Messages in this thread | | | Subject | Re: [PATCH v2 2/2] arm64: uaccess: Implement unsafe accessors | From | James Morse <> | Date | Fri, 21 Dec 2018 14:57:15 +0000 |
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Hi Julien,
On 03/12/2018 13:55, Julien Thierry wrote: > Current implementation of get/put_user_unsafe default to get/put_user > which toggle PAN before each access, despite having been told by the caller > that multiple accesses to user memory were about to happen. > > Provide implementations for user_access_begin/end to turn PAN off/on and > implement unsafe accessors that assume PAN was already turned off.
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h > index 842fb95..4e6477b 100644 > --- a/arch/arm64/include/asm/sysreg.h > +++ b/arch/arm64/include/asm/sysreg.h > @@ -108,6 +108,8 @@ > #define SYS_DC_CSW sys_insn(1, 0, 7, 10, 2) > #define SYS_DC_CISW sys_insn(1, 0, 7, 14, 2) > > +#define SYS_PSTATE_PAN sys_reg(3, 0, 4, 2, 3)
Nit: Could we keep this list in encoding order please. (it makes conflicts easier to resolve in the future)
> #define SYS_OSDTRRX_EL1 sys_reg(2, 0, 0, 0, 2) > #define SYS_MDCCINT_EL1 sys_reg(2, 0, 0, 2, 0) > #define SYS_MDSCR_EL1 sys_reg(2, 0, 0, 2, 2) > 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; > + } 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); > + } > + > + return false; > +}
(Reading the SCTLR bit is a bit of a heavy-hammer, as suggested elsewhere on the thread, can we use alternatives_applied here?)
It may be worth splitting this into three patches, so the 'unsafe' bits can be merged without the debug option.
Either way, for the unsafe parts: Reviewed-by: James Morse <james.morse@arm.com>
Thanks!
James
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