User Account

All Pages

Assembly HW help, Assembly Language

Assignment Help:
I was wondering if you guys could offer me some advice and help on how to proceed - not answers- for a homework problem I am attempting. I am currently working on a "bomb" project in which I progress through stages by discovering passwords or phrases using the gdb debugger to analyze assembly code. I was able to easily complete stages 1-3, but am having a bit of trouble with stage 4. Here is the assembly for this stage:

0x08048d6d <+0>: sub $0x2c,%esp
0x08048d70 <+3>: lea 0x1c(%esp),%eax
0x08048d74 <+7>: mov %eax,0xc(%esp)
0x08048d78 <+11>: lea 0x18(%esp),%eax
0x08048d7c <+15>: mov %eax,0x8(%esp)
0x08048d80 <+19>: movl $0x804a5d1,0x4(%esp) ;%d, %d
0x08048d88 <+27>: mov 0x30(%esp),%eax
0x08048d8c <+31>: mov %eax,(%esp)
0x08048d8f <+34>: call 0x8048850 <__isoc99_sscanf@plt>
0x08048d94 <+39>: cmp $0x2,%eax
0x08048d97 <+42>: jne 0x8048da5
0x08048d99 <+44>: mov 0x1c(%esp),%eax
0x08048d9d <+48>: sub $0x2,%eax
0x08048da0 <+51>: cmp $0x2,%eax
0x08048da3 <+54>: jbe 0x8048daa
0x08048da5 <+56>: call 0x80492f5
0x08048daa <+61>: mov 0x1c(%esp),%eax
0x08048dae <+65>: mov %eax,0x4(%esp)
0x08048db2 <+69>: movl $0x8,(%esp)
0x08048db9 <+76>: call 0x8048d23
0x08048dbe <+81>: cmp 0x18(%esp),%eax
0x08048dc2 <+85>: je 0x8048dc9
0x08048dc4 <+87>: call 0x80492f5
0x08048dc9 <+92>: add $0x2c,%esp
0x08048dcc <+95>: ret
From what I have looked at so far, it looks like this phase accepts two decimals (line 19), the second one must be less than or equal to 4, but greater than 1 (lines 48, 51, 54). Another important aspect to this problem is the inclusion of a recursive "func4" which is as follows:

0x08048d23 <+0>: push %edi
0x08048d24 <+1>: push %esi
0x08048d25 <+2>: push %ebx
0x08048d26 <+3>: sub $0x10,%esp
0x08048d29 <+6>: mov 0x20(%esp),%ebx
0x08048d2d <+10>: mov 0x24(%esp),%esi
0x08048d31 <+14>: test %ebx,%ebx
0x08048d33 <+16>: jle 0x8048d61
0x08048d35 <+18>: mov %esi,%eax
0x08048d37 <+20>: cmp $0x1,%ebx
0x08048d3a <+23>: je 0x8048d66
0x08048d3c <+25>: mov %esi,0x4(%esp)
0x08048d40 <+29>: lea -0x1(%ebx),%eax
0x08048d43 <+32>: mov %eax,(%esp)
0x08048d46 <+35>: call 0x8048d23
0x08048d4b <+40>: lea (%eax,%esi,1),%edi
0x08048d4e <+43>: mov %esi,0x4(%esp)
0x08048d52 <+47>: sub $0x2,%ebx
0x08048d55 <+50>: mov %ebx,(%esp)
0x08048d58 <+53>: call 0x8048d23
0x08048d5d <+58>: add %edi,%eax
0x08048d5f <+60>: jmp 0x8048d66
0x08048d61 <+62>: mov $0x0,%eax
0x08048d66 <+67>: add $0x10,%esp
0x08048d69 <+70>: pop %ebx
0x08048d6a <+71>: pop %esi
0x08048d6b <+72>: pop %edi
0x08048d6c <+73>: ret
This function is where I am having the most trouble...I am totally clueless as to what it does. All I think I know is that it accepts my second input value as an argument, alters in some way and finally compares it to the value 0x18(%esp) (line 81 in the first section)

The project is not due until later this week, but I would really rather have a better understanding of this material asap as right now I am a little lost.Thank you guys for your time.

Related Discussions:- Assembly HW help

Modes of 8254-microprocessor, Modes of 8254 :   Mode 0 (Inter...

Modes of 8254 :   Mode 0 (Interrupt on Terminal Count)-GATE which value is 1 enables counting and GATE  which value is 0 disables counting, and GATE put not effect on

Execution unit and bus interface unit-microprocessor, Execution Unit (EU) a...

Execution Unit (EU) and Bus Interface Unit (BIU) : 8086 consist of two processors called EU and BIU. Two Processors can work parallel. This improves speed of execution. BIU fi

The pentium-micro processor, The Pentium   The next member of the Intel ...

The Pentium   The next member of the Intel family of microprocessors was the Pentium, introduced in the year 1993. With the Pentium, Intel broke its custom of numeric model name

Dma-how dma works-microprocessor, DMA DMA stands for Direct Memory ...

DMA DMA stands for Direct Memory Access It is uses same Address/Data lines on ISA bus It controls the ISA bus instead of the processor ("bus master") Floppy

Program for measures the wind direction-vane, You are to create an assembly...

You are to create an assembly program for the MSP430 that correctly measures the wind direction, to a precision of 45° (N, NW, W, SW, S, SE, E, NE), using the MSP430's ADC. Your

Avr, how to code

how to code

Memory address decoding-microprocessor, Memory Address Decoding Binary ...

Memory Address Decoding Binary Decoders - Decoders have 2n-inputs and n outputs, each input combination results in a single output line contain a 1, and all other lines contain

Iret-loop-unconditional branch instruction-microprocessor, IRET : Return f...

IRET : Return from ISR:- When an interrupt service routine is called, before transferring control to it, the IP, CS  register and flag registers are stored in the stack to ment

Motorola 68000 series, Motorola 68000 Series : 68000microprocessor is a...

Motorola 68000 Series : 68000microprocessor is a 16 bit processor that has addressing space of 65536 locations, each of which holds a 64-bits word; In order to address those lo

PIC lights on, errorlevel -302 ;prevents error code for this...

errorlevel -302 ;prevents error code for this chipset __config 0x373A ;chip config PIC spec page 146 processor 16F877A ;chipset reset code

Write Your Message!

Captcha
Order Assignment

Featured Services

Order Now

Popular Subjects

Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

Submit Assignment

Academics

Major Subjects

Majors

Get In Touch

whatsapp: +91-977-207-8620

Phone: +91-977-207-8620

Email: [email protected]

TERMS & POLICIES

HELP & SUPPORT

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd