diff --git a/AK/Assertions.h b/AK/Assertions.h
index 9e95bcc6c2..3c1e778a6f 100644
--- a/AK/Assertions.h
+++ b/AK/Assertions.h
@@ -1,8 +1,12 @@
 #pragma once
 
 #ifdef SERENITY
+#ifdef KERNEL
 #include <Kernel/kassert.h>
 #else
+#include <LibC/assert.h>
+#endif
+#else
 #include <assert.h>
 #define ASSERT(x) assert(x)
 #define ASSERT_NOT_REACHED() assert(false)
diff --git a/AK/StdLib.h b/AK/StdLib.h
index 607682d784..efe871f014 100644
--- a/AK/StdLib.h
+++ b/AK/StdLib.h
@@ -1,8 +1,13 @@
 #pragma once
 
 #ifdef SERENITY
+#ifdef KERNEL
 #include <Kernel/StdLib.h>
 #else
+#include <LibC/stdlib.h>
+#include <LibC/string.h>
+#endif
+#else
 #include <cstring>
 #include <cstdlib>
 #include <utility>
diff --git a/AK/kmalloc.h b/AK/kmalloc.h
index 0ade91659a..02b66c2aab 100644
--- a/AK/kmalloc.h
+++ b/AK/kmalloc.h
@@ -3,10 +3,52 @@
 #include "Compiler.h"
 
 #ifdef SERENITY
-#ifdef USERLAND
-#include <LibC/stdlib.h>
-#else
+#ifdef KERNEL
 #include <Kernel/kmalloc.h>
+#else
+#include <LibC/stdlib.h>
+
+extern "C" {
+
+void* kcalloc(size_t nmemb, size_t size);
+void* kmalloc(size_t size) MALLOC_ATTR;
+void kfree(void* ptr);
+void* krealloc(void* ptr, size_t size);
+
+}
+
+inline void* operator new(size_t size)
+{
+    return kmalloc(size);
+}
+
+inline void* operator new[](size_t size)
+{
+    return kmalloc(size);
+}
+
+inline void operator delete(void* ptr)
+{
+    return kfree(ptr);
+}
+
+inline void operator delete[](void* ptr)
+{
+    return kfree(ptr);
+}
+
+inline void operator delete(void* ptr, size_t)
+{
+    return kfree(ptr);
+}
+
+inline void operator delete[](void* ptr, size_t)
+{
+    return kfree(ptr);
+}
+
+inline void* operator new(size_t, void* p) { return p; }
+inline void* operator new[](size_t, void* p) { return p; }
 #endif
 #else
 #include <new>
diff --git a/Kernel/Makefile b/Kernel/Makefile
index b93376664a..c7dfcd6ce2 100644
--- a/Kernel/Makefile
+++ b/Kernel/Makefile
@@ -59,7 +59,7 @@ FLAVOR_FLAGS = -mregparm=3 -march=i386 -m32 -fno-exceptions -fno-rtti -fmerge-al
 OPTIMIZATION_FLAGS = -Os -fno-asynchronous-unwind-tables
 INCLUDE_FLAGS = -I.. -I.
 
-DEFINES = -DSERENITY -DSANITIZE_PTRS
+DEFINES = -DSERENITY -DKERNEL -DSANITIZE_PTRS
 
 CXXFLAGS = $(WARNING_FLAGS) $(OPTIMIZATION_FLAGS) $(KERNEL_FLAGS) $(FLAVOR_FLAGS) $(ARCH_FLAGS) $(STANDARD_FLAGS) $(INCLUDE_FLAGS) $(DEFINES)
 #CXX = /usr/local/gcc-4.8.1-for-linux64/bin/x86_64-pc-linux-g++
diff --git a/Kernel/Task.cpp b/Kernel/Task.cpp
index 10326fe03d..bbec8f0fe5 100644
--- a/Kernel/Task.cpp
+++ b/Kernel/Task.cpp
@@ -142,6 +142,7 @@ Task::Region* Task::allocateRegion(size_t size, String&& name)
 
 bool Task::deallocateRegion(Region& region)
 {
+    InterruptDisabler disabler;
     for (size_t i = 0; i < m_regions.size(); ++i) {
         if (m_regions[i].ptr() == &region) {
             // FIXME: This seems racy.
diff --git a/LibC/Makefile b/LibC/Makefile
index d0ab3ef533..c376122965 100644
--- a/LibC/Makefile
+++ b/LibC/Makefile
@@ -1,4 +1,11 @@
-OBJS = \
+AK_OBJS = \
+    ../AK/StringImpl.o \
+    ../AK/String.o \
+    ../AK/StringBuilder.o \
+    ../AK/FileSystemPath.o \
+    ../AK/kmalloc.o
+
+LIBC_OBJS = \
        stdio.o \
        unistd.o \
        string.o \
@@ -8,8 +15,11 @@ OBJS = \
        stdlib.o \
        time.o \
        utsname.o \
+       assert.o \
        entry.o
 
+OBJS = $(AK_OBJS) $(LIBC_OBJS)
+
 LIBRARY = LibC.a
 ARCH_FLAGS =
 STANDARD_FLAGS = -std=c++17 -nostdinc++ -nostdlib
@@ -19,7 +29,7 @@ FLAVOR_FLAGS = -fomit-frame-pointer -mregparm=3 -march=i386 -m32 -fno-exceptions
 OPTIMIZATION_FLAGS = -Os -fno-asynchronous-unwind-tables
 INCLUDE_FLAGS = -I.. -I.
 
-DEFINES = -DSERENITY -DSANITIZE_PTRS
+DEFINES = -DSERENITY -DUSERLAND -DSANITIZE_PTRS
 
 CXXFLAGS = $(WARNING_FLAGS) $(OPTIMIZATION_FLAGS) $(LIBC_FLAGS) $(FLAVOR_FLAGS) $(ARCH_FLAGS) $(STANDARD_FLAGS) $(INCLUDE_FLAGS) $(DEFINES)
 CXX = g++-8
diff --git a/LibC/assert.cpp b/LibC/assert.cpp
new file mode 100644
index 0000000000..4aa774c3fd
--- /dev/null
+++ b/LibC/assert.cpp
@@ -0,0 +1,14 @@
+#include "assert.h"
+#include "stdlib.h"
+#include "stdio.h"
+
+extern "C" {
+
+extern void __assertion_failed(const char* msg, const char* file, unsigned line, const char* func)
+{
+    printf("ASSERTION FAILED: %s\n%s:%u in %s\n", msg, file, line, func);
+    abort();
+}
+
+}
+
diff --git a/LibC/assert.h b/LibC/assert.h
new file mode 100644
index 0000000000..1f5610dd2e
--- /dev/null
+++ b/LibC/assert.h
@@ -0,0 +1,14 @@
+#pragma once
+
+extern "C" {
+
+void __assertion_failed(const char* msg, const char* file, unsigned line, const char* func);
+
+#define assert(expr) (static_cast<bool>(expr) ? (void)0 : __assertion_failed(#expr, __FILE__, __LINE__, __PRETTY_FUNCTION__))
+#define CRASH() do { asm volatile("ud2"); } while(0)
+#define ASSERT assert
+#define RELEASE_ASSERT assert
+#define ASSERT_NOT_REACHED() assert(false)
+
+}
+
diff --git a/LibC/entry.cpp b/LibC/entry.cpp
index 5d5eb27078..c3657b704b 100644
--- a/LibC/entry.cpp
+++ b/LibC/entry.cpp
@@ -1,4 +1,5 @@
 #include <Kernel/Syscall.h>
+#include <AK/StringImpl.h>
 
 extern "C" int main(int, char**);
 
@@ -8,6 +9,8 @@ extern "C" int _start()
 {
     errno = 0;
 
+    StringImpl::initializeGlobals();
+
     int argc;
     char** argv;
     int rc = Syscall::invoke(Syscall::GetArguments, (dword)&argc, (dword)&argv);
diff --git a/LibC/stdlib.cpp b/LibC/stdlib.cpp
index 7d0f1b5e8f..5feceaec5f 100644
--- a/LibC/stdlib.cpp
+++ b/LibC/stdlib.cpp
@@ -1,5 +1,7 @@
 #include "stdlib.h"
 #include "mman.h"
+#include <Kernel/Syscall.h>
+#include <AK/Assertions.h>
 
 extern "C" {
 
@@ -20,5 +22,28 @@ void free(void* ptr)
     munmap(ptr, 4096);
 }
 
+void* calloc(size_t nmemb, size_t)
+{
+    ASSERT_NOT_REACHED();
+    return nullptr;
+}
+
+void* realloc(void *ptr, size_t)
+{
+    ASSERT_NOT_REACHED();
+    return nullptr;
+}
+
+void exit(int status)
+{
+    Syscall::invoke(Syscall::PosixExit, (dword)status);
+}
+
+void abort()
+{
+    // FIXME: Implement proper abort().
+    exit(253);
+}
+
 }
 
diff --git a/LibC/stdlib.h b/LibC/stdlib.h
index 55cd47c9f7..4ebff011da 100644
--- a/LibC/stdlib.h
+++ b/LibC/stdlib.h
@@ -6,6 +6,11 @@ extern "C" {
 
 void* malloc(size_t);
 void free(void*);
+void* calloc(size_t nmemb, size_t);
+void* realloc(void *ptr, size_t);
+
+void exit(int status);
+void abort();
 
 }
 
diff --git a/LibC/string.cpp b/LibC/string.cpp
index a72bbb7cda..a48e1c2a4f 100644
--- a/LibC/string.cpp
+++ b/LibC/string.cpp
@@ -21,6 +21,17 @@ int strcmp(const char* s1, const char* s2)
     return *(const unsigned char*)s1 < *(const unsigned char*)s2 ? -1 : 1;
 }
 
+int memcmp(const void* v1, const void* v2, size_t n)
+{
+    auto* s1 = (const byte*)v1;
+    auto* s2 = (const byte*)v2;
+    while (n-- > 0) {
+        if (*s1++ != *s2++)
+            return s1[-1] < s2[-1] ? -1 : 1;
+    }
+    return 0;
+}
+
 void memcpy(void* dest, const void* src, size_t n)
 {
     auto* bdest = (unsigned char*)dest;
diff --git a/LibC/string.h b/LibC/string.h
index 32444fd90d..6ef56e075b 100644
--- a/LibC/string.h
+++ b/LibC/string.h
@@ -6,6 +6,7 @@ extern "C" {
 
 size_t strlen(const char*);
 int strcmp(const char*, const char*);
+int memcmp(const void*, const void*, size_t);
 void memcpy(void*, const void*, size_t);
 const char* strerror(int errnum);
 
diff --git a/Userland/sh.cpp b/Userland/sh.cpp
index faed58e715..b172f6fa9c 100644
--- a/Userland/sh.cpp
+++ b/Userland/sh.cpp
@@ -4,21 +4,25 @@
 #include <LibC/errno.h>
 #include <LibC/string.h>
 #include <LibC/stdlib.h>
+#include <AK/FileSystemPath.h>
 
-char* g_cwd = nullptr;
-char g_hostname[32];
+struct GlobalState {
+    String cwd;
+    char hostname[32];
+};
+static GlobalState* g;
 
 static void prompt()
 {
     if (getuid() == 0)
         printf("# ");
     else
-        printf("\033[32;1m%s\033[0m:\033[34;1m%s\033[0m$> ", g_hostname, g_cwd);
+        printf("\033[32;1m%s\033[0m:\033[34;1m%s\033[0m$> ", g->hostname, g->cwd.characters());
 }
 
 static int sh_pwd(int, const char**)
 {
-    printf("%s\n", g_cwd);
+    printf("%s\n", g->cwd.characters());
     return 0;
 }
 
@@ -30,26 +34,34 @@ static int sh_cd(int argc, const char** argv)
     }
 
     char pathbuf[128];
-    if (argv[1][1] == '/')
-        memcpy(pathbuf, argv[1], strlen(argv[1]));
+    if (argv[1][0] == '/')
+        memcpy(pathbuf, argv[1], strlen(argv[1]) + 1);
     else
-        sprintf(pathbuf, "%s/%s", g_cwd, argv[1]);
+        sprintf(pathbuf, "%s/%s", g->cwd.characters(), argv[1]);
+
+    FileSystemPath canonicalPath(pathbuf);
+    if (!canonicalPath.isValid()) {
+        printf("FileSystemPath failed to canonicalize '%s'\n", pathbuf);
+        return 1;
+    }
+    const char* path = canonicalPath.string().characters();
+
     struct stat st;
-    int rc = lstat(pathbuf, &st);
+    int rc = lstat(path, &st);
     if (rc < 0) {
-        printf("lstat(%s) failed: %s\n", pathbuf, strerror(errno));
+        printf("lstat(%s) failed: %s\n", path, strerror(errno));
         return 1;
     }
     if (!S_ISDIR(st.st_mode)) {
-        printf("Not a directory: %s\n", pathbuf);
+        printf("Not a directory: %s\n", path);
         return 1;
     }
-    rc = chdir(pathbuf);
+    rc = chdir(path);
     if (rc < 0) {
-        printf("chdir(%s) failed: %s\n", pathbuf, strerror(errno));
+        printf("chdir(%s) failed: %s\n", path, strerror(errno));
         return 1;
     }
-    memcpy(g_cwd, pathbuf, strlen(pathbuf));
+    g->cwd = canonicalPath.string();
     return 0;
 }
 
@@ -115,7 +127,8 @@ static int runcmd(char* cmd)
 
 int main(int, char**)
 {
-    int rc = gethostname(g_hostname, sizeof(g_hostname));
+    g = new GlobalState;
+    int rc = gethostname(g->hostname, sizeof(g->hostname));
     if (rc < 0)
         perror("gethostname");
 
@@ -128,9 +141,7 @@ int main(int, char**)
         printf("failed to open /dev/keyboard :(\n");
         return 1;
     }
-    g_cwd = (char*)malloc(1024);
-    g_cwd[0] = '/';
-    g_cwd[1] = '\0';
+    g->cwd = "/";
     prompt();
     for (;;) {
         char keybuf[16];
diff --git a/Userland/tst.cpp b/Userland/tst.cpp
index 31a1439e64..0799e161bb 100644
--- a/Userland/tst.cpp
+++ b/Userland/tst.cpp
@@ -1,4 +1,4 @@
-#include <LibC/stdio.cpp>
+#include <LibC/stdio.h>
 
 int main(int argc, char** argv)
 {