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/* Create new context.
Copyright (C) 2012-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
#include "ucontext_i.h"
ENTRY(__makecontext)
move.l 4(%sp), %a0
/* Get the address of the function we are supposed to run. */
move.l 8(%sp), oPC(%a0)
/* Compute the address of the stack. The information comes from
to us_stack element. */
move.l oSS_SP(%a0), %a1
add.l oSS_SIZE(%a0), %a1
/* Remember the number of parameters for the exit handler since
it has to remove them. We store the number in the D7 register
which the function we will call must preserve. */
move.l 12(%sp), %d1
move.l %d1, oGREGS+7*4(%a0)
/* Make room on the new stack for the parameters.
Room for the arguments, return address (== 1f) and
oLINK pointer is needed. */
neg.l %d1
lea -8(%a1,%d1.l*4), %a1
neg.l %d1
/* Store the future stack pointer. */
move.l %a1, oSP(%a0)
/* Put the next context on the new stack (from the uc_link
element). */
move.l oLINK(%a0), 4(%a1,%d1.l*4)
/* Copy all the parameters. */
1: subq.l #1,%d1
jmi 2f
move.l 16(%sp,%d1.l*4), 4(%a1,%d1.l*4)
jra 1b
2:
/* If the function we call returns we must continue with the
context which is given in the uc_link element. To do this
set the return address for the function the user provides
to a little bit of helper code which does the magic (see
below). */
lea 1f(%pc), %a0
move.l %a0, (%a1)
/* 'makecontext' returns no value. */
rts
/* This is the helper code which gets called if a function which
is registered with 'makecontext' returns. In this case we
have to install the context listed in the uc_link element of
the context 'makecontext' manipulated at the time of the
'makecontext' call. If the pointer is NULL the process must
terminate.
Make sure to separate the return label from the previous unwind
region, because the unwinder uses ra-1 to find the FDE. */
cfi_endproc
nop
1:
/* This removes the parameters passed to the function given to
'makecontext' from the stack. D7 contains the number of
parameters (see above). */
lea (%sp,%d7.l*4), %sp
tst.l (%sp) /* Check the next context. */
jeq 2f /* If it is zero exit. */
jbsr JUMPTARGET(__setcontext)
/* If this returns (which can happen if the syscall fails) we'll
exit the program with the return error value (-1). */
move.l %d0, (%sp)
2: jbsr HIDDEN_JUMPTARGET(exit)
/* The 'exit' call should never return. In case it does cause
the process to terminate. */
illegal
cfi_startproc
END(__makecontext)
weak_alias (__makecontext, makecontext)
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