hi i just have a quick question, ill attach my source incase i've mistyped
anyway i'm doing the book's exercises in a vm of ubuntu mate, i was having
no issues until trying to run the first program in chapter 4, it compiles
and links just fine but when i try to run it i get this error: 'Cannot
execute binary file: Exec format error'
attached is my source, i believe that the problem may be that i am running
in a VM but if so im not sure what to do, any help would be appreciated.
regards,
Johnathan
#PURPOSE: program to illustrate how functions work
# this program will compute the value of
# 2^3 + 5^2
#
#everything in the main program is stored in registers so the data section
doesnt need anything
.section data
.section text
.globl _start
_start:
pushl $3 #push second argument
pushl $2 #push first argument
call power #call the function
addl $8, %esp #move the stack pointer back(after the function runs)
pushl %eax #save the first answer before
#calling the next function
pushl $2 #push second argument
pushl $5 #push first argument
call power #call the function
addl $8,%esp #move the stack pointer back
popl %ebx #the second answer is already
#in %eax we saved the
#first answer onto the stack
#so now we can just pop it
#out into %ebx
addl %eax, %ebx #add them together
#the result is stored in the second one addl first number,
second number which is also the destination register
movl $1, %eax #exit (%ebx is returned)
int $0x80
#PURPOSE This function is used to computer the value of a number raised to a
power.
#
#
#
#input: first argument - the base number
# second argument - the power to
# raise it to.
#output: will give the result as a return value through eax
#
#notes: the power must be 1 or greater
#
#variables:
# %ebx- holds the base number
# %ecx- holds the power
#
# -4(%ebp) - holds the current result
#
# %eax is used for temporary storage
#
.type power, @function
power:
pushl %ebp #save old base pointer
movl %esp,%ebp #make stack pointer the base pointer
subl $4, %esp #get room for our local storage by subtracting one word (4
bytes) from the stack pointer
movl 8(%ebp), %ebx #put the first agument in ebx
movl 12(%ebp),%ecx #put the second argument in %ecx
movl %ebx, -4(%ebp) #store current result
power_loop_start:
cmpl $1, %ecx #if the power is 1 we are done
je end_power
movl -4(%ebp), %eax #move the current result into eax(on first run this
will be the first argument)
imull %ebx, %eax #multiply the current result by the base number(it gets
stored in the second register)
movl %eax, -4(%ebp) #store the result
decl %ecx #decrease the power
jmp power_loop_start #run for the next power
end_power:
movl -4(%ebp),%eax #return value goes in eax
movl %ebp,%esp #restore the stack pointer
popl %ebp #restore the base pointer
ret
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