Introduce ENABLE_ON_TEST

The MMU test suite relies on rv32emu's syscall function instead of
its syscall table, unlike the Linux kernel. Therefore, use the
ON_TEST macro to distinguish between the Linux kernel and MMU test
suite as the emulation target.

Author: ChinYikMing

.github/workflows/main.yml

@@ -71,7 +71,7 @@ jobs:
     - name: MMU test
       run: |
             make -C tests/system/mmu/
-            make distclean && make ENABLE_USE_ELF=1 ENABLE_SYSTEM=1 mmu-test -j$(nproc)
+            make distclean && make ENABLE_ON_TEST=1 ENABLE_USE_ELF=1 ENABLE_SYSTEM=1 mmu-test -j$(nproc)
     - name: gdbstub test
       run: |
             make distclean && make ENABLE_GDBSTUB=1 gdbstub-test -j$(nproc)

Makefile

@@ -20,6 +20,15 @@ ifeq ($(call has, USE_ELF), 1)
 DEFINE_USE_ELF := -DUSE_ELF
 endif
 
+# The MMU test suite relies on rv32emu's syscall function instead of
+# its syscall table, unlike the Linux kernel. Therefore, use the
+# ON_TEST macro to distinguish between the Linux kernel and MMU test
+# suite as the emulation target.
+ENABLE_ON_TEST ?= 0
+ifeq ($(call has, ON_TEST), 1)
+DEFINE_ON_TEST := -DON_TEST
+endif
+
 ENABLE_SYSTEM ?= 0
 $(call set-feature, SYSTEM)
 
@@ -251,7 +260,7 @@ endif
 
 $(OUT)/%.o: src/%.c $(deps_emcc)
 	$(VECHO) "  CC\t$@\n"
-	$(Q)$(CC) $(DEFINE_USE_ELF) -o $@ $(CFLAGS) $(CFLAGS_emcc) -c -MMD -MF $@.d $<
+	$(Q)$(CC) $(DEFINE_USE_ELF) $(DEFINE_ON_TEST) -o $@ $(CFLAGS) $(CFLAGS_emcc) -c -MMD -MF $@.d $<
 
 $(BIN): $(OBJS) $(DEV_OBJS)
 	$(VECHO) "  LD\t$@\n"

src/emulate.c

@@ -1203,7 +1203,15 @@ void ebreak_handler(riscv_t *rv)
 void ecall_handler(riscv_t *rv)
 {
     assert(rv);
-#if RV32_HAS(SYSTEM)
+
+/*
+ * FIXME: MMU test suite rely on rv32emu syscall instead of its own syscall
+ * table
+ */
+#if defined(ON_TEST)
+    rv->PC += 4;
+    syscall_handler(rv);
+#elif RV32_HAS(SYSTEM)
     if (rv->priv_mode == RV_PRIV_U_MODE) {
         SET_CAUSE_AND_TVAL_THEN_TRAP(rv, ECALL_U, 0);
     } else if (rv->priv_mode ==