Messages in this thread | | | Subject | Re: [PATCH v2 2/2] arm64: uaccess: Implement unsafe accessors | From | Julien Thierry <> | Date | Fri, 7 Dec 2018 08:38:11 +0000 |
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On 12/06/2018 06:25 PM, Catalin Marinas wrote: > 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. >
True, I can do that in 1 line.
>> + } 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()? >
Yes, the issue I can into is that for cpufeatures, .cpu_enable() callbacks are called inside stop_machine() which obviously might_sleep and so attempts to check whether user_access is on. But for features that get enabled before PAN, the PAN bit will be set.
Thanks,
Julien
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