feat(el3-runtime): introduce system register trap handler
At the moment we only handle SMC traps from lower ELs, but ignore any
other synchronous traps and just panic.
To cope with system register traps, which we might need to emulate,
introduce a C function to handle those traps, and wire that up in the
exception handler to be called.
We provide a dispatcher function (in C), that will call platform
specific implementation for certain (classes of) system registers.
For now this is empty.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Change-Id: If147bcb49472eb02791498700300926afbcf75ff
diff --git a/include/bl31/sync_handle.h b/include/bl31/sync_handle.h
new file mode 100644
index 0000000..6ff88f9
--- /dev/null
+++ b/include/bl31/sync_handle.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2022, ARM Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef TRAP_HANDLE_H
+#define TRAP_HANDLE_H
+
+#include <stdbool.h>
+#include <context.h>
+
+#define ISS_SYSREG_OPCODE_MASK 0x3ffc1eUL
+#define ISS_SYSREG_REG_MASK 0x0003e0UL
+#define ISS_SYSREG_REG_SHIFT 5U
+#define ISS_SYSREG_DIRECTION_MASK 0x000001UL
+
+#define TRAP_RET_UNHANDLED -1
+#define TRAP_RET_REPEAT 0
+#define TRAP_RET_CONTINUE 1
+
+#ifndef __ASSEMBLER__
+static inline unsigned int get_sysreg_iss_rt(uint64_t esr)
+{
+ return (esr & ISS_SYSREG_REG_MASK) >> ISS_SYSREG_REG_SHIFT;
+}
+
+static inline bool is_sysreg_iss_write(uint64_t esr)
+{
+ return !(esr & ISS_SYSREG_DIRECTION_MASK);
+}
+
+/**
+ * handle_sysreg_trap() - Handle AArch64 system register traps from lower ELs
+ * @esr_el3: The content of ESR_EL3, containing the trap syndrome information
+ * @ctx: Pointer to the lower EL context, containing saved registers
+ *
+ * Called by the exception handler when a synchronous trap identifies as a
+ * system register trap (EC=0x18). ESR contains the encoding of the op[x] and
+ * CRm/CRn fields, to identify the system register, and the target/source
+ * GPR plus the direction (MRS/MSR). The lower EL's context can be altered
+ * by the function, to inject back the result of the emulation.
+ *
+ * Return: indication how to proceed with the trap:
+ * TRAP_RET_UNHANDLED(-1): trap is unhandled, trigger panic
+ * TRAP_RET_REPEAT(0): trap was handled, return to the trapping instruction
+ * (repeating it)
+ * TRAP_RET_CONTINUE(1): trap was handled, return to the next instruction
+ * (continuing after it)
+ */
+int handle_sysreg_trap(uint64_t esr_el3, cpu_context_t *ctx);
+
+#endif /* __ASSEMBLER__ */
+
+#endif