[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.

diff --git a/ChangeLog.hppa b/ChangeLog.hppa
index faad5e9..2ccc911 100644 (file)
--- a/ChangeLog.hppa
+++ b/ChangeLog.hppa
@@ -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):

diff --git a/sysdeps/unix/sysv/linux/hppa/nptl/pt-vfork.S b/sysdeps/unix/sysv/linux/hppa/nptl/pt-vfork.S
index 83a70b7..15efa98 100644 (file)
--- a/sysdeps/unix/sysv/linux/hppa/nptl/pt-vfork.S
+++ b/sysdeps/unix/sysv/linux/hppa/nptl/pt-vfork.S
@@ -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 */