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Top Forums Programming write() issue during a low level hdd access Post 302397631 by sponnusa on Monday 22nd of February 2010 07:30:46 PM
Old 02-22-2010
Quote:
Originally Posted by fpmurphy
Just attempting to read a disk sector is completely different than attempting to write a disk sector following by attempting to read the same disk sector. That is why disk vendors have what are typically called low level utilities for bad disk sector scanning and the like.
yep. you are right. For (IDE) PATA / SATA (t13.org) disks there are the ATA / ATAPI standards which specifies how to query the device directly and SCSI has a loads of standards (t10.org) for interfacing with the drives. The ATA part can be easily coded in DOS / FreeDOS with Assembly / C counterparts.

Win32 support is available too for direct querying / interfacing of the devices (with DDK/SDK apis) and device ioctl calls. There are multiple utilities from various HDD vendors which either falls in either of the above two categories (DOS or WINDOWS).

I would like to know if Linux has anything like that? If I call libata calls directly in my program would it allow me to talk to the drive directly? At least for the (IDE) PATA / SATA drives?

Though Linux is programmer friendly, I feel not much control is given to the programmer (well, it also relates to the security feature! Smilie and unlike windows, where there are many security exploits / overflows when the kernel address space is hacked from user space leading to privilege escalations, and loads of other issues, not to mention BSOD! Smilie).

I don't know if I am going into a vicious circle of kernel hacking / Linux abuse mode, but I just don't feel some things are right with Linux! Smilie

I certainly mean no offense with my above words and for the great minds here. The above words are purely because of my frustration in trying to get the program to work partially at least if not completely.

Now for update:

I have tried posix_fadvise, but the read / write calls are locking up on the bad sectors as said by you.

I have removed the O_DIRECT and using O_WRONLY mode with posix_fadvise on the handle with POSIX_FADV_DONTNEED flag for the entire device starting from sector 0 to (last sector * 512). Is that the right option to be used?

Is there any timeout option that can be set on the Read / Write operations to say to the program / kernel to move on to the next sector / block based on the timeout (time consumed for the current sector)?

I tried with the FDSET , but i believe it is only for socket descriptors and not for file handles. (So dumb of myself! Smilie )

Thanks for the replies.
 

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hdio(7I)							  Ioctl Requests							  hdio(7I)

NAME
hdio - SMD and IPI disk control operations SYNOPSIS
#include <sys/hdio.h> DESCRIPTION
Note - The SMC and IPI drivers have been discontinued. dkio(7I) is now the preferred method for retrieving disk information. The SMD and IPI disk drivers supplied with this release support a set of ioctl(2) requests for diagnostics and bad sector information. Basic to these ioctl() requests are the definitions in <sys/hdio.h>. IOCTLS
HDKIOCGTYPE The argument is a pointer to a hdk_type structure (described below). This ioctl() gets specific information from the hard disk. HDKIOCSTYPE The argument is a pointer to a hdk_type structure (described below). This ioctl() sets specific information about the hard disk. /* * Used for drive info */ struct hdk_type { ushort_t hdkt_hsect; /* hard sector count (read only) */ ushort_t hdkt_promrev; /* prom revision (read only) */ uchar_t hdkt_drtype; /* drive type (ctlr specific) */ uchar_t hdkt_drstat; /* drive status (ctlr specific, ro) */ }; HDKIOCGBAD The argument is a pointer to a hdk_badmap structure (described below). This ioctl() is used to get the bad sector map from the disk. HDKIOCSBAD The argument is a pointer to a hdk_badmap structure (described below). This ioctl() is used to set the bad sector map on the disk. /* * Used for bad sector map */ struct hdk_badmap { caddr_t hdkb_bufaddr; /* address of user's map buffer */ }; HDKIOCGDIAG The argument is a pointer to a hdk_diag structure (described below). This ioctl() gets the most recent command that failed along with the sector and error number from the hard disk. /* * Used for disk diagnostics */ struct hdk_diag { ushort_t hdkd_errcmd; /* most recent command in error */ daddr_t hdkd_errsect; /* most recent sector in error */ uchar_t hdkd_errno; /* most recent error number */ uchar_t hdkd_severe; /* severity of most recent error */ }; SEE ALSO
ioctl(2), dkio(7I) SunOS 5.10 13 Aug 2002 hdio(7I)
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