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authorCatalin Marinas <catalin.marinas@arm.com>2016-07-05 12:25:15 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2016-11-21 18:48:55 +0000
commit9cf09d68b89ae5fe0261dcc69464bcc676900af6 (patch)
treea9f9ad57e9d9e6b8e09dfb7b9b3ae4df64566629 /arch/arm64/xen
parentarm64: Handle faults caused by inadvertent user access with PAN enabled (diff)
downloadlinux-dev-9cf09d68b89ae5fe0261dcc69464bcc676900af6.tar.xz
linux-dev-9cf09d68b89ae5fe0261dcc69464bcc676900af6.zip
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 <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>
Diffstat (limited to 'arch/arm64/xen')
-rw-r--r--arch/arm64/xen/hypercall.S15
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S
index 329c8027b0a9..b41aff25426d 100644
--- a/arch/arm64/xen/hypercall.S
+++ b/arch/arm64/xen/hypercall.S
@@ -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);