HP Ski Simulator, IA-64 manual Changing the Data Window Display

Ski IA-64 Simulator Reference Manual 1.0L

type “ dj r12” or “ dj 9ffffffffff780”, as shown in Figure 1-7and the Data Window changes to display the hexadec- imal data stored at the location, as shown in Figure 1-8.Find the value of r12 in your program and use “ dj” now. (You might wonder why “ dj” exists, instead of a simple scroll bar. Imagine scrolling through the entire IA-64 address space– it would take a long, long time!)

Figure 1-7. Changing the Data Window Display

Figure 1-8. The Data Window Showing the argv and envp Vectors

Looking at the Data Window, you can see that the first 16 bytes of the stack are all zeros. This is a scratch storage area. The next 8-byte word contains argc, the argument count. It has a value of 1 as the only argument passed to the program is the program name itself. The argc count is then followed by the argv and envp vectors. All C programs receive the same kind of data structure for argv: a variable-length vector of char * pointers whose end is marked with a NULL pointer. In Figure 1-8,the first of the char * pointers is 9ffffffffffff938. (The first char * pointer may be in a different place on your system. Adjust the following instructions accordingly.) Jump the Data Window there using the command “ dj 9ffffffffffff938” (12 f’s) and you will see Figure 1-9,showing the hexadecimal codes for the null-terminated ASCII

1-6 Getting Started: A Ski Tutorial Copyright © 2000 Hewlett-Packard Co.