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SubjectRe: [PATCH 4/4] hvc_dcc: disable user-space access to DCC
On 06/30/2015 02:23 PM, Timur Tabi wrote:
> diff --git a/arch/arm/include/asm/dcc.h b/arch/arm/include/asm/dcc.h
> index b74899d..c50056b 100644
> --- a/arch/arm/include/asm/dcc.h
> +++ b/arch/arm/include/asm/dcc.h
> @@ -9,8 +9,11 @@
> * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> * GNU General Public License for more details.
> */
> +#ifndef __ASM_DCC_H
> +#define __ASM_DCC_H
>
> #include <asm/barrier.h>
> +#include <asm/hardware/cp14.h>

That's new.

>
> static inline u32 __dcc_getstatus(void)
> {
> @@ -39,3 +42,15 @@ static inline void __dcc_putchar(char c)
> : "r" (c));
> isb();
> }
> +
> +static inline void __dcc_initialize(void)
> +{
> + u32 val;
> +
> + /* Disable user-space access to DCC */
> + val = MRC14(0, c0, c1, 0);
> + val |= 1 << 12; /* DSCR[Comms] */
> + MCR14(val, 0, c0, c1, 0);
> +}

Nitpick: We do raw cp14 accesses for other functions in this file, so it
would be nice to be consistent throughout.

> +
> +#endif
> diff --git a/arch/arm64/include/asm/dcc.h b/arch/arm64/include/asm/dcc.h
> index fcb8d7d..7843e62 100644
> --- a/arch/arm64/include/asm/dcc.h
> +++ b/arch/arm64/include/asm/dcc.h
> @@ -49,4 +49,15 @@ static inline void __dcc_putchar(char c)
> isb();
> }
>
> +static inline void __dcc_initialize(void)
> +{
> + u32 val;
> +
> + /* Disable user-space access to DCC */
> + asm ("mrs %0, mdscr_el1\n"

shouldn't this be volatile?

> + " orr %0, %0, #4096\n" /* Set the TDCC bit */

arm64 has some #defines in debug-monitors.h which we should probably
extend to have this bit as a #define too.

> + " msr mdscr_el1, %0\n"
> + : "=r" (val));
> +}
> +
> #endif
>

--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project



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