target/riscv: Fix bug in getting trap cause name for trace_riscv_trap

When the cause number is equal to or greater than 23, print "(unknown)" in
trace_riscv_trap. The max valid number of riscv_excp_names is 23, so the last
excpetion "guest_store_page_fault" can not be printed.

In addition, the current check of cause is invalid for riscv_intr_names. So
introduce riscv_cpu_get_trap_name to get the trap cause name.

Signed-off-by: Yifei Jiang <jiangyifei@huawei.com>
Signed-off-by: Yipeng Yin <yinyipeng1@huawei.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20200814035819.1214-1-jiangyifei@huawei.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -96,6 +96,17 @@ const char * const riscv_intr_names[] = {
     "reserved"
 };
 
+const char *riscv_cpu_get_trap_name(target_ulong cause, bool async)
+{
+    if (async) {
+        return (cause < ARRAY_SIZE(riscv_intr_names)) ?
+               riscv_intr_names[cause] : "(unknown)";
+    } else {
+        return (cause < ARRAY_SIZE(riscv_excp_names)) ?
+               riscv_excp_names[cause] : "(unknown)";
+    }
+}
+
 static void set_misa(CPURISCVState *env, target_ulong misa)
 {
     env->misa_mask = env->misa = misa;

target/riscv/cpu.h

@@ -312,6 +312,7 @@ extern const char * const riscv_fpr_regnames[];
 extern const char * const riscv_excp_names[];
 extern const char * const riscv_intr_names[];
 
+const char *riscv_cpu_get_trap_name(target_ulong cause, bool async);
 void riscv_cpu_do_interrupt(CPUState *cpu);
 int riscv_cpu_gdb_read_register(CPUState *cpu, GByteArray *buf, int reg);
 int riscv_cpu_gdb_write_register(CPUState *cpu, uint8_t *buf, int reg);

target/riscv/cpu_helper.c

@@ -892,8 +892,8 @@ void riscv_cpu_do_interrupt(CPUState *cs)
         }
     }
 
-    trace_riscv_trap(env->mhartid, async, cause, env->pc, tval, cause < 23 ?
+    trace_riscv_trap(env->mhartid, async, cause, env->pc, tval,
-        (async ? riscv_intr_names : riscv_excp_names)[cause] : "(unknown)");
+        riscv_cpu_get_trap_name(cause, async));
 
     if (env->priv <= PRV_S &&
             cause < TARGET_LONG_BITS && ((deleg >> cause) & 1)) {