vfsmount.cpp

Last change on this file was 106061, checked in by vboxsync, 3 months ago
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1	/* $Id: vfsmount.cpp 106061 2024-09-16 14:03:52Z vboxsync $ */
2	/** @file
3	* IPRT - Virtual File System, Mounting.
4	*/
5
6	/*
7	* Copyright (C) 2012-2024 Oracle and/or its affiliates.
8	*
9	* This file is part of VirtualBox base platform packages, as
10	* available from https://www.virtualbox.org.
11	*
12	* This program is free software; you can redistribute it and/or
13	* modify it under the terms of the GNU General Public License
14	* as published by the Free Software Foundation, in version 3 of the
15	* License.
16	*
17	* This program is distributed in the hope that it will be useful, but
18	* WITHOUT ANY WARRANTY; without even the implied warranty of
19	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20	* General Public License for more details.
21	*
22	* You should have received a copy of the GNU General Public License
23	* along with this program; if not, see <https://www.gnu.org/licenses>.
24	*
25	* The contents of this file may alternatively be used under the terms
26	* of the Common Development and Distribution License Version 1.0
27	* (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
28	* in the VirtualBox distribution, in which case the provisions of the
29	* CDDL are applicable instead of those of the GPL.
30	*
31	* You may elect to license modified versions of this file under the
32	* terms and conditions of either the GPL or the CDDL or both.
33	*
34	* SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
35	*/
36
37
38	/*********************************************************************************************************************************
39	* Header Files *
40	*********************************************************************************************************************************/
41	#define LOG_GROUP RTLOGGROUP_VFS
42	#include <iprt/vfs.h>
43
44	#define RT_ASM_INCLUDE_PAGE_SIZE
45	#include <iprt/asm-mem.h>
46	#include <iprt/asm.h> /* ASMByteSwapU32/U16 on sparc */
47	#include <iprt/assert.h>
48	#include <iprt/err.h>
49	#include <iprt/file.h>
50	#include <iprt/fsvfs.h>
51	#include <iprt/mem.h>
52	#include <iprt/log.h>
53	#include <iprt/string.h>
54	#include <iprt/vfslowlevel.h>
55
56	#include <iprt/formats/fat.h>
57	#include <iprt/formats/iso9660.h>
58	#include <iprt/formats/udf.h>
59	#include <iprt/formats/ext.h>
60
61
62	/*********************************************************************************************************************************
63	* Structures and Typedefs *
64	*********************************************************************************************************************************/
65	/** Buffer structure for the detection routines. */
66	typedef union RTVFSMOUNTBUF
67	{
68	uint8_t ab[2048];
69	uint32_t au32[2048/4];
70	FATBOOTSECTOR Bootsector;
71	ISO9660VOLDESCHDR IsoHdr;
72	} RTVFSMOUNTBUF;
73	AssertCompileSize(RTVFSMOUNTBUF, 2048);
74	typedef RTVFSMOUNTBUF *PRTVFSMOUNTBUF;
75
76
77
78	/**
79	* Checks if the given 2K sector at offset 32KB looks like ISO-9660 or UDF.
80	*
81	* @returns true if likely ISO or UDF, otherwise false.
82	* @param pVolDescHdr Whatever is at offset 32KB. 2KB buffer.
83	*/
84	static bool rtVfsMountIsIsoFs(PCISO9660VOLDESCHDR pVolDescHdr)
85	{
86	if ( memcmp(pVolDescHdr->achStdId, RT_STR_TUPLE(ISO9660VOLDESC_STD_ID)) == 0
87	&& pVolDescHdr->bDescType <= ISO9660VOLDESC_TYPE_PARTITION
88	&& pVolDescHdr->bDescVersion != 0
89	&& pVolDescHdr->bDescVersion <= 3 /* don't be too picky, just increase the likelyhood */ )
90	return true;
91
92	if ( memcmp(pVolDescHdr->achStdId, RT_STR_TUPLE(UDF_EXT_VOL_DESC_STD_ID_BEGIN)) == 0
93	&& pVolDescHdr->bDescType == UDF_EXT_VOL_DESC_TYPE
94	&& pVolDescHdr->bDescVersion == UDF_EXT_VOL_DESC_VERSION)
95	return true;
96
97	return false;
98	}
99
100
101	/**
102	* Check if the given bootsector is a NTFS boot sector.
103	*
104	* @returns true if NTFS, false if not.
105	* @param pBootSector The boot sector to inspect.
106	*/
107	static bool rtVfsMountIsNtfs(PCFATBOOTSECTOR pBootSector)
108	{
109	if (memcmp(pBootSector->achOemName, RT_STR_TUPLE("NTFS ")) != 0)
110	return false;
111
112	uint16_t cbSector = RT_LE2H_U16(pBootSector->Bpb.Bpb331.cbSector);
113	if ( cbSector < 0x100
114	\|\| cbSector >= 0x1000
115	\|\| (cbSector & 0xff) != 0)
116	{
117	Log2(("rtVfsMountIsNtfs: cbSector=%#x: out of range\n", cbSector));
118	return false;
119	}
120
121	if ( !RT_IS_POWER_OF_TWO(pBootSector->Bpb.Bpb331.cSectorsPerCluster)
122	\|\| pBootSector->Bpb.Bpb331.cSectorsPerCluster == 0
123	\|\| pBootSector->Bpb.Bpb331.cSectorsPerCluster > 128)
124	{
125	Log2(("rtVfsMountIsNtfs: cSectorsPerCluster=%#x: out of range\n", pBootSector->Bpb.Bpb331.cSectorsPerCluster));
126	return false;
127	}
128
129	if ((uint32_t)pBootSector->Bpb.Bpb331.cSectorsPerCluster * cbSector > _64K)
130	{
131	Log2(("rtVfsMountIsNtfs: cSectorsPerCluster=%#x * cbSector=%#x => %#x: out of range\n",
132	pBootSector->Bpb.Bpb331.cSectorsPerCluster, cbSector,
133	(uint32_t)pBootSector->Bpb.Bpb331.cSectorsPerCluster * cbSector));
134	return false;
135	}
136
137	if ( pBootSector->Bpb.Bpb331.cReservedSectors != 0
138	\|\| pBootSector->Bpb.Bpb331.cMaxRootDirEntries != 0
139	\|\| pBootSector->Bpb.Bpb331.cTotalSectors16 != 0
140	\|\| pBootSector->Bpb.Bpb331.cTotalSectors32 != 0
141	\|\| pBootSector->Bpb.Bpb331.cSectorsPerFat != 0
142	\|\| pBootSector->Bpb.Bpb331.cFats != 0)
143	{
144	Log2(("rtVfsMountIsNtfs: cReservedSectors=%#x cMaxRootDirEntries=%#x cTotalSectors=%#x cTotalSectors32=%#x cSectorsPerFat=%#x cFats=%#x: should all be zero, but one or more aren't\n",
145	RT_LE2H_U16(pBootSector->Bpb.Bpb331.cReservedSectors),
146	RT_LE2H_U16(pBootSector->Bpb.Bpb331.cMaxRootDirEntries),
147	RT_LE2H_U16(pBootSector->Bpb.Bpb331.cTotalSectors16),
148	RT_LE2H_U32(pBootSector->Bpb.Bpb331.cTotalSectors32),
149	RT_LE2H_U16(pBootSector->Bpb.Bpb331.cSectorsPerFat),
150	pBootSector->Bpb.Bpb331.cFats));
151	return false;
152	}
153
154	/** @todo NTFS specific checks: MFT cluster number, cluster per index block. */
155
156	return true;
157	}
158
159
160	/**
161	* Check if the given bootsector is a HPFS boot sector.
162	*
163	* @returns true if NTFS, false if not.
164	* @param pBootSector The boot sector to inspect.
165	* @param hVfsFileIn The volume file.
166	* @param pBuf2 A 2nd buffer.
167	*/
168	static bool rtVfsMountIsHpfs(PCFATBOOTSECTOR pBootSector, RTVFSFILE hVfsFileIn, PRTVFSMOUNTBUF pBuf2)
169	{
170	if (memcmp(pBootSector->Bpb.Ebpb.achType, RT_STR_TUPLE("HPFS ")) != 0)
171	return false;
172
173	/* Superblock is at sector 16, spare superblock at 17. */
174	int rc = RTVfsFileReadAt(hVfsFileIn, 16 * 512, pBuf2, 512 * 2, NULL);
175	if (RT_FAILURE(rc))
176	{
177	Log2(("rtVfsMountIsHpfs: Error reading superblock: %Rrc\n", rc));
178	return false;
179	}
180
181	if ( RT_LE2H_U32(pBuf2->au32[0]) != UINT32_C(0xf995e849)
182	\|\| RT_LE2H_U32(pBuf2->au32[1]) != UINT32_C(0xfa53e9c5)
183	\|\| RT_LE2H_U32(pBuf2->au32[512/4 + 0]) != UINT32_C(0xf9911849)
184	\|\| RT_LE2H_U32(pBuf2->au32[512/4 + 1]) != UINT32_C(0xfa5229c5))
185	{
186	Log2(("rtVfsMountIsHpfs: Superblock or spare superblock signature mismatch: %#x %#x %#x %#x\n",
187	RT_LE2H_U32(pBuf2->au32[0]), RT_LE2H_U32(pBuf2->au32[1]),
188	RT_LE2H_U32(pBuf2->au32[512/4 + 0]), RT_LE2H_U32(pBuf2->au32[512/4 + 1]) ));
189	return false;
190	}
191
192	return true;
193	}
194
195
196	/**
197	* Check if the given bootsector is a FAT boot sector.
198	*
199	* @returns true if NTFS, false if not.
200	* @param pBootSector The boot sector to inspect.
201	* @param pbRaw Pointer to the raw boot sector buffer.
202	* @param cbRaw Number of bytes read starting with the boot
203	* sector (which @a pbRaw points to).
204	* @param hVfsFileIn The volume file.
205	* @param pBuf2 A 2nd buffer.
206	*/
207	static bool rtVfsMountIsFat(PCFATBOOTSECTOR pBootSector, uint8_t const *pbRaw, size_t cbRaw,
208	RTVFSFILE hVfsFileIn, PRTVFSMOUNTBUF pBuf2)
209	{
210	Assert(cbRaw >= 1024);
211
212	/*
213	* Check the DOS signature first. The PC-DOS 1.0 boot floppy does not have
214	* a signature and we ASSUME this is the case for all floppies formated by it.
215	*/
216	if (pBootSector->uSignature != FATBOOTSECTOR_SIGNATURE)
217	{
218	if (pBootSector->uSignature != 0)
219	return false;
220
221	/*
222	* PC-DOS 1.0 does a 2fh byte short jump w/o any NOP following it.
223	* Instead the following are three words and a 9 byte build date
224	* string. The remaining space is zero filled.
225	*
226	* Note! No idea how this would look like for 8" floppies, only got 5"1/4'.
227	*
228	* ASSUME all non-BPB disks are using this format.
229	*/
230	if ( pBootSector->abJmp[0] != 0xeb /* jmp rel8 */
231	\|\| pBootSector->abJmp[1] < 0x2f
232	\|\| pBootSector->abJmp[1] >= 0x80
233	\|\| pBootSector->abJmp[2] == 0x90 /* nop */)
234	{
235	Log2(("rtVfsMountIsFat: No DOS v1.0 bootsector either - invalid jmp: %.3Rhxs\n", pBootSector->abJmp));
236	return false;
237	}
238
239	/* Check the FAT ID so we can tell if this is double or single sided, as well as being a valid FAT12 start. */
240	if ( (pbRaw[512] != 0xfe && pbRaw[0] != 0xff)
241	\|\| pbRaw[512 + 1] != 0xff
242	\|\| pbRaw[512 + 2] != 0xff)
243	{
244	Log2(("rtVfsMountIsFat: No DOS v1.0 bootsector either - unexpected start of FAT: %.3Rhxs\n", &pbRaw[512]));
245	return false;
246	}
247
248	uint32_t const offJump = 2 + pBootSector->abJmp[1];
249	uint32_t const offFirstZero = 2 /jmp / + 3 * 2 /* words / + 9 / date string */;
250	Assert(offFirstZero >= RT_UOFFSETOF(FATBOOTSECTOR, Bpb));
251	uint32_t const cbZeroPad = RT_MIN(offJump - offFirstZero,
252	sizeof(pBootSector->Bpb.Bpb20) - (offFirstZero - RT_UOFFSETOF(FATBOOTSECTOR, Bpb)));
253
254	if (!ASMMemIsAllU8((uint8_t const *)pBootSector + offFirstZero, cbZeroPad, 0))
255	{
256	Log2(("rtVfsMountIsFat: No DOS v1.0 bootsector either - expected zero padding %#x LB %#x: %.*Rhxs\n",
257	offFirstZero, cbZeroPad, cbZeroPad, (uint8_t const *)pBootSector + offFirstZero));
258	return false;
259	}
260	}
261	else
262	{
263	/*
264	* DOS 2.0 or later.
265	*
266	* Start by checking if we've got a known jump instruction first, because
267	* that will give us a max (E)BPB size hint.
268	*/
269	uint8_t offJmp = UINT8_MAX;
270	if ( pBootSector->abJmp[0] == 0xeb
271	&& pBootSector->abJmp[1] <= 0x7f)
272	offJmp = pBootSector->abJmp[1] + 2;
273	else if ( pBootSector->abJmp[0] == 0x90
274	&& pBootSector->abJmp[1] == 0xeb
275	&& pBootSector->abJmp[2] <= 0x7f)
276	offJmp = pBootSector->abJmp[2] + 3;
277	else if ( pBootSector->abJmp[0] == 0xe9
278	&& pBootSector->abJmp[2] <= 0x7f)
279	offJmp = RT_MIN(127, RT_MAKE_U16(pBootSector->abJmp[1], pBootSector->abJmp[2]));
280	uint8_t const cbMaxBpb = offJmp - RT_UOFFSETOF(FATBOOTSECTOR, Bpb);
281	if (cbMaxBpb < sizeof(FATBPB20))
282	{
283	Log2(("rtVfsMountIsFat: DOS signature, but jmp too short for any BPB: %#x (max %#x BPB)\n", offJmp, cbMaxBpb));
284	return false;
285	}
286
287	if ( pBootSector->Bpb.Bpb20.cFats == 0
288	\|\| pBootSector->Bpb.Bpb20.cFats > 4)
289	{
290	if (pBootSector->Bpb.Bpb20.cFats == 0)
291	Log2(("rtVfsMountIsFat: DOS signature, number of FATs is zero, so not FAT file system\n"));
292	else
293	Log2(("rtVfsMountIsFat: DOS signature, too many FATs: %#x\n", pBootSector->Bpb.Bpb20.cFats));
294	return false;
295	}
296
297	if (!FATBPB_MEDIA_IS_VALID(pBootSector->Bpb.Bpb20.bMedia))
298	{
299	Log2(("rtVfsMountIsFat: DOS signature, invalid media byte: %#x\n", pBootSector->Bpb.Bpb20.bMedia));
300	return false;
301	}
302
303	uint16_t cbSector = RT_LE2H_U16(pBootSector->Bpb.Bpb20.cbSector);
304	if ( cbSector != 512
305	&& cbSector != 4096
306	&& cbSector != 1024
307	&& cbSector != 128)
308	{
309	Log2(("rtVfsMountIsFat: DOS signature, unsupported sector size: %#x\n", cbSector));
310	return false;
311	}
312
313	if ( !RT_IS_POWER_OF_TWO(pBootSector->Bpb.Bpb20.cSectorsPerCluster)
314	\|\| !pBootSector->Bpb.Bpb20.cSectorsPerCluster)
315	{
316	Log2(("rtVfsMountIsFat: DOS signature, cluster size not non-zero power of two: %#x",
317	pBootSector->Bpb.Bpb20.cSectorsPerCluster));
318	return false;
319	}
320
321	uint16_t const cReservedSectors = RT_LE2H_U16(pBootSector->Bpb.Bpb20.cReservedSectors);
322	if ( cReservedSectors == 0
323	\|\| cReservedSectors >= _32K)
324	{
325	Log2(("rtVfsMountIsFat: DOS signature, bogus reserved sector count: %#x\n", cReservedSectors));
326	return false;
327	}
328
329	/*
330	* Match the media byte with the first FAT byte and check that the next
331	* 4 bits are set. (To match further bytes in the FAT we'd need to
332	* determin the FAT type, which is too much hazzle to do here.)
333	*/
334	uint8_t const *pbFat;
335	if ((size_t)cReservedSectors * cbSector < cbRaw)
336	pbFat = &pbRaw[cReservedSectors * cbSector];
337	else
338	{
339	int rc = RTVfsFileReadAt(hVfsFileIn, cReservedSectors * cbSector, pBuf2, 512, NULL);
340	if (RT_FAILURE(rc))
341	{
342	Log2(("rtVfsMountIsFat: error reading first FAT sector at %#x: %Rrc\n", cReservedSectors * cbSector, rc));
343	return false;
344	}
345	pbFat = pBuf2->ab;
346	}
347	if (*pbFat != pBootSector->Bpb.Bpb20.bMedia)
348	{
349	Log2(("rtVfsMountIsFat: Media byte and FAT ID mismatch: %#x vs %#x (%.8Rhxs)\n",
350	pbFat[0], pBootSector->Bpb.Bpb20.bMedia, pbFat));
351	return false;
352	}
353	if ((pbFat[1] & 0xf) != 0xf)
354	{
355	Log2(("rtVfsMountIsFat: Media byte and FAT ID mismatch: %#x vs %#x (%.8Rhxs)\n",
356	pbFat[0], pBootSector->Bpb.Bpb20.bMedia, pbFat));
357	return false;
358	}
359	}
360
361	return true;
362	}
363
364
365	/**
366	* Check if the given bootsector is an ext2/3/4 super block.
367	*
368	* @returns true if NTFS, false if not.
369	* @param pSuperBlock The ext2 superblock.
370	*/
371	static bool rtVfsMountIsExt(PCEXTSUPERBLOCK pSuperBlock)
372	{
373	if (RT_LE2H_U16(pSuperBlock->u16Signature) != EXT_SB_SIGNATURE)
374	return false;
375
376	uint32_t cShift = RT_LE2H_U32(pSuperBlock->cLogBlockSize);
377	if (cShift > 54)
378	{
379	Log2(("rtVfsMountIsExt: cLogBlockSize=%#x: out of range\n", cShift));
380	return false;
381	}
382
383	cShift = RT_LE2H_U32(pSuperBlock->cLogClusterSize);
384	if (cShift > 54)
385	{
386	Log2(("rtVfsMountIsExt: cLogClusterSize=%#x: out of range\n", cShift));
387	return false;
388	}
389
390	/* Some more checks here would be nice actually since a 16-bit word and a
391	couple of field limits doesn't feel all that conclusive. */
392
393	return true;
394	}
395
396
397	/**
398	* Does the file system detection and mounting.
399	*
400	* Since we only support a handful of file systems at the moment and the
401	* interface isn't yet extensible in any way, we combine the file system
402	* recognition code for all. This reduces the number of reads we need to do and
403	* avoids unnecessary processing.
404	*
405	* @returns IPRT status code.
406	* @param hVfsFileIn The volume file.
407	* @param fFlags RTVFSMTN_F_XXX.
408	* @param pBuf Pointer to the primary buffer
409	* @param pBuf2 Pointer to the secondary buffer.
410	* @param phVfs Where to return the .
411	* @param pErrInfo Where to return additional error information.
412	* Optional.
413	*/
414	static int rtVfsMountInner(RTVFSFILE hVfsFileIn, uint32_t fFlags, RTVFSMOUNTBUF *pBuf,
415	RTVFSMOUNTBUF *pBuf2, PRTVFS phVfs, PRTERRINFO pErrInfo)
416	{
417	AssertCompile(sizeof(*pBuf) >= ISO9660_SECTOR_SIZE);
418
419	/* Start by checking for ISO-9660 and UDFS since these may have confusing
420	data at the start of the volume. */
421	int rc = RTVfsFileReadAt(hVfsFileIn, _32K, pBuf, ISO9660_SECTOR_SIZE, NULL);
422	if (RT_SUCCESS(rc))
423	{
424	if (rtVfsMountIsIsoFs(&pBuf->IsoHdr))
425	{
426	Log(("RTVfsMount: Detected ISO-9660 or UDF.\n"));
427	return RTFsIso9660VolOpen(hVfsFileIn, 0 /fFlags/, phVfs, pErrInfo);
428	}
429	}
430
431	/* Now read the boot sector and whatever the next 1536 bytes may contain.
432	With ext2 superblock at 1024, we can recognize quite a bit thru this read. */
433	rc = RTVfsFileReadAt(hVfsFileIn, 0, pBuf, sizeof(*pBuf), NULL);
434	if (RT_FAILURE(rc))
435	return RTErrInfoSet(pErrInfo, rc, "Error reading boot sector");
436
437	if (rtVfsMountIsNtfs(&pBuf->Bootsector))
438	return RTFsNtfsVolOpen(hVfsFileIn, fFlags, 0 /fNtfsFlags/, phVfs, pErrInfo);
439
440	if (rtVfsMountIsHpfs(&pBuf->Bootsector, hVfsFileIn, pBuf2))
441	return RTERRINFO_LOG_SET(pErrInfo, VERR_VFS_UNSUPPORTED_FORMAT, "HPFS not yet supported");
442
443	if (rtVfsMountIsFat(&pBuf->Bootsector, pBuf->ab, sizeof(*pBuf), hVfsFileIn, pBuf2))
444	{
445	Log(("RTVfsMount: Detected ISO-9660 or UDF.\n"));
446	return RTFsFatVolOpen(hVfsFileIn, RT_BOOL(fFlags & RTVFSMNT_F_READ_ONLY), 0 /offBootSector/, phVfs, pErrInfo);
447	}
448
449	AssertCompile(sizeof(*pBuf) >= 1024 + sizeof(EXTSUPERBLOCK));
450	if (rtVfsMountIsExt((PCEXTSUPERBLOCK)&pBuf->ab[1024]))
451	{
452	Log(("RTVfsMount: Detected EXT2/3/4.\n"));
453	return RTFsExtVolOpen(hVfsFileIn, fFlags, 0 /fExt2Flags/, phVfs, pErrInfo);
454	}
455
456	return VERR_VFS_UNSUPPORTED_FORMAT;
457	}
458
459
460	RTDECL(int) RTVfsMountVol(RTVFSFILE hVfsFileIn, uint32_t fFlags, PRTVFS phVfs, PRTERRINFO pErrInfo)
461	{
462	AssertReturn(!(fFlags & ~RTVFSMNT_F_VALID_MASK), VERR_INVALID_FLAGS);
463	AssertPtrReturn(hVfsFileIn, VERR_INVALID_HANDLE);
464	AssertPtrReturn(phVfs, VERR_INVALID_HANDLE);
465
466	*phVfs = NIL_RTVFS;
467
468	RTVFSMOUNTBUF pBufs = (RTVFSMOUNTBUF )RTMemTmpAlloc(sizeof(pBufs) 2);
469	AssertReturn(pBufs, VERR_NO_TMP_MEMORY);
470
471	int rc = rtVfsMountInner(hVfsFileIn, fFlags, pBufs, pBufs + 1, phVfs, pErrInfo);
472
473	RTMemTmpFree(pBufs);
474
475	return rc;
476	}
477
478
479	/**
480	* @interface_method_impl{RTVFSCHAINELEMENTREG,pfnValidate}
481	*/
482	static DECLCALLBACK(int) rtVfsChainMountVol_Validate(PCRTVFSCHAINELEMENTREG pProviderReg, PRTVFSCHAINSPEC pSpec,
483	PRTVFSCHAINELEMSPEC pElement, uint32_t *poffError, PRTERRINFO pErrInfo)
484	{
485	RT_NOREF(pProviderReg);
486
487	/*
488	* Basic checks.
489	*/
490	if (pElement->enmTypeIn != RTVFSOBJTYPE_FILE)
491	return pElement->enmTypeIn == RTVFSOBJTYPE_INVALID ? VERR_VFS_CHAIN_CANNOT_BE_FIRST_ELEMENT : VERR_VFS_CHAIN_TAKES_FILE;
492	if ( pElement->enmType != RTVFSOBJTYPE_VFS
493	&& pElement->enmType != RTVFSOBJTYPE_DIR)
494	return VERR_VFS_CHAIN_ONLY_DIR_OR_VFS;
495	if (pElement->cArgs > 1)
496	return VERR_VFS_CHAIN_AT_MOST_ONE_ARG;
497
498	/*
499	* Parse the flag if present, save in pElement->uProvider.
500	*/
501	bool fReadOnly = (pSpec->fOpenFile & RTFILE_O_ACCESS_MASK) == RTFILE_O_READ;
502	if (pElement->cArgs > 0)
503	{
504	const char *psz = pElement->paArgs[0].psz;
505	if (*psz)
506	{
507	if (!strcmp(psz, "ro"))
508	fReadOnly = true;
509	else if (!strcmp(psz, "rw"))
510	fReadOnly = false;
511	else
512	{
513	*poffError = pElement->paArgs[0].offSpec;
514	return RTErrInfoSet(pErrInfo, VERR_VFS_CHAIN_INVALID_ARGUMENT, "Expected 'ro' or 'rw' as argument");
515	}
516	}
517	}
518
519	pElement->uProvider = fReadOnly ? RTVFSMNT_F_READ_ONLY : 0;
520	return VINF_SUCCESS;
521	}
522
523
524	/**
525	* @interface_method_impl{RTVFSCHAINELEMENTREG,pfnInstantiate}
526	*/
527	static DECLCALLBACK(int) rtVfsChainMountVol_Instantiate(PCRTVFSCHAINELEMENTREG pProviderReg, PCRTVFSCHAINSPEC pSpec,
528	PCRTVFSCHAINELEMSPEC pElement, RTVFSOBJ hPrevVfsObj,
529	PRTVFSOBJ phVfsObj, uint32_t *poffError, PRTERRINFO pErrInfo)
530	{
531	RT_NOREF(pProviderReg, pSpec, poffError);
532
533	int rc;
534	RTVFSFILE hVfsFileIn = RTVfsObjToFile(hPrevVfsObj);
535	if (hVfsFileIn != NIL_RTVFSFILE)
536	{
537	RTVFS hVfs;
538	rc = RTVfsMountVol(hVfsFileIn, (uint32_t)pElement->uProvider, &hVfs, pErrInfo);
539	RTVfsFileRelease(hVfsFileIn);
540	if (RT_SUCCESS(rc))
541	{
542	*phVfsObj = RTVfsObjFromVfs(hVfs);
543	RTVfsRelease(hVfs);
544	if (*phVfsObj != NIL_RTVFSOBJ)
545	return VINF_SUCCESS;
546	rc = VERR_VFS_CHAIN_CAST_FAILED;
547	}
548	}
549	else
550	rc = VERR_VFS_CHAIN_CAST_FAILED;
551	return rc;
552	}
553
554
555	/**
556	* @interface_method_impl{RTVFSCHAINELEMENTREG,pfnCanReuseElement}
557	*/
558	static DECLCALLBACK(bool) rtVfsChainMountVol_CanReuseElement(PCRTVFSCHAINELEMENTREG pProviderReg,
559	PCRTVFSCHAINSPEC pSpec, PCRTVFSCHAINELEMSPEC pElement,
560	PCRTVFSCHAINSPEC pReuseSpec, PCRTVFSCHAINELEMSPEC pReuseElement)
561	{
562	RT_NOREF(pProviderReg, pSpec, pReuseSpec);
563	if ( pElement->paArgs[0].uProvider == pReuseElement->paArgs[0].uProvider
564	\|\| !pReuseElement->paArgs[0].uProvider)
565	return true;
566	return false;
567	}
568
569
570	/** VFS chain element 'file'. */
571	static RTVFSCHAINELEMENTREG g_rtVfsChainMountVolReg =
572	{
573	/* uVersion = */ RTVFSCHAINELEMENTREG_VERSION,
574	/* fReserved = */ 0,
575	/* pszName = */ "mount",
576	/* ListEntry = */ { NULL, NULL },
577	/* pszHelp = */ "Open a file system, requires a file object on the left side.\n"
578	"First argument is an optional 'ro' (read-only) or 'rw' (read-write) flag.\n",
579	/* pfnValidate = */ rtVfsChainMountVol_Validate,
580	/* pfnInstantiate = */ rtVfsChainMountVol_Instantiate,
581	/* pfnCanReuseElement = */ rtVfsChainMountVol_CanReuseElement,
582	/* uEndMarker = */ RTVFSCHAINELEMENTREG_VERSION
583	};
584
585	RTVFSCHAIN_AUTO_REGISTER_ELEMENT_PROVIDER(&g_rtVfsChainMountVolReg, rtVfsChainMountVolReg);
586

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source: vbox/trunk/src/VBox/Runtime/common/vfs/vfsmount.cpp

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