xref: /tools/include/nolibc/nolibc.h

/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/* nolibc.h
 * Copyright (C) 2017-2018 Willy Tarreau <w@1wt.eu>
 */

/*
 * This file is designed to be used as a libc alternative for minimal programs
 * with very limited requirements. It consists of a small number of syscall and
 * type definitions, and the minimal startup code needed to call main().
 * All syscalls are declared as static functions so that they can be optimized
 * away by the compiler when not used.
 *
 * Syscalls are split into 3 levels:
 *   - The lower level is the arch-specific syscall() definition, consisting in
 *     assembly code in compound expressions. These are called my_syscall0() to
 *     my_syscall6() depending on the number of arguments. The MIPS
 *     implementation is limited to 5 arguments. All input arguments are cast
 *     to a long stored in a register. These expressions always return the
 *     syscall's return value as a signed long value which is often either a
 *     pointer or the negated errno value.
 *
 *   - The second level is mostly architecture-independent. It is made of
 *     static functions called sys_<name>() which rely on my_syscallN()
 *     depending on the syscall definition. These functions are responsible
 *     for exposing the appropriate types for the syscall arguments (int,
 *     pointers, etc) and for setting the appropriate return type (often int).
 *     A few of them are architecture-specific because the syscalls are not all
 *     mapped exactly the same among architectures. For example, some archs do
 *     not implement select() and need pselect6() instead, so the sys_select()
 *     function will have to abstract this.
 *
 *   - The third level is the libc call definition. It exposes the lower raw
 *     sys_<name>() calls in a way that looks like what a libc usually does,
 *     takes care of specific input values, and of setting errno upon error.
 *     There can be minor variations compared to standard libc calls. For
 *     example the open() call always takes 3 args here.
 *
 * The errno variable is declared static and unused. This way it can be
 * optimized away if not used. However this means that a program made of
 * multiple C files may observe different errno values (one per C file). For
 * the type of programs this project targets it usually is not a problem. The
 * resulting program may even be reduced by defining the NOLIBC_IGNORE_ERRNO
 * macro, in which case the errno value will never be assigned.
 *
 * Some stdint-like integer types are defined. These are valid on all currently
 * supported architectures, because signs are enforced, ints are assumed to be
 * 32 bits, longs the size of a pointer and long long 64 bits. If more
 * architectures have to be supported, this may need to be adapted.
 *
 * Some macro definitions like the O_* values passed to open(), and some
 * structures like the sys_stat struct depend on the architecture.
 *
 * The definitions start with the architecture-specific parts, which are picked
 * based on what the compiler knows about the target architecture, and are
 * completed with the generic code. Since it is the compiler which sets the
 * target architecture, cross-compiling normally works out of the box without
 * having to specify anything.
 *
 * Finally some very common libc-level functions are provided. It is the case
 * for a few functions usually found in string.h, ctype.h, or stdlib.h. Nothing
 * is currently provided regarding stdio emulation.
 *
 * The macro NOLIBC is always defined, so that it is possible for a program to
 * check this macro to know if it is being built against and decide to disable
 * some features or simply not to include some standard libc files.
 *
 * Ideally this file should be split in multiple files for easier long term
 * maintenance, but provided as a single file as it is now, it's quite
 * convenient to use. Maybe some variations involving a set of includes at the
 * top could work.
 *
 * A simple static executable may be built this way :
 *      $ gcc -fno-asynchronous-unwind-tables -fno-ident -s -Os -nostdlib \
 *            -static -include nolibc.h -o hello hello.c -lgcc
 *
 * A very useful calling convention table may be found here :
 *      http://man7.org/linux/man-pages/man2/syscall.2.html
 *
 * This doc is quite convenient though not necessarily up to date :
 *      https://w3challs.com/syscalls/
 *
 */

/* standard type definitions */
#include "std.h"

/* system includes */
#include <asm/unistd.h>
#include <asm/signal.h>  // for SIGCHLD
#include <asm/ioctls.h>
#include <asm/errno.h>
#include <linux/fs.h>
#include <linux/loop.h>
#include <linux/time.h>
#include "arch.h"
#include "types.h"

/* Used by programs to avoid std includes */
#define NOLIBC

/* this way it will be removed if unused */
static int errno;

#ifndef NOLIBC_IGNORE_ERRNO
#define SET_ERRNO(v) do { errno = (v); } while (0)
#else
#define SET_ERRNO(v) do { } while (0)
#endif

/* errno codes all ensure that they will not conflict with a valid pointer
 * because they all correspond to the highest addressable memory page.
 */
#define MAX_ERRNO 4095


/* Below are the C functions used to declare the raw syscalls. They try to be
 * architecture-agnostic, and return either a success or -errno. Declaring them
 * static will lead to them being inlined in most cases, but it's still possible
 * to reference them by a pointer if needed.
 */
static __attribute__((unused))
void *sys_brk(void *addr)
{
	return (void *)my_syscall1(__NR_brk, addr);
}

static __attribute__((noreturn,unused))
void sys_exit(int status)
{
	my_syscall1(__NR_exit, status & 255);
	while(1); // shut the "noreturn" warnings.
}

static __attribute__((unused))
int sys_chdir(const char *path)
{
	return my_syscall1(__NR_chdir, path);
}

static __attribute__((unused))
int sys_chmod(const char *path, mode_t mode)
{
#ifdef __NR_fchmodat
	return my_syscall4(__NR_fchmodat, AT_FDCWD, path, mode, 0);
#elif defined(__NR_chmod)
	return my_syscall2(__NR_chmod, path, mode);
#else
#error Neither __NR_fchmodat nor __NR_chmod defined, cannot implement sys_chmod()
#endif
}

static __attribute__((unused))
int sys_chown(const char *path, uid_t owner, gid_t group)
{
#ifdef __NR_fchownat
	return my_syscall5(__NR_fchownat, AT_FDCWD, path, owner, group, 0);
#elif defined(__NR_chown)
	return my_syscall3(__NR_chown, path, owner, group);
#else
#error Neither __NR_fchownat nor __NR_chown defined, cannot implement sys_chown()
#endif
}

static __attribute__((unused))
int sys_chroot(const char *path)
{
	return my_syscall1(__NR_chroot, path);
}

static __attribute__((unused))
int sys_close(int fd)
{
	return my_syscall1(__NR_close, fd);
}

static __attribute__((unused))
int sys_dup(int fd)
{
	return my_syscall1(__NR_dup, fd);
}

#ifdef __NR_dup3
static __attribute__((unused))
int sys_dup3(int old, int new, int flags)
{
	return my_syscall3(__NR_dup3, old, new, flags);
}
#endif

static __attribute__((unused))
int sys_dup2(int old, int new)
{
#ifdef __NR_dup3
	return my_syscall3(__NR_dup3, old, new, 0);
#elif defined(__NR_dup2)
	return my_syscall2(__NR_dup2, old, new);
#else
#error Neither __NR_dup3 nor __NR_dup2 defined, cannot implement sys_dup2()
#endif
}

static __attribute__((unused))
int sys_execve(const char *filename, char *const argv[], char *const envp[])
{
	return my_syscall3(__NR_execve, filename, argv, envp);
}

static __attribute__((unused))
pid_t sys_fork(void)
{
#ifdef __NR_clone
	/* note: some archs only have clone() and not fork(). Different archs
	 * have a different API, but most archs have the flags on first arg and
	 * will not use the rest with no other flag.
	 */
	return my_syscall5(__NR_clone, SIGCHLD, 0, 0, 0, 0);
#elif defined(__NR_fork)
	return my_syscall0(__NR_fork);
#else
#error Neither __NR_clone nor __NR_fork defined, cannot implement sys_fork()
#endif
}

static __attribute__((unused))
int sys_fsync(int fd)
{
	return my_syscall1(__NR_fsync, fd);
}

static __attribute__((unused))
int sys_getdents64(int fd, struct linux_dirent64 *dirp, int count)
{
	return my_syscall3(__NR_getdents64, fd, dirp, count);
}

static __attribute__((unused))
pid_t sys_getpgid(pid_t pid)
{
	return my_syscall1(__NR_getpgid, pid);
}

static __attribute__((unused))
pid_t sys_getpgrp(void)
{
	return sys_getpgid(0);
}

static __attribute__((unused))
pid_t sys_getpid(void)
{
	return my_syscall0(__NR_getpid);
}

static __attribute__((unused))
int sys_gettimeofday(struct timeval *tv, struct timezone *tz)
{
	return my_syscall2(__NR_gettimeofday, tv, tz);
}

static __attribute__((unused))
int sys_ioctl(int fd, unsigned long req, void *value)
{
	return my_syscall3(__NR_ioctl, fd, req, value);
}

static __attribute__((unused))
int sys_kill(pid_t pid, int signal)
{
	return my_syscall2(__NR_kill, pid, signal);
}

static __attribute__((unused))
int sys_link(const char *old, const char *new)
{
#ifdef __NR_linkat
	return my_syscall5(__NR_linkat, AT_FDCWD, old, AT_FDCWD, new, 0);
#elif defined(__NR_link)
	return my_syscall2(__NR_link, old, new);
#else
#error Neither __NR_linkat nor __NR_link defined, cannot implement sys_link()
#endif
}

static __attribute__((unused))
off_t sys_lseek(int fd, off_t offset, int whence)
{
	return my_syscall3(__NR_lseek, fd, offset, whence);
}

static __attribute__((unused))
int sys_mkdir(const char *path, mode_t mode)
{
#ifdef __NR_mkdirat
	return my_syscall3(__NR_mkdirat, AT_FDCWD, path, mode);
#elif defined(__NR_mkdir)
	return my_syscall2(__NR_mkdir, path, mode);
#else
#error Neither __NR_mkdirat nor __NR_mkdir defined, cannot implement sys_mkdir()
#endif
}

static __attribute__((unused))
long sys_mknod(const char *path, mode_t mode, dev_t dev)
{
#ifdef __NR_mknodat
	return my_syscall4(__NR_mknodat, AT_FDCWD, path, mode, dev);
#elif defined(__NR_mknod)
	return my_syscall3(__NR_mknod, path, mode, dev);
#else
#error Neither __NR_mknodat nor __NR_mknod defined, cannot implement sys_mknod()
#endif
}

static __attribute__((unused))
int sys_mount(const char *src, const char *tgt, const char *fst,
	      unsigned long flags, const void *data)
{
	return my_syscall5(__NR_mount, src, tgt, fst, flags, data);
}

static __attribute__((unused))
int sys_open(const char *path, int flags, mode_t mode)
{
#ifdef __NR_openat
	return my_syscall4(__NR_openat, AT_FDCWD, path, flags, mode);
#elif defined(__NR_open)
	return my_syscall3(__NR_open, path, flags, mode);
#else
#error Neither __NR_openat nor __NR_open defined, cannot implement sys_open()
#endif
}

static __attribute__((unused))
int sys_pivot_root(const char *new, const char *old)
{
	return my_syscall2(__NR_pivot_root, new, old);
}

static __attribute__((unused))
int sys_poll(struct pollfd *fds, int nfds, int timeout)
{
#if defined(__NR_ppoll)
	struct timespec t;

	if (timeout >= 0) {
		t.tv_sec  = timeout / 1000;
		t.tv_nsec = (timeout % 1000) * 1000000;
	}
	return my_syscall4(__NR_ppoll, fds, nfds, (timeout >= 0) ? &t : NULL, NULL);
#elif defined(__NR_poll)
	return my_syscall3(__NR_poll, fds, nfds, timeout);
#else
#error Neither __NR_ppoll nor __NR_poll defined, cannot implement sys_poll()
#endif
}

static __attribute__((unused))
ssize_t sys_read(int fd, void *buf, size_t count)
{
	return my_syscall3(__NR_read, fd, buf, count);
}

static __attribute__((unused))
ssize_t sys_reboot(int magic1, int magic2, int cmd, void *arg)
{
	return my_syscall4(__NR_reboot, magic1, magic2, cmd, arg);
}

static __attribute__((unused))
int sys_sched_yield(void)
{
	return my_syscall0(__NR_sched_yield);
}

static __attribute__((unused))
int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeval *timeout)
{
#if defined(__ARCH_WANT_SYS_OLD_SELECT) && !defined(__NR__newselect)
	struct sel_arg_struct {
		unsigned long n;
		fd_set *r, *w, *e;
		struct timeval *t;
	} arg = { .n = nfds, .r = rfds, .w = wfds, .e = efds, .t = timeout };
	return my_syscall1(__NR_select, &arg);
#elif defined(__ARCH_WANT_SYS_PSELECT6) && defined(__NR_pselect6)
	struct timespec t;

	if (timeout) {
		t.tv_sec  = timeout->tv_sec;
		t.tv_nsec = timeout->tv_usec * 1000;
	}
	return my_syscall6(__NR_pselect6, nfds, rfds, wfds, efds, timeout ? &t : NULL, NULL);
#elif defined(__NR__newselect) || defined(__NR_select)
#ifndef __NR__newselect
#define __NR__newselect __NR_select
#endif
	return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout);
#else
#error None of __NR_select, __NR_pselect6, nor __NR__newselect defined, cannot implement sys_select()
#endif
}

static __attribute__((unused))
int sys_setpgid(pid_t pid, pid_t pgid)
{
	return my_syscall2(__NR_setpgid, pid, pgid);
}

static __attribute__((unused))
pid_t sys_setsid(void)
{
	return my_syscall0(__NR_setsid);
}

static __attribute__((unused))
int sys_stat(const char *path, struct stat *buf)
{
	struct sys_stat_struct stat;
	long ret;

#ifdef __NR_newfstatat
	/* only solution for arm64 */
	ret = my_syscall4(__NR_newfstatat, AT_FDCWD, path, &stat, 0);
#elif defined(__NR_stat)
	ret = my_syscall2(__NR_stat, path, &stat);
#else
#error Neither __NR_newfstatat nor __NR_stat defined, cannot implement sys_stat()
#endif
	buf->st_dev     = stat.st_dev;
	buf->st_ino     = stat.st_ino;
	buf->st_mode    = stat.st_mode;
	buf->st_nlink   = stat.st_nlink;
	buf->st_uid     = stat.st_uid;
	buf->st_gid     = stat.st_gid;
	buf->st_rdev    = stat.st_rdev;
	buf->st_size    = stat.st_size;
	buf->st_blksize = stat.st_blksize;
	buf->st_blocks  = stat.st_blocks;
	buf->st_atime   = stat.st_atime;
	buf->st_mtime   = stat.st_mtime;
	buf->st_ctime   = stat.st_ctime;
	return ret;
}


static __attribute__((unused))
int sys_symlink(const char *old, const char *new)
{
#ifdef __NR_symlinkat
	return my_syscall3(__NR_symlinkat, old, AT_FDCWD, new);
#elif defined(__NR_symlink)
	return my_syscall2(__NR_symlink, old, new);
#else
#error Neither __NR_symlinkat nor __NR_symlink defined, cannot implement sys_symlink()
#endif
}

static __attribute__((unused))
mode_t sys_umask(mode_t mode)
{
	return my_syscall1(__NR_umask, mode);
}

static __attribute__((unused))
int sys_umount2(const char *path, int flags)
{
	return my_syscall2(__NR_umount2, path, flags);
}

static __attribute__((unused))
int sys_unlink(const char *path)
{
#ifdef __NR_unlinkat
	return my_syscall3(__NR_unlinkat, AT_FDCWD, path, 0);
#elif defined(__NR_unlink)
	return my_syscall1(__NR_unlink, path);
#else
#error Neither __NR_unlinkat nor __NR_unlink defined, cannot implement sys_unlink()
#endif
}

static __attribute__((unused))
pid_t sys_wait4(pid_t pid, int *status, int options, struct rusage *rusage)
{
	return my_syscall4(__NR_wait4, pid, status, options, rusage);
}

static __attribute__((unused))
pid_t sys_waitpid(pid_t pid, int *status, int options)
{
	return sys_wait4(pid, status, options, 0);
}

static __attribute__((unused))
pid_t sys_wait(int *status)
{
	return sys_waitpid(-1, status, 0);
}

static __attribute__((unused))
ssize_t sys_write(int fd, const void *buf, size_t count)
{
	return my_syscall3(__NR_write, fd, buf, count);
}


/* Below are the libc-compatible syscalls which return x or -1 and set errno.
 * They rely on the functions above. Similarly they're marked static so that it
 * is possible to assign pointers to them if needed.
 */

static __attribute__((unused))
int brk(void *addr)
{
	void *ret = sys_brk(addr);

	if (!ret) {
		SET_ERRNO(ENOMEM);
		return -1;
	}
	return 0;
}

static __attribute__((noreturn,unused))
void exit(int status)
{
	sys_exit(status);
}

static __attribute__((unused))
int chdir(const char *path)
{
	int ret = sys_chdir(path);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int chmod(const char *path, mode_t mode)
{
	int ret = sys_chmod(path, mode);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int chown(const char *path, uid_t owner, gid_t group)
{
	int ret = sys_chown(path, owner, group);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int chroot(const char *path)
{
	int ret = sys_chroot(path);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int close(int fd)
{
	int ret = sys_close(fd);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int dup(int fd)
{
	int ret = sys_dup(fd);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int dup2(int old, int new)
{
	int ret = sys_dup2(old, new);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

#ifdef __NR_dup3
static __attribute__((unused))
int dup3(int old, int new, int flags)
{
	int ret = sys_dup3(old, new, flags);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}
#endif

static __attribute__((unused))
int execve(const char *filename, char *const argv[], char *const envp[])
{
	int ret = sys_execve(filename, argv, envp);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
pid_t fork(void)
{
	pid_t ret = sys_fork();

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int fsync(int fd)
{
	int ret = sys_fsync(fd);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int getdents64(int fd, struct linux_dirent64 *dirp, int count)
{
	int ret = sys_getdents64(fd, dirp, count);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
pid_t getpgid(pid_t pid)
{
	pid_t ret = sys_getpgid(pid);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
pid_t getpgrp(void)
{
	pid_t ret = sys_getpgrp();

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
pid_t getpid(void)
{
	pid_t ret = sys_getpid();

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int gettimeofday(struct timeval *tv, struct timezone *tz)
{
	int ret = sys_gettimeofday(tv, tz);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int ioctl(int fd, unsigned long req, void *value)
{
	int ret = sys_ioctl(fd, req, value);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int kill(pid_t pid, int signal)
{
	int ret = sys_kill(pid, signal);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int link(const char *old, const char *new)
{
	int ret = sys_link(old, new);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
off_t lseek(int fd, off_t offset, int whence)
{
	off_t ret = sys_lseek(fd, offset, whence);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int mkdir(const char *path, mode_t mode)
{
	int ret = sys_mkdir(path, mode);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int mknod(const char *path, mode_t mode, dev_t dev)
{
	int ret = sys_mknod(path, mode, dev);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int mount(const char *src, const char *tgt,
	  const char *fst, unsigned long flags,
	  const void *data)
{
	int ret = sys_mount(src, tgt, fst, flags, data);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int open(const char *path, int flags, mode_t mode)
{
	int ret = sys_open(path, flags, mode);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int pivot_root(const char *new, const char *old)
{
	int ret = sys_pivot_root(new, old);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int poll(struct pollfd *fds, int nfds, int timeout)
{
	int ret = sys_poll(fds, nfds, timeout);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
ssize_t read(int fd, void *buf, size_t count)
{
	ssize_t ret = sys_read(fd, buf, count);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int reboot(int cmd)
{
	int ret = sys_reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, cmd, 0);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
void *sbrk(intptr_t inc)
{
	void *ret;

	/* first call to find current end */
	if ((ret = sys_brk(0)) && (sys_brk(ret + inc) == ret + inc))
		return ret + inc;

	SET_ERRNO(ENOMEM);
	return (void *)-1;
}

static __attribute__((unused))
int sched_yield(void)
{
	int ret = sys_sched_yield();

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeval *timeout)
{
	int ret = sys_select(nfds, rfds, wfds, efds, timeout);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int setpgid(pid_t pid, pid_t pgid)
{
	int ret = sys_setpgid(pid, pgid);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
pid_t setsid(void)
{
	pid_t ret = sys_setsid();

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
unsigned int sleep(unsigned int seconds)
{
	struct timeval my_timeval = { seconds, 0 };

	if (sys_select(0, 0, 0, 0, &my_timeval) < 0)
		return my_timeval.tv_sec + !!my_timeval.tv_usec;
	else
		return 0;
}

static __attribute__((unused))
int msleep(unsigned int msecs)
{
	struct timeval my_timeval = { msecs / 1000, (msecs % 1000) * 1000 };

	if (sys_select(0, 0, 0, 0, &my_timeval) < 0)
		return (my_timeval.tv_sec * 1000) +
			(my_timeval.tv_usec / 1000) +
			!!(my_timeval.tv_usec % 1000);
	else
		return 0;
}

static __attribute__((unused))
int stat(const char *path, struct stat *buf)
{
	int ret = sys_stat(path, buf);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int symlink(const char *old, const char *new)
{
	int ret = sys_symlink(old, new);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int tcsetpgrp(int fd, pid_t pid)
{
	return ioctl(fd, TIOCSPGRP, &pid);
}

static __attribute__((unused))
mode_t umask(mode_t mode)
{
	return sys_umask(mode);
}

static __attribute__((unused))
int umount2(const char *path, int flags)
{
	int ret = sys_umount2(path, flags);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
int unlink(const char *path)
{
	int ret = sys_unlink(path);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
pid_t wait4(pid_t pid, int *status, int options, struct rusage *rusage)
{
	pid_t ret = sys_wait4(pid, status, options, rusage);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
pid_t waitpid(pid_t pid, int *status, int options)
{
	pid_t ret = sys_waitpid(pid, status, options);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
pid_t wait(int *status)
{
	pid_t ret = sys_wait(status);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

static __attribute__((unused))
ssize_t write(int fd, const void *buf, size_t count)
{
	ssize_t ret = sys_write(fd, buf, count);

	if (ret < 0) {
		SET_ERRNO(-ret);
		ret = -1;
	}
	return ret;
}

/* some size-optimized reimplementations of a few common str* and mem*
 * functions. They're marked static, except memcpy() and raise() which are used
 * by libgcc on ARM, so they are marked weak instead in order not to cause an
 * error when building a program made of multiple files (not recommended).
 */

static __attribute__((unused))
void *memmove(void *dst, const void *src, size_t len)
{
	ssize_t pos = (dst <= src) ? -1 : (long)len;
	void *ret = dst;

	while (len--) {
		pos += (dst <= src) ? 1 : -1;
		((char *)dst)[pos] = ((char *)src)[pos];
	}
	return ret;
}

static __attribute__((unused))
void *memset(void *dst, int b, size_t len)
{
	char *p = dst;

	while (len--)
		*(p++) = b;
	return dst;
}

static __attribute__((unused))
int memcmp(const void *s1, const void *s2, size_t n)
{
	size_t ofs = 0;
	int c1 = 0;

	while (ofs < n && !(c1 = ((unsigned char *)s1)[ofs] - ((unsigned char *)s2)[ofs])) {
		ofs++;
	}
	return c1;
}

static __attribute__((unused))
char *strcpy(char *dst, const char *src)
{
	char *ret = dst;

	while ((*dst++ = *src++));
	return ret;
}

static __attribute__((unused))
char *strchr(const char *s, int c)
{
	while (*s) {
		if (*s == (char)c)
			return (char *)s;
		s++;
	}
	return NULL;
}

static __attribute__((unused))
char *strrchr(const char *s, int c)
{
	const char *ret = NULL;

	while (*s) {
		if (*s == (char)c)
			ret = s;
		s++;
	}
	return (char *)ret;
}

static __attribute__((unused))
size_t nolibc_strlen(const char *str)
{
	size_t len;

	for (len = 0; str[len]; len++);
	return len;
}

#define strlen(str) ({                          \
	__builtin_constant_p((str)) ?           \
		__builtin_strlen((str)) :       \
		nolibc_strlen((str));           \
})

static __attribute__((unused))
int isdigit(int c)
{
	return (unsigned int)(c - '0') <= 9;
}

static __attribute__((unused))
long atol(const char *s)
{
	unsigned long ret = 0;
	unsigned long d;
	int neg = 0;

	if (*s == '-') {
		neg = 1;
		s++;
	}

	while (1) {
		d = (*s++) - '0';
		if (d > 9)
			break;
		ret *= 10;
		ret += d;
	}

	return neg ? -ret : ret;
}

static __attribute__((unused))
int atoi(const char *s)
{
	return atol(s);
}

static __attribute__((unused))
const char *ltoa(long in)
{
	/* large enough for -9223372036854775808 */
	static char buffer[21];
	char       *pos = buffer + sizeof(buffer) - 1;
	int         neg = in < 0;
	unsigned long n = neg ? -in : in;

	*pos-- = '\0';
	do {
		*pos-- = '0' + n % 10;
		n /= 10;
		if (pos < buffer)
			return pos + 1;
	} while (n);

	if (neg)
		*pos-- = '-';
	return pos + 1;
}

__attribute__((weak,unused))
void *memcpy(void *dst, const void *src, size_t len)
{
	return memmove(dst, src, len);
}

/* needed by libgcc for divide by zero */
__attribute__((weak,unused))
int raise(int signal)
{
	return kill(getpid(), signal);
}

/* Here come a few helper functions */

static __attribute__((unused))
void FD_ZERO(fd_set *set)
{
	memset(set, 0, sizeof(*set));
}

static __attribute__((unused))
void FD_SET(int fd, fd_set *set)
{
	if (fd < 0 || fd >= FD_SETSIZE)
		return;
	set->fd32[fd / 32] |= 1 << (fd & 31);
}

/* WARNING, it only deals with the 4096 first majors and 256 first minors */
static __attribute__((unused))
dev_t makedev(unsigned int major, unsigned int minor)
{
	return ((major & 0xfff) << 8) | (minor & 0xff);
}