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3680f14a7d
In a multithreaded environment the call to vfork was incorrectly creating a stack frame. Given that the child unwinds the stack frame first to call exec, it will corrupt any values the parent stored in the stack frame. The solution is to avoid creating a stack frame unless required to call an error function, in which case we are assured no child was created.
108 lines
3.3 KiB
ArmAsm
108 lines
3.3 KiB
ArmAsm
/* Copyright (C) 2005, 2010 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <sysdep.h>
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#define _ERRNO_H 1
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#include <bits/errno.h>
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#include <tcb-offsets.h>
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/* Clone the calling process, but without copying the whole address space.
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The calling process is suspended until the new process exits or is
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replaced by a call to `execve'. Return -1 for errors, 0 to the new process,
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and the process ID of the new process to the old process. */
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/* Load the thread register.
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Load the saved PID value.
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Negate the value.
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Store the temporary PID. */
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#define SAVE_PID \
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mfctl %cr27, %r26 ASM_LINE_SEP \
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ldw PID_THREAD_OFFSET(%r26),%r1 ASM_LINE_SEP \
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sub %r0,%r1,%r1 ASM_LINE_SEP \
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stw %r1,PID_THREAD_OFFSET(%r26) ASM_LINE_SEP
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/* If we are the parent...
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Get the thread pointer.
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Load the saved PID.
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Negate the value (got back original)
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Restore the PID. */
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#define RESTORE_PID \
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cmpb,=,n %r0,%ret0,.Lthread_start ASM_LINE_SEP \
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mfctl %cr27, %r26 ASM_LINE_SEP \
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ldw PID_THREAD_OFFSET(%r26),%r1 ASM_LINE_SEP \
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sub %r0,%r1,%r1 ASM_LINE_SEP \
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stw %r1,PID_THREAD_OFFSET(%r26) ASM_LINE_SEP \
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.Lthread_start: ASM_LINE_SEP
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/* r26, r25, r24, r23 are free since vfork has no arguments */
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ENTRY(__vfork)
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/* We must not create a frame. When the child unwinds to call
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exec it will clobber the same frame that the parent
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needs to unwind. */
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/* Save the PIC register. */
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#ifdef PIC
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copy %r19, %r25 /* parent */
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#endif
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/* Save the process PID */
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SAVE_PID
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/* Syscall saves and restores all register states */
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ble 0x100(%sr2,%r0)
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ldi __NR_vfork,%r20
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/* Conditionally restore the PID */
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RESTORE_PID
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/* Check for error */
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ldi -4096,%r1
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comclr,>>= %r1,%ret0,%r0 /* Note: unsigned compare. */
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b,n .Lerror
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/* Return, and DO NOT restore rp. The child may have called
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functions that updated the frame's rp. This works because
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the kernel ensures rp is preserved across the vfork
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syscall. */
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bv,n %r0(%rp)
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.Lerror:
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/* Now we need a stack to call a function. We are assured
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that there is no child now, so it's safe to create
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a frame. */
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stw %rp, -20(%sp)
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stwm %r3, 64(%sp)
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stw %sp, -4(%sp)
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sub %r0,%ret0,%r3
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SYSCALL_ERROR_HANDLER
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/* Restore the PIC register (in delay slot) on error */
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#ifdef PIC
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copy %r25, %r19 /* parent */
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#else
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nop
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#endif
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/* Write syscall return into errno location */
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stw %r3, 0(%ret0)
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ldw -84(%sp), %rp
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bv %r0(%rp)
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ldwm -64(%sp), %r3
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PSEUDO_END (__vfork)
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libc_hidden_def (__vfork)
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weak_alias (__vfork, vfork)
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