From 9cf09d68b89ae5fe0261dcc69464bcc676900af6 Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Tue, 5 Jul 2016 12:25:15 +0100 Subject: [PATCH] arm64: xen: Enable user access before a privcmd hvc 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. Reviewed-by: Julien Grall Acked-by: Stefano Stabellini Cc: Will Deacon Cc: James Morse Cc: Kees Cook Cc: Mark Rutland Signed-off-by: Catalin Marinas --- arch/arm64/xen/hypercall.S | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S index 329c802..b41aff2 100644 --- a/arch/arm64/xen/hypercall.S +++ b/arch/arm64/xen/hypercall.S @@ -49,6 +49,7 @@ #include #include +#include #include @@ -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); -- 2.7.4