libcoro/coro.c

/*
 * Copyright (c) 2001-2008 Marc Alexander Lehmann <schmorp@schmorp.de>
 * 
 * Redistribution and use in source and binary forms, with or without modifica-
 * tion, are permitted provided that the following conditions are met:
 * 
 *   1.  Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 * 
 *   2.  Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 * 
 *   3.  The name of the author may not be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This library is modelled strictly after Ralf S. Engelschalls article at
 * http://www.gnu.org/software/pth/rse-pmt.ps.  So most of the credit must
 * go to Ralf S. Engelschall <rse@engelschall.com>.
 */

#include "coro.h"

#if !defined(STACK_ADJUST_PTR)
/* IRIX is decidedly NON-unix */
# if __sgi
#  define STACK_ADJUST_PTR(sp,ss) ((char *)(sp) + (ss) - 8)
#  define STACK_ADJUST_SIZE(sp,ss) ((ss) - 8)
# elif __i386__ && CORO_LINUX
#  define STACK_ADJUST_PTR(sp,ss) ((char *)(sp) + (ss))
#  define STACK_ADJUST_SIZE(sp,ss) (ss)
# elif __amd64__ && CORO_LINUX
#  define STACK_ADJUST_PTR(sp,ss) ((char *)(sp) + (ss) - 8)
#  define STACK_ADJUST_SIZE(sp,ss) (ss)
# else
#  define STACK_ADJUST_PTR(sp,ss) (sp)
#  define STACK_ADJUST_SIZE(sp,ss) (ss)
# endif
#endif

#if CORO_UCONTEXT
# include <stddef.h>
#endif

#if CORO_SJLJ || CORO_LOSER || CORO_LINUX || CORO_IRIX || CORO_ASM

#include <stdlib.h>

#if CORO_SJLJ
# include <stdio.h>
# include <signal.h>
# include <unistd.h>
#endif

static volatile coro_func coro_init_func;
static volatile void *coro_init_arg;
static volatile coro_context *new_coro, *create_coro;

/* what we really want to detect here is wether we use a new-enough version of GAS */
/* instead, check for gcc 3, ELF and GNU/Linux and hope for the best */
#if __GNUC__ >= 3 && __ELF__ && __linux__
# define HAVE_CFI 1
#endif

static void
coro_init (void)
{
  volatile coro_func func = coro_init_func;
  volatile void *arg = coro_init_arg;

  coro_transfer ((coro_context *)new_coro, (coro_context *)create_coro);

  func ((void *)arg);

  /* the new coro returned. bad. just abort() for now */
  abort ();
}

# if CORO_SJLJ

static volatile int trampoline_count;

/* trampoline signal handler */
static void
trampoline (int sig)
{
  if (setjmp (((coro_context *)new_coro)->env))
    {
#if HAVE_CFI
      asm (".cfi_startproc");
#endif
      coro_init (); /* start it */
#if HAVE_CFI
      asm (".cfi_endproc");
#endif
    }
  else
    trampoline_count++;
}

# endif

#endif

#if CORO_ASM
void __attribute__((__noinline__, __fastcall__))
coro_transfer (struct coro_context *prev, struct coro_context *next)
{
  asm volatile (
#if __amd64
# define NUM_CLOBBERED 5
     "push %%rbx\n\t"
     "push %%r12\n\t"
     "push %%r13\n\t"
     "push %%r14\n\t"
     "push %%r15\n\t"
     "mov  %%rsp, %0\n\t"
     "mov  %1, %%rsp\n\t"
     "pop  %%r15\n\t"
     "pop  %%r14\n\t"
     "pop  %%r13\n\t"
     "pop  %%r12\n\t"
     "pop  %%rbx\n\t"
#elif __i386
# define NUM_CLOBBERED 4
     "push %%ebx\n\t"
     "push %%esi\n\t"
     "push %%edi\n\t"
     "push %%ebp\n\t"
     "mov  %%esp, %0\n\t"
     "mov  %1, %%esp\n\t"
     "pop  %%ebp\n\t"
     "pop  %%edi\n\t"
     "pop  %%esi\n\t"
     "pop  %%ebx\n\t"
#else
# error unsupported architecture
#endif
     : "=m" (prev->sp)
     : "m" (next->sp)
  );
}
#endif

/* initialize a machine state */
void coro_create (coro_context *ctx,
                  coro_func coro, void *arg,
                  void *sptr, long ssize)
{
#if CORO_UCONTEXT

  getcontext (&(ctx->uc));

  ctx->uc.uc_link           =  0;
  ctx->uc.uc_stack.ss_sp    = STACK_ADJUST_PTR (sptr,ssize);
  ctx->uc.uc_stack.ss_size  = (size_t) STACK_ADJUST_SIZE (sptr,ssize);
  ctx->uc.uc_stack.ss_flags = 0;

  makecontext (&(ctx->uc), (void (*)()) coro, 1, arg);

#elif CORO_SJLJ || CORO_LOSER || CORO_LINUX || CORO_IRIX || CORO_ASM

# if CORO_SJLJ
  stack_t ostk, nstk;
  struct sigaction osa, nsa;
  sigset_t nsig, osig;
# endif
  coro_context nctx;

  coro_init_func = coro;
  coro_init_arg  = arg;

  new_coro    = ctx;
  create_coro = &nctx;

# if CORO_SJLJ
  /* we use SIGUSR2. first block it, then fiddle with it. */

  sigemptyset (&nsig);
  sigaddset (&nsig, SIGUSR2);
  sigprocmask (SIG_BLOCK, &nsig, &osig);

  nsa.sa_handler = trampoline;
  sigemptyset (&nsa.sa_mask);
  nsa.sa_flags = SA_ONSTACK;

  if (sigaction (SIGUSR2, &nsa, &osa))
    {
      perror ("sigaction");
      abort ();
    }

  /* set the new stack */
  nstk.ss_sp    = STACK_ADJUST_PTR (sptr,ssize); /* yes, some platforms (IRIX) get this wrong. */
  nstk.ss_size  = STACK_ADJUST_SIZE (sptr,ssize);
  nstk.ss_flags = 0;

  if (sigaltstack (&nstk, &ostk) < 0)
    {
      perror ("sigaltstack");
      abort ();
    }

  trampoline_count = 0;
  kill (getpid (), SIGUSR2);
  sigfillset (&nsig); sigdelset (&nsig, SIGUSR2);

  while (!trampoline_count)
    sigsuspend (&nsig);

  sigaltstack (0, &nstk);
  nstk.ss_flags = SS_DISABLE;
  if (sigaltstack (&nstk, 0) < 0)
    perror ("sigaltstack");

  sigaltstack (0, &nstk);
  if (~nstk.ss_flags & SS_DISABLE)
    abort ();

  if (~ostk.ss_flags & SS_DISABLE)
    sigaltstack (&ostk, 0);

  sigaction (SIGUSR2, &osa, 0);

  sigprocmask (SIG_SETMASK, &osig, 0);

# elif CORO_LOSER

  setjmp (ctx->env);
#if __CYGWIN__
  ctx->env[7] = (long)((char *)sptr + ssize);
  ctx->env[8] = (long)coro_init;
#elif defined(_M_IX86)
  ((_JUMP_BUFFER *)&ctx->env)->Eip   = (long)coro_init;
  ((_JUMP_BUFFER *)&ctx->env)->Esp   = (long)STACK_ADJUST_PTR (sptr,ssize);
#elif defined(_M_AMD64)
  ((_JUMP_BUFFER *)&ctx->env)->Rip   = (__int64)coro_init;
  ((_JUMP_BUFFER *)&ctx->env)->Rsp   = (__int64)STACK_ADJUST_PTR (sptr,ssize);
#elif defined(_M_IA64)
  ((_JUMP_BUFFER *)&ctx->env)->StIIP = (__int64)coro_init;
  ((_JUMP_BUFFER *)&ctx->env)->IntSp = (__int64)STACK_ADJUST_PTR (sptr,ssize);
#else
#error "microsoft libc or architecture not supported"
#endif

# elif CORO_LINUX

  _setjmp (ctx->env);
#if __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 0 && defined (JB_PC) && defined (JB_SP)
  ctx->env[0].__jmpbuf[JB_PC] = (long)coro_init;
  ctx->env[0].__jmpbuf[JB_SP] = (long)STACK_ADJUST_PTR (sptr, ssize);
#elif __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 0 && defined (__mc68000__)
  ctx->env[0].__jmpbuf[0].__aregs[0] = (long int)coro_init;
  ctx->env[0].__jmpbuf[0].__sp = (int *)((char *)sptr + ssize);
#elif defined (__GNU_LIBRARY__) && defined (__i386__)
  ctx->env[0].__jmpbuf[0].__pc = (char *)coro_init;
  ctx->env[0].__jmpbuf[0].__sp = (void *)((char *)sptr + ssize);
#elif defined (__GNU_LIBRARY__) && defined (__amd64__)
  ctx->env[0].__jmpbuf[JB_PC]  = (long)coro_init;
  ctx->env[0].__jmpbuf[JB_RSP] = (long)STACK_ADJUST_PTR (sptr, ssize);
#else
# error "linux libc or architecture not supported"
#endif

# elif CORO_IRIX

  setjmp (ctx->env);
  ctx->env[JB_PC] = (__uint64_t)coro_init;
  ctx->env[JB_SP] = (__uint64_t)STACK_ADJUST_PTR (sptr, ssize);

# elif CORO_ASM

  ctx->sp = (volatile void **)(ssize + (char *)sptr);
  *--ctx->sp = (void *)coro_init;
  *--ctx->sp = (void *)coro_init; // this is needed when the prologue saves ebp
  ctx->sp -= NUM_CLOBBERED;

# endif

  coro_transfer ((coro_context *)create_coro, (coro_context *)new_coro);

#else
# error unsupported architecture
#endif
}

Revision:	1.28
Committed:	Sun Jan 20 17:30:24 2008 UTC (16 years, 4 months ago) by root
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rel-4_4
Changes since 1.27:	+3 -3 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	/*
2	root	1.28	* Copyright (c) 2001-2008 Marc Alexander Lehmann <schmorp@schmorp.de>
3	root	1.1	*
4			* Redistribution and use in source and binary forms, with or without modifica-
5			* tion, are permitted provided that the following conditions are met:
6			*
7			* 1. Redistributions of source code must retain the above copyright notice,
8			* this list of conditions and the following disclaimer.
9			*
10			* 2. Redistributions in binary form must reproduce the above copyright
11			* notice, this list of conditions and the following disclaimer in the
12			* documentation and/or other materials provided with the distribution.
13			*
14			* 3. The name of the author may not be used to endorse or promote products
15			* derived from this software without specific prior written permission.
16			*
17			* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
18			* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
19			* CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
20			* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
21			* CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
22			* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
23			* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24			* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
25			* ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
26			* OF THE POSSIBILITY OF SUCH DAMAGE.
27			*
28			* This library is modelled strictly after Ralf S. Engelschalls article at
29			* http://www.gnu.org/software/pth/rse-pmt.ps. So most of the credit must
30			* go to Ralf S. Engelschall <rse@engelschall.com>.
31			*/
32
33			#include "coro.h"
34
35	root	1.8	#if !defined(STACK_ADJUST_PTR)
36	root	1.5	/* IRIX is decidedly NON-unix */
37	root	1.8	# if __sgi
38			# define STACK_ADJUST_PTR(sp,ss) ((char *)(sp) + (ss) - 8)
39			# define STACK_ADJUST_SIZE(sp,ss) ((ss) - 8)
40			# elif __i386__ && CORO_LINUX
41			# define STACK_ADJUST_PTR(sp,ss) ((char *)(sp) + (ss))
42			# define STACK_ADJUST_SIZE(sp,ss) (ss)
43	root	1.18	# elif __amd64__ && CORO_LINUX
44			# define STACK_ADJUST_PTR(sp,ss) ((char *)(sp) + (ss) - 8)
45			# define STACK_ADJUST_SIZE(sp,ss) (ss)
46	root	1.8	# else
47			# define STACK_ADJUST_PTR(sp,ss) (sp)
48			# define STACK_ADJUST_SIZE(sp,ss) (ss)
49			# endif
50	root	1.5	#endif
51	root	1.7
52	root	1.20	#if CORO_UCONTEXT
53			# include <stddef.h>
54			#endif
55
56	root	1.27	#if CORO_SJLJ \|\| CORO_LOSER \|\| CORO_LINUX \|\| CORO_IRIX \|\| CORO_ASM
57	root	1.1
58	root	1.17	#include <stdlib.h>
59
60	root	1.14	#if CORO_SJLJ
61	root	1.15	# include <stdio.h>
62	root	1.14	# include <signal.h>
63	root	1.17	# include <unistd.h>
64	root	1.14	#endif
65	root	1.1
66			static volatile coro_func coro_init_func;
67			static volatile void *coro_init_arg;
68			static volatile coro_context new_coro, create_coro;
69
70	root	1.25	/* what we really want to detect here is wether we use a new-enough version of GAS */
71	root	1.28	/* instead, check for gcc 3, ELF and GNU/Linux and hope for the best */
72			#if __GNUC__ >= 3 && __ELF__ && __linux__
73	root	1.25	# define HAVE_CFI 1
74			#endif
75
76	root	1.1	static void
77			coro_init (void)
78			{
79			volatile coro_func func = coro_init_func;
80			volatile void *arg = coro_init_arg;
81
82	root	1.2	coro_transfer ((coro_context )new_coro, (coro_context )create_coro);
83	root	1.1
84	root	1.3	func ((void *)arg);
85	root	1.1
86			/* the new coro returned. bad. just abort() for now */
87			abort ();
88			}
89
90			# if CORO_SJLJ
91
92			static volatile int trampoline_count;
93
94			/* trampoline signal handler */
95			static void
96	root	1.14	trampoline (int sig)
97	root	1.1	{
98	root	1.3	if (setjmp (((coro_context *)new_coro)->env))
99	root	1.26	{
100			#if HAVE_CFI
101			asm (".cfi_startproc");
102			#endif
103			coro_init (); /* start it */
104			#if HAVE_CFI
105			asm (".cfi_endproc");
106			#endif
107			}
108	root	1.1	else
109			trampoline_count++;
110			}
111
112			# endif
113
114			#endif
115
116	root	1.27	#if CORO_ASM
117			void __attribute__((__noinline__, __fastcall__))
118			coro_transfer (struct coro_context prev, struct coro_context next)
119			{
120			asm volatile (
121			#if __amd64
122			# define NUM_CLOBBERED 5
123			"push %%rbx\n\t"
124			"push %%r12\n\t"
125			"push %%r13\n\t"
126			"push %%r14\n\t"
127			"push %%r15\n\t"
128			"mov %%rsp, %0\n\t"
129			"mov %1, %%rsp\n\t"
130			"pop %%r15\n\t"
131			"pop %%r14\n\t"
132			"pop %%r13\n\t"
133			"pop %%r12\n\t"
134			"pop %%rbx\n\t"
135			#elif __i386
136			# define NUM_CLOBBERED 4
137			"push %%ebx\n\t"
138			"push %%esi\n\t"
139			"push %%edi\n\t"
140			"push %%ebp\n\t"
141			"mov %%esp, %0\n\t"
142			"mov %1, %%esp\n\t"
143			"pop %%ebp\n\t"
144			"pop %%edi\n\t"
145			"pop %%esi\n\t"
146			"pop %%ebx\n\t"
147			#else
148			# error unsupported architecture
149			#endif
150			: "=m" (prev->sp)
151			: "m" (next->sp)
152			);
153			}
154			#endif
155
156	root	1.1	/* initialize a machine state */
157	root	1.23	void coro_create (coro_context *ctx,
158			coro_func coro, void *arg,
159			void *sptr, long ssize)
160	root	1.1	{
161			#if CORO_UCONTEXT
162
163			getcontext (&(ctx->uc));
164
165	root	1.5	ctx->uc.uc_link = 0;
166	root	1.9	ctx->uc.uc_stack.ss_sp = STACK_ADJUST_PTR (sptr,ssize);
167	root	1.8	ctx->uc.uc_stack.ss_size = (size_t) STACK_ADJUST_SIZE (sptr,ssize);
168	root	1.1	ctx->uc.uc_stack.ss_flags = 0;
169
170			makecontext (&(ctx->uc), (void (*)()) coro, 1, arg);
171
172	root	1.27	#elif CORO_SJLJ \|\| CORO_LOSER \|\| CORO_LINUX \|\| CORO_IRIX \|\| CORO_ASM
173	root	1.1
174			# if CORO_SJLJ
175			stack_t ostk, nstk;
176			struct sigaction osa, nsa;
177			sigset_t nsig, osig;
178			# endif
179			coro_context nctx;
180
181			coro_init_func = coro;
182			coro_init_arg = arg;
183
184			new_coro = ctx;
185			create_coro = &nctx;
186
187			# if CORO_SJLJ
188			/* we use SIGUSR2. first block it, then fiddle with it. */
189
190			sigemptyset (&nsig);
191			sigaddset (&nsig, SIGUSR2);
192			sigprocmask (SIG_BLOCK, &nsig, &osig);
193
194			nsa.sa_handler = trampoline;
195			sigemptyset (&nsa.sa_mask);
196			nsa.sa_flags = SA_ONSTACK;
197
198			if (sigaction (SIGUSR2, &nsa, &osa))
199	root	1.23	{
200			perror ("sigaction");
201			abort ();
202			}
203	root	1.1
204			/* set the new stack */
205	root	1.9	nstk.ss_sp = STACK_ADJUST_PTR (sptr,ssize); /* yes, some platforms (IRIX) get this wrong. */
206	root	1.8	nstk.ss_size = STACK_ADJUST_SIZE (sptr,ssize);
207	root	1.1	nstk.ss_flags = 0;
208
209			if (sigaltstack (&nstk, &ostk) < 0)
210	root	1.23	{
211			perror ("sigaltstack");
212			abort ();
213			}
214	root	1.1
215			trampoline_count = 0;
216			kill (getpid (), SIGUSR2);
217			sigfillset (&nsig); sigdelset (&nsig, SIGUSR2);
218
219			while (!trampoline_count)
220			sigsuspend (&nsig);
221
222			sigaltstack (0, &nstk);
223			nstk.ss_flags = SS_DISABLE;
224			if (sigaltstack (&nstk, 0) < 0)
225			perror ("sigaltstack");
226
227			sigaltstack (0, &nstk);
228			if (~nstk.ss_flags & SS_DISABLE)
229			abort ();
230
231			if (~ostk.ss_flags & SS_DISABLE)
232			sigaltstack (&ostk, 0);
233
234	root	1.19	sigaction (SIGUSR2, &osa, 0);
235	root	1.1
236			sigprocmask (SIG_SETMASK, &osig, 0);
237
238	root	1.16	# elif CORO_LOSER
239	root	1.1
240	root	1.4	setjmp (ctx->env);
241	root	1.21	#if __CYGWIN__
242	pcg	1.11	ctx->env[7] = (long)((char *)sptr + ssize);
243			ctx->env[8] = (long)coro_init;
244	root	1.21	#elif defined(_M_IX86)
245			((_JUMP_BUFFER *)&ctx->env)->Eip = (long)coro_init;
246			((_JUMP_BUFFER *)&ctx->env)->Esp = (long)STACK_ADJUST_PTR (sptr,ssize);
247			#elif defined(_M_AMD64)
248			((_JUMP_BUFFER *)&ctx->env)->Rip = (__int64)coro_init;
249			((_JUMP_BUFFER *)&ctx->env)->Rsp = (__int64)STACK_ADJUST_PTR (sptr,ssize);
250			#elif defined(_M_IA64)
251			((_JUMP_BUFFER *)&ctx->env)->StIIP = (__int64)coro_init;
252			((_JUMP_BUFFER *)&ctx->env)->IntSp = (__int64)STACK_ADJUST_PTR (sptr,ssize);
253			#else
254			#error "microsoft libc or architecture not supported"
255			#endif
256	root	1.4
257			# elif CORO_LINUX
258
259	root	1.22	_setjmp (ctx->env);
260	root	1.24	#if __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 0 && defined (JB_PC) && defined (JB_SP)
261	root	1.10	ctx->env[0].__jmpbuf[JB_PC] = (long)coro_init;
262	root	1.24	ctx->env[0].__jmpbuf[JB_SP] = (long)STACK_ADJUST_PTR (sptr, ssize);
263			#elif __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 0 && defined (__mc68000__)
264	root	1.4	ctx->env[0].__jmpbuf[0].__aregs[0] = (long int)coro_init;
265			ctx->env[0].__jmpbuf[0].__sp = (int )((char )sptr + ssize);
266	root	1.24	#elif defined (__GNU_LIBRARY__) && defined (__i386__)
267	root	1.4	ctx->env[0].__jmpbuf[0].__pc = (char *)coro_init;
268			ctx->env[0].__jmpbuf[0].__sp = (void )((char )sptr + ssize);
269	root	1.24	#elif defined (__GNU_LIBRARY__) && defined (__amd64__)
270	root	1.12	ctx->env[0].__jmpbuf[JB_PC] = (long)coro_init;
271	root	1.24	ctx->env[0].__jmpbuf[JB_RSP] = (long)STACK_ADJUST_PTR (sptr, ssize);
272	root	1.4	#else
273	root	1.27	# error "linux libc or architecture not supported"
274	root	1.4	#endif
275	root	1.5
276			# elif CORO_IRIX
277
278			setjmp (ctx->env);
279	root	1.6	ctx->env[JB_PC] = (__uint64_t)coro_init;
280	root	1.24	ctx->env[JB_SP] = (__uint64_t)STACK_ADJUST_PTR (sptr, ssize);
281	root	1.1
282	root	1.27	# elif CORO_ASM
283
284			ctx->sp = (volatile void *)(ssize + (char )sptr);
285			--ctx->sp = (void )coro_init;
286			--ctx->sp = (void )coro_init; // this is needed when the prologue saves ebp
287			ctx->sp -= NUM_CLOBBERED;
288
289	root	1.1	# endif
290
291	root	1.2	coro_transfer ((coro_context )create_coro, (coro_context )new_coro);
292	root	1.1
293			#else
294	root	1.27	# error unsupported architecture
295	root	1.1	#endif
296			}
297