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SubjectRe: [PATCH v2 2/2] arm64: uaccess: Implement unsafe accessors
On Mon, Dec 03, 2018 at 01:55:18PM +0000, Julien Thierry wrote:
> diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
> index 07c3408..cabfcae 100644
> --- a/arch/arm64/include/asm/uaccess.h
> +++ b/arch/arm64/include/asm/uaccess.h
> @@ -233,6 +233,23 @@ static inline void uaccess_enable_not_uao(void)
> __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
> }
>
> +#define unsafe_user_region_active uaccess_region_active
> +static inline bool uaccess_region_active(void)
> +{
> + if (system_uses_ttbr0_pan()) {
> + u64 ttbr;
> +
> + ttbr = read_sysreg(ttbr1_el1);
> + return ttbr & TTBR_ASID_MASK;

Nitpick: could write this in 1-2 lines.

> + } else if (cpus_have_const_cap(ARM64_ALT_PAN_NOT_UAO)) {
> + return (read_sysreg(sctlr_el1) & SCTLR_EL1_SPAN) ?
> + false :
> + !read_sysreg_s(SYS_PSTATE_PAN);
> + }

ARM64_ALT_PAN_NOT_UAO implies ARM64_HAS_PAN which implies SCTLR_EL1.SPAN
is 0 at run-time. Is this to cope with the case of being called prior to
cpu_enable_pan()?

--
Catalin
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