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flock.cc
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/* flock.cc. NT specific implementation of advisory file locking.
This file is part of Cygwin.
This software is a copyrighted work licensed under the terms of the
Cygwin license. Please consult the file "CYGWIN_LICENSE" for
details. */
/* The basic mechanism as well as the datastructures used in the below
implementation are taken from the FreeBSD repository on 2008-03-18.
The essential code of the lf_XXX functions has been taken from the
module src/sys/kern/kern_lockf.c. It has been adapted to use NT
global namespace subdirs and event objects for synchronization
purposes.
So, the following copyright applies to most of the code in the lf_XXX
functions.
* Copyright (c) 1982, 1986, 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Scooter Morris at Genentech Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)ufs_lockf.c 8.3 (Berkeley) 1/6/94
*/
/*
* The flock() function is based upon source taken from the Red Hat
* implementation used in their imap-2002d SRPM.
*
* $RH: flock.c,v 1.2 2000/08/23 17:07:00 nalin Exp $
*/
/* The lockf function is based upon FreeBSD sources with the following
* copyright.
*/
/*
* Copyright (c) 1997 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Klaus Klein.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "winsup.h"
#include <assert.h>
#include <sys/file.h>
#include <unistd.h>
#include <stdlib.h>
#include "cygerrno.h"
#include "security.h"
#include "shared_info.h"
#include "path.h"
#include "fhandler.h"
#include "dtable.h"
#include "cygheap.h"
#include "pinfo.h"
#include "sigproc.h"
#include "cygtls.h"
#include "tls_pbuf.h"
#include "miscfuncs.h"
#include "ntdll.h"
#include <sys/queue.h>
#include <wchar.h>
#define F_WAIT 0x10 /* Wait until lock is granted */
#define F_FLOCK 0x20 /* Use flock(2) semantics for lock */
#define F_POSIX 0x40 /* Use POSIX semantics for lock */
#ifndef OFF_MAX
#define OFF_MAX LLONG_MAX
#endif
static NO_COPY muto lockf_guard;
#define INODE_LIST_LOCK() (lockf_guard.init ("lockf_guard")->acquire ())
#define INODE_LIST_UNLOCK() (lockf_guard.release ())
#define LOCK_DIR_NAME_FMT L"flock-%08x-%016X"
#define LOCK_DIR_NAME_LEN 31 /* Length of the resulting name */
#define LOCK_DIR_NAME_DEV_OFF 6 /* Offset to device number */
#define LOCK_DIR_NAME_INO_OFF 15 /* Offset to inode number */
/* Don't change format without also changing lockf_t::from_obj_name! */
#define LOCK_OBJ_NAME_FMT L"%02x-%01x-%016X-%016X-%016X-%08x-%04x"
#define LOCK_OBJ_NAME_LEN 69 /* Length of the resulting name */
#define FLOCK_INODE_DIR_ACCESS (DIRECTORY_QUERY \
| DIRECTORY_TRAVERSE \
| DIRECTORY_CREATE_OBJECT \
| READ_CONTROL)
#define FLOCK_EVENT_ACCESS (EVENT_QUERY_STATE \
| SYNCHRONIZE \
| READ_CONTROL)
/* This function takes the own process security descriptor DACL and adds
SYNCHRONIZE permissions for everyone. This allows all processes
to wait for this process to die when blocking in a F_SETLKW on a lock
which is hold by this process. */
static void
allow_others_to_sync ()
{
static NO_COPY bool done;
if (done)
return;
NTSTATUS status;
PACL dacl;
LPVOID ace;
ULONG len;
/* Get this process DACL. We use a rather small stack buffer here which
should be more than sufficient for process ACLs. Can't use tls functions
at this point because this gets called during initialization when the tls
is not really available. */
#define MAX_PROCESS_SD_SIZE 3072
PISECURITY_DESCRIPTOR sd = (PISECURITY_DESCRIPTOR) alloca (MAX_PROCESS_SD_SIZE);
status = NtQuerySecurityObject (NtCurrentProcess (),
DACL_SECURITY_INFORMATION, sd,
MAX_PROCESS_SD_SIZE, &len);
if (!NT_SUCCESS (status))
{
debug_printf ("NtQuerySecurityObject: %y", status);
return;
}
/* Create a valid dacl pointer and set its size to be as big as
there's room in the temporary buffer. Note that the descriptor
is in self-relative format. */
BOOLEAN present, defaulted;
RtlGetDaclSecurityDescriptor (sd, &present, &dacl, &defaulted);
if (!present) /* If so, dacl has undefined value. */
{
dacl = (PACL) (sd + 1);
RtlCreateAcl (dacl, MAX_PROCESS_SD_SIZE - sizeof *sd, ACL_REVISION);
}
else if (dacl == NULL) /* Everyone has all access anyway */
{
done = true;
return;
}
else
{
dacl->AclSize = MAX_PROCESS_SD_SIZE - ((PBYTE) dacl - (PBYTE) sd);
}
/* Allow everyone to SYNCHRONIZE with this process. */
status = RtlAddAccessAllowedAce (dacl, ACL_REVISION, SYNCHRONIZE,
well_known_world_sid);
if (!NT_SUCCESS (status))
{
debug_printf ("RtlAddAccessAllowedAce: %y", status);
return;
}
/* Set the size of the DACL correctly. */
status = RtlFirstFreeAce (dacl, &ace);
if (!NT_SUCCESS (status))
{
debug_printf ("RtlFirstFreeAce: %y", status);
return;
}
dacl->AclSize = (char *) ace - (char *) dacl;
/* Write the DACL back. */
status = NtSetSecurityObject (NtCurrentProcess (), DACL_SECURITY_INFORMATION, sd);
if (!NT_SUCCESS (status))
{
debug_printf ("NtSetSecurityObject: %y", status);
return;
}
done = true;
}
/* Helper struct to construct a local OBJECT_ATTRIBUTES on the stack. */
struct lockfattr_t
{
OBJECT_ATTRIBUTES attr;
UNICODE_STRING uname;
WCHAR name[LOCK_OBJ_NAME_LEN + 1];
};
/* Per lock class. */
class lockf_t
{
public:
uint16_t lf_flags; /* Semantics: F_POSIX, F_FLOCK, F_WAIT */
uint16_t lf_type; /* Lock type: F_RDLCK, F_WRLCK */
off_t lf_start; /* Byte # of the start of the lock */
off_t lf_end; /* Byte # of the end of the lock (-1=EOF) */
int64_t lf_id; /* Cygwin PID for POSIX locks, a unique id per
file table entry for BSD flock locks. */
DWORD lf_wid; /* Win PID of the resource holding the lock */
uint16_t lf_ver; /* Version number of the lock. If a released
lock event yet exists because another process
is still waiting for it, we use the version
field to distinguish old from new locks. */
class lockf_t **lf_head; /* Back pointer to the head of the lockf_t list */
class inode_t *lf_inode; /* Back pointer to the inode_t */
class lockf_t *lf_next; /* Pointer to the next lock on this inode_t */
HANDLE lf_obj; /* Handle to the lock event object. */
lockf_t ()
: lf_flags (0), lf_type (0), lf_start (0), lf_end (0), lf_id (0),
lf_wid (0), lf_ver (0), lf_head (NULL), lf_inode (NULL),
lf_next (NULL), lf_obj (NULL)
{}
lockf_t (class inode_t *node, class lockf_t **head,
short flags, short type, off_t start, off_t end,
long long id, DWORD wid, uint16_t ver)
: lf_flags (flags), lf_type (type), lf_start (start), lf_end (end),
lf_id (id), lf_wid (wid), lf_ver (ver), lf_head (head), lf_inode (node),
lf_next (NULL), lf_obj (NULL)
{}
~lockf_t ();
bool from_obj_name (class inode_t *node, class lockf_t **head,
const wchar_t *name);
/* Used to create all locks list in a given TLS buffer. */
void *operator new (size_t size, void *p)
{ return p; }
/* Used to store own lock list in the cygheap. */
void *operator new (size_t size)
{ return cmalloc (HEAP_FHANDLER, sizeof (lockf_t)); }
/* Never call on node->i_all_lf! */
void operator delete (void *p)
{ cfree (p); }
POBJECT_ATTRIBUTES create_lock_obj_attr (lockfattr_t *attr,
ULONG flags, void *sd_buf);
void create_lock_obj ();
bool open_lock_obj ();
void close_lock_obj () { NtClose (lf_obj); lf_obj = NULL; }
void del_lock_obj (HANDLE fhdl, bool signal = false);
};
/* Per inode_t class */
class inode_t
{
friend class lockf_t;
public:
LIST_ENTRY (inode_t) i_next;
lockf_t *i_lockf; /* List of locks of this process. */
lockf_t *i_all_lf; /* Temp list of all locks for this file. */
dev_t i_dev; /* Device ID */
ino_t i_ino; /* inode number */
private:
HANDLE i_dir;
HANDLE i_mtx;
uint32_t i_cnt; /* # of threads referencing this instance. */
public:
inode_t (dev_t dev, ino_t ino);
~inode_t ();
void *operator new (size_t size)
{ return cmalloc (HEAP_FHANDLER, sizeof (inode_t)); }
void operator delete (void *p)
{ cfree (p); }
static inode_t *get (dev_t dev, ino_t ino,
bool create_if_missing, bool lock);
void LOCK () { WaitForSingleObject (i_mtx, INFINITE); }
void UNLOCK () { ReleaseMutex (i_mtx); }
void use () { ++i_cnt; }
void unuse () { if (i_cnt > 0) --i_cnt; }
bool inuse () { return i_cnt > 0; }
void notused () { i_cnt = 0; }
void unlock_and_remove_if_unused ();
lockf_t *get_all_locks_list ();
bool del_my_locks (long long id, HANDLE fhdl);
};
inode_t::~inode_t ()
{
lockf_t *lock, *n_lock;
for (lock = i_lockf; lock && (n_lock = lock->lf_next, 1); lock = n_lock)
delete lock;
NtClose (i_mtx);
NtClose (i_dir);
}
void
inode_t::unlock_and_remove_if_unused ()
{
UNLOCK ();
INODE_LIST_LOCK ();
unuse ();
if (i_lockf == NULL && !inuse ())
{
LIST_REMOVE (this, i_next);
delete this;
}
INODE_LIST_UNLOCK ();
}
bool
inode_t::del_my_locks (long long id, HANDLE fhdl)
{
lockf_t *lock, *n_lock;
lockf_t **prev = &i_lockf;
for (lock = *prev; lock && (n_lock = lock->lf_next, 1); lock = n_lock)
{
if (lock->lf_flags & F_POSIX)
{
/* Delete all POSIX locks. */
*prev = n_lock;
/* When called during fork, the POSIX lock must get deleted but
*not* signalled. The lock is still active and locked in the
parent. So in case of fork, we call close_lock_obj explicitely,
since del_lock_obj is called from the destructor. */
if (!id)
lock->close_lock_obj ();
delete lock;
}
else if (id && lock->lf_id == id)
{
int cnt = 0;
cygheap_fdenum cfd (true);
while (cfd.next () >= 0)
if (cfd->get_unique_id () == lock->lf_id && ++cnt > 1)
break;
/* Delete BSD flock lock when no other fd in this process references
it anymore. */
if (cnt <= 1)
{
*prev = n_lock;
lock->del_lock_obj (fhdl);
delete lock;
}
}
else
prev = &lock->lf_next;
}
return i_lockf == NULL;
}
/* Used to delete the locks on a file hold by this process. Called from
close(2) and fixup_after_fork, as well as from fixup_after_exec in
case the close_on_exec flag is set. The whole inode is deleted as
soon as no lock exists on it anymore. */
void
fhandler_base::del_my_locks (del_lock_called_from from)
{
inode_t *node = inode_t::get (get_dev (), get_ino (), false, true);
if (node)
{
/* When we're called from fixup_after_exec, the fhandler is a
close-on-exec fhandler. In this case our io handle is already
invalid. We can't use it to test for the object reference count.
However, that shouldn't be necessary for the following reason.
After exec, there are no threads in the current process waiting for
the lock. So, either we're the only process accessing the file table
entry and there are no threads which require signalling, or we have
a parent process still accessing the file object and signalling the
lock event would be premature. */
node->del_my_locks (from == after_fork ? 0 : get_unique_id (),
from == after_exec ? NULL : get_handle ());
node->unlock_and_remove_if_unused ();
}
}
/* Called in an execed child. The exec'ed process must allow SYNCHRONIZE
access to everyone if at least one inode exists.
The lock owner's Windows PID changed and all POSIX lock event objects
have to be relabeled so that waiting processes know which process to
wait on. If the node has been abandoned due to close_on_exec on the
referencing fhandlers, remove the inode entirely. */
void
fixup_lockf_after_exec (bool exec)
{
inode_t *node, *next_node;
INODE_LIST_LOCK ();
if (LIST_FIRST (&cygheap->inode_list))
allow_others_to_sync ();
LIST_FOREACH_SAFE (node, &cygheap->inode_list, i_next, next_node)
{
node->notused ();
int cnt = 0;
cygheap_fdenum cfd (true);
while (cfd.next () >= 0)
if (cfd->get_dev () == node->i_dev
&& cfd->get_ino () == node->i_ino
&& ++cnt >= 1)
break;
if (cnt == 0)
{
LIST_REMOVE (node, i_next);
delete node;
}
else
{
node->LOCK ();
lockf_t *lock, *n_lock;
lockf_t **prev = &node->i_lockf;
for (lock = *prev; lock && (n_lock = lock->lf_next, 1); lock = n_lock)
if (lock->lf_flags & F_POSIX)
{
if (exec)
{
/* The parent called exec. The lock is passed to the child.
Recreate lock object with changed ownership. */
lock->del_lock_obj (NULL);
lock->lf_wid = myself->dwProcessId;
lock->lf_ver = 0;
lock->create_lock_obj ();
}
else
{
/* The parent called spawn. The parent continues to hold
the POSIX lock, ownership is not passed to the child.
Give up the lock in the child. */
*prev = n_lock;
lock->close_lock_obj ();
delete lock;
}
}
node->UNLOCK ();
}
}
INODE_LIST_UNLOCK ();
}
/* static method to return a pointer to the inode_t structure for a specific
file. The file is specified by the device and inode_t number. If inode_t
doesn't exist, create it. */
inode_t *
inode_t::get (dev_t dev, ino_t ino, bool create_if_missing, bool lock)
{
inode_t *node;
INODE_LIST_LOCK ();
LIST_FOREACH (node, &cygheap->inode_list, i_next)
if (node->i_dev == dev && node->i_ino == ino)
break;
if (!node && create_if_missing)
{
node = new inode_t (dev, ino);
if (node)
LIST_INSERT_HEAD (&cygheap->inode_list, node, i_next);
}
if (node)
node->use ();
INODE_LIST_UNLOCK ();
if (node && lock)
node->LOCK ();
return node;
}
inode_t::inode_t (dev_t dev, ino_t ino)
: i_lockf (NULL), i_all_lf (NULL), i_dev (dev), i_ino (ino), i_cnt (0L)
{
HANDLE parent_dir;
WCHAR name[48];
UNICODE_STRING uname;
OBJECT_ATTRIBUTES attr;
NTSTATUS status;
parent_dir = get_shared_parent_dir ();
/* Create a subdir which is named after the device and inode_t numbers
of the given file, in hex notation. */
int len = __small_swprintf (name, LOCK_DIR_NAME_FMT, dev, ino);
RtlInitCountedUnicodeString (&uname, name, len * sizeof (WCHAR));
InitializeObjectAttributes (&attr, &uname, OBJ_INHERIT | OBJ_OPENIF,
parent_dir, everyone_sd (FLOCK_INODE_DIR_ACCESS));
status = NtCreateDirectoryObject (&i_dir, FLOCK_INODE_DIR_ACCESS, &attr);
if (!NT_SUCCESS (status))
api_fatal ("NtCreateDirectoryObject(inode): %y", status);
/* Create a mutex object in the file specific dir, which is used for
access synchronization on the dir and its objects. */
InitializeObjectAttributes (&attr, &ro_u_mtx, OBJ_INHERIT | OBJ_OPENIF, i_dir,
everyone_sd (CYG_MUTANT_ACCESS));
status = NtCreateMutant (&i_mtx, CYG_MUTANT_ACCESS, &attr, FALSE);
if (!NT_SUCCESS (status))
api_fatal ("NtCreateMutant(inode): %y", status);
}
/* Enumerate all lock event objects for this file and create a lockf_t
list in the i_all_lf member. This list is searched in lf_getblock
for locks which potentially block our lock request. */
/* Number of lockf_t structs which fit in the temporary buffer. */
#define MAX_LOCKF_CNT ((intptr_t)((NT_MAX_PATH * sizeof (WCHAR)) \
/ sizeof (lockf_t)))
bool
lockf_t::from_obj_name (inode_t *node, lockf_t **head, const wchar_t *name)
{
wchar_t *endptr;
/* "%02x-%01x-%016X-%016X-%016X-%08x-%04x",
lf_flags, lf_type, lf_start, lf_end, lf_id, lf_wid, lf_ver */
lf_flags = wcstol (name, &endptr, 16);
if ((lf_flags & ~(F_FLOCK | F_POSIX)) != 0
|| ((lf_flags & (F_FLOCK | F_POSIX)) == (F_FLOCK | F_POSIX)))
return false;
lf_type = wcstol (endptr + 1, &endptr, 16);
if ((lf_type != F_RDLCK && lf_type != F_WRLCK) || !endptr || *endptr != L'-')
return false;
lf_start = (off_t) wcstoull (endptr + 1, &endptr, 16);
if (lf_start < 0 || !endptr || *endptr != L'-')
return false;
lf_end = (off_t) wcstoull (endptr + 1, &endptr, 16);
if (lf_end < -1LL
|| (lf_end > 0 && lf_end < lf_start)
|| !endptr || *endptr != L'-')
return false;
lf_id = wcstoll (endptr + 1, &endptr, 16);
if (!endptr || *endptr != L'-'
|| ((lf_flags & F_POSIX) && (lf_id < 1 || lf_id > UINT32_MAX)))
return false;
lf_wid = wcstoul (endptr + 1, &endptr, 16);
if (!endptr || *endptr != L'-')
return false;
lf_ver = wcstoul (endptr + 1, &endptr, 16);
if (endptr && *endptr != L'\0')
return false;
lf_head = head;
lf_inode = node;
lf_next = NULL;
lf_obj = NULL;
return true;
}
lockf_t *
inode_t::get_all_locks_list ()
{
tmp_pathbuf tp;
ULONG context;
NTSTATUS status;
BOOLEAN restart = TRUE;
bool last_run = false;
lockf_t newlock, *lock = i_all_lf;
PDIRECTORY_BASIC_INFORMATION dbi_buf = (PDIRECTORY_BASIC_INFORMATION)
tp.w_get ();
while (!last_run)
{
status = NtQueryDirectoryObject (i_dir, dbi_buf, 65536, FALSE, restart,
&context, NULL);
if (!NT_SUCCESS (status))
{
debug_printf ("NtQueryDirectoryObject, status %y", status);
break;
}
if (status != STATUS_MORE_ENTRIES)
last_run = true;
restart = FALSE;
for (PDIRECTORY_BASIC_INFORMATION dbi = dbi_buf;
dbi->ObjectName.Length > 0;
dbi++)
{
if (dbi->ObjectName.Length != LOCK_OBJ_NAME_LEN * sizeof (WCHAR))
continue;
dbi->ObjectName.Buffer[LOCK_OBJ_NAME_LEN] = L'\0';
if (!newlock.from_obj_name (this, &i_all_lf, dbi->ObjectName.Buffer))
continue;
if (lock - i_all_lf >= MAX_LOCKF_CNT)
{
system_printf ("Warning, can't handle more than %d locks per file.",
MAX_LOCKF_CNT);
break;
}
if (lock > i_all_lf)
lock[-1].lf_next = lock;
new (lock++) lockf_t (newlock);
}
}
/* If no lock has been found, return NULL. */
if (lock == i_all_lf)
return NULL;
return i_all_lf;
}
/* Create the lock object name. The name is constructed from the lock
properties which identify it uniquely, all values in hex. */
POBJECT_ATTRIBUTES
lockf_t::create_lock_obj_attr (lockfattr_t *attr, ULONG flags, void *sd_buf)
{
__small_swprintf (attr->name, LOCK_OBJ_NAME_FMT,
lf_flags & (F_POSIX | F_FLOCK), lf_type, lf_start, lf_end,
lf_id, lf_wid, lf_ver);
RtlInitCountedUnicodeString (&attr->uname, attr->name,
LOCK_OBJ_NAME_LEN * sizeof (WCHAR));
InitializeObjectAttributes (&attr->attr, &attr->uname, flags, lf_inode->i_dir,
_everyone_sd (sd_buf, FLOCK_EVENT_ACCESS));
return &attr->attr;
}
DWORD
create_lock_in_parent (PVOID param)
{
HANDLE lf_obj;
ULONG size;
OBJECT_NAME_INFORMATION *ntfn;
NTSTATUS status;
wchar_t *lockname, *inodename, *endptr;
dev_t dev;
ino_t ino;
inode_t *node;
lockf_t newlock, *lock;
int cnt;
/* param is the handle to the lock object, created by caller. */
lf_obj = (HANDLE) param;
/* Fetch object path from handle. Typically the length of the path
is 146 characters, starting with
"\BaseNamedObject\cygwin-1S5-<16-hex-digits>\..." */
size = sizeof (OBJECT_NAME_INFORMATION) + 256 * sizeof (WCHAR);
ntfn = (OBJECT_NAME_INFORMATION *) alloca (size);
memset (ntfn, 0, size);
status = NtQueryObject (lf_obj, ObjectNameInformation, ntfn, size, &size);
if (!NT_SUCCESS (status))
goto err;
ntfn->Name.Buffer[ntfn->Name.Length / sizeof (WCHAR)] = L'\0';
/* Sanity check so that we don't peek into unchartered territory. */
if (ntfn->Name.Length < LOCK_OBJ_NAME_LEN + LOCK_DIR_NAME_LEN + 1)
goto err;
/* The names have fixed size, so we know where the substrings start. */
lockname = ntfn->Name.Buffer + ntfn->Name.Length / sizeof (WCHAR)
- LOCK_OBJ_NAME_LEN;
inodename = lockname - LOCK_DIR_NAME_LEN - 1;
dev = wcstoul (inodename + LOCK_DIR_NAME_DEV_OFF, &endptr, 16);
if (*endptr != L'-')
goto err;
ino = wcstoull (inodename + LOCK_DIR_NAME_INO_OFF, &endptr, 16);
if (*endptr != L'\\')
goto err;
if (!newlock.from_obj_name (NULL, NULL, lockname))
goto err;
/* Check if we have an open file handle with the same unique id. */
{
cnt = 0;
cygheap_fdenum cfd (true);
while (cfd.next () >= 0)
if (cfd->get_unique_id () == newlock.lf_id && ++cnt > 0)
break;
}
/* If not, close handle and return. */
if (!cnt)
{
NtClose (lf_obj);
return 0;
}
/* The handle gets created non-inheritable. That's fine, unless the parent
starts another process accessing this object. So, after it's clear we
have to store the handle for further use, make sure it gets inheritable
by child processes. */
if (!SetHandleInformation (lf_obj, HANDLE_FLAG_INHERIT, HANDLE_FLAG_INHERIT))
goto err;
/* otherwise generate inode from directory name... */
node = inode_t::get (dev, ino, true, false);
/* ...and generate lock from object name. */
lock = new lockf_t (newlock);
lock->lf_inode = node;
lock->lf_head = &node->i_lockf;
lock->lf_next = node->i_lockf;
lock->lf_obj = lf_obj;
node->i_lockf = lock;
node->unuse ();
return 0;
err:
system_printf ("Adding <%S> lock failed", &ntfn->Name);
NtClose (lf_obj);
return 1;
}
DWORD
delete_lock_in_parent (PVOID param)
{
inode_t *node, *next_node;
lockf_t *lock, **prev;
/* Scan list of all inodes, and reap stale BSD lock if lf_id matches.
Remove inode if empty. */
INODE_LIST_LOCK ();
LIST_FOREACH_SAFE (node, &cygheap->inode_list, i_next, next_node)
if (!node->inuse ())
{
for (prev = &node->i_lockf, lock = *prev; lock; lock = *prev)
{
if ((lock->lf_flags & F_FLOCK) && IsEventSignalled (lock->lf_obj))
{
*prev = lock->lf_next;
delete lock;
}
else
prev = &lock->lf_next;
}
if (node->i_lockf == NULL)
{
LIST_REMOVE (node, i_next);
delete node;
}
}
INODE_LIST_UNLOCK ();
return 0;
}
/* Create the lock event object in the file's subdir in the NT global
namespace. */
void
lockf_t::create_lock_obj ()
{
lockfattr_t attr;
NTSTATUS status;
PSECURITY_DESCRIPTOR sd_buf = alloca (SD_MIN_SIZE);
POBJECT_ATTRIBUTES lock_obj_attr;
do
{
lock_obj_attr = create_lock_obj_attr (&attr, OBJ_INHERIT, sd_buf);
status = NtCreateEvent (&lf_obj, CYG_EVENT_ACCESS, lock_obj_attr,
NotificationEvent, FALSE);
if (!NT_SUCCESS (status))
{
if (status != STATUS_OBJECT_NAME_COLLISION)
api_fatal ("NtCreateEvent(lock): %y", status);
/* If we get a STATUS_OBJECT_NAME_COLLISION, the event still exists
because some other process is waiting for it in lf_setlock.
If so, check the event's signal state. If we can't open it, it
has been closed in the meantime, so just try again. If we can
open it and the object is not signalled, it's surely a bug in the
code somewhere. Otherwise, close the event and retry to create
a new event with another name. */
if (open_lock_obj ())
{
if (!IsEventSignalled (lf_obj))
api_fatal ("NtCreateEvent(lock): %y", status);
close_lock_obj ();
/* Increment the lf_ver field until we have no collision. */
++lf_ver;
}
}
}
while (!NT_SUCCESS (status));
/* For BSD locks, notify the parent process. */
if (lf_flags & F_FLOCK)
{
HANDLE parent_proc, parent_thread, parent_lf_obj;
pinfo p (myself->ppid);
if (!p) /* No access or not a Cygwin parent. */
return;
parent_proc = OpenProcess (PROCESS_DUP_HANDLE
| PROCESS_CREATE_THREAD
| PROCESS_QUERY_INFORMATION
| PROCESS_VM_OPERATION
| PROCESS_VM_WRITE
| PROCESS_VM_READ,
FALSE, p->dwProcessId);
if (!parent_proc)
{
debug_printf ("OpenProcess (%u): %E", p->dwProcessId);
return;
}
if (!DuplicateHandle (GetCurrentProcess (), lf_obj, parent_proc,
&parent_lf_obj, TRUE, FALSE, DUPLICATE_SAME_ACCESS))
debug_printf ("DuplicateHandle (lf_obj): %E");
else
{
parent_thread = CreateRemoteThread (parent_proc, NULL, 256 * 1024,
create_lock_in_parent,
parent_lf_obj,
STACK_SIZE_PARAM_IS_A_RESERVATION,
NULL);
if (!parent_thread)
{
debug_printf ("CreateRemoteThread: %E");
/* If thread didn't get started, close object handle in parent,
otherwise suffer handle leaks. */
DuplicateHandle (parent_proc, parent_lf_obj, parent_proc,
NULL, 0, FALSE, DUPLICATE_CLOSE_SOURCE);
}
else
{
/* Must wait to avoid race conditions. */
WaitForSingleObject (parent_thread, INFINITE);
CloseHandle (parent_thread);
}
}
CloseHandle (parent_proc);
}
}
/* Open a lock event object for SYNCHRONIZE access (to wait for it). */
bool
lockf_t::open_lock_obj ()
{
lockfattr_t attr;
NTSTATUS status;
status = NtOpenEvent (&lf_obj, FLOCK_EVENT_ACCESS,
create_lock_obj_attr (&attr, 0, alloca (SD_MIN_SIZE)));
if (!NT_SUCCESS (status))
{
SetLastError (RtlNtStatusToDosError (status));
lf_obj = NULL; /* Paranoia... */
}
return lf_obj != NULL;
}
/* Delete a lock event handle. The important thing here is to signal it
before closing the handle. This way all threads waiting for this lock
can wake up. */
void
lockf_t::del_lock_obj (HANDLE fhdl, bool signal)
{
if (lf_obj)
{
/* Only signal the event if it's either a POSIX lock, or, in case of
BSD flock locks, if it's an explicit unlock or if the calling fhandler
holds the last reference to the file table entry. The file table
entry in UNIX terms is equivalent to the FILE_OBJECT in Windows NT
terms. It's what the handle/descriptor references when calling
CreateFile/open. Calling DuplicateHandle/dup only creates a new
handle/descriptor to the same FILE_OBJECT/file table entry. */
if ((lf_flags & F_POSIX) || signal
|| (fhdl && get_obj_handle_count (fhdl) <= 1))
{
NTSTATUS status = NtSetEvent (lf_obj, NULL);
if (!NT_SUCCESS (status))
system_printf ("NtSetEvent, %y", status);
/* For BSD locks, notify the parent process. */
if (lf_flags & F_FLOCK)
{
HANDLE parent_proc, parent_thread;
pinfo p (myself->ppid);
if (p && (parent_proc = OpenProcess (PROCESS_CREATE_THREAD
| PROCESS_QUERY_INFORMATION
| PROCESS_VM_OPERATION
| PROCESS_VM_WRITE
| PROCESS_VM_READ,
FALSE, p->dwProcessId)))
{
parent_thread = CreateRemoteThread (parent_proc, NULL,
256 * 1024, delete_lock_in_parent,
NULL,
STACK_SIZE_PARAM_IS_A_RESERVATION,
NULL);
if (parent_thread)
{
/* Must wait to avoid race conditions. */
WaitForSingleObject (parent_thread, INFINITE);
CloseHandle (parent_thread);
}
CloseHandle (parent_proc);
}
}
}
close_lock_obj ();
}
}
lockf_t::~lockf_t ()
{
del_lock_obj (NULL);
}
/*
* This variable controls the maximum number of processes that will
* be checked in doing deadlock detection.
*/
#ifndef __CYGWIN__
#define MAXDEPTH 50
static int maxlockdepth = MAXDEPTH;
#endif
#define NOLOCKF (struct lockf_t *)0
#define SELF 0x1
#define OTHERS 0x2
static int lf_clearlock (lockf_t *, lockf_t **, HANDLE);
static int lf_findoverlap (lockf_t *, lockf_t *, int, lockf_t ***, lockf_t **);
static lockf_t *lf_getblock (lockf_t *, inode_t *node);
static int lf_getlock (lockf_t *, inode_t *, struct flock *);
static int lf_setlock (lockf_t *, inode_t *, lockf_t **, HANDLE);
static void lf_split (lockf_t *, lockf_t *, lockf_t **);
static void lf_wakelock (lockf_t *, HANDLE);
/* This is the fcntl advisory lock implementation. For the implementation
of mandatory locks using the Windows mandatory locking functions, see the
fhandler_disk_file::mand_lock method at the end of this file. */
int
fhandler_base::lock (int a_op, struct flock *fl)
{
off_t start, end, oadd;
int error = 0;
short a_flags = fl->l_type & (F_POSIX | F_FLOCK);
short type = fl->l_type & (F_RDLCK | F_WRLCK | F_UNLCK);
if (!a_flags)
a_flags = F_POSIX; /* default */
/* FIXME: For BSD flock(2) we need a valid, per file table entry OS handle.
Therefore we can't allow using flock(2) on nohandle devices. */
if ((a_flags & F_FLOCK) && nohandle ())
{
set_errno (EINVAL);
debug_printf ("BSD locking on nohandle and old-style console devices "
"not supported");
return -1;
}
if (a_op == F_SETLKW)
{
a_op = F_SETLK;
a_flags |= F_WAIT;
}
if (a_op == F_SETLK)
switch (type)
{
case F_UNLCK:
a_op = F_UNLCK;
break;
case F_RDLCK:
/* flock semantics don't specify a requirement that the file has
been opened with a specific open mode, in contrast to POSIX locks
which require that a file is opened for reading to place a read
lock and opened for writing to place a write lock. */
/* CV 2013-10-22: Test POSIX R/W mode flags rather than Windows R/W
access flags. The reason is that POSIX mode flags are set for
all types of fhandlers, while Windows access flags are only set
for most of the actual Windows device backed fhandlers. */
if ((a_flags & F_POSIX)
&& ((get_flags () & O_ACCMODE) == O_WRONLY))
{
debug_printf ("request F_RDLCK on O_WRONLY file: EBADF");
set_errno (EBADF);
return -1;
}
break;
case F_WRLCK:
/* See above comment. */
if ((a_flags & F_POSIX)
&& ((get_flags () & O_ACCMODE) == O_RDONLY))
{
debug_printf ("request F_WRLCK on O_RDONLY file: EBADF");
set_errno (EBADF);
return -1;
}
break;