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* path.cc (struct _FAST_CWD): Redefine to new layout used since patch 

for KB 2393802.  Adjust comments throughout.
	(struct _FAST_CWD_OLD): Rename former definition.
	(cwdstuff::override_win32_cwd): Check if the OS is using the old or the
	new FAST_CWD structure layout and handle accordingly.
This commit is contained in:
Corinna Vinschen 2011-02-13 15:43:00 +00:00
parent 8447bf9f9f
commit 32d86d2ab2
2 changed files with 107 additions and 31 deletions
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8
winsup/cygwin/ChangeLog
View File

@ -1,3 +1,11 @@
2011-02-13 Corinna Vinschen <corinna@vinschen.de>
* path.cc (struct _FAST_CWD): Redefine to new layout used since patch
for KB 2393802. Adjust comments throughout.
(struct _FAST_CWD_OLD): Rename former definition.
(cwdstuff::override_win32_cwd): Check if the OS is using the old or the
new FAST_CWD structure layout and handle accordingly.
2011-02-11 Christopher Faylor <me+cygwin@cgf.cx>
* mkstatic: Make sure that we are not cd'ed to temporary directory on

130
winsup/cygwin/path.cc
View File

@ -3432,6 +3432,20 @@ cygwin_split_path (const char *path, char *dir, char *file)
minimal locking and it's much more multi-thread friendly. Presumably
it minimizes contention when accessing the CWD. */
typedef struct _FAST_CWD {
UNICODE_STRING Path; /* Path's Buffer member always refers
to the following Buffer array. */
HANDLE DirectoryHandle;
LONG FSCharacteristics; /* Taken from FileFsDeviceInformation */
LONG ReferenceCount; /* Only release when this is 0. */
ULONG OldDismountCount; /* Reflects the system DismountCount
at the time the CWD has been set. */
WCHAR Buffer[MAX_PATH];
} FAST_CWD, *PFAST_CWD;
/* This is the old FAST_CWD structure up to the patch from KB 2393802,
release in February 2011. Hopefully it's not used for long anymore,
but for quite some time we can't rely on this fact. */
typedef struct _FAST_CWD_OLD {
LONG ReferenceCount; /* Only release when this is 0. */
HANDLE DirectoryHandle;
ULONG OldDismountCount; /* Reflects the system DismountCount
@ -3439,7 +3453,7 @@ typedef struct _FAST_CWD {
UNICODE_STRING Path; /* Path's Buffer member always refers
to the following Buffer array. */
WCHAR Buffer[MAX_PATH];
} FAST_CWD, *PFAST_CWD;
} FAST_CWD_OLD, *PFAST_CWD_OLD;
/* fast_cwd_ptr is a pointer to the global pointer in ntdll.dll pointing
to the FAST_CWD structure which constitutes the CWD.
@ -3556,7 +3570,10 @@ cwdstuff::override_win32_cwd (bool init, ULONG old_dismount_count)
fast_cwd_ptr, we can simply replace the RtlSetCurrentDirectory_U
function entirely, just as on pre-Vista. */
PVOID heap = peb.ProcessHeap;
/* First allocate a new FAST_CWD strcuture on the heap. */
/* First allocate a new FAST_CWD structure on the heap.
The new FAST_CWD structure is 4 byte bigger than the old one,
but we simply don't care, so we allocate always room for the
new one. */
PFAST_CWD f_cwd = (PFAST_CWD)
RtlAllocateHeap (heap, 0, sizeof (FAST_CWD));
if (!f_cwd)
@ -3564,35 +3581,82 @@ cwdstuff::override_win32_cwd (bool init, ULONG old_dismount_count)
debug_printf ("RtlAllocateHeap failed");
return;
}
/* Fill in the values. */
f_cwd->ReferenceCount = 1;
f_cwd->DirectoryHandle = dir;
f_cwd->OldDismountCount = old_dismount_count;
RtlInitEmptyUnicodeString (&f_cwd->Path, f_cwd->Buffer,
MAX_PATH * sizeof (WCHAR));
copy_cwd_str (&f_cwd->Path, error ? &ro_u_pipedir : &win32);
/* Use PEB lock when switching fast_cwd_ptr to the new FAST_CWD
structure and writing the CWD to the user process parameter
block. This is equivalent to calling RtlAcquirePebLock/
RtlReleasePebLock, but without having to go through the FS
selector again. */
RtlEnterCriticalSection (peb.FastPebLock);
PFAST_CWD old_cwd = *fast_cwd_ptr;
*fast_cwd_ptr = f_cwd;
upp_cwd_str = f_cwd->Path;
upp_cwd_hdl = dir;
RtlLeaveCriticalSection (peb.FastPebLock);
/* Decrement the reference count. If it's down to 0, free structure
from heap. */
if (old_cwd && InterlockedDecrement (&old_cwd->ReferenceCount) == 0)
/* Fill in the values. Fortunately it's simple to check for the
new structure. Path.MaximumLength takes the same space as the
high word of the old ReferenceCount. We know that MaximumLength
is always MAX_PATH. For the ref count this would account for a
pratically impossible value between 34078720 and 34079240. */
if ((*fast_cwd_ptr)->Path.MaximumLength == MAX_PATH * sizeof (WCHAR))
{
/* In contrast to pre-Vista, the handle on init is always a fresh
one and not the handle inherited from the parent process. So
we always have to close it here. However, the handle could
be NULL, if we cd'ed into a virtual dir. */
if (old_cwd->DirectoryHandle)
NtClose (old_cwd->DirectoryHandle);
RtlFreeHeap (heap, 0, old_cwd);
/* New FAST_CWD structure. */
IO_STATUS_BLOCK io;
FILE_FS_DEVICE_INFORMATION ffdi;
RtlInitEmptyUnicodeString (&f_cwd->Path, f_cwd->Buffer,
MAX_PATH * sizeof (WCHAR));
f_cwd->DirectoryHandle = dir;
/* The new structure stores the device characteristics of the
volume holding the dir. RtlGetCurrentDirectory_U checks
if the FILE_REMOVABLE_MEDIA flag is set and, if so, checks if
the volume is still the same as the one used when opening
the directory handle.
We don't call NtQueryVolumeInformationFile for the \\?\PIPE,
though. It just returns STATUS_INVALID_HANDLE anyway. */
f_cwd->FSCharacteristics =
(!error
&& NT_SUCCESS (NtQueryVolumeInformationFile (dir, &io, &ffdi,
sizeof ffdi, FileFsDeviceInformation)))
? ffdi.Characteristics : 0;
f_cwd->ReferenceCount = 1;
f_cwd->OldDismountCount = old_dismount_count;
copy_cwd_str (&f_cwd->Path, error ? &ro_u_pipedir : &win32);
/* Use PEB lock when switching fast_cwd_ptr to the new FAST_CWD
structure and writing the CWD to the user process parameter
block. This is equivalent to calling RtlAcquirePebLock/
RtlReleasePebLock, but without having to go through the FS
selector again. */
RtlEnterCriticalSection (peb.FastPebLock);
PFAST_CWD old_cwd = *fast_cwd_ptr;
*fast_cwd_ptr = f_cwd;
upp_cwd_str = f_cwd->Path;
upp_cwd_hdl = dir;
RtlLeaveCriticalSection (peb.FastPebLock);
/* Decrement the reference count. If it's down to 0, free
structure from heap. */
if (InterlockedDecrement (&old_cwd->ReferenceCount) == 0)
{
/* In contrast to pre-Vista, the handle on init is always a
fresh one and not the handle inherited from the parent
process. So we always have to close it here. However, the
handle could be NULL, if we cd'ed into a virtual dir. */
if (old_cwd->DirectoryHandle)
NtClose (old_cwd->DirectoryHandle);
RtlFreeHeap (heap, 0, old_cwd);
}
}
else
{
/* Old FAST_CWD structure. Otherwise same procedure as above,
except for the non-existant FSCharacteristics member. */
PFAST_CWD_OLD f_cwd_old = (PFAST_CWD_OLD) f_cwd;
f_cwd_old->ReferenceCount = 1;
f_cwd_old->DirectoryHandle = dir;
f_cwd_old->OldDismountCount = old_dismount_count;
RtlInitEmptyUnicodeString (&f_cwd_old->Path, f_cwd_old->Buffer,
MAX_PATH * sizeof (WCHAR));
copy_cwd_str (&f_cwd_old->Path, error ? &ro_u_pipedir : &win32);
RtlEnterCriticalSection (peb.FastPebLock);
PFAST_CWD_OLD old_cwd = (PFAST_CWD_OLD) *fast_cwd_ptr;
*fast_cwd_ptr = (PFAST_CWD) f_cwd_old;
upp_cwd_str = f_cwd_old->Path;
upp_cwd_hdl = dir;
RtlLeaveCriticalSection (peb.FastPebLock);
if (InterlockedDecrement (&old_cwd->ReferenceCount) == 0)
{
if (old_cwd->DirectoryHandle)
NtClose (old_cwd->DirectoryHandle);
RtlFreeHeap (heap, 0, old_cwd);
}
}
}
else
@ -3636,8 +3700,12 @@ cwdstuff::override_win32_cwd (bool init, ULONG old_dismount_count)
PFAST_CWD f_cwd = (PFAST_CWD)
((PBYTE) upp_cwd_str.Buffer
- __builtin_offsetof (struct _FAST_CWD, Buffer));
if (f_cwd->Path.MaximumLength == MAX_PATH * sizeof (WCHAR))
f_cwd->DirectoryHandle = dir;
else
((PFAST_CWD_OLD) f_cwd)->DirectoryHandle = dir;
h = upp_cwd_hdl;
f_cwd->DirectoryHandle = upp_cwd_hdl = dir;
upp_cwd_hdl = dir;
RtlLeaveCriticalSection (peb.FastPebLock);
/* In contrast to pre-Vista, the handle on init is always a fresh one
and not the handle inherited from the parent process. So we always