/* Create new context. Copyright (C) 2001,2002,2005,2007,2008,2009 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Ulrich Drepper <drepper@redhat.com>, 2001. 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 <http://www.gnu.org/licenses/>. */ #include <sysdep.h> #include "ucontext_i.h" ENTRY(__makecontext) movl 4(%esp), %eax /* Load the address of the function we are supposed to run. */ movl 8(%esp), %ecx /* Compute the address of the stack. The information comes from to us_stack element. */ movl oSS_SP(%eax), %edx movl %ecx, oEIP(%eax) addl oSS_SIZE(%eax), %edx /* Remember the number of parameters for the exit handler since it has to remove them. We store the number in the EBX register which the function we will call must preserve. */ movl 12(%esp), %ecx movl %ecx, oEBX(%eax) /* Make room on the new stack for the parameters. Room for the arguments, return address (== L(exitcode)) and oLINK pointer is needed. One of the pointer sizes is subtracted after aligning the stack. */ negl %ecx leal -4(%edx,%ecx,4), %edx negl %ecx /* Align the stack. */ andl $0xfffffff0, %edx subl $4, %edx /* Store the future stack pointer. */ movl %edx, oESP(%eax) /* Put the next context on the new stack (from the uc_link element). */ movl oLINK(%eax), %eax movl %eax, 4(%edx,%ecx,4) /* Copy all the parameters. */ jecxz 2f 1: movl 12(%esp,%ecx,4), %eax movl %eax, (%edx,%ecx,4) decl %ecx jnz 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). */ #ifdef __PIC__ call 1f cfi_adjust_cfa_offset (4) 1: popl %ecx cfi_adjust_cfa_offset (-4) addl $L(exitcode)-1b, %ecx movl %ecx, (%edx) #else movl $L(exitcode), (%edx) #endif /* 'makecontext' returns no value. */ L(pseudo_end): ret /* 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. */ cfi_endproc L(exitcode): /* This removes the parameters passed to the function given to 'makecontext' from the stack. EBX contains the number of parameters (see above). */ leal (%esp,%ebx,4), %esp #ifdef __PIC__ call 1f 1: popl %ebx addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %ebx #endif cmpl $0, (%esp) /* Check the next context. */ je 2f /* If it is zero exit. */ call JUMPTARGET(__setcontext) /* If this returns (which can happen if the syscall fails) we'll exit the program with the return error value (-1). */ movl %eax, (%esp) 2: call HIDDEN_JUMPTARGET(exit) /* The 'exit' call should never return. In case it does cause the process to terminate. */ hlt cfi_startproc END(__makecontext) weak_alias (__makecontext, makecontext)