From: sboyd@codeaurora•org (sboyd at codeaurora.org)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 2/3] [v4] ARM64: TTY: hvc_dcc: Add support for ARM64 dcc
Date: Mon, 24 Aug 2015 16:51:44 -0700 [thread overview]
Message-ID: <20150824235144.GH14330@codeaurora.org> (raw)
In-Reply-To: <20150819163736.GC6281@e103592.cambridge.arm.com>
On 08/19, Dave Martin wrote:
> On Wed, Aug 19, 2015 at 11:16:52AM -0500, Timur Tabi wrote:
> > On 08/19/2015 05:14 AM, Dave Martin wrote:
> > >>>So does that mean that ldrb will zero-extend the byte to all 64 bits of x3?
> > >Yes. No extra operation is required.
> >
> > So my patch is actually correct as-is?
>
> +static inline void __dcc_putchar(char c)
> +{
> + asm volatile("msr dbgdtrtx_el0, %0"
> + : /* No output register */
> + : "r" (c));
>
> For safety, you still need to make sure that c is appropriately masked
> before passing it to the asm. Something like this should definitely be
> safe:
>
> : "r" ((unsigned long)(unsigned char)c)
>
> GCC can then emit uxtb or not, depending on whether it's needed in each
> context where the asm is inlined.
Does this mean we ought to do the same thing in the arm header
file too?
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
next prev parent reply other threads:[~2015-08-24 23:51 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-08 0:16 [PATCH 1/3] [v2] hvc_dcc: don't ignore errors during initialization Timur Tabi
2015-08-08 0:16 ` [PATCH 2/3] [v4] ARM64: TTY: hvc_dcc: Add support for ARM64 dcc Timur Tabi
2015-08-10 9:40 ` Will Deacon
2015-08-17 23:56 ` Timur Tabi
2015-08-18 8:21 ` Dave Martin
2015-08-18 19:07 ` Timur Tabi
2015-08-19 10:14 ` Dave Martin
2015-08-19 16:16 ` Timur Tabi
2015-08-19 16:37 ` Dave Martin
2015-08-24 23:51 ` sboyd at codeaurora.org [this message]
2015-09-02 11:10 ` Dave Martin
2015-08-08 0:16 ` [PATCH 3/3] [v2] hvc_dcc: disable user-space access to DCC Timur Tabi
2015-08-10 9:47 ` Will Deacon
2015-08-17 22:45 ` Timur Tabi
2015-08-10 9:48 ` [PATCH 1/3] [v2] hvc_dcc: don't ignore errors during initialization Will Deacon
2015-08-19 22:51 ` Timur Tabi
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