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Drop has_fast_cwd flag

This commit is contained in:
Corinna Vinschen 2015-12-15 15:17:18 +01:00
parent 90e6582918
commit ffcef702e7
3 changed files with 77 additions and 111 deletions
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179
winsup/cygwin/path.cc
View File

@ -3894,12 +3894,11 @@ fcwd_access_t::Free (PVOID heap)
{
/* Decrement the reference count. If it's down to 0, free
structure from heap. */
if (this && InterlockedDecrement (&ReferenceCount ()) == 0)
if (InterlockedDecrement (&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. */
/* The handle on init is always a fresh one, not the handle inherited
from the parent process. We always have to close it here.
Note: The handle could be NULL, if we cd'ed into a virtual dir. */
HANDLE h = DirectoryHandle ();
if (h)
NtClose (h);
@ -4247,113 +4246,89 @@ cwdstuff::override_win32_cwd (bool init, ULONG old_dismount_count)
UNICODE_STRING &upp_cwd_str = peb.ProcessParameters->CurrentDirectoryName;
HANDLE &upp_cwd_hdl = peb.ProcessParameters->CurrentDirectoryHandle;
if (wincap.has_fast_cwd ())
if (fast_cwd_ptr == (fcwd_access_t **) -1)
fast_cwd_ptr = find_fast_cwd ();
if (fast_cwd_ptr)
{
if (fast_cwd_ptr == (fcwd_access_t **) -1)
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. */
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,
but we simply don't care, so we allocate always room for the
new one. */
fcwd_access_t *f_cwd = (fcwd_access_t *)
RtlAllocateHeap (heap, 0, sizeof (fcwd_access_t));
if (!f_cwd)
{
/* 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. */
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,
but we simply don't care, so we allocate always room for the
new one. */
fcwd_access_t *f_cwd = (fcwd_access_t *)
RtlAllocateHeap (heap, 0, sizeof (fcwd_access_t));
if (!f_cwd)
{
debug_printf ("RtlAllocateHeap failed");
return;
}
/* Fill in the values. */
f_cwd->FillIn (dir, error ? &ro_u_pipedir : &win32,
old_dismount_count);
/* 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);
fcwd_access_t *old_cwd = *fast_cwd_ptr;
*fast_cwd_ptr = f_cwd;
f_cwd->CopyPath (upp_cwd_str);
upp_cwd_hdl = dir;
RtlLeaveCriticalSection (peb.FastPebLock);
old_cwd->Free (heap);
}
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.
Note that the call to RtlSetCurrentDirectory_U also closes our
old dir handle, so there won't be any handle left open.
This method is prone to two race conditions:
- Due to the way RtlSetCurrentDirectory_U opens the directory
handle, the directory is locked against deletion or renaming
between the RtlSetCurrentDirectory_U and the subsequent NtClose
call.
- When another thread calls SetCurrentDirectory at exactly the
same time, a crash might occur, or worse, unrelated data could
be overwritten or NtClose could be called on an unrelated handle.
Therefore, use this *only* as a fallback. */
if (!init)
{
NTSTATUS status =
RtlSetCurrentDirectory_U (error ? &ro_u_pipedir : &win32);
if (!NT_SUCCESS (status))
{
debug_printf ("RtlSetCurrentDirectory_U(%S) failed, %y",
error ? &ro_u_pipedir : &win32, status);
return;
}
}
else if (upp_cwd_hdl == NULL)
return;
RtlEnterCriticalSection (peb.FastPebLock);
fcwd_access_t::SetDirHandleFromBufferPointer(upp_cwd_str.Buffer, dir);
h = upp_cwd_hdl;
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
have to close it here. */
NtClose (h);
debug_printf ("RtlAllocateHeap failed");
return;
}
/* Fill in the values. */
f_cwd->FillIn (dir, error ? &ro_u_pipedir : &win32,
old_dismount_count);
/* 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);
fcwd_access_t *old_cwd = *fast_cwd_ptr;
*fast_cwd_ptr = f_cwd;
f_cwd->CopyPath (upp_cwd_str);
upp_cwd_hdl = dir;
RtlLeaveCriticalSection (peb.FastPebLock);
if (old_cwd)
old_cwd->Free (heap);
}
else
{
/* This method is used for all pre-Vista OSes. We simply set the values
for the CWD in the user process parameter block entirely by ourselves
under PEB lock condition. This is how RtlSetCurrentDirectory_U worked
in these older OSes, so we're safe.
/* 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.
Note that we can't just RtlEnterCriticalSection (peb.FastPebLock)
on pre-Vista. RtlAcquirePebLock was way more complicated back then. */
RtlAcquirePebLock ();
Note that the call to RtlSetCurrentDirectory_U also closes our
old dir handle, so there won't be any handle left open.
This method is prone to two race conditions:
- Due to the way RtlSetCurrentDirectory_U opens the directory
handle, the directory is locked against deletion or renaming
between the RtlSetCurrentDirectory_U and the subsequent NtClose
call.
- When another thread calls SetCurrentDirectory at exactly the
same time, a crash might occur, or worse, unrelated data could
be overwritten or NtClose could be called on an unrelated handle.
Therefore, use this *only* as a fallback. */
if (!init)
copy_cwd_str (&upp_cwd_str, error ? &ro_u_pipedir : &win32);
{
NTSTATUS status =
RtlSetCurrentDirectory_U (error ? &ro_u_pipedir : &win32);
if (!NT_SUCCESS (status))
{
debug_printf ("RtlSetCurrentDirectory_U(%S) failed, %y",
error ? &ro_u_pipedir : &win32, status);
return;
}
}
else if (upp_cwd_hdl == NULL)
return;
RtlEnterCriticalSection (peb.FastPebLock);
fcwd_access_t::SetDirHandleFromBufferPointer(upp_cwd_str.Buffer, dir);
h = upp_cwd_hdl;
upp_cwd_hdl = dir;
RtlReleasePebLock ();
/* Only on init, the handle is potentially a native handle. However,
if it's identical to dir, it's the inherited handle from a Cygwin
parent process and must not be closed. */
if (h && h != dir)
NtClose (h);
RtlLeaveCriticalSection (peb.FastPebLock);
/* The handle on init is always a fresh one, not the handle inherited
from the parent process. We always have to close it here. */
NtClose (h);
}
}

7
winsup/cygwin/wincap.cc
View File

@ -25,7 +25,6 @@ wincaps wincap_xpsp2 __attribute__((section (".cygwin_dll_common"), shared)) = {
has_gaa_largeaddress_bug:false,
has_transactions:false,
has_broken_alloc_console:false,
has_fast_cwd:false,
has_restricted_raw_disk_access:false,
use_dont_resolve_hack:true,
has_console_logon_sid:false,
@ -51,7 +50,6 @@ wincaps wincap_2003 __attribute__((section (".cygwin_dll_common"), shared)) = {
has_gaa_largeaddress_bug:false,
has_transactions:false,
has_broken_alloc_console:false,
has_fast_cwd:false,
has_restricted_raw_disk_access:false,
use_dont_resolve_hack:true,
has_console_logon_sid:false,
@ -77,7 +75,6 @@ wincaps wincap_vista __attribute__((section (".cygwin_dll_common"), shared)) = {
has_gaa_largeaddress_bug:true,
has_transactions:true,
has_broken_alloc_console:false,
has_fast_cwd:true,
has_restricted_raw_disk_access:true,
use_dont_resolve_hack:false,
has_console_logon_sid:false,
@ -103,7 +100,6 @@ wincaps wincap_7 __attribute__((section (".cygwin_dll_common"), shared)) = {
has_gaa_largeaddress_bug:true,
has_transactions:true,
has_broken_alloc_console:true,
has_fast_cwd:true,
has_restricted_raw_disk_access:true,
use_dont_resolve_hack:false,
has_console_logon_sid:true,
@ -129,7 +125,6 @@ wincaps wincap_8 __attribute__((section (".cygwin_dll_common"), shared)) = {
has_gaa_largeaddress_bug:false,
has_transactions:true,
has_broken_alloc_console:true,
has_fast_cwd:true,
has_restricted_raw_disk_access:true,
use_dont_resolve_hack:false,
has_console_logon_sid:true,
@ -155,7 +150,6 @@ wincaps wincap_10 __attribute__((section (".cygwin_dll_common"), shared)) = {
has_gaa_largeaddress_bug:false,
has_transactions:true,
has_broken_alloc_console:true,
has_fast_cwd:true,
has_restricted_raw_disk_access:true,
use_dont_resolve_hack:false,
has_console_logon_sid:true,
@ -181,7 +175,6 @@ wincaps wincap_10_1511 __attribute__((section (".cygwin_dll_common"), shared)) =
has_gaa_largeaddress_bug:false,
has_transactions:true,
has_broken_alloc_console:true,
has_fast_cwd:true,
has_restricted_raw_disk_access:true,
use_dont_resolve_hack:false,
has_console_logon_sid:true,

2
winsup/cygwin/wincap.h
View File

@ -18,7 +18,6 @@ struct wincaps
unsigned has_gaa_largeaddress_bug : 1;
unsigned has_transactions : 1;
unsigned has_broken_alloc_console : 1;
unsigned has_fast_cwd : 1;
unsigned has_restricted_raw_disk_access : 1;
unsigned use_dont_resolve_hack : 1;
unsigned has_console_logon_sid : 1;
@ -69,7 +68,6 @@ public:
bool IMPLEMENT (has_gaa_largeaddress_bug)
bool IMPLEMENT (has_transactions)
bool IMPLEMENT (has_broken_alloc_console)
bool IMPLEMENT (has_fast_cwd)
bool IMPLEMENT (has_restricted_raw_disk_access)
bool IMPLEMENT (use_dont_resolve_hack)
bool IMPLEMENT (has_console_logon_sid)