From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Julien Grall <julien.grall@linaro.org>
Cc: xen-devel@lists.xenproject.org, tim@xen.org,
ian.campbell@citrix.com, stefano.stabellini@citrix.com
Subject: Re: [PATCH for-4.5] xen/arm: Correct the opcode for BUG_INSTR on arm32
Date: Thu, 4 Dec 2014 14:34:34 -0500 [thread overview]
Message-ID: <20141204193434.GB6225@laptop.dumpdata.com> (raw)
In-Reply-To: <1417721215-32639-1-git-send-email-julien.grall@linaro.org>
On Thu, Dec 04, 2014 at 07:26:55PM +0000, Julien Grall wrote:
> A 0 was forgotten when the arm32 BUG instruction opcode has been added in commit
> 3e802c6ca1fb9a9549258c2855a57cad483f3cbd "xen/arm: Correctly support WARN_ON".
>
> This will result to use a valid instruction (mcreq 0, 3, r0, cr15, cr0, {7}),
> and inhibit usage of BUG/WARN_ON and co.
>
> Signed-off-by: Julien Grall <julien.grall@linaro.org>
>
> ---
>
> Not sure, why I dropped the 0 when I implemented the patch...
> This is a bug fixed for Xen 4.5. This is only affected ARM32 where the
> BUG opcode was malformed.
>
> With the malformed opcode, the ASSERT/BUG_ON is skipped and the
> processor may execute another patch (because the compiler has optimized
s/patch/path/ ?
> due the unreachable in both macro).
>
> The code modified is only executed when Xen is in bad state.
Release-Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
> xen/include/asm-arm/arm32/bug.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/xen/include/asm-arm/arm32/bug.h b/xen/include/asm-arm/arm32/bug.h
> index 155b420..3e66f35 100644
> --- a/xen/include/asm-arm/arm32/bug.h
> +++ b/xen/include/asm-arm/arm32/bug.h
> @@ -6,7 +6,7 @@
> /* ARMv7 provides a list of undefined opcode (see A8.8.247 DDI 0406C.b)
> * Use one them encoding A1 to go in exception mode
> */
> -#define BUG_OPCODE 0xe7f00f0
> +#define BUG_OPCODE 0xe7f000f0
>
> #define BUG_INSTR ".word " __stringify(BUG_OPCODE)
>
> --
> 2.1.3
>
next prev parent reply other threads:[~2014-12-04 19:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-04 19:26 [PATCH for-4.5] xen/arm: Correct the opcode for BUG_INSTR on arm32 Julien Grall
2014-12-04 19:34 ` Konrad Rzeszutek Wilk [this message]
2014-12-05 10:53 ` Julien Grall
2014-12-05 10:54 ` Ian Campbell
2014-12-09 15:06 ` Ian Campbell
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