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Fix various OS-related comments

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Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen
2015-12-15 21:43:33 +01:00
parent bb0fc7a2c0
commit 00e9bf2bb3
12 changed files with 68 additions and 93 deletions
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51
winsup/cygwin/path.cc
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@ -2889,9 +2889,7 @@ restart:
/* Reparse points are potentially symlinks. This check must be
performed before checking the SYSTEM attribute for sysfile
symlinks, since reparse points can have this flag set, too.
For instance, Vista starts to create a couple of reparse points
with SYSTEM and HIDDEN flags set. */
symlinks, since reparse points can have this flag set, too. */
if ((fileattr & FILE_ATTRIBUTE_REPARSE_POINT))
{
res = check_reparse_point (h, fs.is_remote_drive ());
@ -3974,13 +3972,9 @@ fcwd_access_t::SetVersionFromPointer (PBYTE buf_p, bool is_buffer)
}
/* This function scans the code in ntdll.dll to find the address of the
global variable used to access the CWD starting with Vista. While the
pointer is global, it's not exported from the DLL, unfortunately.
Therefore we have to use some knowledge to figure out the address.
This code has been tested on Vista 32/64 bit, Server 2008 32/64 bit,
Windows 7 32/64 bit, Server 2008 R2 (which is only 64 bit anyway),
Windows 8 32/64 bit, Windows 8.1 32/64 bit, and Server 2012 R2. */
global variable used to access the CWD. While the pointer is global,
it's not exported from the DLL, unfortunately. Therefore we have to
use some knowledge to figure out the address. */
#ifdef __x86_64__
@ -4240,9 +4234,8 @@ cwdstuff::override_win32_cwd (bool init, ULONG old_dismount_count)
fast_cwd_ptr = find_fast_cwd ();
if (fast_cwd_ptr)
{
/* Default method starting with Vista. If we got a valid value for
fast_cwd_ptr, we can simply replace the RtlSetCurrentDirectory_U
function entirely, just as on pre-Vista. */
/* If we got a valid value for fast_cwd_ptr, we can simply replace
the RtlSetCurrentDirectory_U function entirely. */
PVOID heap = peb.ProcessHeap;
/* First allocate a new fcwd_access_t structure on the heap.
The new fcwd_access_t structure is 4 byte bigger than the old one,
@ -4274,14 +4267,13 @@ cwdstuff::override_win32_cwd (bool init, ULONG old_dismount_count)
}
else
{
/* This is more a hack, and it's only used on Vista and later if we
failed to find the fast_cwd_ptr value. What we do here is to call
RtlSetCurrentDirectory_U and let it set up a new FAST_CWD
structure. Afterwards, compute the address of that structure
utilizing the fact that the buffer address in the user process
parameter block is actually pointing to the buffer in that
FAST_CWD structure. Then replace the directory handle in that
structure with our own handle and close the original one.
/* This is more a hack, and it's only used if we failed to find the
fast_cwd_ptr value. We call RtlSetCurrentDirectory_U and let it
set up a new FAST_CWD structure. Afterwards, compute the address
of that structure utilizing the fact that the buffer address in
the user process parameter block is actually pointing to the buffer
in that FAST_CWD structure. Then replace the directory handle in
that structure with our own handle and close the original one.
Note that the call to RtlSetCurrentDirectory_U also closes our
old dir handle, so there won't be any handle left open.
@ -4374,13 +4366,6 @@ cwdstuff::set (path_conv *nat_cwd, const char *posix_cwd)
- SetCurrentDirectory can naturally not work on virtual Cygwin paths
like /proc or /cygdrive.
Unfortunately, even though we have access to the Win32 process parameter
block, we can't just replace the directory handle. Starting with Vista,
the handle is used elsewhere, and just replacing the handle in the process
parameter block shows quite surprising results.
FIXME: If we ever find a *safe* way to replace the directory handle in
the process parameter block, we're back in business.
Nevertheless, doing entirely without SetCurrentDirectory is not really
feasible, because it breaks too many mixed applications using the Win32
API.
@ -4401,11 +4386,11 @@ cwdstuff::set (path_conv *nat_cwd, const char *posix_cwd)
}
/* Memorize old DismountCount before opening the dir. This value is
stored in the FAST_CWD structure on Vista and later. It would be
simpler to fetch the old DismountCount in override_win32_cwd, but
Windows also fetches it before opening the directory handle. It's
not quite clear if that's really required, but since we don't know
the side effects of this action, we better follow Windows' lead. */
stored in the FAST_CWD structure. It would be simpler to fetch the
old DismountCount in override_win32_cwd, but Windows also fetches
it before opening the directory handle. It's not quite clear if
that's really required, but since we don't know the side effects of
this action, we better follow Windows' lead. */
ULONG old_dismount_count = SharedUserData.DismountCount;
/* Open a directory handle with FILE_OPEN_FOR_BACKUP_INTENT and with all
sharing flags set. The handle is right now used in exceptions.cc only,