Qtspim (MIPS emulator) extra code showing up?

Question

I installed Qtspim to try out some MIPS commands. I've written a few text files, saved with a ".asm" extension, with some commands. Here's one:

.text
.globl main
main:
    addi $t0, $zero, 3
    addi $t1, $zero, 5
    add $t2, $t0, $t1
li  $v0, 10
syscall

However, when I try the "Reinitialize and Load File" command in Qtspim, the text that shows up in the "text" section of the program does not correspond to my text file. My code is in the middle of it, but with a bunch of EXTRA code that wasn't in my file. Why is this? Am I loading it wrong somehow? What's all this other code?

   User Text Segment [00400000]..[00440000]
   [00400000] 8fa40000  lw $4, 0($29)            ; 183: lw $a0 0($sp) # argc 
   [00400004] 27a50004  addiu $5, $29, 4         ; 184: addiu $a1 $sp 4 # argv 
   [00400008] 24a60004  addiu $6, $5, 4          ; 185: addiu $a2 $a1 4 # envp 
   [0040000c] 00041080  sll $2, $4, 2            ; 186: sll $v0 $a0 2 
   [00400010] 00c23021  addu $6, $6, $2          ; 187: addu $a2 $a2 $v0 
   [00400014] 0c100009  jal 0x00400024 [main]    ; 188: jal main 
   [00400018] 00000000  nop                      ; 189: nop 
   [0040001c] 3402000a  ori $2, $0, 10           ; 191: li $v0 10 
   [00400020] 0000000c  syscall                  ; 192: syscall # syscall 10 (exit) 
   [00400024] 20080003  addi $8, $0, 3           ; 2: addi $t0, $zero, 3 
   [00400028] 20090005  addi $9, $0, 5           ; 3: addi $t1, $zero, 5 
   [0040002c] 01095020  add $10, $8, $9          ; 4: add $t2, $t0, $t1 
   [00400030] 3402000a  ori $2, $0, 10           ; 5: li $v0, 10 
   [00400034] 0000000c  syscall                  ; 6: syscall 

   Kernel Text Segment [80000000]..[80010000]
   [80000180] 0001d821  addu $27, $0, $1         ; 90: move $k1 $at # Save $at 
   [80000184] 3c019000  lui $1, -28672           ; 92: sw $v0 s1 # Not re-entrant and we can't trust $sp 
   [80000188] ac220200  sw $2, 512($1)           
   [8000018c] 3c019000  lui $1, -28672           ; 93: sw $a0 s2 # But we need to use these registers 
   [80000190] ac240204  sw $4, 516($1)           
   [80000194] 401a6800  mfc0 $26, $13            ; 95: mfc0 $k0 $13 # Cause register 
   [80000198] 001a2082  srl $4, $26, 2           ; 96: srl $a0 $k0 2 # Extract ExcCode Field 
   [8000019c] 3084001f  andi $4, $4, 31          ; 97: andi $a0 $a0 0x1f 
   [800001a0] 34020004  ori $2, $0, 4            ; 101: li $v0 4 # syscall 4 (print_str) 
   [800001a4] 3c049000  lui $4, -28672 [__m1_]   ; 102: la $a0 __m1_ 
   [800001a8] 0000000c  syscall                  ; 103: syscall 
   [800001ac] 34020001  ori $2, $0, 1            ; 105: li $v0 1 # syscall 1 (print_int) 
   [800001b0] 001a2082  srl $4, $26, 2           ; 106: srl $a0 $k0 2 # Extract ExcCode Field 
   [800001b4] 3084001f  andi $4, $4, 31          ; 107: andi $a0 $a0 0x1f 
   [800001b8] 0000000c  syscall                  ; 108: syscall 
   [800001bc] 34020004  ori $2, $0, 4            ; 110: li $v0 4 # syscall 4 (print_str) 
   [800001c0] 3344003c  andi $4, $26, 60         ; 111: andi $a0 $k0 0x3c 
   [800001c4] 3c019000  lui $1, -28672           ; 112: lw $a0 __excp($a0) 
   [800001c8] 00240821  addu $1, $1, $4          
   [800001cc] 8c240180  lw $4, 384($1)           
   [800001d0] 00000000  nop                      ; 113: nop 
   [800001d4] 0000000c  syscall                  ; 114: syscall 
   [800001d8] 34010018  ori $1, $0, 24           ; 116: bne $k0 0x18 ok_pc # Bad PC exception requires special checks 
   [800001dc] 143a0008  bne $1, $26, 32 [ok_pc-0x800001dc] 
   [800001e0] 00000000  nop                      ; 117: nop 
   [800001e4] 40047000  mfc0 $4, $14             ; 119: mfc0 $a0 $14 # EPC 
   [800001e8] 30840003  andi $4, $4, 3           ; 120: andi $a0 $a0 0x3 # Is EPC word-aligned? 
   [800001ec] 10040004  beq $0, $4, 16 [ok_pc-0x800001ec]
   [800001f0] 00000000  nop                      ; 122: nop 
   [800001f4] 3402000a  ori $2, $0, 10           ; 124: li $v0 10 # Exit on really bad PC 
   [800001f8] 0000000c  syscall                  ; 125: syscall 
   [800001fc] 34020004  ori $2, $0, 4            ; 128: li $v0 4 # syscall 4 (print_str) 
   [80000200] 3c019000  lui $1, -28672 [__m2_]   ; 129: la $a0 __m2_ 
   [80000204] 3424000d  ori $4, $1, 13 [__m2_]   
   [80000208] 0000000c  syscall                  ; 130: syscall 
   [8000020c] 001a2082  srl $4, $26, 2           ; 132: srl $a0 $k0 2 # Extract ExcCode Field 
   [80000210] 3084001f  andi $4, $4, 31          ; 133: andi $a0 $a0 0x1f 
   [80000214] 14040002  bne $0, $4, 8 [ret-0x80000214]; 134: bne $a0 0 ret # 0 means exception was an interrupt 
   [80000218] 00000000  nop                      ; 135: nop 
   [8000021c] 401a7000  mfc0 $26, $14            ; 145: mfc0 $k0 $14 # Bump EPC register 
   [80000220] 275a0004  addiu $26, $26, 4        ; 146: addiu $k0 $k0 4 # Skip faulting instruction 
   [80000224] 409a7000  mtc0 $26, $14            ; 148: mtc0 $k0 $14 
   [80000228] 3c019000  lui $1, -28672           ; 153: lw $v0 s1 # Restore other registers 
   [8000022c] 8c220200  lw $2, 512($1)           
   [80000230] 3c019000  lui $1, -28672           ; 154: lw $a0 s2 
   [80000234] 8c240204  lw $4, 516($1)           
   [80000238] 001b0821  addu $1, $0, $27         ; 157: move $at $k1 # Restore $at 
   [8000023c] 40806800  mtc0 $0, $13             ; 160: mtc0 $0 $13 # Clear Cause register 
   [80000240] 401a6000  mfc0 $26, $12            ; 162: mfc0 $k0 $12 # Set Status register 
   [80000244] 375a0001  ori $26, $26, 1          ; 163: ori $k0 0x1 # Interrupts enabled 
   [80000248] 409a6000  mtc0 $26, $12            ; 164: mtc0 $k0 $12 
   [8000024c] 42000018  eret                     ; 167: eret 

Answer 1

That looks fine to me. The code ahead of your code is just some stuff that SPIM inserts to simulate your program being linked against a crt0. As you can see at address 00400014 there's a jal instruction that will call your main function.

The code following your code (the kernel text segment) is a different memory area, and not something you'll typically have to concern yourself with.