diff --git a/.gitignore b/.gitignore
index e9b5ce8..20f6130 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,4 @@ googletest-*
 *.gcno
 coverage
 codecov
+*.dSYM
diff --git a/LICENSE b/LICENSE
index 1bb04f3..04f1913 100644
--- a/LICENSE
+++ b/LICENSE
@@ -7,7 +7,7 @@ Individual files contain the following tag instead of the full license text.
 
 	SPDX-License-Identifier: MPL-1.1 OR GPL-2.0-or-later
 
-Some ASM codes for new porting OS/CPU, "utest" and "porting" directory is
+All source code in the "tools", "utest" and "porting" directory is
 distributed under the MIT style license.
 
     SPDX-License-Identifier: MIT
diff --git a/porting/.gitignore b/tools/porting/.gitignore
similarity index 100%
rename from porting/.gitignore
rename to tools/porting/.gitignore
diff --git a/porting/Makefile b/tools/porting/Makefile
similarity index 89%
rename from porting/Makefile
rename to tools/porting/Makefile
index b1fc081..e31722b 100644
--- a/porting/Makefile
+++ b/tools/porting/Makefile
@@ -1,5 +1,7 @@
 .PHONY: clean
 
+CFLAGS=-g -O0
+
 ./porting:  porting.c
 	$(CC) $(CPPFLAGS) $(CFLAGS) $(LDFLAGS) -Wall -o $@ $^ $(LDLIBS)
 
diff --git a/porting/porting.c b/tools/porting/porting.c
similarity index 68%
rename from porting/porting.c
rename to tools/porting/porting.c
index ada15be..d07db2f 100644
--- a/porting/porting.c
+++ b/tools/porting/porting.c
@@ -20,7 +20,7 @@ int main(int argc, char** argv)
     printf("\nCPU specs:\n");
 #ifdef __mips__
     // https://s3-eu-west-1.amazonaws.com/downloads-mips/documents/MD00565-2B-MIPS32-QRC-01.01.pdf
-    printf("__mips__: %d, __mips:%d, __mips_isa_rev:%d, _MIPSEL:%d\n", __mips__, __mips, __mips_isa_rev, _MIPSEL);
+    printf("__mips__: %d, __mips:%d, _MIPSEL:%d\n", __mips__, __mips, _MIPSEL);
 #endif
 #ifdef __x86_64__
     printf("__x86_64__: %d\n", __x86_64__);
@@ -48,20 +48,20 @@ int main(int argc, char** argv)
 void print_jmpbuf()
 {
     // https://en.wikipedia.org/wiki/MIPS_architecture#Calling_conventions
-    register long int gp asm("gp");
-    register long int sp asm("sp");
-    register long int fp asm("fp");
+    register void* gp asm("gp");
+    register void* sp asm("sp");
+    register void* fp asm("fp");
     // $s0–$s7	$16–$23	saved temporaries
-    register long int s0 asm("s0");
-    register long int s1 asm("s1");
-    register long int s2 asm("s2");
-    register long int s3 asm("s3");
-    register long int s4 asm("s4");
-    register long int s5 asm("s5");
-    register long int s6 asm("s6");
-    register long int s7 asm("s7");
+    register void* s0 asm("s0");
+    register void* s1 asm("s1");
+    register void* s2 asm("s2");
+    register void* s3 asm("s3");
+    register void* s4 asm("s4");
+    register void* s5 asm("s5");
+    register void* s6 asm("s6");
+    register void* s7 asm("s7");
     printf("gp=%p, fp=%p, sp=%p, s0=%p, s1=%p, s2=%p, s3=%p, s4=%p, s5=%p, s6=%p, s7=%p\n",
-        (void*)gp, (void*)fp, (void*)sp, (void*)s0, (void*)s1, (void*)s2, (void*)s3, (void*)s4, (void*)s5, (void*)s6, (void*)s7);
+        gp, fp, sp, s0, s1, s2, s3, s4, s5, s6, s7);
 
     /*
     typedef unsigned long long __jmp_buf[13];
@@ -88,15 +88,17 @@ void print_jmpbuf()
 void print_jmpbuf()
 {
     // https://courses.cs.washington.edu/courses/cse378/10au/sections/Section1_recap.pdf
-    register long int rsp asm("rsp");
-    register long int rbx asm("rbx");
-    register long int rbp asm("rbp");
-    register long int r12 asm("r12");
-    register long int r13 asm("r13");
-    register long int r14 asm("r14");
-    register long int r15 asm("r15");
-    printf("rsp=%p, rbx=%p, rbp=%p, r12=%p, r13=%p, r14=%p, r15=%p\n",
-        (void*)rbx, (void*)rbp, (void*)r12, (void*)r13, (void*)r14, (void*)r15);
+    void *rbx, *rbp, *r12, *r13, *r14, *r15, *rsp;
+    __asm__ __volatile__ ("movq %%rbx,%0": "=r"(rbx): /* No input */);
+    __asm__ __volatile__ ("movq %%rbp,%0": "=r"(rbp): /* No input */);
+    __asm__ __volatile__ ("movq %%r12,%0": "=r"(r12): /* No input */);
+    __asm__ __volatile__ ("movq %%r13,%0": "=r"(r13): /* No input */);
+    __asm__ __volatile__ ("movq %%r14,%0": "=r"(r14): /* No input */);
+    __asm__ __volatile__ ("movq %%r15,%0": "=r"(r15): /* No input */);
+    __asm__ __volatile__ ("movq %%rsp,%0": "=r"(rsp): /* No input */);
+
+    printf("rbx=%p, rbp=%p,%p, r12=%p, r13=%p, r14=%p, r15=%p, rsp=%p\n",
+        rbx, rbp, rbp2, r12, r13, r14, r15, rsp);
 
     jmp_buf ctx = {0};
     setjmp(ctx);
diff --git a/tools/verify/.gitignore b/tools/verify/.gitignore
new file mode 100644
index 0000000..0b59873
--- /dev/null
+++ b/tools/verify/.gitignore
@@ -0,0 +1 @@
+verify
diff --git a/tools/verify/Makefile b/tools/verify/Makefile
new file mode 100644
index 0000000..5b1671b
--- /dev/null
+++ b/tools/verify/Makefile
@@ -0,0 +1,11 @@
+.PHONY: clean
+
+LDLIBS=../../obj/libst.a
+CFLAGS=-g -O0
+
+./verify:  verify.c
+	$(CC) $(CPPFLAGS) $(CFLAGS) $(LDFLAGS) -Wall -o $@ $^ $(LDLIBS)
+
+clean:
+	rm -f verify
+
diff --git a/tools/verify/verify.c b/tools/verify/verify.c
new file mode 100644
index 0000000..d04dbd2
--- /dev/null
+++ b/tools/verify/verify.c
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: MIT */
+/* Copyright (c) 2021 Winlin */
+
+#include <stdio.h>
+
+#include <setjmp.h>
+extern int _st_md_cxt_save(jmp_buf env);
+extern void _st_md_cxt_restore(jmp_buf env, int val);
+
+void verify_jmpbuf();
+void print_buf(unsigned char* p, int nn_jb);
+
+int main(int argc, char** argv)
+{
+    verify_jmpbuf();
+    return 0;
+}
+
+#ifdef __linux__
+#ifdef __mips__
+void verify_jmpbuf()
+{
+    // https://en.wikipedia.org/wiki/MIPS_architecture#Calling_conventions
+    register void* gp asm("gp");
+    register void* sp asm("sp");
+    register void* fp asm("fp");
+    // $s0–$s7	$16–$23	saved temporaries
+    register void* s0 asm("s0");
+    register void* s1 asm("s1");
+    register void* s2 asm("s2");
+    register void* s3 asm("s3");
+    register void* s4 asm("s4");
+    register void* s5 asm("s5");
+    register void* s6 asm("s6");
+    register void* s7 asm("s7");
+    printf("gp=%p, fp=%p, sp=%p, s0=%p, s1=%p, s2=%p, s3=%p, s4=%p, s5=%p, s6=%p, s7=%p\n",
+        gp, fp, sp, s0, s1, s2, s3, s4, s5, s6, s7);
+
+    jmp_buf ctx = {0};
+    _st_md_cxt_save(ctx);
+
+    int nn_jb = sizeof(ctx[0].__jb);
+    unsigned char* p = (unsigned char*)ctx[0].__jb;
+    print_buf(p, nn_jb);
+}
+#endif
+#endif
+
+#ifdef __APPLE__
+#ifdef __x86_64__
+void verify_jmpbuf()
+{
+    // https://courses.cs.washington.edu/courses/cse378/10au/sections/Section1_recap.pdf
+    void *rbx, *rbp, *r12, *r13, *r14, *r15, *rsp;
+    __asm__ __volatile__ ("movq %%rbx,%0": "=r"(rbx): /* No input */);
+    __asm__ __volatile__ ("movq %%rbp,%0": "=r"(rbp): /* No input */);
+    __asm__ __volatile__ ("movq %%r12,%0": "=r"(r12): /* No input */);
+    __asm__ __volatile__ ("movq %%r13,%0": "=r"(r13): /* No input */);
+    __asm__ __volatile__ ("movq %%r14,%0": "=r"(r14): /* No input */);
+    __asm__ __volatile__ ("movq %%r15,%0": "=r"(r15): /* No input */);
+    __asm__ __volatile__ ("movq %%rsp,%0": "=r"(rsp): /* No input */);
+
+    printf("rbx=%p, rbp=%p,%p, r12=%p, r13=%p, r14=%p, r15=%p, rsp=%p\n",
+        rbx, rbp, rbp2, r12, r13, r14, r15, rsp);
+
+    jmp_buf ctx = {0};
+    _st_md_cxt_save(ctx);
+
+    int nn_jb = sizeof(ctx);
+    printf("sizeof(jmp_buf)=%d (unsigned long long [%d])\n", nn_jb, nn_jb/8);
+
+    unsigned char* p = (unsigned char*)ctx;
+    print_buf(p, nn_jb);
+}
+#endif
+#endif
+
+void print_buf(unsigned char* p, int nn_jb)
+{
+    printf("    ");
+
+    for (int i = 0; i < nn_jb; i++) {
+        printf("0x%02x ", (unsigned char)p[i]);
+
+        int newline = ((i + 1) % sizeof(void*));
+        if (!newline || i == nn_jb - 1) {
+            printf("\n");
+        }
+
+        if (!newline && i < nn_jb - 1) {
+            printf("    ");
+        }
+    }
+}
+