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* sigproc.cc (child_info::child_info): Move old comment about msv_count here.

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Edit it slightly to reflect new sensibilities.
This commit is contained in:
Christopher Faylor 2006-12-11 19:17:20 +00:00
parent 6dcb2ec441
commit 7dfad3a0c6
2 changed files with 28 additions and 0 deletions
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5
winsup/cygwin/ChangeLog
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@ -1,3 +1,8 @@
2006-12-11 Christopher Faylor <me@cgf.cx>
* sigproc.cc (child_info::child_info): Move old comment about msv_count
here. Edit it slightly to reflect new sensibilities.
2006-12-11 Christopher Faylor <me+cygwin@cgf.cx>
* child_info.h (child_info_spawn::__stdin): New element.

23
winsup/cygwin/sigproc.cc
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@ -788,6 +788,29 @@ child_info::child_info (unsigned in_cb, child_info_types chtype, bool need_subpr
memset (this, 0, in_cb);
cb = in_cb;
/* It appears that when running under WOW64 on Vista 64, the first DWORD
value in the datastructure lpReserved2 is pointing to (msv_count in
Cygwin), has to reflect the size of that datastructure as used in the
Microsoft C runtime (a count value, counting the number of elements in
two subsequent arrays, BYTE[count and HANDLE[count]), even though the C
runtime isn't used. Otherwise, if msv_count is 0 or too small, the
datastructure gets overwritten.
This seems to be a bug in Vista's WOW64, which apparently copies the
lpReserved2 datastructure not using the cbReserved2 size information,
but using the information given in the first DWORD within lpReserved2
instead. 32 bit Windows and former WOW64 don't care if msv_count is 0
or a sensible non-0 count value. However, it's not clear if a non-0
count doesn't result in trying to evaluate the content, so we do this
really only for Vista 64 for now.
However, since this doesn't seem to harm normal windows operation we'll
just set it unconditionally until we hear complaints.
The value is sizeof (child_info_*) / 5 which results in a count which
covers the full datastructure, plus not more than 4 extra bytes. This
is ok as long as the child_info structure is cosily stored within a bigger
datastructure. */
msv_count = in_cb / 5;
intro = PROC_MAGIC_GENERIC;