KernelTrap blogs

Function Growth: Big O vs. Small o

Eus — Wed, 17 Nov 2010 22:26:15 +0000

When I started to study Computational Complexity based on Oded Goldreich's book, I encountered brief explanations of big O and small o notations in section 1.1.5. So, I used Wikipedia to dig deeper which was very helpful. But, I got the true enlightment about the intuitions of big O and small o notations in the class when someone sitting beside me asked the teaching assistant (TA) about the meaning of the small o notation.

Elvis Long Path Or File Name Bug

Eus — Wed, 17 Nov 2010 21:50:33 +0000

Some days ago when I wanted to edit a file having a long file name that is located in a deep subdirectory also bearing long name with Elvis 2.2.0 on GNU/Linux Ubuntu 9.04, Elvis crashed because the system's C library detected buffer overflow. Since Emacs could open the same file properly, I concluded that this is Elvis' problem.

GIMP: Cannot Erase To Background Color

Eus — Sun, 14 Nov 2010 11:11:45 +0000

The other day when I was working with the GIMP, I was very surprised that whenever I erased something, GIMP started to erase to transparent background. Previously whenever I erased something, GIMP erased to the background color, which was I wanted. I googled for "gimp erase to background color". But, the results were mostly the exact opposite: how to erase to transparent background. Finally, I figured out the solution myself.

advengame

advengame — Tue, 09 Nov 2010 14:53:14 +0000

Bike Games |
Car Games |
Racing Games |
Action Games |
Adventure Games

Database Modeling vs. Implementation: Making All Entities Strong

Eus — Mon, 08 Nov 2010 20:04:26 +0000

When I was following the Database course in my undergraduate study, I was introduced to Entity-Relationship model, in particular, the notion of weak entity. But, having learned the notions of strong and weak entity, I always wondered whether or not I should model an entity as a strong or weak entity when both were possible.

Making ramfs - VFS: Unable to mount root fs

Eus — Mon, 01 Nov 2010 10:24:42 +0000

I was following a step-by-step instruction of making a ramfs to be run on QEMU's ARM machine. The instruction says that the ramfs is to be created from BusyBox's _install directory with the following command: "find . | cpio -H newc -o | gzip > ../ramfs.img". But, after reading "info cpio", I decided to change "find ." with "find . -depth", which is considered a good practice to avoid problem with strict directory permission during cpio extraction since the directory permission is only set after all files inside the directory are copied into the directory. However, running qemu-system-arm, the kernel panics saying that it cannot mount the root filesystem as follows:

Emacs Octave Mode: Underscore As Word Separator

Eus — Thu, 28 Oct 2010 21:59:03 +0000

I was using octave-mode in Emacs when I found a little inconvenience when editing an Octave function name that has underscores in it, for example, "C_square_exp". Specifically, when I wanted to change "square" to "triangle" when the cursor is after the last character, pressing Alt+B made the cursor jump to the first character instead to the character after the last underscore.

Rough Overview of Agent-oriented Software Engineering

Eus — Wed, 20 Oct 2010 20:42:25 +0000

For this week, the course on Agent-oriented Software Engineering (AOSE) was taught by a post-doc student named Amit Chopra. Chopra presented his PhD dissertation topic on the interaction in a multi-agent system (MAS) based on the concept of commitment. It was very enlightening and gave me the key to understand the advantage of Agent-oriented Software Engineering over Object-oriented Software Engineering.

Tapping WLAN: It Is Just Another Radio

Eus — Sun, 10 Oct 2010 12:51:49 +0000

About 1.5 years ago when I were with my friend in his office in our alma mater university in the evening, I tried to tap his wireless communication. With iwconfig I put my WLAN card to monitor mode and fired Wireshark. But, data packets were not received although WLAN management frames were captured. I wondered what was wrong but didn't pursue the matter further.

How to allow tracing of VLAN Tags in wireshark

bhal — Thu, 07 Oct 2010 15:02:57 +0000

Problem:
--------

Wireshark captured the incoming Ethernet Frames without any VLAN tags because the driver stripped VLAN tags from the received frames. How can I see VLAN tags in incoming frames?

Solution:
---------

Patch the ixgbe driver:

File: ixgbe_main.c

Function: static int __devinit ixgbe_probe(struct pci_dev *pdev,
const struct pci_device_id *ent)