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//========================================================================

// syscalls.c : Newlib operating system interface                       

//========================================================================

// This is the maven implementation of the narrow newlib operating

// system interface. It is based on the minimum stubs in the newlib

// documentation, the error stubs in libnosys, and the previous scale

// implementation. Please do not include any additional system calls or

// other functions in this file. Additional header and source files

// should be in the machine subdirectory.

//

// Here is a list of the functions which make up the operating system

// interface. The file management instructions execute syscall assembly

// instructions so that a proxy kernel (or the simulator) can marshal up

// the request to the host machine. The process management functions are

// mainly just stubs since for now maven only supports a single process.

//

//  - File management functions

//     + open   : (v) open file

//     + lseek  : (v) set position in file

//     + read   : (v) read from file

//     + write  : (v) write to file

//     + fstat  : (z) status of an open file

//     + stat   : (z) status of a file by name

//     + close  : (z) close a file

//     + link   : (z) rename a file

//     + unlink : (z) remote file's directory entry

//

//  - Process management functions

//     + execve : (z) transfer control to new proc

//     + fork   : (z) create a new process 

//     + getpid : (v) get process id 

//     + kill   : (z) send signal to child process

//     + wait   : (z) wait for a child process

//     

//  - Misc functions

//     + isatty : (v) query whether output stream is a terminal

//     + times  : (z) timing information for current process

//     + sbrk   : (v) increase program data space

//     + _exit  : (-) exit program without cleaning up files

//

// There are two types of system calls. Those which return a value when

// everything is okay (marked with (v) in above list) and those which

// return a zero when everything is okay (marked with (z) in above

// list). On an error (ie. when the error flag is 1) the return value is

// always an errno which should correspond to the numbers in

// newlib/libc/include/sys/errno.h 

//

// Note that really I think we are supposed to define versions of these

// functions with an underscore prefix (eg. _open). This is what some of

// the newlib documentation says, and all the newlib code calls the

// underscore version. This is because technically I don't think we are

// supposed to pollute the namespace with these function names. If you

// define MISSING_SYSCALL_NAMES in xcc/src/newlib/configure.host

// then xcc/src/newlib/libc/include/_syslist.h will essentially define

// all of the underscore versions to be equal to the non-underscore

// versions. I tried not defining MISSING_SYSCALL_NAMES, and newlib

// compiled fine but libstdc++ complained about not being able to fine

// write, read, etc. So for now we do not use underscores (and we do

// define MISSING_SYSCALL_NAMES).

//

// See the newlib documentation for more information 

// http://sourceware.org/newlib/libc.html#Syscalls

#include <machine/syscall.h>

#include <sys/stat.h>

#include <sys/times.h>

#include <sys/time.h>

#include <sys/timeb.h>

#include <errno.h>

#include <string.h>

#include <unistd.h>

#include <utime.h>

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

// environment                                                          

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

// A pointer to a list of environment variables and their values. For a

// minimal environment, this empty list is adequate. We used to define

// environ here but it is already defined in

// xcc/src/newlib/libc/stdlib/environ.c so to avoid multiple definition

// errors we have commented this out for now.

//

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

// char** environ = __env;

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

// open                                                                 

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

// Open a file.

#define syscall_errno(n, a, b, c, d) \

        __internal_syscall(n, (long)(a), (long)(b), (long)(c), (long)(d))

long __syscall_error(long a0)

{

  errno = -a0;

  return -1;

}

int open(const char* name, int flags, int mode)

{

  return syscall_errno(SYS_open, name, flags, mode, 0);

}

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

// openat                                                                

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

// Open file relative to given directory

int openat(int dirfd, const char* name, int flags, int mode)

{

  return syscall_errno(SYS_openat, dirfd, name, flags, mode);

}

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

// lseek                                                                

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

// Set position in a file.

off_t lseek(int file, off_t ptr, int dir)

{

  return syscall_errno(SYS_lseek, file, ptr, dir, 0);

}

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

// read                                                                 

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

// Read from a file.

ssize_t read(int file, void* ptr, size_t len)

{

  return syscall_errno(SYS_read, file, ptr, len, 0);

}

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

// write                                                                

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

// Write to a file.

ssize_t write(int file, const void* ptr, size_t len)

{

  return syscall_errno(SYS_write, file, ptr, len, 0);

}

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

// fstat                                                                

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

// Status of an open file. The sys/stat.h header file required is

// distributed in the include subdirectory for this C library.

int fstat(int file, struct stat* st)

{

  return syscall_errno(SYS_fstat, file, st, 0, 0);

}

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

// stat                                                                 

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

// Status of a file (by name).

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

{

  return syscall_errno(SYS_stat, file, st, 0, 0);

}

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

// lstat                                                                 

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

// Status of a link (by name).

int lstat(const char* file, struct stat* st)

{

  return syscall_errno(SYS_lstat, file, st, 0, 0);

}

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

// fstatat                                                                 

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

// Status of a file (by name) in a given directory.

int fstatat(int dirfd, const char* file, struct stat* st, int flags)

{

  return syscall_errno(SYS_fstatat, dirfd, file, st, flags);

}

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

// access                                                                 

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

// Permissions of a file (by name).

int access(const char* file, int mode)

{

  return syscall_errno(SYS_access, file, mode, 0, 0);

}

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

// faccessat                                                                 

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

// Permissions of a file (by name) in a given directory.

int faccessat(int dirfd, const char* file, int mode, int flags)

{

  return syscall_errno(SYS_faccessat, dirfd, file, mode, flags);

}

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

// close                                                                

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

// Close a file.

int close(int file)

{

  return syscall_errno(SYS_close, file, 0, 0, 0);

}

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

// link                                                                 

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

// Establish a new name for an existing file.

int link(const char* old_name, const char* new_name)

{

  return syscall_errno(SYS_link, old_name, new_name, 0, 0);

}

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

// unlink                                                               

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

// Remove a file's directory entry.

int unlink(const char* name)

{

  return syscall_errno(SYS_unlink, name, 0, 0, 0);

}

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

// execve                                                               

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

// Transfer control to a new process. Minimal implementation for a

// system without processes from newlib documentation.

int execve(const char* name, char* const argv[], char* const env[])

{

  errno = ENOMEM;

  return -1;

}

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

// fork                                                                 

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

// Create a new process. Minimal implementation for a system without

// processes from newlib documentation.

int fork()

{

  errno = EAGAIN;

  return -1;

}

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

// getpid                                                               

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

// Get process id. This is sometimes used to generate strings unlikely

// to conflict with other processes. Minimal implementation for a

// system without processes just returns 1.

int getpid()

{

  return 1;

}

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

// kill                                                                 

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

// Send a signal. Minimal implementation for a system without processes

// just causes an error.

int kill(int pid, int sig)

{

  errno = EINVAL;

  return -1;

}

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

// wait                                                                 

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

// Wait for a child process. Minimal implementation for a system without

// processes just causes an error.

int wait(int* status)

{

  errno = ECHILD;

  return -1;

}

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

// isatty                                                               

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

// Query whether output stream is a terminal. For consistency with the

// other minimal implementations, which only support output to stdout,

// this minimal implementation is suggested by the newlib docs.

int isatty(int file)

{

  struct stat s;

  int ret = fstat(file,&s);

  return ret == -1 ? -1 : !!(s.st_mode & S_IFCHR);

}

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

// times                                                                

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

// Timing information for current process. From

// newlib/libc/include/sys/times.h the tms struct fields are as follows:

//

//  - clock_t tms_utime  : user clock ticks

//  - clock_t tms_stime  : system clock ticks

//  - clock_t tms_cutime : children's user clock ticks

//  - clock_t tms_cstime : children's system clock ticks

//

// Since maven does not currently support processes we set both of the

// children's times to zero. Eventually we might want to separately

// account for user vs system time, but for now we just return the total

// number of cycles since starting the program.

clock_t times(struct tms* buf)

{

  // when called for the first time, initialize t0

  static struct timeval t0;

  if(t0.tv_sec == 0)

    gettimeofday(&t0,0);

  struct timeval t;

  gettimeofday(&t,0);

  long long utime = (t.tv_sec-t0.tv_sec)*1000000 + (t.tv_usec-t0.tv_usec);

  buf->tms_utime = utime*CLOCKS_PER_SEC/1000000;

  buf->tms_stime = buf->tms_cstime = buf->tms_cutime = 0;

  return -1;

}

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

// gettimeofday                                                                 

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

// Get the current time.  Only relatively correct.

int gettimeofday(struct timeval* tp, void* tzp)

{

  return syscall_errno(SYS_gettimeofday, tp, 0, 0, 0);

}

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

// ftime                                                                 

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

// Get the current time.  Only relatively correct.

int ftime(struct timeb* tp)

{

  tp->time = tp->millitm = 0;

  return 0;

}

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

// utime

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

// Stub.

int utime(const char* path, const struct utimbuf* times)

{

  return -1;

}

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

// chown

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

// Stub.

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

{

  return -1;

}

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

// chmod

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

// Stub.

int chmod(const char* path, mode_t mode)

{

  return -1;

}

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

// chdir

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

// Stub.

int chdir(const char* path)

{

  return -1;

}

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

// getcwd

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

// Stub.

char* getcwd(char* buf, size_t size)

{

  return NULL;

}

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

// sysconf

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

// Get configurable system variables

long sysconf(int name)

{

  switch(name)

  {

    case _SC_CLK_TCK:

      return CLOCKS_PER_SEC;

  }

  return -1;

}

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

// sbrk                                                                 

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

// Increase program data space. As malloc and related functions depend

// on this, it is useful to have a working implementation. The following

// is suggested by the newlib docs and suffices for a standalone

// system.

void* sbrk(ptrdiff_t incr)

{

  extern unsigned char _end[]; // Defined by linker

  static unsigned long heap_end;

  if (heap_end == 0)

    heap_end = (long)_end;

  if (syscall_errno(SYS_brk, heap_end + incr, 0, 0, 0) != heap_end + incr)

    return (void*)-1;

  heap_end += incr;

  return heap_end - incr;

}

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

// _exit                                                                

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

// Exit a program without cleaning up files.

void _exit(int exit_status)

{

  syscall_errno(SYS_exit, exit_status, 0, 0, 0);

  while (1);

}