COMP 3000 Lab 6 2011 - Revision history

Saran: /* Part B */

2011-12-05T02:22:01Z

Part B

← Older revision		Revision as of 02:22, 5 December 2011
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	2		2
			/* A descriptor ring is a structure that a PCI device and the kernel have in common */
			struct atl1e_tpd_desc desc; / descriptor ring virtual address */
			/* Physical address of the ring for the Network card driver to use. */
			dma_addr_t dma; /* descriptor ring physical address */
			/* Number of transmit ring buffers */
			u16 count; /* the count of transmit rings */
			/* Transmit read/write lock */
			rwlock_t tx_lock;
			/* Next ring to use */
			u16 next_to_use;
			/* Next ring to clean up */
			atomic_t next_to_clean;
			/* Transmit buffer */
			struct atl1e_tx_buffer *tx_buffer;


			/* The CMB dma address of the ring initialized : [here http://lxr.linux.no/linux+v3.1.4/drivers/net/atl1e/atl1e_main.c#L853]
			cmb is a pointer to the virtual address.
			These are written into the registers of the network device as shown [here http://lxr.linux.no/linux+v3.1.4/drivers/net/atl1e/atl1e_main.c#L897]
			Seems to be a device specific internal data structure.
			*/
			dma_addr_t cmb_dma;
			u32 *cmb;

Saran: /* Part B */

2011-12-05T01:52:00Z

Part B

← Older revision		Revision as of 01:52, 5 December 2011
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	return ret;		return ret;

	~~'''~~2~~'''~~		2

Saran: /* Part B */

2011-12-05T01:17:26Z

Part B

← Older revision		Revision as of 01:17, 5 December 2011
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	return ret;		return ret;

	#		'''2'''

Saran: /* Part B */

2011-12-05T01:14:27Z

Part B

← Older revision		Revision as of 01:14, 5 December 2011
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	===Part B===		===Part B===
	#		#
	*
	/* If the file descriptor is not opened with WRITE mode, returns an error. */		/* If the file descriptor is not opened with WRITE mode, returns an error. */
	if (!(file->f_mode & FMODE_WRITE))		if (!(file->f_mode & FMODE_WRITE))
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	return ret;		return ret;

	*		#

Saran: /* Part B */

2011-12-05T01:13:53Z

Part B

← Older revision		Revision as of 01:13, 5 December 2011
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	#		#
	*		*
	~~<nowiki>~~
	/* If the file descriptor is not opened with WRITE mode, returns an error. */		/* If the file descriptor is not opened with WRITE mode, returns an error. */
	if (!(file->f_mode & FMODE_WRITE))		if (!(file->f_mode & FMODE_WRITE))
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	/* Returns the number of bytes written. */		/* Returns the number of bytes written. */
	return ret;		return ret;

	~~</nowiki>~~

	*		*

Saran: /* Part B */

2011-12-05T01:13:23Z

Part B

← Older revision		Revision as of 01:13, 5 December 2011
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	===Part B===		===Part B===
			#
			*
			<nowiki>
			/* If the file descriptor is not opened with WRITE mode, returns an error. */
			if (!(file->f_mode & FMODE_WRITE))
			return -EBADF;

			/* If file_operations is NULL, or if write or asynchronous write functions in it are NULL, returns an error */
			if (!file->f_op \|\| (!file->f_op->write && !file->f_op->aio_write))
			return -EINVAL;

			/* unlikely tells the compiler that the statement inside it is unlikely - so, the compiler can optimize in its jump statements. access_ok functions checks if memory range is withing bounds, i.e count bytes can be read from buf. Returns an error if any of these checks fail. */
			if (unlikely(!access_ok(VERIFY_READ, buf, count)))
			return -EFAULT;

			/* Checks if "count" bytes can be written to the "file" starting at "pos". Returns how many bytes can be written. */
			ret = rw_verify_area(WRITE, file, pos, count);

			/* Writes using the write function provided in file_operations, which will, in general, depend on the filesystem type. */
			if (file->f_op->write)
			ret = file->f_op->write(file, buf, count, pos);

			/* Writes using do_sync_write, which calls file's aio_write function. */
			else
			ret = do_sync_write(file, buf, count, pos);

			/* If some bytes were written, it marks the file as "modified", so anyone listening for filesystem notifications could be called. add_wchar is for accounting - it adds, "ret" bytes to task_io_accounting structure of the current process. */
			if (ret > 0) {
			fsnotify_modify(file);
			add_wchar(current, ret);
			}
			/* Again, accounting - Increments the number of "write" system calls for the current process */
			inc_syscw(current);

			/* Returns the number of bytes written. */
			return ret;

			</nowiki>

			*

Saran: /* Solutions */

2011-12-05T00:22:26Z

Solutions

← Older revision		Revision as of 00:22, 5 December 2011
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	# The brk system call modifies the data segment size, and down_write(&mm->mmap_sem) is used to acquire a read/write semaphore before performing the memory operation.		# The brk system call modifies the data segment size, and down_write(&mm->mmap_sem) is used to acquire a read/write semaphore before performing the memory operation.
	# In drivers/net/atl1e/atl1e.h		# In drivers/net/atl1e/atl1e.h

			===Part B===

Saran: /* Part A */

2011-12-05T00:20:52Z

Part A

← Older revision		Revision as of 00:20, 5 December 2011
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	## bprm is a pointer to a structure of type linux_binprm. This structure is used to hold arguments that are used when loading binaries, like argc, filename, vm related structures.		## bprm is a pointer to a structure of type linux_binprm. This structure is used to hold arguments that are used when loading binaries, like argc, filename, vm related structures.
	## The goto's handle error messages, and provide the same functionality as a jump statement in assembly. The retval conditional statements before the goto calls determine what return value the program is providing to the function.		## The goto's handle error messages, and provide the same functionality as a jump statement in assembly. The retval conditional statements before the goto calls determine what return value the program is providing to the function.
	if (displaced)		## if (displaced) put_files_struct(displaced);
	put_files_struct(displaced);
	# do_fork		# do_fork
	# SYSCALL_DEFINE1 is a macro defined in syscall.h, used to define system calls. (In this case the brk system call )		# SYSCALL_DEFINE1 is a macro defined in syscall.h, used to define system calls. (In this case the brk system call )
	# The brk system call modifies the data segment size, and down_write(&mm->mmap_sem) is used to acquire a read/write semaphore before performing the memory operation.		# The brk system call modifies the data segment size, and down_write(&mm->mmap_sem) is used to acquire a read/write semaphore before performing the memory operation.
	# In drivers/net/atl1e/atl1e.h		# In drivers/net/atl1e/atl1e.h

Saran at 00:20, 5 December 2011

2011-12-05T00:20:16Z

← Older revision		Revision as of 00:20, 5 December 2011
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	# [6 pts] Briefly explain what each statement does in <tt>[http://lxr.linux.no/linux+*/fs/read_write.c#L404 vfs_write()]</tt> in fs/read_write.c. Your explanation for each line should take up two lines at most.		# [6 pts] Briefly explain what each statement does in <tt>[http://lxr.linux.no/linux+*/fs/read_write.c#L404 vfs_write()]</tt> in fs/read_write.c. Your explanation for each line should take up two lines at most.
	# [3 pts] What is the purpose of each field in the struct <tt>atl1e_tx_ring</tt>? (Note: the last two fields are extra credit!)		# [3 pts] What is the purpose of each field in the struct <tt>atl1e_tx_ring</tt>? (Note: the last two fields are extra credit!)

			==Solutions==
			===Part A===
			# In fs/exec.c
			## bprm is a pointer to a structure of type linux_binprm. This structure is used to hold arguments that are used when loading binaries, like argc, filename, vm related structures.
			## The goto's handle error messages, and provide the same functionality as a jump statement in assembly. The retval conditional statements before the goto calls determine what return value the program is providing to the function.
			if (displaced)
			put_files_struct(displaced);
			# do_fork
			# SYSCALL_DEFINE1 is a macro defined in syscall.h, used to define system calls. (In this case the brk system call )
			# The brk system call modifies the data segment size, and down_write(&mm->mmap_sem) is used to acquire a read/write semaphore before performing the memory operation.
			# In drivers/net/atl1e/atl1e.h

Nhoda: /* Part B */

2011-11-18T20:57:45Z

Part B

← Older revision		Revision as of 20:57, 18 November 2011
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	==Part B==		==Part B==
	# [6 pts] Briefly explain what each statement does in <tt>vfs_write()</tt> in fs/read_write.c. Your explanation for each line should take up two lines at most.		# [6 pts] Briefly explain what each statement does in <tt>[http://lxr.linux.no/linux+*/fs/read_write.c#L404 vfs_write()]</tt> in fs/read_write.c. Your explanation for each line should take up two lines at most.
	# [3 pts] What is the purpose of each field in the struct <tt>atl1e_tx_ring</tt>? (Note: the last two fields are extra credit!)		# [3 pts] What is the purpose of each field in the struct <tt>atl1e_tx_ring</tt>? (Note: the last two fields are extra credit!)