Implement environment call properly

Implement ecall instruction with control and status
registers (CSRs).

Author: Risheng1128

README.md

@@ -84,10 +84,7 @@ Current progress of this emulator in riscv-arch-test(RV32):
     - `M`: Standard Extension for Integer Multiplication and Division
     - `C`: Standard Extension for Compressed Instruction
     - `Zifencei`: Instruction-Fetch Fence
-* Failed Tests
     - `privilege`: RISCV Privileged Specification
-        + 1 system calls
-            * `ecall`
 * Unsupported tests (runnable but incomplete)
     - `F` Standard Extension for Single-Precision Floating-Point
 

src/emulate.c

@@ -40,7 +40,12 @@ extern struct target_ops gdbstub_ops;
     _(breakpoint)       /* Breakpoint */                     \
     _(load_misaligned)  /* Load address misaligned */        \
     _(load_fault)       /* Load access fault */              \
-    _(store_misaligned) /* Store/AMO address misaligned */
+    _(store_misaligned) /* Store/AMO address misaligned */   \
+    _(store_fault)      /* Store/AMO access fault */         \
+    _(ecall_U)          /* Environment call from U-mode */   \
+    _(ecall_S)          /* Environment call from S-mode */   \
+    _(reserved)         /* Reserved */                       \
+    _(ecall_M)          /* Environment call from M-mode */
 
 enum {
 #define _(type) GET_EXCEPTION_CODE(type),
@@ -775,7 +780,7 @@ static inline bool op_system(struct riscv_t *rv, uint32_t insn)
         switch (funct12) { /* dispatch from imm field */
         case 0:            /* ECALL: Environment Call */
             rv->io.on_ecall(rv);
-            break;
+            return true;
         case 1: /* EBREAK: Environment Break */
             rv->io.on_ebreak(rv);
             return true;
@@ -2141,3 +2146,10 @@ void ebreak_handler(struct riscv_t *rv)
     assert(rv);
     rv_except_breakpoint(rv, rv->PC);
 }
+
+void ecall_handler(struct riscv_t *rv)
+{
+    assert(rv);
+    rv_except_ecall_M(rv, 0);
+    syscall_handler(rv);
+}

src/main.c

@@ -199,7 +199,7 @@ int main(int argc, char **args)
         .mem_write_b = MEMIO(write_b),
 
         /* system */
-        .on_ecall = syscall_handler,
+        .on_ecall = ecall_handler,
         .on_ebreak = ebreak_handler,
     };
 

src/riscv.h

@@ -130,6 +130,9 @@ riscv_word_t rv_get_reg(struct riscv_t *, uint32_t reg);
 /* system call handler */
 void syscall_handler(struct riscv_t *rv);
 
+/* environment call handler */
+void ecall_handler(struct riscv_t *rv);
+
 /* breakpoint exception handler */
 void ebreak_handler(struct riscv_t *rv);
 

src/syscall.c

@@ -336,7 +336,6 @@ void syscall_handler(struct riscv_t *rv)
 #undef _
     default:
         fprintf(stderr, "unknown syscall %d\n", (int) syscall);
-        rv_halt(rv);
         break;
     }
 }