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SubjectRe: [PATCH 01/11] Initialize the mapping of KASan shadow memory
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On 22/11/17 12:56, Liuwenliang (Abbott Liu) wrote:
> On Nov 22, 2017 20:30 Mark Rutland [mailto:mark.rutland@arm.com] wrote:
>> On Tue, Nov 21, 2017 at 07:59:01AM +0000, Liuwenliang (Abbott Liu) wrote:
>>> On Nov 17, 2017 21:49 Marc Zyngier [mailto:marc.zyngier@arm.com] wrote:
>>>> On Sat, 18 Nov 2017 10:40:08 +0000
>>>> "Liuwenliang (Abbott Liu)" <liuwenliang@huawei.com> wrote:
>>>>> On Nov 17, 2017 15:36 Christoffer Dall [mailto:cdall@linaro.org] wrote:
>
>>> Please don't ask people to limit to 4GB of physical space on CPU
>>> supporting LPAE, please don't ask people to guaranteed to have some
>>> memory below 4GB on CPU supporting LPAE.
>
>> I don't think that Marc is suggesting that you'd always use the 32-bit
>> accessors on an LPAE system, just that all the definitions should exist
>> regardless of configuration.
>
>> So rather than this:
>
>>> +#ifdef CONFIG_ARM_LPAE
>>> +#define TTBR0 __ACCESS_CP15_64(0, c2)
>>> +#define TTBR1 __ACCESS_CP15_64(1, c2)
>>> +#define PAR __ACCESS_CP15_64(0, c7)
>>> +#else
>>> +#define TTBR0 __ACCESS_CP15(c2, 0, c0, 0)
>>> +#define TTBR1 __ACCESS_CP15(c2, 0, c0, 1)
>>> +#define PAR __ACCESS_CP15(c7, 0, c4, 0)
>>> +#endif
>
>> ... you'd have the following in cp15.h:
>
>> #define TTBR0_64 __ACCESS_CP15_64(0, c2)
>> #define TTBR1_64 __ACCESS_CP15_64(1, c2)
>> #define PAR_64 __ACCESS_CP15_64(0, c7)
>
>> #define TTBR0_32 __ACCESS_CP15(c2, 0, c0, 0)
>> #define TTBR1_32 __ACCESS_CP15(c2, 0, c0, 1)
>> #define PAR_32 __ACCESS_CP15(c7, 0, c4, 0)
>
>> ... and elsewhere, where it matters, we choose which to use depending on
>> the kernel configuration, e.g.
>
>> void set_ttbr0(u64 val)
>> {
>> if (IS_ENABLED(CONFIG_ARM_LPAE))
>> write_sysreg(val, TTBR0_64);
>> else
>> write_sysreg(val, TTBR0_32);
>> }
>
>> Thanks,
>> Mark.
>
> Thanks for your solution.
> I didn't know there was a IS_ENABLED macro that I can use, so I can't write a function
> like:
> void set_ttbr0(u64 val)
> {
> if (IS_ENABLED(CONFIG_ARM_LPAE))
> write_sysreg(val, TTBR0_64);
> else
> write_sysreg(val, TTBR0_32);
> }
>
>
> Here is the code I tested on vexpress_a9 and vexpress_a15:
> diff --git a/arch/arm/include/asm/cp15.h b/arch/arm/include/asm/cp15.h
> index dbdbce1..5eb0185 100644
> --- a/arch/arm/include/asm/cp15.h
> +++ b/arch/arm/include/asm/cp15.h
> @@ -2,6 +2,7 @@
> #define __ASM_ARM_CP15_H
>
> #include <asm/barrier.h>
> +#include <linux/stringify.h>
>
> /*
> * CR1 bits (CP#15 CR1)
> @@ -64,8 +65,93 @@
> #define __write_sysreg(v, r, w, c, t) asm volatile(w " " c : : "r" ((t)(v)))
> #define write_sysreg(v, ...) __write_sysreg(v, __VA_ARGS__)
>
> +#define TTBR0_32 __ACCESS_CP15(c2, 0, c0, 0)
> +#define TTBR1_32 __ACCESS_CP15(c2, 0, c0, 1)
> +#define TTBR0_64 __ACCESS_CP15_64(0, c2)
> +#define TTBR1_64 __ACCESS_CP15_64(1, c2)
> +#define PAR __ACCESS_CP15_64(0, c7)

Please define both PAR accessors. Yes, I know the 32bit version is not
used yet, but it doesn't hurt to make it visible.

Thanks,

M.
--
Jazz is not dead. It just smells funny...

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