[PATCH] Cygwin: Add /dev/disk/by-id symlinks
Christian Franke
Christian.Franke@t-online.de
Fri Nov 3 11:06:43 GMT 2023
Corinna Vinschen wrote:
> On Nov 3 10:55, Corinna Vinschen wrote:
>> Hi Christian,
>>
>> On Oct 3 14:39, Christian Franke wrote:
>>> Christian Franke wrote:
>>>> This is a first attempt to partly emulate the Linux directory
>>>> /dev/disk/by-id. Useful to make sure the correct device is accessed in
>>>> conjunction with dd, ddrescue, fdisk, ....
>>> Attached is the second attempt.
>>>
>>>
>>>> The additional '*-partN' links to partitions are not yet included.
>>> These are now included.
>>>
>>>
>>>> This only works properly if Win32 path '\\.\PhysicalDriveN' is always
>>>> trivially mapped to NT path '\Device\HarddiskN\Partition0'.
>>>> IOCTL_STORAGE_QUERY_PROPERTY with a handle from NtOpenFile(.,
>>>> READ_CONTROL,...) instead of CreateFile(., 0, ...) did not work with all
>>>> drivers. With stornvme.sys, it fails with permission denied. Perhaps
>>>> other permission bits are required for NtOpenFile(). Thanks for any info
>>>> regarding this.
>>> According to NtQueryObject(., ObjectBasicInformation, ...), using
>>> NtOpenFile(., MAXIMUM_ALLOWED, ...) without admin rights sets GrantedAccess
>>> to 0x001200a0 (FILE_EXECUTE|FILE_READ_ATTRIBUTES|READ_CONTROL|SYNCHRONIZE).
>>> For some unknown reason, NVMe drives behind stornvme.sys additionally
>>> require SYNCHRONIZE to use IOCTL_STORAGE_QUERY_PROPERTY. Possibly a harmless
>>> bug in the access check somewhere in the NVMe stack.
>>>
>>> The disk scanning from the first patch has been reworked based on code
>>> borrowed from proc.cc:format_proc_partitions(). For the longer term, it may
>>> make sense to provide one flexible scanning function for /dev/sdXN,
>>> /proc/partitions and /proc/disk/by-id.
>> I applied your patch locally (patch looks pretty well, btw) but found
Thanks!
Meantime I found 4 missing NtClose() in the main loop of
get_by_id_table(). Will be fixed in the next version of the patch.
>> that /dev/disk/by-id is empty, even when running with admin rights.
Admin rights should not be necessary for IOCTL_STORAGE_QUERY_PROPERTY.
>>
>> I ran this on Windows 11 and Windows 2K19 in a QEMU/KVM VM. A
>> \Device\Harddisk0\Partition0 symlink pointing to \Device\Harddisk0\DR0
>> exists in both cases. I straced it, and found the following debug
>> output:
>>
>> 1015 1155432 [main] ls 361 stordesc_to_id_name: Harddisk0\Partition0: 'Red_Hat' 'VirtIO' '' (ignored)
>>
>> Is that really desired?
Yes - if IOCTL_STORAGE_QUERY_PROPERTY{... PropertyStandardQuery} does
not return a serial number (''), the device is intentionally ignored.
> Thread 1 "ls" hit Breakpoint 2, stordesc_to_id_name (upath=0x7ffffc500,
> ioctl_buf=0x10e0720 "(", name=...)
> at /home/corinna/src/cygwin/vanilla/winsup/cygwin/fhandler/dev_disk.cc:44
> 44 const STORAGE_DEVICE_DESCRIPTOR *desc =
> (gdb) n
> 47 int vendor_len = 0, product_len = 0, serial_len = 0;
> (gdb)
> 48 if (desc->VendorIdOffset)
> (gdb)
> 49 vendor_len = sanitize_id_string (ioctl_buf + desc->VendorIdOffset);
> (gdb)
> 50 if (desc->ProductIdOffset)
> (gdb)
> 51 product_len = sanitize_id_string (ioctl_buf + desc->ProductIdOffset);
> (gdb)
> 52 if (desc->SerialNumberOffset)
> (gdb)
> 53 serial_len = sanitize_id_string (ioctl_buf + desc->SerialNumberOffset);
If possibly, please check whether (desc->SerialNumberOffset) is 0 or
(ioctl_buf + desc->SerialNumberOffset) points to '\0' or a string of
spaces. If no, there is possibly something wrong in sanitize_id_string().
> (gdb)
> 55 bool valid = (4 <= vendor_len + product_len && 4 <= serial_len
> (gdb) p vendor_len
> $1 = 7
> (gdb) p product_len
> $2 = 6
> (gdb) p serial_len
> $3 = 0
> (gdb) n
> [New Thread 3944.0x1958]
> 56 && (20 + vendor_len + 1 + product_len + 1 + serial_len + 10)
> (gdb) n
> 55 bool valid = (4 <= vendor_len + product_len && 4 <= serial_len
> (gdb)
> 55 bool valid = (4 <= vendor_len + product_len && 4 <= serial_len
> (gdb)
> 58 debug_printf ("%S: '%s' '%s' '%s'%s", upath,
> (gdb) p valid
> $4 = false
--
Regards,
Christian
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