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[hppa] Fix incorrect stack frame usage in vfork. 

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.
This commit is contained in:
Carlos O'Donell 2010-06-24 12:13:36 -04:00
parent 131fafa7da
commit 3680f14a7d
2 changed files with 22 additions and 9 deletions
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6
ChangeLog.hppa
View File

@ -1,3 +1,9 @@
2010-06-24 Carlos O'Donell <carlos@codesourcery.com>
* sysdeps/unix/sysv/linux/hppa/nptl/pt-vfork.S: Only create stack
frame around call to SYSCALL_ERROR_HANDLER. Do not restore %rp
from the stack frame on successfull return.
2010-06-23 Carlos O'Donell <carlos@codesourcery.com>
* sysdeps/unix/sysv/linux/hppa/getcontext.S (__getcontext_ret):

25
sysdeps/unix/sysv/linux/hppa/nptl/pt-vfork.S
View File

@ -1,4 +1,4 @@
/* Copyright (C) 2005 Free Software Foundation, Inc.
/* Copyright (C) 2005, 2010 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
@ -50,10 +50,9 @@
/* r26, r25, r24, r23 are free since vfork has no arguments */
ENTRY(__vfork)
/* Prologue */
stwm %r3, 64(%sp)
stw %sp, -4(%sp)
stw %r19, -32(%sp)
/* We must not create a frame. When the child unwinds to call
exec it will clobber the same frame that the parent
needs to unwind. */
/* Save the PIC register. */
#ifdef PIC
@ -75,12 +74,20 @@ ENTRY(__vfork)
comclr,>>= %r1,%ret0,%r0 /* Note: unsigned compare. */
b,n .Lerror
/* Return, no need to restore the PIC register. */
ldw -84(%sp), %rp
bv %r0(%rp)
ldwm -64(%sp), %r3
/* Return, and DO NOT restore rp. The child may have called
functions that updated the frame's rp. This works because
the kernel ensures rp is preserved across the vfork
syscall. */
bv,n %r0(%rp)
.Lerror:
/* Now we need a stack to call a function. We are assured
that there is no child now, so it's safe to create
a frame. */
stw %rp, -20(%sp)
stwm %r3, 64(%sp)
stw %sp, -4(%sp)
sub %r0,%ret0,%r3
SYSCALL_ERROR_HANDLER
/* Restore the PIC register (in delay slot) on error */