path: root/winsup/cygwin/cygtls.cc

/* cygtls.cc

   Copyright 2003, 2004, 2005, 2006 Red Hat, Inc.

This software is a copyrighted work licensed under the terms of the
Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
details. */

#include "winsup.h"
#include <sys/time.h>
#define USE_SYS_TYPES_FD_SET
#include <winsock.h>
#include "thread.h"
#include "cygtls.h"
#include "assert.h"
#include <syslog.h>
#include <signal.h>
#include <malloc.h>
#include "exceptions.h"
#include "sync.h"
#include "cygerrno.h"
#include "path.h"
#include "fhandler.h"
#include "dtable.h"
#include "cygheap.h"
#include "pinfo.h"
#include "sigproc.h"

class sentry
{
  static muto lock;
  int destroy;
public:
  void init ();
  bool acquired () {return lock.acquired ();}
  sentry () {destroy = 0;}
  sentry (DWORD wait) {destroy = lock.acquire (wait);}
  ~sentry () {if (destroy) lock.release ();}
  friend void _cygtls::init ();
};

muto NO_COPY sentry::lock;

static size_t NO_COPY nthreads;

#define THREADLIST_CHUNK 256

void
_cygtls::init ()
{
  if (cygheap->threadlist)
    memset (cygheap->threadlist, 0, cygheap->sthreads * sizeof (cygheap->threadlist[0]));
  else
    {
      cygheap->sthreads = THREADLIST_CHUNK;
      cygheap->threadlist = (_cygtls **) ccalloc (HEAP_TLS, cygheap->sthreads,
						     sizeof (cygheap->threadlist[0]));
    }
  sentry::lock.init ("sentry_lock");
}

/* Two calls to get the stack right... */
void
_cygtls::call (DWORD (*func) (void *, void *), void *arg)
{
  char buf[CYGTLS_PADSIZE];
  _my_tls.call2 (func, arg, buf);
}

void
_cygtls::call2 (DWORD (*func) (void *, void *), void *arg, void *buf)
{
  init_thread (buf, func);
  DWORD res = func (arg, buf);
  remove (INFINITE);
  /* Don't call ExitThread on the main thread since we may have been
     dynamically loaded.  */
  if ((void *) func != (void *) dll_crt0_1
      && (void *) func != (void *) dll_dllcrt0_1)
    ExitThread (res);
}

void
_cygtls::init_thread (void *x, DWORD (*func) (void *, void *))
{
  if (x)
    {
      memset (this, 0, sizeof (*this));
      stackptr = stack;
      if (_GLOBAL_REENT)
	{
	  local_clib._stdin = _GLOBAL_REENT->_stdin;
	  local_clib._stdout = _GLOBAL_REENT->_stdout;
	  local_clib._stderr = _GLOBAL_REENT->_stderr;
	  local_clib.__sdidinit = _GLOBAL_REENT->__sdidinit ? -1 : 0;
	  local_clib.__cleanup = _GLOBAL_REENT->__cleanup;
	  local_clib.__sglue._niobs = 3;
	  local_clib.__sglue._iobs = &_GLOBAL_REENT->__sf[0];
	}
      local_clib._current_locale = "C";
      locals.process_logmask = LOG_UPTO (LOG_DEBUG);
      /* Initialize this thread's ability to respond to things like
	 SIGSEGV or SIGFPE. */
      init_exception_handler (handle_exceptions);
    }

  thread_id = GetCurrentThreadId ();
  initialized = CYGTLS_INITIALIZED;
  locals.exitsock = INVALID_SOCKET;
  errno_addr = &(local_clib._errno);

  if ((void *) func == (void *) cygthread::stub
      || (void *) func == (void *) cygthread::simplestub)
    return;

  if (wincap.has_security ())
    cygheap->user.reimpersonate ();

  sentry here (INFINITE);
  if (nthreads >= cygheap->sthreads)
    {
      cygheap->threadlist = (_cygtls **)
	crealloc (cygheap->threadlist, (cygheap->sthreads += THREADLIST_CHUNK)
		 * sizeof (cygheap->threadlist[0]));
      memset (cygheap->threadlist + nthreads, 0, THREADLIST_CHUNK * sizeof (cygheap->threadlist[0]));
    }

  cygheap->threadlist[nthreads++] = this;
}

void
_cygtls::fixup_after_fork ()
{
  if (sig)
    {
      pop ();
      sig = 0;
    }
  stacklock = spinning = 0;
  locals.exitsock = INVALID_SOCKET;
  wq.thread_ev = NULL;
}

#define free_local(x) \
  if (locals.x) \
    { \
      free (locals.x); \
      locals.x = NULL; \
    }

void
_cygtls::remove (DWORD wait)
{
  initialized = 0;
  if (!locals.exitsock || exit_state >= ES_FINAL)
    return;

  debug_printf ("wait %p", wait);
  if (wait)
    {
      /* FIXME: Need some sort of atthreadexit function to allow things like
	 select to control this themselves. */
      if (locals.exitsock != INVALID_SOCKET)
	{
	  closesocket (locals.exitsock);
	  locals.exitsock = (SOCKET) NULL;
	}
      free_local (process_ident);
      free_local (ntoa_buf);
      free_local (protoent_buf);
      free_local (servent_buf);
      free_local (hostent_buf);
    }

  do
    {
      sentry here (wait);
      if (here.acquired ())
	{
	  for (size_t i = 0; i < nthreads; i++)
	    if (this == cygheap->threadlist[i])
	      {
		if (i < --nthreads)
		  cygheap->threadlist[i] = cygheap->threadlist[nthreads];
		debug_printf ("removed %p element %d", this, i);
		break;
	      }
	}
    } while (0);
  remove_wq (wait);
}

void
_cygtls::push (__stack_t addr)
{
  *stackptr++ = (__stack_t) addr;
}

#define BAD_IX ((size_t) -1)
static size_t NO_COPY threadlist_ix = BAD_IX;

_cygtls *
_cygtls::find_tls (int sig)
{
  debug_printf ("sig %d\n", sig);
  sentry here (INFINITE);
  __asm__ volatile (".equ _threadlist_exception_return,.");
  _cygtls *res = NULL;
  for (threadlist_ix = 0; threadlist_ix < nthreads; threadlist_ix++)
    if (sigismember (&(cygheap->threadlist[threadlist_ix]->sigwait_mask), sig))
      {
	res = cygheap->threadlist[threadlist_ix];
	break;
      }
  threadlist_ix = BAD_IX;
  return res;
}

void
_cygtls::set_siginfo (sigpacket *pack)
{
  infodata = pack->si;
}

extern "C" DWORD __stdcall RtlUnwind (void *, void *, void *, DWORD);
int
_cygtls::handle_threadlist_exception (EXCEPTION_RECORD *e, exception_list *frame, CONTEXT *c, void *)
{
  if (e->ExceptionCode != STATUS_ACCESS_VIOLATION)
    {
      system_printf ("unhandled exception %p at %p", e->ExceptionCode, c->Eip);
      return 1;
    }

  sentry here;
  if (threadlist_ix == BAD_IX)
    {
      api_fatal ("called with threadlist_ix %d", BAD_IX);
      return 1;
    }

  if (!here.acquired ())
    {
      system_printf ("couldn't aquire muto");
      return 1;
    }

  extern void *threadlist_exception_return;
  cygheap->threadlist[threadlist_ix]->remove (INFINITE);
  threadlist_ix = 0;
  RtlUnwind (frame, threadlist_exception_return, e, 0);
  return 0;
}

/* Set up the exception handler for the current thread.  The x86 uses segment
   register fs, offset 0 to point to the current exception handler. */

extern exception_list *_except_list asm ("%fs:0");

void
_cygtls::init_exception_handler (exception_handler *eh)
{
  el.handler = eh;
  /* Apparently Windows stores some information about an exception and tries
     to figure out if the SEH which returned 0 last time actually solved the
     problem, or if the problem still persists (e.g. same exception at same
     address).  In this case Windows seems to decide that it can't trust
     that SEH and calls the next handler in the chain instead.

     At one point this was a loop (el.prev = &el;).  This outsmarted the
     above behaviour.  Unfortunately this trick doesn't work anymore with
     Windows 2008, which irremediably gets into an endless loop, taking 100%
     CPU.  That's why we reverted to a normal SEH chain.

     On the bright side, Windows' behaviour is covered by POSIX:

     "If and when the function returns, if the value of sig was SIGFPE,
     SIGILL, or SIGSEGV or any other implementation-defined value
     corresponding to a computational exception, the behavior is undefined." */
  el.prev = _except_list;
  _except_list = &el;
}

void
_cygtls::init_threadlist_exceptions ()
{
  init_exception_handler (handle_threadlist_exception);
}