diff --git a/CMakeLists.txt b/CMakeLists.txt
index cbc3219..a26ea07 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -39,7 +39,7 @@ set(CMAKE_EXE_LINKER_FLAGS
     "${CMAKE_EXE_LINKER_FLAGS} -ffreestanding -nostdlib -lgcc")
 
 set(photon_libc_sources "")
-set(generic_dirs string)
+set(generic_dirs string stdio)
 
 foreach (dir ${generic_dirs})
     file(GLOB dir_sources ${CMAKE_CURRENT_SOURCE_DIR}/photon/libc/${dir}/*.c)
@@ -74,6 +74,7 @@ target_compile_options(c PRIVATE -ffreestanding -nostdlib -nostdinc)
 target_link_libraries(c crt)
 
 target_include_directories(c PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/photon/libc/include)
+target_include_directories(c PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/photon/libc/sys/${PLATFORM}/)
 
 add_custom_target(sysroot
     DEPENDS ${photon_libc_headers}
diff --git a/photon/libc/include/stdio.h b/photon/libc/include/stdio.h
index 0b8c7d3..ccf0589 100644
--- a/photon/libc/include/stdio.h
+++ b/photon/libc/include/stdio.h
@@ -23,6 +23,8 @@ extern FILE *stdin;
 extern FILE *stdout;
 extern FILE *stderr;
 
+extern int fileno(FILE *fp);
+
 #if defined(__cplusplus)
 }
 #endif
diff --git a/photon/libc/include/time.h b/photon/libc/include/time.h
new file mode 100644
index 0000000..c0aa0b3
--- /dev/null
+++ b/photon/libc/include/time.h
@@ -0,0 +1,11 @@
+#ifndef TIME_H_
+#define TIME_H_
+
+#include <sys/types.h>
+
+struct timespec {
+    time_t tv_sec;
+    long tv_nsec;
+};
+
+#endif
diff --git a/photon/libc/stdio/fileno.c b/photon/libc/stdio/fileno.c
new file mode 100644
index 0000000..0cb6a3c
--- /dev/null
+++ b/photon/libc/stdio/fileno.c
@@ -0,0 +1,7 @@
+#include <__fio.h>
+#include <stdio.h>
+
+int fileno(FILE *f)
+{
+    return __fileno(f);
+}
diff --git a/photon/libc/sys/linux/__fio.h b/photon/libc/sys/linux/__fio.h
index 362c0a8..7774336 100644
--- a/photon/libc/sys/linux/__fio.h
+++ b/photon/libc/sys/linux/__fio.h
@@ -13,6 +13,8 @@ struct __io_file {
     unsigned int fd;
 };
 
+extern int __fileno(struct __io_file *f);
+
 #if defined(__cplusplus)
 }
 #endif
diff --git a/photon/libc/sys/linux/__syscall.h b/photon/libc/sys/linux/__syscall.h
new file mode 100644
index 0000000..c2f0060
--- /dev/null
+++ b/photon/libc/sys/linux/__syscall.h
@@ -0,0 +1,17 @@
+#ifndef SYS_LINUX___SYSCALL_H_
+#define SYS_LINUX___SYSCALL_H_
+
+#include <stdint.h>
+
+extern intptr_t __syscall0(unsigned int id);
+extern intptr_t __syscall1(unsigned int id, uintptr_t p0);
+extern intptr_t __syscall2(unsigned int id, uintptr_t p0, uintptr_t p1);
+extern intptr_t __syscall3(uintptr_t id, uintptr_t p0, uintptr_t p1, uintptr_t p2);
+extern intptr_t __syscall4(unsigned int id, uintptr_t p0, uintptr_t p1, uintptr_t p2,
+        uintptr_t p3);
+extern intptr_t __syscall5(unsigned int id, uintptr_t p0, uintptr_t p1, uintptr_t p2,
+        uintptr_t p3, uintptr_t p4);
+extern intptr_t __syscall6(unsigned int id, uintptr_t p0, uintptr_t p1, uintptr_t p2,
+        uintptr_t p3, uintptr_t p4, uintptr_t p5);
+
+#endif
diff --git a/photon/libc/sys/linux/fio.c b/photon/libc/sys/linux/fio.c
index 150a651..9d2c413 100644
--- a/photon/libc/sys/linux/fio.c
+++ b/photon/libc/sys/linux/fio.c
@@ -1,4 +1,5 @@
 #include "__fio.h"
+#include "__syscall.h"
 
 struct __io_file __stdin = {};
 struct __io_file __stdout = {};
@@ -14,3 +15,8 @@ void __fio_init()
     __stdout.fd = 1;
     __stderr.fd = 2;
 }
+
+int __fileno(struct __io_file *f)
+{
+    return f->fd;
+}
diff --git a/photon/libc/sys/linux/machine/x86_64/syscall.c b/photon/libc/sys/linux/machine/x86_64/syscall.c
new file mode 100644
index 0000000..dc54634
--- /dev/null
+++ b/photon/libc/sys/linux/machine/x86_64/syscall.c
@@ -0,0 +1,108 @@
+#include <stdint.h>
+
+intptr_t __syscall0(uintptr_t id)
+{
+    intptr_t ret = 0;
+    asm volatile("mov %1, %%rax; syscall; mov %%rax, %0"
+            : "=m" (ret)
+            : "m" (id));
+    return ret;
+}
+
+intptr_t __syscall1(uintptr_t id, uintptr_t p0)
+{
+    intptr_t ret = 0;
+    asm volatile(
+            "mov %1, %%rax;"
+            "mov %2, %%rdi;"
+            "syscall;"
+            "mov %%rax, %0"
+            : "=m" (ret)
+            : "m" (id), "m" (p0));
+    return ret;
+}
+
+intptr_t __syscall2(uintptr_t id, uintptr_t p0, uintptr_t p1)
+{
+    intptr_t ret = 0;
+    asm volatile(
+            "mov %1, %%rax;"
+            "mov %2, %%rdi;"
+            "mov %3, %%rsi;"
+            "syscall;"
+            "mov %%rax, %0"
+            : "=m" (ret)
+            : "m" (id), "m" (p0), "m" (p1));
+    return ret;
+}
+
+intptr_t __syscall3(uintptr_t id, uintptr_t p0, uintptr_t p1, uintptr_t p2)
+{
+    intptr_t ret = 0;
+    asm volatile(
+            "movq %1, %%rax;"
+            "mov %2, %%rdi;"
+            "mov %3, %%rsi;"
+            "mov %4, %%rdx;"
+            "syscall;"
+            "mov %%rax, %0"
+            : "=m" (ret)
+            : "m" (id), "m" (p0), "m" (p1), "m" (p2));
+    return ret;
+}
+
+intptr_t __syscall4(uintptr_t id, uintptr_t p0, uintptr_t p1, uintptr_t p2,
+        uintptr_t p3)
+{
+    intptr_t ret = 0;
+    asm volatile(
+            "mov %1, %%rax;"
+            "mov %2, %%rdi;"
+            "mov %3, %%rsi;"
+            "mov %4, %%rdx;"
+            "mov %5, %%r10;"
+            "syscall;"
+            "mov %%rax, %0"
+            : "=m" (ret)
+            : "m" (id), "m" (p0), "m" (p1), "m" (p2), "m" (p3));
+    return ret;
+}
+
+intptr_t __syscall5(uintptr_t id, uintptr_t p0, uintptr_t p1, uintptr_t p2,
+        uintptr_t p3, uintptr_t p4)
+{
+    intptr_t ret = 0;
+    asm volatile(
+            "mov %1, %%rax;"
+            "mov %2, %%rdi;"
+            "mov %3, %%rsi;"
+            "mov %4, %%rdx;"
+            "mov %5, %%r10;"
+            "mov %6, %%r8;"
+            "syscall;"
+            "mov %%rax, %0"
+            : "=m" (ret)
+            : "m" (id), "m" (p0), "m" (p1), "m" (p2), "m" (p3), "m" (p4));
+    return ret;
+}
+
+intptr_t __syscall6(uintptr_t id, uintptr_t p0, uintptr_t p1, uintptr_t p2,
+        uintptr_t p3, uintptr_t p4, uintptr_t p5)
+{
+    intptr_t ret = 0;
+    asm volatile(
+            "mov %1, %%rax;"
+            "mov %2, %%rdi;"
+            "mov %3, %%rsi;"
+            "mov %4, %%rdx;"
+            "mov %5, %%r10;"
+            "mov %6, %%r8;"
+            "mov %7, %%r9;"
+            "syscall;"
+            "mov %%rax, %0"
+            : "=m" (ret)
+            : "m" (id), "m" (p0), "m" (p1), "m" (p2), "m" (p3), "m" (p4),
+                "m" (p5));
+    return ret;
+}
+
diff --git a/photon/libc/sys/linux/poll.h b/photon/libc/sys/linux/poll.h
new file mode 100644
index 0000000..b34fb09
--- /dev/null
+++ b/photon/libc/sys/linux/poll.h
@@ -0,0 +1,33 @@
+#ifndef SYS_LINUX_POLL_H_
+#define SYS_LINUX_POLL_H_
+
+#define POLLIN 0x1
+#define POLLPRI 0x2
+#define POLLOUT 0x4
+#define POLLERR 0x8
+#define POLLHUP 0x10
+#define POLLNVAL 0x20
+#define POLLRDNORM 0x40
+#define POLLRDBAND 0x80
+#define POLLWRNORM 0x100
+#define POLLWRBAND 0x200
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+typedef unsigned long long nfds_t;
+
+struct pollfd {
+    int fd;
+    short events;
+    short revents;
+};
+
+extern int poll(struct pollfd *fds, nfds_t nfds, int timeout);
+
+#if defined(__cplusplus)
+}
+#endif
+
+#endif
diff --git a/photon/libc/sys/linux/_fconst.h b/photon/libc/sys/linux/sys/_fconst.h
similarity index 60%
rename from photon/libc/sys/linux/_fconst.h
rename to photon/libc/sys/linux/sys/_fconst.h
index 9696e9c..1733158 100644
--- a/photon/libc/sys/linux/_fconst.h
+++ b/photon/libc/sys/linux/sys/_fconst.h
@@ -1,5 +1,5 @@
-#ifndef SYS_LINUX__FCONST_H_
-#define SYS_LINUX__FCONST_H_
+#ifndef SYS_LINUX_SYS__FCONST_H_
+#define SYS_LINUX_SYS__FCONST_H_
 
 #define __FILENAME_MAX 1024
 
diff --git a/photon/libc/sys/linux/sys/stat.h b/photon/libc/sys/linux/sys/stat.h
new file mode 100644
index 0000000..9de447e
--- /dev/null
+++ b/photon/libc/sys/linux/sys/stat.h
@@ -0,0 +1,24 @@
+#ifndef SYS_LINUX_SYS_STAT_H_
+#define SYS_LINUX_SYS_STAT_H_
+
+#include <time.h>
+#include <sys/types.h>
+
+struct stat {
+    dev_t st_dev;
+    ino_t st_ino;
+    mode_t st_mode;
+    nlink_t st_nlink;
+    uid_t st_uid;
+    gid_t st_gid;
+    dev_t st_rdev;
+    off_t st_size;
+    blksize_t st_blksize;
+    blkcnt_t st_blocks;
+
+    struct timespec st_atim;
+    struct timespec st_mtim;
+    struct timespec st_ctim;
+};
+
+#endif
diff --git a/photon/libc/sys/linux/sys/syscall.h b/photon/libc/sys/linux/sys/syscall.h
new file mode 100644
index 0000000..02511cd
--- /dev/null
+++ b/photon/libc/sys/linux/sys/syscall.h
@@ -0,0 +1,22 @@
+#ifndef SYS_LINUX_SYSCALL_H_
+#define SYS_LINUX_SYSCALL_H_
+
+#define SYS_read 0
+#define SYS_write 1
+#define SYS_open 2
+#define SYS_close 3
+#define SYS_stat 4
+#define SYS_fstat 5
+#define SYS_lstat 6
+#define SYS_poll 7
+#define SYS_lseek 8
+#define SYS_mmap 9
+#define SYS_mprotect 10
+#define SYS_munmap 11
+#define SYS_brk 12
+#define SYS_rt_sigaction 13
+#define SYS_rt_sigprocmask 14
+#define SYS_rt_sigreturn 15
+#define SYS_ioctl 16
+
+#endif
diff --git a/photon/libc/sys/linux/sys/types.h b/photon/libc/sys/linux/sys/types.h
new file mode 100644
index 0000000..2676d28
--- /dev/null
+++ b/photon/libc/sys/linux/sys/types.h
@@ -0,0 +1,24 @@
+#ifndef SYS_LINUX_SYS_TYPES_H_
+#define SYS_LINUX_SYS_TYPES_H_
+
+typedef signed long long blkcnt_t;
+typedef signed long long blksize_t;
+typedef unsigned long long clock_t;
+typedef unsigned int clockid_t;
+typedef unsigned long long fsblkcnt_t;
+typedef unsigned long long fsfilcnt_t;
+typedef unsigned int gid_t;
+typedef unsigned int id_t;
+typedef unsigned long long ino_t;
+typedef unsigned int key_t;
+typedef unsigned int mode_t;
+typedef unsigned long long nlink_t;
+typedef signed long long off_t;
+typedef signed int pid_t;
+typedef unsigned long long time_t;
+typedef unsigned int timer_t;
+typedef unsigned int uid_t;
+typedef unsigned long useconds_t;
+typedef unsigned long long dev_t;
+
+#endif
diff --git a/photon/libc/sys/linux/syscall.c b/photon/libc/sys/linux/syscall.c
new file mode 100644
index 0000000..d696e3a
--- /dev/null
+++ b/photon/libc/sys/linux/syscall.c
@@ -0,0 +1,155 @@
+#include "poll.h"
+#include "sys/syscall.h"
+#include "__syscall.h"
+#include "unistd.h"
+
+ssize_t read(int fd, void *buf, size_t count)
+{
+    intptr_t res = __syscall3(SYS_read, (uintptr_t)fd, (uintptr_t)buf,
+            (uintptr_t)count);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (ssize_t)res;
+}
+
+ssize_t write(int fd, const void *buf, size_t count)
+{
+    intptr_t res = __syscall3(SYS_write, (uintptr_t)fd, (uintptr_t)buf,
+            (uintptr_t)count);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (ssize_t)res;
+}
+
+int open(const char *pathname, int flags)
+{
+    intptr_t res = __syscall3(SYS_open, (uintptr_t)pathname,
+            (uintptr_t)flags, 0);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (int)res;
+}
+
+int close(int fd)
+{
+    intptr_t res = __syscall1(SYS_close, (uintptr_t)fd);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (int)res;
+}
+
+int stat(const char *pathname, struct stat *statbuf)
+{
+    intptr_t res = __syscall2(SYS_stat, (uintptr_t)pathname,
+            (uintptr_t)statbuf);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (int)res;
+}
+
+int fstat(int fd, struct stat *statbuf)
+{
+    intptr_t res = __syscall2(SYS_fstat, (uintptr_t)fd,
+            (uintptr_t)statbuf);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (int)res;
+}
+
+int lstat(const char *pathname, struct stat *statbuf)
+{
+    intptr_t res = __syscall2(SYS_lstat, (uintptr_t)pathname,
+            (uintptr_t)statbuf);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (int)res;
+}
+
+int poll(struct pollfd *fds, nfds_t nfds, int timeout)
+{
+    intptr_t res = __syscall3(SYS_poll, (uintptr_t)fds,
+            (uintptr_t)nfds, (uintptr_t)timeout);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (int)res;
+}
+
+off_t lseek(int fd, off_t offset, int whence)
+{
+    intptr_t res = __syscall3(SYS_lseek, (uintptr_t)fd,
+            (uintptr_t)offset, (uintptr_t)whence);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (int)res;
+}
+
+void *mmap(void *addr, size_t len, int prot, int flags, int fd, off_t off)
+{
+    intptr_t res = __syscall6(SYS_mmap, (uintptr_t)addr, (uintptr_t)len,
+            (uintptr_t)prot, (uintptr_t)flags, (uintptr_t)fd, (uintptr_t)off);
+    if (res < 0) {
+        return NULL;
+    }
+
+    return (void *)res;
+}
+
+int mprotect(void *addr, size_t len, int prot)
+{
+    intptr_t res = __syscall3(SYS_mprotect, (uintptr_t)addr, (uintptr_t)len,
+            (uintptr_t)prot);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (int)res;
+}
+
+int munmap(void *addr, size_t length)
+{
+    intptr_t res = __syscall2(SYS_munmap, (uintptr_t)addr, (uintptr_t)length);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (int)res;
+}
+
+int brk(void *addr)
+{
+    intptr_t res = __syscall1(SYS_brk, (uintptr_t)addr);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (int)res;
+}
+
+int ioctl(int fd, unsigned long req, void *arg)
+{
+    intptr_t res = __syscall3(SYS_ioctl, (uintptr_t)fd, (uintptr_t)req,
+            (uintptr_t)arg);
+    if (res < 0) {
+        return -1;
+    }
+
+    return (int)res;
+}
diff --git a/photon/libc/sys/linux/unistd.h b/photon/libc/sys/linux/unistd.h
new file mode 100644
index 0000000..18310e1
--- /dev/null
+++ b/photon/libc/sys/linux/unistd.h
@@ -0,0 +1,27 @@
+#ifndef SYS_LINUX_UNISTD_H_
+#define SYS_LINUX_UNISTD_H_
+
+#include <stddef.h>
+#include <sys/types.h>
+
+struct stat;
+struct pollfd;
+
+typedef __intptr_t ssize_t;
+
+extern ssize_t read(int fd, void *buf, size_t count);
+extern ssize_t write(int fd, const void *buf, size_t count);
+extern int open(const char *pathname, int flags);
+extern int close(int fd);
+extern int stat(const char *pathname, struct stat *statbuf);
+extern int fstat(int fd, struct stat *statbuf);
+extern int lstat(const char *pathname, struct stat *statbuf);
+extern off_t lseek(int fd, off_t offset, int whence);
+extern void *mmap(void *addr, size_t length, int prot, int flags,
+        int fd, off_t offset);
+extern int mprotect(void *addr, size_t len, int prot);
+extern int munmap(void *addr, size_t length);
+extern int brk(void *addr);
+extern int ioctl(int fd, unsigned long request, void *arg);
+
+#endif
diff --git a/scripts/create-sysroot.sh b/scripts/create-sysroot.sh
index b6b6626..6855bf7 100755
--- a/scripts/create-sysroot.sh
+++ b/scripts/create-sysroot.sh
@@ -10,8 +10,10 @@ mkdir -p $build_dir/sysroot/usr/include/{sys,machine}
 
 cp $source_dir/photon/libc/include/*.h $build_dir/sysroot/usr/include
 
-platform_headers=$(find $source_dir/photon/libc/sys/$platform -type f \( -iname "*.h" ! -iname "__*" \))
-cp -t $build_dir/sysroot/usr/include/sys $platform_headers
+platform_headers=$(find $source_dir/photon/libc/sys/$platform -maxdepth 1 -type f \( -iname "*.h" ! -iname "__*" \))
+platform_sys_headers=$(find $source_dir/photon/libc/sys/$platform/sys -maxdepth 1 -type f \( -iname "*.h" ! -iname "__*" \))
+cp -t $build_dir/sysroot/usr/include $platform_headers
+cp -t $build_dir/sysroot/usr/include/sys $platform_sys_headers
 
 machine_arch_headers=$(find $source_dir/photon/libc/machine/$machine/ \
                     -type f \( -iname "*.h" ! -iname "__*" \))
diff --git a/tests/start.c b/tests/start.c
index b9b1667..09c33b0 100644
--- a/tests/start.c
+++ b/tests/start.c
@@ -1,7 +1,9 @@
+#include <unistd.h>
 #include <stdio.h>
-#include <stdint.h>
 
 int main(int argc, char **argv)
 {
-    return 42;
+    const char *msg = "Hello!\n";
+    write(fileno(stdout), msg, 7);
+    return 0;
 }