diff --git a/Makefile b/Makefile
index 312a81e..a5acc0b 100644
--- a/Makefile
+++ b/Makefile
@@ -13,3 +13,4 @@ include make/libkb.mk
 include make/libaux.mk
 include make/libarena.mk
 include make/libioutil.mk
+include make/libmath.mk
diff --git a/aux/compiledb.sh b/aux/compiledb.sh
index 8c28bb2..3dbbd14 100755
--- a/aux/compiledb.sh
+++ b/aux/compiledb.sh
@@ -12,3 +12,4 @@ make -B all_compiledb_libkb
 make -B all_compiledb_libaux
 make -B all_compiledb_libarena
 make -B all_compiledb_libioutil
+make -B all_compiledb_libmath
diff --git a/aux/devel.sh b/aux/devel.sh
index 66d9561..91f70f8 100755
--- a/aux/devel.sh
+++ b/aux/devel.sh
@@ -19,6 +19,7 @@ make -B all_libkb         "$bt"
 make -B all_libaux        "$bt"
 make -B all_libarena      "$bt"
 make -B all_libioutil     "$bt"
+make -B all_libmath       "$bt"
 make -B all_apps          "$bt"
 make -B all_dist
 ./aux/limine_iso_amd64.sh
diff --git a/aux/docs.sh b/aux/docs.sh
index 2d727f8..cbd69df 100755
--- a/aux/docs.sh
+++ b/aux/docs.sh
@@ -13,5 +13,6 @@ make -B docs_libkb
 make -B docs_libaux
 make -B docs_libarena
 make -B docs_libioutil
+make -B docs_libmath
 
 mkdocs build
diff --git a/aux/format.sh b/aux/format.sh
index 8253fab..d1faf8b 100755
--- a/aux/format.sh
+++ b/aux/format.sh
@@ -12,4 +12,5 @@ make -B format_libkb
 make -B format_libaux
 make -B format_libarena
 make -B format_libioutil
+make -B format_libmath
 make -B format_apps
diff --git a/libaux/amd64/.gitignore b/libaux/amd64/.gitignore
new file mode 100644
index 0000000..5761abc
--- /dev/null
+++ b/libaux/amd64/.gitignore
@@ -0,0 +1 @@
+*.o
diff --git a/libaux/amd64/setjmp.c b/libaux/amd64/setjmp.c
new file mode 100644
index 0000000..f2a9077
--- /dev/null
+++ b/libaux/amd64/setjmp.c
@@ -0,0 +1,34 @@
+#include <setjmp.h>
+
+/*  https://nullprogram.com/blog/2023/02/12 */
+
+__attribute__ ((naked, returns_twice)) int setjmp (jmp_buf buf) {
+  __asm__ volatile ("mov (%rsp), %rax\n"
+                    "mov %rax,  0(%rcx)\n"
+                    "lea 8(%rsp), %rax\n"
+                    "mov %rax,  8(%rcx)\n"
+                    "mov %rbp, 16(%rcx)\n"
+                    "mov %rbx, 24(%rcx)\n"
+                    "mov %rdi, 32(%rcx)\n"
+                    "mov %rsi, 40(%rcx)\n"
+                    "mov %r12, 48(%rcx)\n"
+                    "mov %r13, 56(%rcx)\n"
+                    "mov %r14, 64(%rcx)\n"
+                    "mov %r15, 72(%rcx)\n"
+                    "xor %eax, %eax\n"
+                    "ret\n");
+}
+
+__attribute__ ((naked, noreturn)) void longjmp (jmp_buf buf, int ret) {
+  __asm__ volatile ("mov 72(%rcx), %r15\n"
+                    "mov 64(%rcx), %r14\n"
+                    "mov 56(%rcx), %r13\n"
+                    "mov 48(%rcx), %r12\n"
+                    "mov 40(%rcx), %rsi\n"
+                    "mov 32(%rcx), %rdi\n"
+                    "mov 24(%rcx), %rbx\n"
+                    "mov 16(%rcx), %rbp\n"
+                    "mov  8(%rcx), %rsp\n"
+                    "mov %edx, %eax\n"
+                    "jmp *0(%rcx)\n");
+}
diff --git a/libaux/amd64/src.mk b/libaux/amd64/src.mk
new file mode 100644
index 0000000..1fd23a6
--- /dev/null
+++ b/libaux/amd64/src.mk
@@ -0,0 +1,3 @@
+c += amd64/setjmp.c
+
+o += amd64/setjmp.o
diff --git a/libaux/assert.h b/libaux/assert.h
new file mode 100644
index 0000000..5d1fca0
--- /dev/null
+++ b/libaux/assert.h
@@ -0,0 +1,12 @@
+#ifndef _LIBAUX_ASSERT_H
+#define _LIBAUX_ASSERT_H
+
+#include <system.h>
+
+#define assert(x)                                                                                  \
+  do {                                                                                             \
+    if (!!(x))                                                                                     \
+      quit ();                                                                                     \
+  } while (0)
+
+#endif // _LIBAUX_ASSERT_H
diff --git a/libaux/setjmp.h b/libaux/setjmp.h
new file mode 100644
index 0000000..81efbb7
--- /dev/null
+++ b/libaux/setjmp.h
@@ -0,0 +1,12 @@
+#ifndef _LIBAUX_SETJMP_H
+#define _LIBAUX_SETJMP_H
+
+#if defined(__x86_64__)
+typedef void* jmp_buf[10];
+#endif
+
+__attribute__ ((naked, returns_twice)) int setjmp (jmp_buf buf);
+
+__attribute__ ((naked, noreturn)) void longjmp (jmp_buf buf, int ret);
+
+#endif // _LIBAUX_SETJMP_H
diff --git a/libaux/src.mk b/libaux/src.mk
index 204de35..483f18d 100644
--- a/libaux/src.mk
+++ b/libaux/src.mk
@@ -1,3 +1,5 @@
+include $(platform)/src.mk
+
 c += printf.c \
 		 path.c
 
diff --git a/libmath/.gitignore b/libmath/.gitignore
new file mode 100644
index 0000000..de276e3
--- /dev/null
+++ b/libmath/.gitignore
@@ -0,0 +1,4 @@
+*.o
+*.json
+docs/
+.cache/
diff --git a/libmath/Makefile b/libmath/Makefile
new file mode 100644
index 0000000..71ea81f
--- /dev/null
+++ b/libmath/Makefile
@@ -0,0 +1,5 @@
+include ../make/ufuncs.mk
+
+libname := libmath
+
+include ../make/lib.mk
diff --git a/libmath/build/.gitignore b/libmath/build/.gitignore
new file mode 100644
index 0000000..10301e2
--- /dev/null
+++ b/libmath/build/.gitignore
@@ -0,0 +1 @@
+*.a
diff --git a/libmath/math.c b/libmath/math.c
new file mode 100644
index 0000000..5b76979
--- /dev/null
+++ b/libmath/math.c
@@ -0,0 +1,5 @@
+#include <math.h>
+
+double fmod (double a, double b) { return a - ((double)((long long)(a / b))) * b; }
+
+float fmodf (float a, float b) { return a - ((float)((long)(a / b))) * b; }
diff --git a/libmath/math.h b/libmath/math.h
new file mode 100644
index 0000000..53ba2ce
--- /dev/null
+++ b/libmath/math.h
@@ -0,0 +1,8 @@
+#ifndef _LIBMATH_MATH_H
+#define _LIBMATH_MATH_H
+
+double fmod (double a, double b);
+
+float fmodf (float a, float b);
+
+#endif // _LIBMATH_MATH_H
diff --git a/libmath/src.mk b/libmath/src.mk
new file mode 100644
index 0000000..f4df5ac
--- /dev/null
+++ b/libmath/src.mk
@@ -0,0 +1,3 @@
+c += math.c
+
+o += math.o
diff --git a/libstring/string.c b/libstring/string.c
index ccca77f..01d5e8d 100644
--- a/libstring/string.c
+++ b/libstring/string.c
@@ -132,33 +132,59 @@ char* strcat (char* dest, const char* src) {
   return rdest;
 }
 
-int isalnum (int c) { return isalpha (c) || isdigit (c); }
-
-int isalpha (int c) { return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'); }
-
-int iscntrl (int c) { return (c >= 0 && c <= 32) || (c == 127); }
-
-int isdigit (int c) { return (c >= '0' && c <= '9'); }
-
-int isgraph (int c) { return (c > 32 && c <= 126); }
-
-int islower (int c) { return (c >= 'A' && c <= 'z'); }
-
-int isprint (int c) { return (c >= 32 && c <= 126); }
-
-int ispunct (int c) { return isgraph (c) && !isalnum (c); }
-
-int isspace (int c) {
-  return (c == ' ' || c == '\f' || c == '\n' || c == '\r' || c == '\t' || c == '\v');
+int strncmp (const char* s1, const char* s2, size_t n) {
+  while (n && *s1 && (*s1 == *s2)) {
+    ++s1;
+    ++s2;
+    --n;
+  }
+  if (n == 0) {
+    return 0;
+  } else {
+    return (*(unsigned char*)s1 - *(unsigned char*)s2);
+  }
 }
 
-int isupper (int c) { return (c >= 'A' && c <= 'Z'); }
+/* https://stackoverflow.com/questions/49131175/recreate-the-strstr-function */
+char* strstr (const char* str, const char* substring) {
+  const char* a;
+  const char* b;
 
-int isxdigit (int c) { return isdigit (c) || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f'); }
+  b = substring;
 
-int isascii (int c) { return (c >= 0 && c <= 127); }
+  if (*b == 0) {
+    return (char*)str;
+  }
 
-int isblank (int c) { return (c == ' ' || c == '\t'); }
+  for (; *str != 0; str += 1) {
+    if (*str != *b) {
+      continue;
+    }
+
+    a = str;
+    while (1) {
+      if (*b == 0) {
+        return (char*)str;
+      }
+      if (*a++ != *b++) {
+        break;
+      }
+    }
+    b = substring;
+  }
+
+  return NULL;
+}
+
+/* https://github.com/gcc-mirror/gcc/blob/master/libiberty/strchr.c */
+char* strchr (register const char* s, int c) {
+  do {
+    if (*s == c) {
+      return (char*)s;
+    }
+  } while (*s++);
+  return (0);
+}
 
 /* SOURCE: https://aticleworld.com/memmove-function-implementation-in-c/ */
 void* memmove (void* dest, const void* src, unsigned int n) {
@@ -194,3 +220,43 @@ char* strncat (char* dest, const char* src, size_t n) {
   *ptr = '\0';
   return dest;
 }
+
+/* https://stackoverflow.com/questions/14476627/strcpy-implementation-in-c */
+char* strcpy (char* strDest, const char* strSrc) {
+  char* temp = strDest;
+  while ((*strDest++ = *strSrc++))
+    ;
+  return temp;
+}
+
+int isalnum (int c) { return isalpha (c) || isdigit (c); }
+
+int isalpha (int c) { return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'); }
+
+int iscntrl (int c) { return (c >= 0 && c <= 32) || (c == 127); }
+
+int isdigit (int c) { return (c >= '0' && c <= '9'); }
+
+int isgraph (int c) { return (c > 32 && c <= 126); }
+
+int islower (int c) { return (c >= 'A' && c <= 'z'); }
+
+int isprint (int c) { return (c >= 32 && c <= 126); }
+
+int ispunct (int c) { return isgraph (c) && !isalnum (c); }
+
+int isspace (int c) {
+  return (c == ' ' || c == '\f' || c == '\n' || c == '\r' || c == '\t' || c == '\v');
+}
+
+int isupper (int c) { return (c >= 'A' && c <= 'Z'); }
+
+int isxdigit (int c) { return isdigit (c) || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f'); }
+
+int isascii (int c) { return (c >= 0 && c <= 127); }
+
+int isblank (int c) { return (c == ' ' || c == '\t'); }
+
+int tolower (int chr) { return (chr >= 'A' && chr <= 'Z') ? (chr + 32) : (chr); }
+
+int toupper (int chr) { return (chr >= 'a' && chr <= 'z') ? (chr - 32) : (chr); }
diff --git a/libstring/string.h b/libstring/string.h
index cd3f702..41a3c3f 100644
--- a/libstring/string.h
+++ b/libstring/string.h
@@ -39,6 +39,14 @@ void* memchr (const void* s, unsigned char c, size_t n);
 
 void str_split_lines (const char* str, size_t total_len, void* ctx, strtokenize_cb_func_t cb);
 
+char* strcpy (char* strDest, const char* strSrc);
+
+int strncmp (const char* s1, const char* s2, size_t n);
+
+char* strstr (const char* str, const char* substring);
+
+char* strchr (register const char* s, int c);
+
 int isalnum (int c);
 
 int isalpha (int c);
@@ -65,4 +73,8 @@ int isascii (int c);
 
 int isblank (int c);
 
+int tolower (int chr);
+
+int toupper (int chr);
+
 #endif // _LIBSTRING_STRING_H
diff --git a/make/apps.mk b/make/apps.mk
index 65ec7eb..5078c0b 100644
--- a/make/apps.mk
+++ b/make/apps.mk
@@ -1,7 +1,7 @@
 apps := 		\
 	init 			\
 	spin			\
-	ce
+	ce				\
 
 all_apps:
 	@for d in $(apps); do make -C $$d platform=$(platform) all; done
diff --git a/make/libmath.mk b/make/libmath.mk
new file mode 100644
index 0000000..58257b7
--- /dev/null
+++ b/make/libmath.mk
@@ -0,0 +1,16 @@
+all_libmath:
+	make -C libmath platform=$(platform) all
+
+all_compiledb_libmath:
+	bear --output libmath/compile_commands.json -- make -C libmath platform=$(platform) all
+
+clean_libmath:
+	make -C libmath platform=$(platform) clean
+
+format_libmath:
+	make -C libmath platform=$(platform) format
+
+docs_libmath:
+	make -C libmath platform=$(platform) docs
+
+.PHONY: all_libmath clean_libmath format_libmath docs_libmath all_compiledb_libmath
diff --git a/make/user.mk b/make/user.mk
index 301b294..3d2c7f2 100644
--- a/make/user.mk
+++ b/make/user.mk
@@ -4,16 +4,19 @@ o :=
 c :=
 ldflags += -L ../libsystem/build -l:libsystem.a -L ../liballoc/build -l:liballoc.a
 cflags += -isystem ../libsystem -isystem ../liballoc
+extra_deps +=
 
 include src.mk
 include app.mk
 include ../generic/flags.mk
 include ../$(platform)/flags.mk
 
+FORMAT ?= clang-format -i $$(git ls-files '*.c' '*.h')
+
 all: $(app)
 
-$(app): $(o)
-	$(ld) -o $@ $(ldflags) -T ../$(platform)/link.ld $^
+$(app): $(extra_deps) $(o)
+	$(ld) -o $@ $(ldflags) -T ../$(platform)/link.ld $(o)
 
 %.o: %.c
 	$(cc) -c -o $@ $(cflags) $<
@@ -25,6 +28,6 @@ clean:
 	rm -f $(o) $(app)
 
 format:
-	clang-format -i $$(git ls-files '*.c' '*.h')
+	$(FORMAT)
 
 .PHONY: all clean format