sysdeps/unix/sysv/linux/i386/clone.S

   1 /* Copyright (C) 1996-2000,02,03,04,2005 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Richard Henderson (rth@tamu.edu)
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 /* clone() is even more special than fork() as it mucks with stacks
  21    and invokes a function in the right context after its all over.  */
  22
  23 #include <sysdep.h>
  24 #define _ERRNO_H        1
  25 #include <bits/errno.h>
  26 #include <asm-syntax.h>
  27 #include <bp-sym.h>
  28 #include <bp-asm.h>
  29
  30 /* int clone(int (*fn)(void *arg), void *child_stack, int flags, void *arg,
  31              pid_t *ptid, struct user_desc *tls, pid_t *ctid); */
  32
  33 #define PARMS   LINKAGE         /* no space for saved regs */
  34 #define FUNC    PARMS
  35 #define STACK   FUNC+4
  36 #define FLAGS   STACK+PTR_SIZE
  37 #define ARG     FLAGS+4
  38 #define PTID    ARG+PTR_SIZE
  39 #define TLS     PTID+PTR_SIZE
  40 #define CTID    TLS+PTR_SIZE
  41
  42 #define __NR_clone 120
  43 #define SYS_clone 120
  44
  45 #define CLONE_VM        0x00000100
  46 #define CLONE_THREAD    0x00010000
  47
  48         .text
  49 ENTRY (BP_SYM (__clone))
  50         /* Sanity check arguments.  */
  51         movl    $-EINVAL,%eax
  52         movl    FUNC(%esp),%ecx         /* no NULL function pointers */
  53 #ifdef PIC
  54         jecxz   SYSCALL_ERROR_LABEL
  55 #else
  56         testl   %ecx,%ecx
  57         jz      SYSCALL_ERROR_LABEL
  58 #endif
  59         movl    STACK(%esp),%ecx        /* no NULL stack pointers */
  60 #ifdef PIC
  61         jecxz   SYSCALL_ERROR_LABEL
  62 #else
  63         testl   %ecx,%ecx
  64         jz      SYSCALL_ERROR_LABEL
  65 #endif
  66
  67         /* Insert the argument onto the new stack.  Make sure the new
  68            thread is started with an alignment of (mod 16).  */
  69         andl    $0xfffffff0, %ecx
  70         subl    $28,%ecx
  71         movl    ARG(%esp),%eax          /* no negative argument counts */
  72         movl    %eax,12(%ecx)
  73
  74         /* Save the function pointer as the zeroth argument.
  75            It will be popped off in the child in the ebx frobbing below.  */
  76         movl    FUNC(%esp),%eax
  77         movl    %eax,8(%ecx)
  78         /* Don't leak any information.  */
  79         movl    $0,4(%ecx)
  80 #ifndef RESET_PID
  81         movl    $0,(%ecx)
  82 #endif
  83
  84         /* Do the system call */
  85         pushl   %ebx
  86         cfi_adjust_cfa_offset (4)
  87         pushl   %esi
  88         cfi_adjust_cfa_offset (4)
  89         pushl   %edi
  90         cfi_adjust_cfa_offset (4)
  91
  92         movl    TLS+12(%esp),%esi
  93         cfi_rel_offset (esi, 4)
  94         movl    PTID+12(%esp),%edx
  95         movl    FLAGS+12(%esp),%ebx
  96         cfi_rel_offset (ebx, 8)
  97         movl    CTID+12(%esp),%edi
  98         cfi_rel_offset (edi, 0)
  99         movl    $SYS_ify(clone),%eax
 100
 101 #ifdef RESET_PID
 102         /* Remember the flag value.  */
 103         movl    %ebx, (%ecx)
 104 #endif
 105
 106         /* End FDE now, because in the child the unwind info will be
 107            wrong.  */
 108         cfi_endproc
 109
 110         int     $0x80
 111         popl    %edi
 112         popl    %esi
 113         popl    %ebx
 114
 115         test    %eax,%eax
 116         jl      SYSCALL_ERROR_LABEL
 117         jz      L(thread_start)
 118
 119 L(pseudo_end):
 120         ret
 121
 122 L(thread_start):
 123         cfi_startproc;
 124         /* Clearing frame pointer is insufficient, use CFI.  */
 125         cfi_undefined (eip);
 126         /* Note: %esi is zero.  */
 127         movl    %esi,%ebp       /* terminate the stack frame */
 128 #ifdef RESET_PID
 129         testl   $CLONE_THREAD, %edi
 130         je      L(newpid)
 131 L(haspid):
 132 #endif
 133         call    *%ebx
 134 #ifdef PIC
 135         call    L(here)
 136 L(here):
 137         popl    %ebx
 138         addl    $_GLOBAL_OFFSET_TABLE_+[.-L(here)], %ebx
 139 #endif
 140         movl    %eax, %ebx
 141         movl    $SYS_ify(exit), %eax
 142         ENTER_KERNEL
 143
 144 #ifdef RESET_PID
 145         .subsection 2
 146 L(newpid):
 147         testl   $CLONE_VM, %edi
 148         movl    $-1, %eax
 149         jne     L(nomoregetpid)
 150         movl    $SYS_ify(getpid), %eax
 151         ENTER_KERNEL
 152 L(nomoregetpid):
 153         movl    %eax, %gs:PID
 154         movl    %eax, %gs:TID
 155         jmp     L(haspid)
 156         .previous
 157 #endif
 158         cfi_endproc;
 159
 160         cfi_startproc
 161 PSEUDO_END (BP_SYM (__clone))
 162
 163 weak_alias (BP_SYM (__clone), BP_SYM (clone))