[PATCH 2/5] ARM64: KVM: set and get of sys registers in BE case

[Victor Kamensky]

This patch fixes issue of reading and writing V8 sys registers in
BE case. It is similar to V7 "ARM: kvm one_reg coproc set and get
BE fixes" patch.

It changes reg_from_user and reg_to_user functions to have strong
typed 'u64 *val' argument. And it uses endian angnostic way to
pick up righ word from '*val' in case when register size is 4 bytes.

Signed-off-by: Victor Kamensky <victor.kamensky at linaro.org>
---
 arch/arm64/kvm/sys_regs.c | 39 +++++++++++++++++++++++++++++++++------
 1 file changed, 33 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 02e9d09..e7c3e24 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -701,18 +701,45 @@ static struct sys_reg_desc invariant_sys_regs[] = {
 	  NULL, get_ctr_el0 },
 };
 
-static int reg_from_user(void *val, const void __user *uaddr, u64 id)
+static int reg_from_user(u64 *val, const void __user *uaddr, u64 id)
 {
-	/* This Just Works because we are little endian. */
-	if (copy_from_user(val, uaddr, KVM_REG_SIZE(id)) != 0)
+	unsigned long regsize = KVM_REG_SIZE(id);
+	union {
+		u32	word;
+		u64	dword;
+	} tmp = {0};
+
+	if (copy_from_user(&tmp, uaddr, regsize) != 0)
 		return -EFAULT;
+	switch (regsize) {
+	case 4:
+		*val = tmp.word;
+		break;
+	case 8:
+		*val = tmp.dword;
+		break;
+	}
 	return 0;
 }
 
-static int reg_to_user(void __user *uaddr, const void *val, u64 id)
+static int reg_to_user(void __user *uaddr, const u64 *val, u64 id)
 {
-	/* This Just Works because we are little endian. */
-	if (copy_to_user(uaddr, val, KVM_REG_SIZE(id)) != 0)
+	unsigned long regsize = KVM_REG_SIZE(id);
+	union {
+		u32	word;
+		u64	dword;
+	} tmp;
+
+	switch (regsize) {
+	case 4:
+		tmp.word = *val;
+		break;
+	case 8:
+		tmp.dword = *val;
+		break;
+	}
+
+	if (copy_to_user(uaddr, &tmp, regsize) != 0)
 		return -EFAULT;
 	return 0;
 }
-- 
1.8.1.4