTERNATIVE
> - ALTERNATIVE "jmp .Lskip_rsb_\@", \
> - __stringify(__FILL_RETURN_BUFFER(\reg,\nr,%_ASM_SP)) \
> - \ftr
> + ALTERNATIVE "jmp .Lskip_rsb_\@", "", \ftr
> + __FILL_RETURN_BUFFER(\reg,\nr,%_ASM_SP)
I almost gave my "you can't change the stack in an alternative" lecture,
then I did a double take :-)
We do still need a patch to prevent other code from doing that though.
--
Josh
next prev parent reply other threads:[~2020-04-24 19:05 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-23 12:47 [PATCH 0/8] objtool vs retpoline Peter Zijlstra
2020-04-23 12:47 ` [PATCH 1/8] objtool: is_fentry_call() crashes if call has no destination Peter Zijlstra
2020-04-23 12:47 ` [PATCH 2/8] objtool: UNWIND_HINT_RET_OFFSET should not check registers Peter Zijlstra
2020-04-23 12:47 ` [PATCH 3/8] objtool: Rework allocating stack_ops on decode Peter Zijlstra
2020-04-23 15:40 ` Alexandre Chartre
2020-04-23 15:54 ` Peter Zijlstra
2020-04-24 7:06 ` Alexandre Chartre
2020-04-23 16:16 ` Peter Zijlstra
2020-04-24 9:43 ` Miroslav Benes
2020-04-23 12:47 ` [PATCH 4/8] objtool: Add support for intra-function calls Peter Zijlstra
2020-04-23 14:34 ` Miroslav Benes
2020-04-23 15:22 ` Peter Zijlstra
2020-04-24 9:37 ` Miroslav Benes
2020-04-24 14:07 ` Miroslav Benes
2020-04-23 12:47 ` [PATCH 5/8] x86/speculation: Change FILL_RETURN_BUFFER to work with objtool Peter Zijlstra
2020-04-23 15:45 ` Alexandre Chartre
2020-04-24 19:04 ` Josh Poimboeuf [this message]
2020-04-23 12:47 ` [PATCH 6/8] x86: Simplify retpoline declaration Peter Zijlstra
2020-04-24 19:09 ` Josh Poimboeuf
2020-04-23 12:47 ` [PATCH 7/8] x86: Change {JMP,CALL}_NOSPEC argument Peter Zijlstra
2020-04-23 12:47 ` [PATCH 8/8] x86/retpoline: Fix retpoline unwind Peter Zijlstra
2020-04-23 12:59 ` Peter Zijlstra
2020-04-24 19:30 ` Josh Poimboeuf
2020-04-28 18:30 ` Peter Zijlstra
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