diff --git a/Makefile b/Makefile
index cda3c5027..c3641968a 100644
--- a/Makefile
+++ b/Makefile
@@ -11,11 +11,6 @@ CFLAGS = -std=gnu99 -O2 -Wall -Wextra
 CFLAGS += -Wno-unused-label
 CFLAGS += -include src/common.h
 
-# Set the default stack pointer
-CFLAGS += -D DEFAULT_STACK_ADDR=0xFFFFE000
-# Set the default args starting address
-CFLAGS += -D DEFAULT_ARGS_ADDR=0xFFFFF000
-
 # Enable link-time optimization (LTO)
 ENABLE_LTO ?= 1
 ifeq ($(call has, LTO), 1)
@@ -121,7 +116,7 @@ endif
 ENABLE_JIT ?= 0
 $(call set-feature, JIT)
 ifeq ($(call has, JIT), 1)
-OBJS_EXT += jit.o 
+OBJS_EXT += jit.o
 ifneq ($(processor),$(filter $(processor),x86_64 aarch64 arm64))
 $(error JIT mode only supports for x64 and arm64 target currently.)
 endif
diff --git a/src/elf.c b/src/elf.c
index 7d4414020..4f3f4e48a 100644
--- a/src/elf.c
+++ b/src/elf.c
@@ -259,12 +259,8 @@ bool elf_get_data_section_range(elf_t *e, uint32_t *start, uint32_t *end)
  * Finding data for section headers:
  *   File start + section_header.offset -> section Data
  */
-bool elf_load(elf_t *e, riscv_t *rv, memory_t *mem)
+bool elf_load(elf_t *e, memory_t *mem)
 {
-    /* set the entry point */
-    if (!rv_set_pc(rv, e->hdr->e_entry))
-        return false;
-
     /* loop over all of the program headers */
     for (int p = 0; p < e->hdr->e_phnum; ++p) {
         /* find next program header */
diff --git a/src/elf.h b/src/elf.h
index e43caf9a0..6ebb80723 100644
--- a/src/elf.h
+++ b/src/elf.h
@@ -145,7 +145,7 @@ const char *elf_find_symbol(elf_t *e, uint32_t addr);
 bool elf_get_data_section_range(elf_t *e, uint32_t *start, uint32_t *end);
 
 /* Load the ELF file into a memory abstraction */
-bool elf_load(elf_t *e, riscv_t *rv, memory_t *mem);
+bool elf_load(elf_t *e, memory_t *mem);
 
 /* get the ELF header */
 struct Elf32_Ehdr *get_elf_header(elf_t *e);
diff --git a/src/emulate.c b/src/emulate.c
index ada47350a..dd3886ce7 100644
--- a/src/emulate.c
+++ b/src/emulate.c
@@ -125,7 +125,7 @@ RV_EXCEPTION_LIST
  */
 #define RV_EXC_MISALIGN_HANDLER(mask_or_pc, type, compress, IO)       \
     IIF(IO)                                                           \
-    (if (!rv->io.allow_misalign && unlikely(addr & (mask_or_pc))),    \
+    (if (!PRIV(rv)->allow_misalign && unlikely(addr & (mask_or_pc))), \
      if (unlikely(insn_is_misaligned(PC))))                           \
     {                                                                 \
         rv->compressed = compress;                                    \
@@ -1182,7 +1182,7 @@ void ecall_handler(riscv_t *rv)
 
 void memset_handler(riscv_t *rv)
 {
-    memory_t *m = ((state_t *) rv->userdata)->mem;
+    memory_t *m = PRIV(rv)->mem;
     memset((char *) m->mem_base + rv->X[rv_reg_a0], rv->X[rv_reg_a1],
            rv->X[rv_reg_a2]);
     rv->PC = rv->X[rv_reg_ra] & ~1U;
@@ -1190,7 +1190,7 @@ void memset_handler(riscv_t *rv)
 
 void memcpy_handler(riscv_t *rv)
 {
-    memory_t *m = ((state_t *) rv->userdata)->mem;
+    memory_t *m = PRIV(rv)->mem;
     memcpy((char *) m->mem_base + rv->X[rv_reg_a0],
            (char *) m->mem_base + rv->X[rv_reg_a1], rv->X[rv_reg_a2]);
     rv->PC = rv->X[rv_reg_ra] & ~1U;
diff --git a/src/io.c b/src/io.c
index ce66ce465..6da5d284c 100644
--- a/src/io.c
+++ b/src/io.c
@@ -17,44 +17,36 @@
 
 static uint8_t *data_memory_base;
 
-/*
- * set memory size to 2^32 - 1 bytes
- *
- * The memory size is set to 2^32 - 1 bytes in order to make this emulator
- * portable for both 32-bit and 64-bit platforms. As a result, it can access
- * any segment of the memory on either platform. Furthermore, it is safe
- * because most of the test cases' data memory usage will not exceed this
- * memory size.
- */
-#define MEM_SIZE 0xFFFFFFFFULL
-
-memory_t *memory_new(void)
+memory_t *memory_new(uint32_t size)
 {
+    if (!size)
+        return NULL;
+
     memory_t *mem = malloc(sizeof(memory_t));
     assert(mem);
 #if HAVE_MMAP
-    data_memory_base = mmap(NULL, MEM_SIZE, PROT_READ | PROT_WRITE,
+    data_memory_base = mmap(NULL, size, PROT_READ | PROT_WRITE,
                             MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
     if (data_memory_base == MAP_FAILED) {
         free(mem);
         return NULL;
     }
 #else
-    data_memory_base = malloc(MEM_SIZE);
+    data_memory_base = malloc(size);
     if (!data_memory_base) {
         free(mem);
         return NULL;
     }
 #endif
     mem->mem_base = data_memory_base;
-    mem->mem_size = MEM_SIZE;
+    mem->mem_size = size;
     return mem;
 }
 
 void memory_delete(memory_t *mem)
 {
 #if HAVE_MMAP
-    munmap(mem->mem_base, MEM_SIZE);
+    munmap(mem->mem_base, mem->mem_size);
 #else
     free(mem->mem_base);
 #endif
diff --git a/src/io.h b/src/io.h
index cc93008f0..9a6741796 100644
--- a/src/io.h
+++ b/src/io.h
@@ -17,7 +17,7 @@ typedef struct {
     uint64_t mem_size;
 } memory_t;
 
-memory_t *memory_new(void);
+memory_t *memory_new(uint32_t size);
 void memory_delete(memory_t *m);
 
 /* read a C-style string from memory */
diff --git a/src/jit.c b/src/jit.c
index a24648dae..8c72658d6 100644
--- a/src/jit.c
+++ b/src/jit.c
@@ -1284,7 +1284,7 @@ static void do_fuse2(struct jit_state *state, riscv_t *rv UNUSED, rv_insn_t *ir)
 
 static void do_fuse3(struct jit_state *state, riscv_t *rv, rv_insn_t *ir)
 {
-    memory_t *m = ((state_t *) rv->userdata)->mem;
+    memory_t *m = PRIV(rv)->mem;
     opcode_fuse_t *fuse = ir->fuse;
     for (int i = 0; i < ir->imm2; i++) {
         emit_load(state, S32, parameter_reg[0], temp_reg[0],
@@ -1300,7 +1300,7 @@ static void do_fuse3(struct jit_state *state, riscv_t *rv, rv_insn_t *ir)
 
 static void do_fuse4(struct jit_state *state, riscv_t *rv, rv_insn_t *ir)
 {
-    memory_t *m = ((state_t *) rv->userdata)->mem;
+    memory_t *m = ((vm_attr_t *) rv->userdata)->mem;
     opcode_fuse_t *fuse = ir->fuse;
     for (int i = 0; i < ir->imm2; i++) {
         emit_load(state, S32, parameter_reg[0], temp_reg[0],
diff --git a/src/main.c b/src/main.c
index 71d900b71..28a468db7 100644
--- a/src/main.c
+++ b/src/main.c
@@ -75,8 +75,10 @@ IO_HANDLER_IMPL(byte, write_b, W)
 #undef W
 
 /* run: printing out an instruction trace */
-static void run_and_trace(riscv_t *rv, elf_t *elf)
+static void run_and_trace(riscv_t *rv, const char *prog_name)
 {
+    elf_t *elf = elf_new();
+    assert(elf && elf_open(elf, prog_name));
     const uint32_t cycles_per_step = 1;
 
     for (; !rv_has_halted(rv);) { /* run until the flag is done */
@@ -88,15 +90,8 @@ static void run_and_trace(riscv_t *rv, elf_t *elf)
         /* step instructions */
         rv_step(rv, cycles_per_step);
     }
-}
 
-static void run(riscv_t *rv)
-{
-    const uint32_t cycles_per_step = 100;
-    for (; !rv_has_halted(rv);) { /* run until the flag is done */
-        /* step instructions */
-        rv_step(rv, cycles_per_step);
-    }
+    elf_delete(elf);
 }
 
 static void print_usage(const char *filename)
@@ -188,8 +183,11 @@ static bool parse_args(int argc, char **args)
     return true;
 }
 
-static void dump_test_signature(elf_t *elf)
+static void dump_test_signature(const char *prog_name)
 {
+    elf_t *elf = elf_new();
+    assert(elf && elf_open(elf, prog_name));
+
     uint32_t start = 0, end = 0;
     const struct Elf32_Sym *sym;
     FILE *f = fopen(signature_out_file, "w");
@@ -212,8 +210,13 @@ static void dump_test_signature(elf_t *elf)
         fprintf(f, "%08x\n", memory_read_w(addr));
 
     fclose(f);
+    elf_delete(elf);
 }
 
+#define MEM_SIZE 0xFFFFFFFFULL  /* 2^32 - 1 */
+#define STACK_SIZE 0x1000       /* 4096 */
+#define ARGS_OFFSET_SIZE 0x1000 /* 4096 */
+
 int main(int argc, char **args)
 {
     if (argc == 1 || !parse_args(argc, args)) {
@@ -221,12 +224,19 @@ int main(int argc, char **args)
         return 1;
     }
 
-    /* open the ELF file from the file system */
-    elf_t *elf = elf_new();
-    if (!elf_open(elf, opt_prog_name)) {
-        fprintf(stderr, "Unable to open ELF file '%s'\n", opt_prog_name);
-        return 1;
-    }
+    vm_attr_t attr = {
+        .mem_size = MEM_SIZE,
+        .stack_size = STACK_SIZE,
+        .args_offset_size = ARGS_OFFSET_SIZE,
+        .argc = prog_argc,
+        .argv = prog_args,
+        .logging_level = 0,
+        .emu_data.vm_user = malloc(sizeof(vm_user_t)),
+        .cycle_per_step = 100,
+        .allow_misalign = opt_misaligned,
+    };
+    assert(attr.emu_data.vm_user);
+    attr.emu_data.vm_user->elf_program = opt_prog_name;
 
     /* install the I/O handlers for the RISC-V runtime */
     const riscv_io_t io = {
@@ -246,33 +256,18 @@ int main(int argc, char **args)
         .on_ebreak = ebreak_handler,
         .on_memcpy = memcpy_handler,
         .on_memset = memset_handler,
-        .allow_misalign = opt_misaligned,
     };
 
-    state_t *state = state_new();
-
-    /* find the start of the heap */
-    const struct Elf32_Sym *end;
-    if ((end = elf_get_symbol(elf, "_end")))
-        state->break_addr = end->st_value;
-
     /* create the RISC-V runtime */
-    riscv_t *rv =
-        rv_create(&io, state, prog_argc, prog_args, !opt_quiet_outputs);
+    riscv_t *rv = rv_create(&io, &attr);
     if (!rv) {
         fprintf(stderr, "Unable to create riscv emulator\n");
         return 1;
     }
 
-    /* load the ELF file into the memory abstraction */
-    if (!elf_load(elf, rv, state->mem)) {
-        fprintf(stderr, "Unable to load ELF file '%s'\n", args[1]);
-        return 1;
-    }
-
     /* run based on the specified mode */
     if (opt_trace) {
-        run_and_trace(rv, elf);
+        run_and_trace(rv, opt_prog_name);
     }
 #if RV32_HAS(GDBSTUB)
     else if (opt_gdbstub) {
@@ -289,14 +284,13 @@ int main(int argc, char **args)
 
     /* dump test result in test mode */
     if (opt_arch_test)
-        dump_test_signature(elf);
+        dump_test_signature(opt_prog_name);
 
     if (opt_prof_data)
         rv_profile(rv, prof_out_file);
     /* finalize the RISC-V runtime */
-    elf_delete(elf);
     rv_delete(rv);
-    state_delete(state);
 
+    printf("inferior exit code %d\n", attr.exit_code);
     return 0;
 }
diff --git a/src/riscv.c b/src/riscv.c
index 1399ff6bf..f835e2550 100644
--- a/src/riscv.c
+++ b/src/riscv.c
@@ -8,6 +8,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "elf.h"
 #include "mpool.h"
 #include "riscv.h"
 #include "riscv_private.h"
@@ -105,11 +106,65 @@ riscv_word_t rv_get_reg(riscv_t *rv, uint32_t reg)
     return ~0U;
 }
 
-riscv_t *rv_create(const riscv_io_t *io,
-                   riscv_user_t userdata,
-                   int argc,
-                   char **args,
-                   bool output_exit_code)
+/*
+ * Remap stdio
+ *
+ * @rv: riscv
+ * @fsp: a list of pair of mapping from fd to FILE *
+ * @fsp_size: list size
+ *
+ * Note: fd inside fsp should be 0 or 1 or 2 only
+ *
+ */
+void rv_remap_stdstream(riscv_t *rv, fd_stream_pair_t *fsp, uint32_t fsp_size)
+{
+    if (!rv)
+        return;
+
+    vm_attr_t *attr = PRIV(rv);
+    if (!attr)
+        return;
+    if (!attr->fd_map)
+        return;
+
+    for (uint32_t i = 0; i < fsp_size; i++) {
+        int fd = fsp[i].fd;
+        FILE *file = fsp[i].file;
+        if (fd != 0 && fd != 1 && fd != 2)
+            continue;
+        if (!file)
+            continue;
+
+        /*
+         * check if stdio_fd exists or not
+         */
+        map_iter_t it;
+        map_find(attr->fd_map, &it, &fd);
+        if (it.node) /* found, remove first */
+            map_erase(attr->fd_map, &it);
+        map_insert(attr->fd_map, &fd, &file);
+
+        /*
+         * store new fd to make the vm_attr_t consistent
+         */
+        int new_fd = fileno(file);
+        switch (fd) {
+        case 0:
+            attr->stdin_fd = new_fd;
+            break;
+        case 1:
+            attr->stdout_fd = new_fd;
+            break;
+        case 2:
+            attr->stderr_fd = new_fd;
+            break;
+        default:
+            break;
+        }
+    }
+}
+
+riscv_t *rv_create(const riscv_io_t *io, riscv_user_t userdata)
 {
     assert(io);
 
@@ -122,7 +177,45 @@ riscv_t *rv_create(const riscv_io_t *io,
     /* copy over the userdata */
     rv->userdata = userdata;
 
-    rv->output_exit_code = output_exit_code;
+    vm_attr_t *attr = PRIV(rv);
+    attr->mem = memory_new(attr->mem_size);
+    assert(attr->mem);
+
+    /* reset */
+    rv_reset(rv, 0U);
+
+    if (attr->emu_data.vm_user) {
+        elf_t *elf = elf_new();
+        assert(elf && elf_open(elf, (attr->emu_data.vm_user)->elf_program));
+
+        const struct Elf32_Sym *end;
+        if ((end = elf_get_symbol(elf, "_end")))
+            attr->break_addr = end->st_value;
+
+        assert(elf_load(elf, attr->mem));
+
+        /* set the entry pc */
+        const struct Elf32_Ehdr *hdr = get_elf_header(elf);
+        assert(rv_set_pc(rv, hdr->e_entry));
+
+        elf_delete(elf);
+    } else {
+        /* TODO: system emulator */
+    }
+
+    /*
+     * default stdio
+     *
+     * rv_remap_stdstream can be called to overwrite them
+     */
+    attr->fd_map = map_init(int, FILE *, map_cmp_int);
+    rv_remap_stdstream(rv,
+                       (fd_stream_pair_t[]){
+                           {0, stdin},
+                           {1, stdout},
+                           {2, stderr},
+                       },
+                       3);
 
     /* create block and IRs memory pool */
     rv->block_mp = mpool_create(sizeof(block_t) << BLOCK_MAP_CAPACITY_BITS,
@@ -141,12 +234,20 @@ riscv_t *rv_create(const riscv_io_t *io,
     rv->block_cache = cache_create(BLOCK_MAP_CAPACITY_BITS);
     assert(rv->block_cache);
 #endif
-    /* reset */
-    rv_reset(rv, 0U, argc, args);
 
     return rv;
 }
 
+void run(riscv_t *rv)
+{
+    vm_attr_t *attr = PRIV(rv);
+
+    for (; !rv_has_halted(rv);) { /* run until the flag is done */
+        /* step instructions */
+        rv_step(rv, attr->cycle_per_step);
+    }
+}
+
 void rv_halt(riscv_t *rv)
 {
     rv->halt = true;
@@ -157,15 +258,13 @@ bool rv_has_halted(riscv_t *rv)
     return rv->halt;
 }
 
-bool rv_enables_to_output_exit_code(riscv_t *rv)
-{
-    return rv->output_exit_code;
-}
-
 void rv_delete(riscv_t *rv)
 {
     assert(rv);
 #if !RV32_HAS(JIT)
+    vm_attr_t *attr = PRIV(rv);
+    map_delete(attr->fd_map);
+    memory_delete(attr->mem);
     block_map_destroy(rv);
 #else
     mpool_destroy(rv->chain_entry_mp);
@@ -175,16 +274,22 @@ void rv_delete(riscv_t *rv)
     free(rv);
 }
 
-void rv_reset(riscv_t *rv, riscv_word_t pc, int argc, char **args)
+void rv_reset(riscv_t *rv, riscv_word_t pc)
 {
     assert(rv);
     memset(rv->X, 0, sizeof(uint32_t) * N_RV_REGS);
 
+    vm_attr_t *attr = PRIV(rv);
+    int argc = attr->argc;
+    char **args = attr->argv;
+    memory_t *mem = attr->mem;
+
     /* set the reset address */
     rv->PC = pc;
 
     /* set the default stack pointer */
-    rv->X[rv_reg_sp] = DEFAULT_STACK_ADDR;
+    rv->X[rv_reg_sp] =
+        attr->mem_size - attr->stack_size - attr->args_offset_size;
 
     /* Store 'argc' and 'args' of the target program in 'state->mem'. Thus,
      * we can use an offset trick to emulate 32/64-bit target programs on
@@ -218,17 +323,15 @@ void rv_reset(riscv_t *rv, riscv_word_t pc, int argc, char **args)
      * TODO: access to envp
      */
 
-    state_t *s = rv_userdata(rv);
-
     /* copy args to RAM */
     uintptr_t args_size = (1 + argc + 1) * sizeof(uint32_t);
-    uintptr_t args_bottom = DEFAULT_ARGS_ADDR;
+    uintptr_t args_bottom = attr->mem_size - attr->stack_size;
     uintptr_t args_top = args_bottom - args_size;
     args_top &= 16;
 
     /* argc */
     uintptr_t *args_p = (uintptr_t *) args_top;
-    memory_write(s->mem, (uintptr_t) args_p, (void *) &argc, sizeof(int));
+    memory_write(mem, (uintptr_t) args_p, (void *) &argc, sizeof(int));
     args_p++;
 
     /* args */
@@ -240,7 +343,7 @@ void rv_reset(riscv_t *rv, riscv_word_t pc, int argc, char **args)
     for (int i = 0; i < argc; i++) {
         const char *arg = args[i];
         args_len = strlen(arg);
-        memory_write(s->mem, (uintptr_t) args_p, (void *) arg,
+        memory_write(mem, (uintptr_t) args_p, (void *) arg,
                      (args_len + 1) * sizeof(uint8_t));
         args_space[args_space_idx++] = args_len + 1;
         args_p = (uintptr_t *) ((uintptr_t) args_p + args_len + 1);
@@ -257,8 +360,8 @@ void rv_reset(riscv_t *rv, riscv_word_t pc, int argc, char **args)
 
     /* argc */
     uintptr_t *sp = (uintptr_t *) stack_top;
-    memory_write(s->mem, (uintptr_t) sp,
-                 (void *) (s->mem->mem_base + (uintptr_t) args_p), sizeof(int));
+    memory_write(mem, (uintptr_t) sp,
+                 (void *) (mem->mem_base + (uintptr_t) args_p), sizeof(int));
     args_p++;
     /* keep argc and args[0] within one word due to RV32 ABI */
     sp = (uintptr_t *) ((uint32_t *) sp + 1);
@@ -266,12 +369,11 @@ void rv_reset(riscv_t *rv, riscv_word_t pc, int argc, char **args)
     /* args */
     for (int i = 0; i < argc; i++) {
         uintptr_t offset = (uintptr_t) args_p;
-        memory_write(s->mem, (uintptr_t) sp, (void *) &offset,
-                     sizeof(uintptr_t));
+        memory_write(mem, (uintptr_t) sp, (void *) &offset, sizeof(uintptr_t));
         args_p = (uintptr_t *) ((uintptr_t) args_p + args_space[i]);
         sp = (uintptr_t *) ((uint32_t *) sp + 1);
     }
-    memory_fill(s->mem, (uintptr_t) sp, sizeof(uint32_t), 0);
+    memory_fill(mem, (uintptr_t) sp, sizeof(uint32_t), 0);
 
     /* reset sp pointing to argc */
     rv->X[rv_reg_sp] = stack_top;
@@ -301,31 +403,6 @@ void rv_reset(riscv_t *rv, riscv_word_t pc, int argc, char **args)
     rv->halt = false;
 }
 
-state_t *state_new(void)
-{
-    state_t *s = malloc(sizeof(state_t));
-    assert(s);
-    s->mem = memory_new();
-    s->break_addr = 0;
-
-    s->fd_map = map_init(int, FILE *, map_cmp_int);
-    FILE *files[] = {stdin, stdout, stderr};
-    for (size_t i = 0; i < ARRAYS_SIZE(files); i++)
-        map_insert(s->fd_map, &i, &files[i]);
-
-    return s;
-}
-
-void state_delete(state_t *s)
-{
-    if (!s)
-        return;
-
-    map_delete(s->fd_map);
-    memory_delete(s->mem);
-    free(s);
-}
-
 static const char *insn_name_table[] = {
 #define _(inst, can_branch, insn_len, translatable, reg_mask) \
     [rv_insn_##inst] = #inst,
diff --git a/src/riscv.h b/src/riscv.h
index b109a12ab..9b91eabc8 100644
--- a/src/riscv.h
+++ b/src/riscv.h
@@ -7,6 +7,7 @@
 
 #include <stdbool.h>
 #include <stdint.h>
+#include <stdio.h>
 
 #include "io.h"
 #include "map.h"
@@ -97,6 +98,8 @@ enum {
 
 #define BLOCK_MAP_CAPACITY_BITS 10
 
+#define PRIV(x) ((vm_attr_t *) x->userdata)
+
 /* forward declaration for internal structure */
 typedef struct riscv_internal riscv_t;
 typedef void *riscv_user_t;
@@ -143,22 +146,19 @@ typedef struct {
     riscv_on_ebreak on_ebreak;
     riscv_on_memset on_memset;
     riscv_on_memcpy on_memcpy;
-    /* enable misaligned memory access */
-    bool allow_misalign;
 } riscv_io_t;
 
+/* run emulation */
+void run(riscv_t *rv);
+
 /* create a RISC-V emulator */
-riscv_t *rv_create(const riscv_io_t *io,
-                   riscv_user_t user_data,
-                   int argc,
-                   char **args,
-                   bool output_exit_code);
+riscv_t *rv_create(const riscv_io_t *io, riscv_user_t user_data);
 
 /* delete a RISC-V emulator */
 void rv_delete(riscv_t *rv);
 
 /* reset the RISC-V processor */
-void rv_reset(riscv_t *rv, riscv_word_t pc, int argc, char **args);
+void rv_reset(riscv_t *rv, riscv_word_t pc);
 
 #if RV32_HAS(GDBSTUB)
 /* Run the RISC-V emulator as gdbstub */
@@ -168,7 +168,19 @@ void rv_debug(riscv_t *rv);
 /* step the RISC-V emulator */
 void rv_step(riscv_t *rv, int32_t cycles);
 
-/* get RISC-V user data bound to an emulator */
+/*
+ * @rv: RICV-V
+ *
+ * get RISC-V user data bound to an emulator
+ *
+ * A structure named "vm_attr_t" must first be set up by the user
+ * before a riscv core can be created. This structure then be passed
+ * to the "rv_create" function.
+ *
+ * The "vm_attr_t" that the user supplied is therefore regarded as user data.
+ * Thus, "vm_attr_t" will be returned by calling "rv_userdata".
+ *
+ */
 riscv_user_t rv_userdata(riscv_t *rv);
 
 /* set the program counter of a RISC-V emulator */
@@ -180,6 +192,14 @@ riscv_word_t rv_get_pc(riscv_t *rv);
 /* set a register of the RISC-V emulator */
 void rv_set_reg(riscv_t *rv, uint32_t reg, riscv_word_t in);
 
+typedef struct {
+    int fd;
+    FILE *file;
+} fd_stream_pair_t;
+
+/* remap stdio stream */
+void rv_remap_stdstream(riscv_t *rv, fd_stream_pair_t *fsp, uint32_t fsp_size);
+
 /* get a register of the RISC-V emulator */
 riscv_word_t rv_get_reg(riscv_t *rv, uint32_t reg);
 
@@ -207,25 +227,82 @@ void rv_halt(riscv_t *rv);
 /* return the halt state */
 bool rv_has_halted(riscv_t *rv);
 
-/* return the flag of outputting exit code */
-bool rv_enables_to_output_exit_code(riscv_t *rv);
+typedef struct {
+    char *elf_program;
+} vm_user_t;
+
+typedef struct {
+    char *kernel_img;
+    char *dtb;
+    char *rootfs_img;
+} vm_sys_t;
+
+typedef union {
+    vm_user_t *vm_user;
+    vm_sys_t *vm_sys;
+} vm_emu_data_t;
 
-/* state structure passed to the runtime */
 typedef struct {
+    /* vm memory object */
     memory_t *mem;
 
-    /* the data segment break address */
-    riscv_word_t break_addr;
+    /*
+     * max memory size is 2^32 - 1 bytes
+     *
+     * it is for portable on both 32-bit and 64-bit platforms. In this way,
+     * emulator can access any segment of the memory on either platform.
+     */
+    uint32_t mem_size;
 
-    /* file descriptor map: int -> (FILE *) */
-    map_t fd_map;
-} state_t;
+    /* vm main stack size */
+    uint32_t stack_size;
+
+    /*
+     * To deal with the RV32 ABI for accessing args list,
+     * offset of args data have to be saved.
+     *
+     * args_offset_size is the memory size to store the offset
+     */
+    uint32_t args_offset_size;
+
+    /* arguments of emulation program */
+    int argc;
+    char **argv;
+    /* FIXME: rv32emu cannot access envp yet */
+
+    /* emulation program exit code */
+    int exit_code;
+
+    /* emulation program error code */
+    int error;
+
+    /* TODO: for logging feature */
+    int logging_level;
 
-/* create a state */
-state_t *state_new(void);
+    /* userspace or system emulation data */
+    vm_emu_data_t emu_data;
 
-/* delete a state */
-void state_delete(state_t *s);
+    /* number of cycle(instruction) in a rv_step call*/
+    int cycle_per_step;
+
+    /* allow misaligned memory access */
+    bool allow_misalign;
+
+    /*
+     * default stdin, stdout, stderr, set by rv_create
+     *
+     * use rv_remap_stdstream to overwrite them
+     */
+    int stdin_fd;
+    int stdout_fd;
+    int stderr_fd;
+
+    /* vm file descriptor map: int -> (FILE *) */
+    map_t fd_map;
+
+    /* the data segment break address */
+    riscv_word_t break_addr;
+} vm_attr_t;
 
 void rv_profile(riscv_t *rv, char *out_file_path);
 
diff --git a/src/riscv_private.h b/src/riscv_private.h
index 0ec29bd4a..c1d2f9883 100644
--- a/src/riscv_private.h
+++ b/src/riscv_private.h
@@ -129,8 +129,7 @@ struct riscv_internal {
     struct mpool *chain_entry_mp;
 #endif
     struct mpool *block_mp, *block_ir_mp;
-    /* print exit code on syscall_exit */
-    bool output_exit_code;
+
     void *jit_state;
 #if RV32_HAS(GDBSTUB)
     /* gdbstub instance */
diff --git a/src/syscall.c b/src/syscall.c
index 8c2e867fa..fb409e183 100644
--- a/src/syscall.c
+++ b/src/syscall.c
@@ -53,12 +53,12 @@ enum {
     O_ACCMODE = 3,
 };
 
-static int find_free_fd(state_t *s)
+static int find_free_fd(vm_attr_t *attr)
 {
     for (int i = 3;; ++i) {
         map_iter_t it;
-        map_find(s->fd_map, &it, &i);
-        if (map_at_end(s->fd_map, &it))
+        map_find(attr->fd_map, &it, &i);
+        if (map_at_end(attr->fd_map, &it))
             return i;
     }
 }
@@ -80,7 +80,7 @@ static const char *get_mode_str(uint32_t flags, uint32_t mode UNUSED)
 static uint8_t tmp[PREALLOC_SIZE];
 static void syscall_write(riscv_t *rv)
 {
-    state_t *s = rv_userdata(rv); /* access userdata */
+    vm_attr_t *attr = rv_userdata(rv); /* access userdata */
 
     /* _write(fde, buffer, count) */
     riscv_word_t fd = rv_get_reg(rv, rv_reg_a0);
@@ -89,12 +89,12 @@ static void syscall_write(riscv_t *rv)
 
     /* lookup the file descriptor */
     map_iter_t it;
-    map_find(s->fd_map, &it, &fd);
+    map_find(attr->fd_map, &it, &fd);
     uint32_t total_write = 0;
 
     while (count > PREALLOC_SIZE) {
-        memory_read(s->mem, tmp, buffer + total_write, PREALLOC_SIZE);
-        if (!map_at_end(s->fd_map, &it)) {
+        memory_read(attr->mem, tmp, buffer + total_write, PREALLOC_SIZE);
+        if (!map_at_end(attr->fd_map, &it)) {
             /* write out the data */
             FILE *handle = map_iter_value(&it, FILE *);
             size_t written = fwrite(tmp, 1, PREALLOC_SIZE, handle);
@@ -105,8 +105,8 @@ static void syscall_write(riscv_t *rv)
         } else
             goto error_handler;
     }
-    memory_read(s->mem, tmp, buffer + total_write, count);
-    if (!map_at_end(s->fd_map, &it)) {
+    memory_read(attr->mem, tmp, buffer + total_write, count);
+    if (!map_at_end(attr->fd_map, &it)) {
         /* write out the data */
         FILE *handle = map_iter_value(&it, FILE *);
         size_t written = fwrite(tmp, 1, count, handle);
@@ -130,11 +130,13 @@ static void syscall_exit(riscv_t *rv)
 {
     rv_halt(rv);
 
-    /* To avoid mixing with JSON output */
-    if (rv_enables_to_output_exit_code(rv)) {
-        riscv_word_t code = rv_get_reg(rv, rv_reg_a0);
-        fprintf(stdout, "inferior exit code %d\n", (int) code);
-    }
+    /*
+     * simply halt cpu and save exit code
+     *
+     * the application decides the usage of exit code
+     */
+    vm_attr_t *attr = rv_userdata(rv); /* access userdata */
+    attr->exit_code = rv_get_reg(rv, rv_reg_a0);
 }
 
 /* brk(increment)
@@ -144,15 +146,15 @@ static void syscall_exit(riscv_t *rv)
  */
 static void syscall_brk(riscv_t *rv)
 {
-    state_t *s = rv_userdata(rv); /* access userdata */
+    vm_attr_t *attr = rv_userdata(rv); /* access userdata */
 
     /* get the increment parameter */
     riscv_word_t increment = rv_get_reg(rv, rv_reg_a0);
     if (increment)
-        s->break_addr = increment;
+        attr->break_addr = increment;
 
     /* return new break address */
-    rv_set_reg(rv, rv_reg_a0, s->break_addr);
+    rv_set_reg(rv, rv_reg_a0, attr->break_addr);
 }
 
 static void syscall_gettimeofday(riscv_t *rv)
@@ -207,21 +209,21 @@ static void syscall_clock_gettime(riscv_t *rv)
 
 static void syscall_close(riscv_t *rv)
 {
-    state_t *s = rv_userdata(rv); /* access userdata */
+    vm_attr_t *attr = rv_userdata(rv); /* access userdata */
 
     /* _close(fd); */
     uint32_t fd = rv_get_reg(rv, rv_reg_a0);
 
     if (fd >= 3) { /* lookup the file descriptor */
         map_iter_t it;
-        map_find(s->fd_map, &it, &fd);
-        if (!map_at_end(s->fd_map, &it)) {
+        map_find(attr->fd_map, &it, &fd);
+        if (!map_at_end(attr->fd_map, &it)) {
             if (fclose(map_iter_value(&it, FILE *))) {
                 /* error */
                 rv_set_reg(rv, rv_reg_a0, -1);
                 return;
             }
-            map_erase(s->fd_map, &it);
+            map_erase(attr->fd_map, &it);
 
             /* success */
             rv_set_reg(rv, rv_reg_a0, 0);
@@ -238,7 +240,7 @@ static void syscall_close(riscv_t *rv)
  */
 static void syscall_lseek(riscv_t *rv)
 {
-    state_t *s = rv_userdata(rv); /* access userdata */
+    vm_attr_t *attr = rv_userdata(rv); /* access userdata */
 
     /* _lseek(fd, offset, whence); */
     uint32_t fd = rv_get_reg(rv, rv_reg_a0);
@@ -247,8 +249,8 @@ static void syscall_lseek(riscv_t *rv)
 
     /* find the file descriptor */
     map_iter_t it;
-    map_find(s->fd_map, &it, &fd);
-    if (map_at_end(s->fd_map, &it)) {
+    map_find(attr->fd_map, &it, &fd);
+    if (map_at_end(attr->fd_map, &it)) {
         /* error */
         rv_set_reg(rv, rv_reg_a0, -1);
         return;
@@ -267,7 +269,7 @@ static void syscall_lseek(riscv_t *rv)
 
 static void syscall_read(riscv_t *rv)
 {
-    state_t *s = rv_userdata(rv); /* access userdata */
+    vm_attr_t *attr = rv_userdata(rv); /* access userdata */
 
     /* _read(fd, buf, count); */
     uint32_t fd = rv_get_reg(rv, rv_reg_a0);
@@ -276,8 +278,8 @@ static void syscall_read(riscv_t *rv)
 
     /* lookup the file */
     map_iter_t it;
-    map_find(s->fd_map, &it, &fd);
-    if (map_at_end(s->fd_map, &it)) {
+    map_find(attr->fd_map, &it, &fd);
+    if (map_at_end(attr->fd_map, &it)) {
         /* error */
         rv_set_reg(rv, rv_reg_a0, -1);
         return;
@@ -289,14 +291,14 @@ static void syscall_read(riscv_t *rv)
 
     while (count > PREALLOC_SIZE) {
         size_t r = fread(tmp, 1, PREALLOC_SIZE, handle);
-        memory_write(s->mem, buf + total_read, tmp, r);
+        memory_write(attr->mem, buf + total_read, tmp, r);
         count -= r;
         total_read += r;
         if (r != PREALLOC_SIZE)
             break;
     }
     size_t r = fread(tmp, 1, count, handle);
-    memory_write(s->mem, buf + total_read, tmp, r);
+    memory_write(attr->mem, buf + total_read, tmp, r);
     total_read += r;
     if (total_read != rv_get_reg(rv, rv_reg_a2) && ferror(handle)) {
         /* error */
@@ -314,7 +316,7 @@ static void syscall_fstat(riscv_t *rv UNUSED)
 
 static void syscall_open(riscv_t *rv)
 {
-    state_t *s = rv_userdata(rv); /* access userdata */
+    vm_attr_t *attr = rv_userdata(rv); /* access userdata */
 
     /* _open(name, flags, mode); */
     uint32_t name = rv_get_reg(rv, rv_reg_a0);
@@ -323,8 +325,8 @@ static void syscall_open(riscv_t *rv)
 
     /* read name from runtime memory */
     char name_str[256] = {'\0'};
-    uint32_t read =
-        memory_read_str(s->mem, (uint8_t *) name_str, name, sizeof(name_str));
+    uint32_t read = memory_read_str(attr->mem, (uint8_t *) name_str, name,
+                                    sizeof(name_str));
     if (read > sizeof(name_str)) {
         rv_set_reg(rv, rv_reg_a0, -1);
         return;
@@ -343,10 +345,10 @@ static void syscall_open(riscv_t *rv)
         return;
     }
 
-    const int fd = find_free_fd(s); /* find a free file descriptor */
+    const int fd = find_free_fd(attr); /* find a free file descriptor */
 
     /* insert into the file descriptor map */
-    map_insert(s->fd_map, (void *) &fd, &handle);
+    map_insert(attr->fd_map, (void *) &fd, &handle);
 
     /* return the file descriptor */
     rv_set_reg(rv, rv_reg_a0, fd);
@@ -376,4 +378,12 @@ void syscall_handler(riscv_t *rv)
         fprintf(stderr, "unknown syscall %d\n", (int) syscall);
         break;
     }
+
+    /*
+     * save return code
+     *
+     * the application decides the usage of the return code
+     */
+    vm_attr_t *attr = rv_userdata(rv); /* access userdata */
+    attr->error = rv_get_reg(rv, rv_reg_a0);
 }
diff --git a/src/syscall_sdl.c b/src/syscall_sdl.c
index 6bd7e2166..a78ab1959 100644
--- a/src/syscall_sdl.c
+++ b/src/syscall_sdl.c
@@ -149,10 +149,10 @@ static submission_queue_t submission_queue = {
 
 static submission_t submission_pop(riscv_t *rv)
 {
-    state_t *s = rv_userdata(rv);
+    vm_attr_t *attr = rv_userdata(rv);
     submission_t submission;
     memory_read(
-        s->mem, (void *) &submission,
+        attr->mem, (void *) &submission,
         submission_queue.base + submission_queue.start * sizeof(submission_t),
         sizeof(submission_t));
     ++submission_queue.start;
@@ -162,16 +162,17 @@ static submission_t submission_pop(riscv_t *rv)
 
 static void event_push(riscv_t *rv, event_t event)
 {
-    state_t *s = rv_userdata(rv);
-    memory_write(s->mem, event_queue.base + event_queue.end * sizeof(event_t),
+    vm_attr_t *attr = rv_userdata(rv);
+    memory_write(attr->mem,
+                 event_queue.base + event_queue.end * sizeof(event_t),
                  (void *) &event, sizeof(event_t));
     ++event_queue.end;
     event_queue.end &= queues_capacity - 1;
 
     uint32_t count;
-    memory_read(s->mem, (void *) &count, event_count, sizeof(uint32_t));
+    memory_read(attr->mem, (void *) &count, event_count, sizeof(uint32_t));
     count += 1;
-    memory_write(s->mem, event_count, (void *) &count, sizeof(uint32_t));
+    memory_write(attr->mem, event_count, (void *) &count, sizeof(uint32_t));
 }
 
 static inline uint32_t round_pow2(uint32_t x)
@@ -279,7 +280,7 @@ static bool check_sdl(riscv_t *rv, int width, int height)
 
 void syscall_draw_frame(riscv_t *rv)
 {
-    state_t *s = rv_userdata(rv); /* access userdata */
+    vm_attr_t *attr = rv_userdata(rv); /* access userdata */
 
     /* draw_frame(base, width, height) */
     const uint32_t screen = rv_get_reg(rv, rv_reg_a0);
@@ -294,7 +295,7 @@ void syscall_draw_frame(riscv_t *rv)
     void *pixels_ptr;
     if (SDL_LockTexture(texture, NULL, &pixels_ptr, &pitch))
         exit(-1);
-    memory_read(s->mem, pixels_ptr, screen, width * height * 4);
+    memory_read(attr->mem, pixels_ptr, screen, width * height * 4);
     SDL_UnlockTexture(texture);
 
     int actual_width, actual_height;
@@ -677,13 +678,14 @@ static void *music_handler(void *arg)
 
 static void play_sfx(riscv_t *rv)
 {
-    state_t *s = rv_userdata(rv); /* access userdata */
+    vm_attr_t *attr = rv_userdata(rv); /* access userdata */
 
     const uint32_t sfxinfo_addr = (uint32_t) rv_get_reg(rv, rv_reg_a1);
     int volume = rv_get_reg(rv, rv_reg_a2);
 
     sfxinfo_t sfxinfo;
-    memory_read(s->mem, (uint8_t *) &sfxinfo, sfxinfo_addr, sizeof(sfxinfo_t));
+    memory_read(attr->mem, (uint8_t *) &sfxinfo, sfxinfo_addr,
+                sizeof(sfxinfo_t));
 
     /* The data and size in the application must be positioned in the first two
      * fields of the structure. This ensures emulator compatibility with
@@ -692,7 +694,7 @@ static void play_sfx(riscv_t *rv)
     uint32_t sfx_data_offset = *((uint32_t *) &sfxinfo);
     uint32_t sfx_data_size = *(uint32_t *) ((uint32_t *) &sfxinfo + 1);
     uint8_t sfx_data[SFX_SAMPLE_SIZE];
-    memory_read(s->mem, sfx_data, sfx_data_offset,
+    memory_read(attr->mem, sfx_data, sfx_data_offset,
                 sizeof(uint8_t) * sfx_data_size);
 
     sound_t sfx = {
@@ -705,14 +707,14 @@ static void play_sfx(riscv_t *rv)
 
 static void play_music(riscv_t *rv)
 {
-    state_t *s = rv_userdata(rv); /* access userdata */
+    vm_attr_t *attr = rv_userdata(rv); /* access userdata */
 
     const uint32_t musicinfo_addr = (uint32_t) rv_get_reg(rv, rv_reg_a1);
     int volume = rv_get_reg(rv, rv_reg_a2);
     int looping = rv_get_reg(rv, rv_reg_a3);
 
     musicinfo_t musicinfo;
-    memory_read(s->mem, (uint8_t *) &musicinfo, musicinfo_addr,
+    memory_read(attr->mem, (uint8_t *) &musicinfo, musicinfo_addr,
                 sizeof(musicinfo_t));
 
     /* The data and size in the application must be positioned in the first two
@@ -722,7 +724,7 @@ static void play_music(riscv_t *rv)
     uint32_t music_data_offset = *((uint32_t *) &musicinfo);
     uint32_t music_data_size = *(uint32_t *) ((uint32_t *) &musicinfo + 1);
     uint8_t music_data[MUSIC_MAX_SIZE];
-    memory_read(s->mem, music_data, music_data_offset, music_data_size);
+    memory_read(attr->mem, music_data, music_data_offset, music_data_size);
 
     sound_t music = {
         .data = music_data,
diff --git a/tools/gen-jit-template.py b/tools/gen-jit-template.py
index 02c55f586..5199525b7 100755
--- a/tools/gen-jit-template.py
+++ b/tools/gen-jit-template.py
@@ -219,7 +219,7 @@ def parse_argv(EXT_LIST, SKIP_LIST):
             elif items[0] == "jmp_off":
                 asm = "emit_jump_target_offset(state, JUMP_LOC, state->offset);"
             elif items[0] == "mem":
-                asm = "memory_t *m = ((state_t *) rv->userdata)->mem;"
+                asm = "memory_t *m = PRIV(rv)->mem;"
             elif items[0] == "call":
                 asm = "emit_call(state, (intptr_t) rv->io.on_{});".format(
                     items[1])