interrupt: filter out reserved int number by decoding risc-v JAL instruction

components/riscv/instruction_decode.c

@@ -0,0 +1,38 @@
+// Copyright 2020 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <stdlib.h>
+#include "riscv/instruction_decode.h"
+
+typedef union {
+    struct {
+        unsigned int opcode: 7;
+        unsigned int rd: 5;
+        int imm_19_12: 8;
+        int imm_11: 1;
+        int imm_10_1: 10;
+        int imm20: 1;
+    };
+    unsigned int inst;
+} riscv_jal_intruction_t;
+
+int riscv_decode_offset_from_jal_instruction(const intptr_t inst_addr)
+{
+    riscv_jal_intruction_t *jal_inst = (riscv_jal_intruction_t *)inst_addr;
+    // check if it's a valid JAL instruction
+    if (jal_inst->opcode != 0x6f && jal_inst->rd != 0) {
+        abort();
+    }
+    return (jal_inst->imm_10_1 | jal_inst->imm_11 << 10 | jal_inst->imm_19_12 << 11 | jal_inst->imm20 << 19) << 1;
+}