Macro to access Kernel objectys structure

ankur0921 · 01-29-2011, 12:14 PM

Dear All,

Can anybody help me out by telling the exact macro name and location, by which I can gain control over the following kernel base level structure

1. strct super_block of Virtual File System, for super block object.
2. strct inode for inode ofject of VFS.
3 file structure for file object of VFS.

in addition to these if you know location to access other kernel structure.Please let me know.My main objective is to get the access to the structure pointer of these structure by which i can have access over the individual fields o these structure.

If you know some other mechanism to do same please let me know.

Thanks & Regards.

ankur

Aquarius_Girl · 01-30-2011, 10:06 PM

See if you get something from here: http://www.gnugeneration.com/books/l...20/kernel-api/

ankur0921 · 01-31-2011, 09:02 AM

Dear Anisha,

Thanks for the link you have provided its the good link.I didnt receive my purposeful information fron the same but I got from thehttp://www.gnugeneration.com/books/linux/2.6.20/filesystems/re44.html .But the thing is how these API can be implemented.Here only description has been provided, from which header fil it can be taken.. and other such type of information has not been provided here.Do you have some idea or some reference documents.If you have kindlt provide.. In the wait of that.

Thanks for providing the useful link..

ankur

Aquarius_Girl · 01-31-2011, 10:09 AM

There are two ways to search for the header files:
1. To Google extensively with appropriate keywords.
2. To search the follwing path:

Code:

anisha@linux-dpjj:/usr/src/linux-2.6.31.5-0.1> grep -r get_super *
arch/parisc/hpux/sys_hpux.c:	s = user_get_super(dev);
arch/s390/hypfs/inode.c:static int hypfs_get_super(struct file_system_type *fst, int flags,
arch/s390/hypfs/inode.c:	.get_sb		= hypfs_get_super,
drivers/parport/parport_pc.c:static int get_superio_dma(struct parport *p)
drivers/parport/parport_pc.c:static int get_superio_irq(struct parport *p)
drivers/parport/parport_pc.c:		pb->irq = get_superio_irq(pb);
drivers/parport/parport_pc.c:		p->dma = get_superio_dma(p);
drivers/parport/ChangeLog:	(get_superio_dma): Likewise.
drivers/parport/ChangeLog:	(get_superio_irq): Likewise.
drivers/misc/ibmasm/ibmasmfs.c:static int ibmasmfs_get_super(struct file_system_type *fst,
drivers/misc/ibmasm/ibmasmfs.c:	.get_sb         = ibmasmfs_get_super,
drivers/block/pktcdvd.c:		sb = get_super(pkt_bdev);
fs/super.c: *	get_super - get the superblock of a device
fs/super.c:struct super_block * get_super(struct block_device *bdev)
fs/super.c:EXPORT_SYMBOL(get_super);
fs/super.c:struct super_block * user_get_super(dev_t dev)
fs/super.c:        s = user_get_super(new_decode_dev(dev));
fs/jbd2/journal.c:static int journal_get_superblock(journal_t *journal)
fs/jbd2/journal.c:	err = journal_get_superblock(journal);
fs/jbd2/journal.c:	err = journal_get_superblock(journal);
fs/reiserfs/super.c:static int get_super_block(struct file_system_type *fs_type,
fs/reiserfs/super.c:	.get_sb = get_super_block,
fs/reiserfs/procfs.c: *  . use get_super() in procfs.c
fs/block_dev.c:	struct super_block *sb = get_super(bdev);
fs/block_dev.c:		sb = get_super(bdev);
fs/block_dev.c:	sb = get_super(bdev);
fs/block_dev.c:	struct super_block *sb = get_super(bdev);
fs/block_dev.c:		 * no need to lock the super, get_super holds the
fs/fs-writeback.c:			/* we're making our own get_super here */
fs/compat.c:	sb = user_get_super(new_decode_dev(dev));
fs/quota/quota.c:	sb = get_super(bdev);
fs/nfs/super.c:		nfs_fscache_get_super_cookie(s, data);
fs/nfs/super.c:		nfs_fscache_get_super_cookie(s, data);
fs/nfs/fscache.c:void nfs_fscache_get_super_cookie(struct super_block *sb,
fs/nfs/fscache.h:extern void nfs_fscache_get_super_cookie(struct super_block *,
fs/nfs/fscache.h:static inline void nfs_fscache_get_super_cookie(
fs/jbd/journal.c:static int journal_get_superblock(journal_t *journal)
fs/jbd/journal.c:	err = journal_get_superblock(journal);
fs/jbd/journal.c:	err = journal_get_superblock(journal);
include/linux/reiserfs_fs.h:					   called. saves calls to reiserfs_get_super
include/linux/fs.h:extern struct super_block *get_super(struct block_device *);
include/linux/fs.h:extern struct super_block *user_get_super(dev_t);

Aquarius_Girl · 01-31-2011, 10:52 AM

ankur0921 · 02-01-2011, 12:20 AM

Dear Anisha,

Thanks for your great help.I am obliged to you.

Ankur

Aquarius_Girl · 02-01-2011, 12:26 AM

Most welcome, I *think* the way to include that particular header file would be:

Code:

#include <linux/fs>

ankur0921 · 02-01-2011, 07:18 AM

Hi All,

Can anybody help me where I am making wrong.I tried it all possible way..

Program :
#include<stdio.h>
#include</usr/include/sys/vfs.h>
int main()
{
char *path="/dev/hda1";
struct super_block *sb;
printf("Path = %s",path);
sb=get_super(path);
printf("Block size in bytes = %ld",sb->s_blocksize);
}

Error:
sp.c: In function ‘main’:
sp.c:8: warning: assignment makes pointer from integer without a cast
sp.c:9: error: dereferencing pointer to incomplete type

Thanks & Regards.

ankur

Aquarius_Girl · 02-01-2011, 07:56 AM

Code:

struct super_block * get_super(struct block_device *bdev)

and you have passed a char* to it???

Put your code in [code] tags and create a new thread for it.

ankur0921 · 02-02-2011, 12:20 AM

Dear All,

Below is a test program, with error produced.I understand that block_device pointer *bd sholuld get initialized.Program should produce initialization error for *bd. Compiler is producing '->'.I am not understanding why ?

Can anybody help me to get this program working fine ?
I have doubt of its working in user space as this program is accessing the kernel resources.

If anybody can provide me working code would be a great help, just to initiate things.Just a working this or any other kernel-API Code, would be a great help.

[#include<stdio.h>
#include</usr/include/sys/vfs.h>
int main()
{
//struct super_block * get_super (struct block_device *bdev);
struct block_device *bd;
printf("Block size in bytes = %ld",*get_super(bd)->s_blocksize);
}]

error:
sp.c: In function ‘main’:
sp.c:7: error: invalid type argument of ‘->’

Thanks & Regards.

ankur

Aquarius_Girl · 02-02-2011, 12:33 AM

Did you understand the last line of post number 9?

and bookmark the following links for future:
1. http://ugweb.cs.ualberta.ca/~rod/tut...messagesC.html
2. http://www.gnu.org/s/libc/manual/htm...rror-Reporting

ankur0921 · 02-02-2011, 04:32 AM

Anisha,

Its fine it become complicated, but its the direct way to implement, even if we are doing same with another variable at the place of *get_super(bd), i mean same type of pointer.Same error is being produced, even sometime s_blocksize is unrecognized.I have check same field with structure .So at least this error should not get produced.What you say? Do you ever tried some 2.6 kernel API , if yes kindly provide the way how you had done that or code.

Regards.

ankur