arm64: xen: Enable user access before a privcmd hvc call (9cf09d68) · Commits · 戴 / test

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. Reviewed-by:

Julien Grall <julien.grall@arm.com> Acked-by:

Stefano Stabellini <sstabellini@kernel.org> Cc: Will Deacon <will.deacon@arm.com> Cc: James Morse <james.morse@arm.com> Cc: Kees Cook <keescook@chromium.org> Cc: Mark Rutland <mark.rutland@arm.com> Signed-off-by:

Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/xen/hypercall.S

+15 −0

Original line number	Diff line number	Diff line
		@@ -49,6 +49,7 @@

		#include <linux/linkage.h>
		#include <asm/assembler.h>
		#include <asm/uaccess.h>
		#include <xen/interface/xen.h>


		@@ -91,6 +92,20 @@ ENTRY(privcmd_call)
		mov x2, x3
		mov x3, x4
		mov x4, x5
		/*
		* 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 emulation
		* is enabled (it implies that hardware UAO and PAN disabled).
		*/
		uaccess_ttbr0_enable x6, x7
		hvc XEN_IMM

		/*
		* Disable userspace access from kernel once the hyp call completed.
		*/
		uaccess_ttbr0_disable x6
		ret
		ENDPROC(privcmd_call);

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