Why is data stored in memory reversed?

This is the source code I have:

section .data           
msg:    db "pppaaa"     
len:    equ $
section .text           
    global  main    
main:                    
    mov     edx,len 
    mov     ecx,msg 
    mov     ebx,1   
    mov     eax,4   
    int     0x80

And when I debug this code I will see:

(gdb) info register ecx
ecx            0x804a010        134520848
(gdb) x 0x804a010
0x804a010 <msg>:        0x61707070
(gdb) x 0x804a014
0x804a014:      0x00006161

"70" here represents the character 'p' and "61" the character 'a' obviously.

What I am confused about is, why is the data in location 0x804a010 is 0x61707070 (appp) and moving 4 bytes forward at 0x804a014 the data is --aa ?

I would expect to see (pppa) for the first location and (aa--) for the second location. Why is this the case?

Solution

GDB doesn't know that you have a bunch of chars. You are just asking it to look at a memory location and it is displaying what is there, defaulting to a 4-byte integer. It assumes the integer is stored least significant byte first, because that is how it is done on Intel, so you get your bytes reversed.

To fix this, use a format specifier with your x command, like this:

 x/10c 0x804a010

(will print 10 chars beginning at 0x804a010).

help x in GDB will give more information.