| Message ID | 1471015666-23125-7-git-send-email-catalin.marinas@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Catalin, I have CCed Stefano who is maintaining the Xen ARM code in Linux. On 12/08/2016 17:27, Catalin Marinas wrote: > Privcmd calls are issued by the userspace. The kernel needs to enable > access to TTBR0_EL1 as the hypervisor would issue stage 1 translations > to user memory via AT instructions. Since AT instructions are not > affected by the PAN bit (ARMv8.1), we only need the explicit > uaccess_enable/disable if the TTBR0 PAN option is enabled. > > Cc: Julien Grall <julien.grall@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: James Morse <james.morse@arm.com> > Cc: Kees Cook <keescook@chromium.org> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Julien Grall <julien.grall@arm.com> Regards, > --- > arch/arm64/xen/hypercall.S | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S > index 329c8027b0a9..4c509f4f4dcc 100644 > --- a/arch/arm64/xen/hypercall.S > +++ b/arch/arm64/xen/hypercall.S > @@ -91,6 +91,24 @@ ENTRY(privcmd_call) > mov x2, x3 > mov x3, x4 > mov x4, x5 > +#ifdef CONFIG_ARM64_TTBR0_PAN > + /* > + * Privcmd calls are issued by the userspace. The kernel needs to > + * enable access to TTBR0_EL1 as the hypervisor would issue stage 1 > + * translations to user memory via AT instructions. Since AT > + * instructions are not affected by the PAN bit (ARMv8.1), we only > + * need the explicit uaccess_enable/disable if the TTBR0 PAN option is > + * enabled. > + */ > + uaccess_enable x6, x7, x8 > +#endif > hvc XEN_IMM > + > +#ifdef CONFIG_ARM64_TTBR0_PAN > + /* > + * Disable userspace access from kernel once the hyp call completed. > + */ > + uaccess_disable x6 > +#endif > ret > ENDPROC(privcmd_call); > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
On Mon, 15 Aug 2016, Julien Grall wrote: > Hi Catalin, > > I have CCed Stefano who is maintaining the Xen ARM code in Linux. > > On 12/08/2016 17:27, Catalin Marinas wrote: > > Privcmd calls are issued by the userspace. The kernel needs to enable > > access to TTBR0_EL1 as the hypervisor would issue stage 1 translations > > to user memory via AT instructions. Since AT instructions are not > > affected by the PAN bit (ARMv8.1), we only need the explicit > > uaccess_enable/disable if the TTBR0 PAN option is enabled. > > > > Cc: Julien Grall <julien.grall@arm.com> > > Cc: Will Deacon <will.deacon@arm.com> > > Cc: James Morse <james.morse@arm.com> > > Cc: Kees Cook <keescook@chromium.org> > > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > > Reviewed-by: Julien Grall <julien.grall@arm.com> > > Regards, > > > --- > > arch/arm64/xen/hypercall.S | 18 ++++++++++++++++++ > > 1 file changed, 18 insertions(+) > > > > diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S > > index 329c8027b0a9..4c509f4f4dcc 100644 > > --- a/arch/arm64/xen/hypercall.S > > +++ b/arch/arm64/xen/hypercall.S > > @@ -91,6 +91,24 @@ ENTRY(privcmd_call) > > mov x2, x3 > > mov x3, x4 > > mov x4, x5 > > +#ifdef CONFIG_ARM64_TTBR0_PAN > > + /* > > + * Privcmd calls are issued by the userspace. The kernel needs to > > + * enable access to TTBR0_EL1 as the hypervisor would issue stage 1 > > + * translations to user memory via AT instructions. Since AT > > + * instructions are not affected by the PAN bit (ARMv8.1), we only > > + * need the explicit uaccess_enable/disable if the TTBR0 PAN option is > > + * enabled. That's a pity but it is how it is. Acked-by: Stefano Stabellini <sstabellini@kernel.org> Given that the patch is part of your PAN series, I expect that it is going to go via your tree. > > + uaccess_enable x6, x7, x8 > > +#endif > > hvc XEN_IMM > > + > > +#ifdef CONFIG_ARM64_TTBR0_PAN > > + /* > > + * Disable userspace access from kernel once the hyp call completed. > > + */ > > + uaccess_disable x6 > > +#endif > > ret > > ENDPROC(privcmd_call); > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-kernel@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > > > -- > Julien Grall >
diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S index 329c8027b0a9..4c509f4f4dcc 100644 --- a/arch/arm64/xen/hypercall.S +++ b/arch/arm64/xen/hypercall.S @@ -91,6 +91,24 @@ ENTRY(privcmd_call) mov x2, x3 mov x3, x4 mov x4, x5 +#ifdef CONFIG_ARM64_TTBR0_PAN + /* + * Privcmd calls are issued by the userspace. The kernel needs to + * enable access to TTBR0_EL1 as the hypervisor would issue stage 1 + * translations to user memory via AT instructions. Since AT + * instructions are not affected by the PAN bit (ARMv8.1), we only + * need the explicit uaccess_enable/disable if the TTBR0 PAN option is + * enabled. + */ + uaccess_enable x6, x7, x8 +#endif hvc XEN_IMM + +#ifdef CONFIG_ARM64_TTBR0_PAN + /* + * Disable userspace access from kernel once the hyp call completed. + */ + uaccess_disable x6 +#endif ret ENDPROC(privcmd_call);
Privcmd calls are issued by the userspace. The kernel needs to enable access to TTBR0_EL1 as the hypervisor would issue stage 1 translations to user memory via AT instructions. Since AT instructions are not affected by the PAN bit (ARMv8.1), we only need the explicit uaccess_enable/disable if the TTBR0 PAN option is enabled. Cc: Julien Grall <julien.grall@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: James Morse <james.morse@arm.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> --- arch/arm64/xen/hypercall.S | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)