[PATCH v3 03/10] arm64: Add new hcall HVC_CALL_FUNC
james.morse at arm.com
Thu Nov 26 09:32:41 PST 2015
From: Geoff Levand <geoff at infradead.org>
Add the new hcall HVC_CALL_FUNC that allows execution of a function at EL2.
During CPU reset the CPU must be brought to the exception level it had on
entry to the kernel. The HVC_CALL_FUNC hcall will provide the mechanism
needed for this exception level switch.
To allow the HVC_CALL_FUNC exception vector to work without a stack, which is
needed to support an hcall at CPU reset, this implementation uses register x18
to store the link register across the caller provided function. This dictates
that the caller provided function must preserve the contents of register x18.
Signed-off-by: Geoff Levand <geoff at infradead.org>
Signed-off-by: James Morse <james.morse at arm.com>
arch/arm64/include/asm/virt.h | 13 +++++++++++++
arch/arm64/kernel/hyp-stub.S | 13 ++++++++++++-
2 files changed, 25 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index eb10368c329e..30700961f28c 100644
@@ -45,6 +45,19 @@
#define HVC_SET_VECTORS 2
+ * HVC_CALL_FUNC - Execute a function at EL2.
+ * @x0: Physical address of the function to be executed.
+ * @x1: Passed as the first argument to the function.
+ * @x2: Passed as the second argument to the function.
+ * @x3: Passed as the third argument to the function.
+ * The called function must preserve the contents of register x18.
+#define HVC_CALL_FUNC 3
#define BOOT_CPU_MODE_EL1 (0xe11)
#define BOOT_CPU_MODE_EL2 (0xe12)
diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
index 017ab519aaf1..e8febe90c036 100644
@@ -67,8 +67,19 @@ el1_sync:
1: cmp x18, #HVC_SET_VECTORS
- b.ne 2f
+ b.ne 1f
msr vbar_el2, x0
+ b 2f
+1: cmp x18, #HVC_CALL_FUNC
+ b.ne 2f
+ mov x18, lr
+ mov lr, x0
+ mov x0, x1
+ mov x1, x2
+ mov x2, x3
+ blr lr
+ mov lr, x18
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