engine_control/source/system/stm32f4xx/_syscalls.c

//
// This file is part of the µOS++ III distribution.
// Parts of this file are from the newlib sources, issued under GPL.
// Copyright (c) 2014 Liviu Ionescu
//

// ----------------------------------------------------------------------------

int errno;
void *__dso_handle __attribute__ ((weak));

// ----------------------------------------------------------------------------

#if !defined(OS_USE_SEMIHOSTING)

#include <_ansi.h>
#include <_syslist.h>
#include <errno.h>
//#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/times.h>
#include <limits.h>
#include <signal.h>

void
__initialize_args(int* p_argc, char*** p_argv);

// This is the standard default implementation for the routine to
// process args. It returns a single empty arg.
// For semihosting applications, this is redefined to get the real
// args from the debugger. You can also use it if you decide to keep
// some args in a non-volatile memory.

void __attribute__((weak))
__initialize_args(int* p_argc, char*** p_argv)
{
  // By the time we reach this, the data and bss should have been initialised.

  // The strings pointed to by the argv array shall be modifiable by the
  // program, and retain their last-stored values between program startup
  // and program termination. (static, no const)
  static char name[] = "";

  // The string pointed to by argv[0] represents the program name;
  // argv[0][0] shall be the null character if the program name is not
  // available from the host environment. argv[argc] shall be a null pointer.
  // (static, no const)
  static char* argv[2] =
    { name, NULL };

  *p_argc = 1;
  *p_argv = &argv[0];
  return;
}

// These functions are defined here to avoid linker errors in freestanding
// applications. They might be called in some error cases from library
// code.
//
// If you detect other functions to be needed, just let us know
// and we'll add them.

int
raise(int sig __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int
kill(pid_t pid, int sig);

int
kill(pid_t pid __attribute__((unused)), int sig __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

#endif // !defined(OS_USE_SEMIHOSTING)

// ----------------------------------------------------------------------------

// If you need the empty definitions, remove the -ffreestanding option.

#if __STDC_HOSTED__ == 1

char* __env[1] =
  { 0 };
char** environ = __env;

#if !defined(OS_USE_SEMIHOSTING)

// Forward declarations

int
_chown(const char* path, uid_t owner, gid_t group);

int
_close(int fildes);

int
_execve(char* name, char** argv, char** env);

int
_fork(void);

int
_fstat(int fildes, struct stat* st);

int
_getpid(void);

int
_gettimeofday(struct timeval* ptimeval, void* ptimezone);

int
_isatty(int file);

int
_kill(int pid, int sig);

int
_link(char* existing, char* _new);

int
_lseek(int file, int ptr, int dir);

int
_open(char* file, int flags, int mode);

int
_read(int file, char* ptr, int len);

int
_readlink(const char* path, char* buf, size_t bufsize);

int
_stat(const char* file, struct stat* st);

int
_symlink(const char* path1, const char* path2);

clock_t
_times(struct tms* buf);

int
_unlink(char* name);

int
_wait(int* status);

int
_write(int file, char* ptr, int len);

// Definitions

int __attribute__((weak))
_chown(const char* path __attribute__((unused)),
    uid_t owner __attribute__((unused)), gid_t group __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_close(int fildes __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_execve(char* name __attribute__((unused)), char** argv __attribute__((unused)),
    char** env __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_fork(void)
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_fstat(int fildes __attribute__((unused)),
    struct stat* st __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_getpid(void)
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_gettimeofday(struct timeval* ptimeval __attribute__((unused)),
    void* ptimezone __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_isatty(int file __attribute__((unused)))
{
  errno = ENOSYS;
  return 0;
}

int __attribute__((weak))
_kill(int pid __attribute__((unused)), int sig __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_link(char* existing __attribute__((unused)),
    char* _new __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_lseek(int file __attribute__((unused)), int ptr __attribute__((unused)),
    int dir __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_open(char* file __attribute__((unused)), int flags __attribute__((unused)),
    int mode __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_read(int file __attribute__((unused)), char* ptr __attribute__((unused)),
    int len __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_readlink(const char* path __attribute__((unused)),
    char* buf __attribute__((unused)), size_t bufsize __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_stat(const char* file __attribute__((unused)),
    struct stat* st __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_symlink(const char* path1 __attribute__((unused)),
    const char* path2 __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

clock_t __attribute__((weak))
_times(struct tms* buf __attribute__((unused)))
{
  errno = ENOSYS;
  return ((clock_t) -1);
}

int __attribute__((weak))
_unlink(char* name __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_wait(int* status __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

int __attribute__((weak))
_write(int file __attribute__((unused)), char* ptr __attribute__((unused)),
    int len __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

// ----------------------------------------------------------------------------

#else // defined(OS_USE_SEMIHOSTING)

// ----------------------------------------------------------------------------

/* Support files for GNU libc.  Files in the system namespace go here.
 Files in the C namespace (ie those that do not start with an
 underscore) go in .c.  */

#include <_ansi.h>
#include <stdint.h>
//#include <sys/types.h>
#include <sys/stat.h>
#include <sys/fcntl.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <sys/time.h>
#include <sys/times.h>
#include <errno.h>
#include <reent.h>
#include <unistd.h>
#include <sys/wait.h>
#include <ctype.h>
#include <signal.h>

#include "arm/semihosting.h"

int
_kill (int pid, int sig);

void
__attribute__((noreturn))
_exit (int status);

// Forward declarations.
int
_system (const char*);
int
_rename (const char*, const char*);
int
_isatty (int);
clock_t
_times (struct tms*);
int
_gettimeofday (struct timeval *, void*);
int
_unlink (const char*);
int
_link (void);

int
_stat (const char*, struct stat*);

int
_fstat (int, struct stat*);
int
_swistat (int fd, struct stat* st);
int
_getpid (int);
int
_close (int);
clock_t
_clock (void);
int
_swiclose (int);
int
_open (const char*, int, ...);
int
_swiopen (const char*, int);
int
_write (int, char*, int);
int
_swiwrite (int, char*, int);
int
_lseek (int, int, int);
int
_swilseek (int, int, int);
int
_read (int, char*, int);
int
_swiread (int, char*, int);

void
initialise_monitor_handles (void);

void
__initialize_args (int* p_argc, char*** p_argv);

static int
checkerror (int);
static int
error (int);
static int
get_errno (void);

// ----------------------------------------------------------------------------

#define ARGS_BUF_ARRAY_SIZE 80
#define ARGV_BUF_ARRAY_SIZE 10

typedef struct
{
  char* pCommandLine;
  int size;
} CommandLineBlock;

void
__initialize_args (int* p_argc, char*** p_argv)
{

  // Array of chars to receive the command line from the host
  static char args_buf[ARGS_BUF_ARRAY_SIZE];

  // Array of pointers to store the final argv pointers (pointing
  // in the above array).
  static char* argv_buf[ARGV_BUF_ARRAY_SIZE];

  int argc = 0;
  int isInArgument = 0;

  CommandLineBlock cmdBlock;
  cmdBlock.pCommandLine = args_buf;
  cmdBlock.size = sizeof(args_buf) - 1;

  int ret = call_host (SEMIHOSTING_SYS_GET_CMDLINE, &cmdBlock);
  if (ret == 0)
    {

      // In case the host send more than we can chew, limit the
      // string to our buffer.
      args_buf[ARGS_BUF_ARRAY_SIZE - 1] = '\0';

      // The command line is a null terminated string
      char* p = cmdBlock.pCommandLine;

      int delim = '\0';
      int ch;

      while ((ch = *p) != '\0')
	{
	  if (isInArgument == 0)
	    {
	      if (!isblank(ch))
		{
		  if (argc
		      >= (int) ((sizeof(argv_buf) / sizeof(argv_buf[0])) - 1))
		    break;

		  if (ch == '"' || ch == '\'')
		    {
		      // Remember the delimiter to search for the
		      // corresponding terminator
		      delim = ch;
		      ++p;                        // skip the delimiter
		      ch = *p;
		    }
		  // Remember the arg beginning address
		  argv_buf[argc++] = p;
		  isInArgument = 1;
		}
	    }
	  else if (delim != '\0')
	    {
	      if ((ch == delim))
		{
		  delim = '\0';
		  *p = '\0';
		  isInArgument = 0;
		}
	    }
	  else if (isblank(ch))
	    {
	      delim = '\0';
	      *p = '\0';
	      isInArgument = 0;
	    }
	  ++p;
	}
    }

  if (argc == 0)
    {
      // No args found in string, return a single empty name.
      args_buf[0] = '\0';
      argv_buf[0] = &args_buf[0];
      ++argc;
    }

  // Must end the array with a null pointer.
  argv_buf[argc] = NULL;

  *p_argc = argc;
  *p_argv = &argv_buf[0];

  // temporary here
  initialise_monitor_handles ();

  return;
}

// ----------------------------------------------------------------------------

void
_exit (int status)
{
  /* There is only one SWI for both _exit and _kill. For _exit, call
   the SWI with the second argument set to -1, an invalid value for
   signum, so that the SWI handler can distinguish the two calls.
   Note: The RDI implementation of _kill throws away both its
   arguments.  */
  report_exception (
      status == 0 ? ADP_Stopped_ApplicationExit : ADP_Stopped_RunTimeError);
}

// ----------------------------------------------------------------------------

int __attribute__((weak))
_kill (int pid __attribute__((unused)), int sig __attribute__((unused)))
{
  errno = ENOSYS;
  return -1;
}

// ----------------------------------------------------------------------------

/* Struct used to keep track of the file position, just so we
 can implement fseek(fh,x,SEEK_CUR).  */
struct fdent
{
  int handle;
  int pos;
};

#define MAX_OPEN_FILES 20

/* User file descriptors (fd) are integer indexes into
 the openfiles[] array. Error checking is done by using
 findslot().

 This openfiles array is manipulated directly by only
 these 5 functions:

 findslot() - Translate entry.
 newslot() - Find empty entry.
 initilise_monitor_handles() - Initialize entries.
 _swiopen() - Initialize entry.
 _close() - Handle stdout == stderr case.

 Every other function must use findslot().  */

static struct fdent openfiles[MAX_OPEN_FILES];

static struct fdent*
findslot (int);
static int
newslot (void);

/* Register name faking - works in collusion with the linker.  */
register char* stack_ptr asm ("sp");

/* following is copied from libc/stdio/local.h to check std streams */
extern void _EXFUN(__sinit,(struct _reent*));
#define CHECK_INIT(ptr) \
  do                                            \
    {                                           \
      if ((ptr) && !(ptr)->__sdidinit)          \
        __sinit (ptr);                          \
    }                                           \
  while (0)

static int monitor_stdin;
static int monitor_stdout;
static int monitor_stderr;

/* Return a pointer to the structure associated with
 the user file descriptor fd. */
static struct fdent*
findslot (int fd)
{
  CHECK_INIT(_REENT);

  /* User file descriptor is out of range. */
  if ((unsigned int) fd >= MAX_OPEN_FILES)
    {
      return NULL;
    }

  /* User file descriptor is open? */
  if (openfiles[fd].handle == -1)
    {
      return NULL;
    }

  /* Valid. */
  return &openfiles[fd];
}

/* Return the next lowest numbered free file
 structure, or -1 if we can't find one. */
static int
newslot (void)
{
  int i;

  for (i = 0; i < MAX_OPEN_FILES; i++)
    {
      if (openfiles[i].handle == -1)
        {
          break;
        }
    }

  if (i == MAX_OPEN_FILES)
    {
      return -1;
    }

  return i;
}

void
initialise_monitor_handles (void)
{
  int i;

  /* Open the standard file descriptors by opening the special
   * teletype device, ":tt", read-only to obtain a descriptor for
   * standard input and write-only to obtain a descriptor for standard
   * output. Finally, open ":tt" in append mode to obtain a descriptor
   * for standard error. Since this is a write mode, most kernels will
   * probably return the same value as for standard output, but the
   * kernel can differentiate the two using the mode flag and return a
   * different descriptor for standard error.
   */

  int volatile block[3];

  block[0] = (int) ":tt";
  block[2] = 3; /* length of filename */
  block[1] = 0; /* mode "r" */
  monitor_stdin = call_host (SEMIHOSTING_SYS_OPEN, (void*) block);

  block[0] = (int) ":tt";
  block[2] = 3; /* length of filename */
  block[1] = 4; /* mode "w" */
  monitor_stdout = call_host (SEMIHOSTING_SYS_OPEN, (void*) block);

  block[0] = (int) ":tt";
  block[2] = 3; /* length of filename */
  block[1] = 8; /* mode "a" */
  monitor_stderr = call_host (SEMIHOSTING_SYS_OPEN, (void*) block);

  /* If we failed to open stderr, redirect to stdout. */
  if (monitor_stderr == -1)
    {
      monitor_stderr = monitor_stdout;
    }

  for (i = 0; i < MAX_OPEN_FILES; i++)
    {
      openfiles[i].handle = -1;
    }

  openfiles[0].handle = monitor_stdin;
  openfiles[0].pos = 0;
  openfiles[1].handle = monitor_stdout;
  openfiles[1].pos = 0;
  openfiles[2].handle = monitor_stderr;
  openfiles[2].pos = 0;
}

static int
get_errno (void)
{
  return call_host (SEMIHOSTING_SYS_ERRNO, NULL);
}

/* Set errno and return result. */
static int
error (int result)
{
  errno = get_errno ();
  return result;
}

/* Check the return and set errno appropriately. */
static int
checkerror (int result)
{
  if (result == -1)
    {
      return error (-1);
    }

  return result;
}

/* fh, is a valid internal file handle.
 ptr, is a null terminated string.
 len, is the length in bytes to read.
 Returns the number of bytes *not* written. */
int
_swiread (int fh, char* ptr, int len)
{
  int block[3];

  block[0] = fh;
  block[1] = (int) ptr;
  block[2] = len;

  return checkerror (call_host (SEMIHOSTING_SYS_READ, block));
}

/* fd, is a valid user file handle.
 Translates the return of _swiread into
 bytes read. */
int
_read (int fd, char* ptr, int len)
{
  int res;
  struct fdent *pfd;

  pfd = findslot (fd);
  if (pfd == NULL)
    {
      errno = EBADF;
      return -1;
    }

  res = _swiread (pfd->handle, ptr, len);

  if (res == -1)
    {
      return res;
    }

  pfd->pos += len - res;

  /* res == len is not an error,
   at least if we want feof() to work.  */
  return len - res;
}

/* fd, is a user file descriptor. */
int
_swilseek (int fd, int ptr, int dir)
{
  int res;
  struct fdent *pfd;

  /* Valid file descriptor? */
  pfd = findslot (fd);
  if (pfd == NULL)
    {
      errno = EBADF;
      return -1;
    }

  /* Valid whence? */
  if ((dir != SEEK_CUR) && (dir != SEEK_SET) && (dir != SEEK_END))
    {
      errno = EINVAL;
      return -1;
    }

  /* Convert SEEK_CUR to SEEK_SET */
  if (dir == SEEK_CUR)
    {
      ptr = pfd->pos + ptr;
      /* The resulting file offset would be negative. */
      if (ptr < 0)
        {
          errno = EINVAL;
          if ((pfd->pos > 0) && (ptr > 0))
            {
              errno = EOVERFLOW;
            }
          return -1;
        }
      dir = SEEK_SET;
    }

  int block[2];
  if (dir == SEEK_END)
    {
      block[0] = pfd->handle;
      res = checkerror (call_host (SEMIHOSTING_SYS_FLEN, block));
      if (res == -1)
        {
          return -1;
        }
      ptr += res;
    }

  /* This code only does absolute seeks.  */
  block[0] = pfd->handle;
  block[1] = ptr;
  res = checkerror (call_host (SEMIHOSTING_SYS_SEEK, block));

  /* At this point ptr is the current file position. */
  if (res >= 0)
    {
      pfd->pos = ptr;
      return ptr;
    }
  else
    {
      return -1;
    }
}

int
_lseek (int fd, int ptr, int dir)
{
  return _swilseek (fd, ptr, dir);
}

/* fh, is a valid internal file handle.
 Returns the number of bytes *not* written. */
int
_swiwrite (int fh, char* ptr, int len)
{
  int block[3];

  block[0] = fh;
  block[1] = (int) ptr;
  block[2] = len;

  return checkerror (call_host (SEMIHOSTING_SYS_WRITE, block));
}

/* fd, is a user file descriptor. */
int
_write (int fd, char* ptr, int len)
{
  int res;
  struct fdent *pfd;

  pfd = findslot (fd);
  if (pfd == NULL)
    {
      errno = EBADF;
      return -1;
    }

  res = _swiwrite (pfd->handle, ptr, len);

  /* Clearly an error. */
  if (res < 0)
    {
      return -1;
    }

  pfd->pos += len - res;

  /* We wrote 0 bytes?
   Retrieve errno just in case. */
  if ((len - res) == 0)
    {
      return error (0);
    }

  return (len - res);
}

int
_swiopen (const char* path, int flags)
{
  int aflags = 0, fh;
  uint32_t block[3];

  int fd = newslot ();

  if (fd == -1)
    {
      errno = EMFILE;
      return -1;
    }

  /* It is an error to open a file that already exists. */
  if ((flags & O_CREAT) && (flags & O_EXCL))
    {
      struct stat st;
      int res;
      res = _stat (path, &st);
      if (res != -1)
        {
          errno = EEXIST;
          return -1;
        }
    }

  /* The flags are Unix-style, so we need to convert them. */
#ifdef O_BINARY
  if (flags & O_BINARY)
    {
      aflags |= 1;
    }
#endif

  /* In O_RDONLY we expect aflags == 0. */

  if (flags & O_RDWR)
    {
      aflags |= 2;
    }

  if ((flags & O_CREAT) || (flags & O_TRUNC) || (flags & O_WRONLY))
    {
      aflags |= 4;
    }

  if (flags & O_APPEND)
    {
      /* Can't ask for w AND a; means just 'a'.  */
      aflags &= ~4;
      aflags |= 8;
    }

  block[0] = (uint32_t) path;
  block[2] = strlen (path);
  block[1] = (uint32_t) aflags;

  fh = call_host (SEMIHOSTING_SYS_OPEN, block);

  /* Return a user file descriptor or an error. */
  if (fh >= 0)
    {
      openfiles[fd].handle = fh;
      openfiles[fd].pos = 0;
      return fd;
    }
  else
    {
      return error (fh);
    }
}

int
_open (const char* path, int flags, ...)
{
  return _swiopen (path, flags);
}

/* fh, is a valid internal file handle. */
int
_swiclose (int fh)
{
  return checkerror (call_host (SEMIHOSTING_SYS_CLOSE, &fh));
}

/* fd, is a user file descriptor. */
int
_close (int fd)
{
  int res;
  struct fdent *pfd;

  pfd = findslot (fd);
  if (pfd == NULL)
    {
      errno = EBADF;
      return -1;
    }

  /* Handle stderr == stdout. */
  if ((fd == 1 || fd == 2) && (openfiles[1].handle == openfiles[2].handle))
    {
      pfd->handle = -1;
      return 0;
    }

  /* Attempt to close the handle. */
  res = _swiclose (pfd->handle);

  /* Reclaim handle? */
  if (res == 0)
    {
      pfd->handle = -1;
    }

  return res;
}

int __attribute__((weak))
_getpid (int n __attribute__ ((unused)))
{
  return 1;
}

int
_swistat (int fd, struct stat* st)
{
  struct fdent *pfd;
  int res;

  pfd = findslot (fd);
  if (pfd == NULL)
    {
      errno = EBADF;
      return -1;
    }

  /* Always assume a character device,
   with 1024 byte blocks. */
  st->st_mode |= S_IFCHR;
  st->st_blksize = 1024;
  res = checkerror (call_host (SEMIHOSTING_SYS_FLEN, &pfd->handle));
  if (res == -1)
    {
      return -1;
    }

  /* Return the file size. */
  st->st_size = res;
  return 0;
}

int __attribute__((weak))
_fstat (int fd, struct stat* st)
{
  memset (st, 0, sizeof(*st));
  return _swistat (fd, st);
}

int __attribute__((weak))
_stat (const char*fname, struct stat *st)
{
  int fd, res;
  memset (st, 0, sizeof(*st));
  /* The best we can do is try to open the file readonly.
   If it exists, then we can guess a few things about it. */
  if ((fd = _open (fname, O_RDONLY)) == -1)
    {
      return -1;
    }
  st->st_mode |= S_IFREG | S_IREAD;
  res = _swistat (fd, st);
  /* Not interested in the error. */
  _close (fd);
  return res;
}

int __attribute__((weak))
_link (void)
{
  errno = ENOSYS;
  return -1;
}

int
_unlink (const char* path)
{
  int res;
  uint32_t block[2];
  block[0] = (uint32_t) path;
  block[1] = strlen (path);
  res = call_host (SEMIHOSTING_SYS_REMOVE, block);

  if (res == -1)
    {
      return error (res);
    }
  return 0;
}

int
_gettimeofday (struct timeval* tp, void* tzvp)
{
  struct timezone* tzp = tzvp;
  if (tp)
    {
      /* Ask the host for the seconds since the Unix epoch.  */
      tp->tv_sec = call_host (SEMIHOSTING_SYS_TIME, NULL);
      tp->tv_usec = 0;
    }

  /* Return fixed data for the timezone.  */
  if (tzp)
    {
      tzp->tz_minuteswest = 0;
      tzp->tz_dsttime = 0;
    }

  return 0;
}

/* Return a clock that ticks at 100Hz.  */
clock_t
_clock (void)
{
  clock_t timeval;

  timeval = (clock_t) call_host (SEMIHOSTING_SYS_CLOCK, NULL);
  return timeval;
}

/* Return a clock that ticks at 100Hz.  */
clock_t
_times (struct tms* tp)
{
  clock_t timeval = _clock ();

  if (tp)
    {
      tp->tms_utime = timeval; /* user time */
      tp->tms_stime = 0; /* system time */
      tp->tms_cutime = 0; /* user time, children */
      tp->tms_cstime = 0; /* system time, children */
    }

  return timeval;
}

int
_isatty (int fd)
{
  struct fdent *pfd;
  int tty;

  pfd = findslot (fd);
  if (pfd == NULL)
    {
      errno = EBADF;
      return 0;
    }

  tty = call_host (SEMIHOSTING_SYS_ISTTY, &pfd->handle);

  if (tty == 1)
    {
      return 1;
    }

  errno = get_errno ();
  return 0;
}

int
_system (const char* s)
{
  uint32_t block[2];
  int e;

  /* Hmmm.  The ARM debug interface specification doesn't say whether
   SYS_SYSTEM does the right thing with a null argument, or assign any
   meaning to its return value.  Try to do something reasonable....  */
  if (!s)
    {
      return 1; /* maybe there is a shell available? we can hope. :-P */
    }
  block[0] = (uint32_t) s;
  block[1] = strlen (s);
  e = checkerror (call_host (SEMIHOSTING_SYS_SYSTEM, block));
  if ((e >= 0) && (e < 256))
    {
      /* We have to convert e, an exit status to the encoded status of
       the command.  To avoid hard coding the exit status, we simply
       loop until we find the right position.  */
      int exit_code;

      for (exit_code = e; e && WEXITSTATUS (e) != exit_code; e <<= 1)
        {
          continue;
        }
    }
  return e;
}

int
_rename (const char* oldpath, const char* newpath)
{
  uint32_t block[4];
  block[0] = (uint32_t) oldpath;
  block[1] = strlen (oldpath);
  block[2] = (uint32_t) newpath;
  block[3] = strlen (newpath);
  return checkerror (call_host (SEMIHOSTING_SYS_RENAME, block)) ? -1 : 0;
}

// ----------------------------------------------------------------------------
// Required by Google Tests

int
mkdir (const char *path __attribute__((unused)),
       mode_t mode __attribute__((unused)))
{
#if 0
  // always return true
  return 0;
#else
  errno = ENOSYS;
  return -1;
#endif
}

char *
getcwd (char *buf, size_t size)
{
  // no cwd available via semihosting, so we use the temporary folder
  strncpy (buf, "/tmp", size);
  return buf;
}

#endif // defined OS_USE_SEMIHOSTING

#endif // __STDC_HOSTED__ == 1