GDB stack trace and assembly debugging

GDB stack trace and assembly debugging

Analysis process

Gcc-g 32-bit assembly on a 64-bit machine using the example.c-o example-m32 Directive error: fatal error

You need to download the installation library file

Command: sudo apt-get install libc6-dev-i386

Then one more operation will produce the Assembly

? Open the GdB debugger with the gdb gdb1 directive

? Use the break main directive to set a breakpoint at the main function, and remember to run the code with the r instruction first, and you can see the error that occurs when the runtime stops at the main function position:

Use the disassemble directive to get the assembly code (because there are-m32 in the previously executed command, so here is the 32-bit assembly code shown here)

? Use the I r command to view the values of each register

Visible at this time the main function's stack base address is 0xffffd068, with the x 0xffffd068 instruction to see the values in the memory addresses:

As a result, the current%ESP refers to the stack content of 0,%EBP refers to the content is also 0

? use display/i $pc (combined with the display command and register/PC internal variables) instructions to set

This allows the currently executed statement to be displayed at each execution of the next assembly statement for easy viewing.

? Debug the assembly code as follows, and view the%esp,%EBP, and stack contents:

? (1), single-step tracking of a machine instruction using SI command

? (2), use the i r command to see the values of each register (see%EIP,%eax,%esp and%EBP here)

? (3), use x/na%esp corresponding value instruction to view stack changes

Repeat the above three steps until the end

? Main function Assembly code

? Starting with the main function, the push $0x13 allocates 4 bytes of stack space and sets the arg1=19

Call calls F (0x80483e6)

? Execute the F function, F initialize the frame pointer, put the base address of the previous function into the stack, and the current%ESP as the new base address

F Allocate stack space to prepare for the transfer of parameters

? PUSHL 0x8 (%EBP) to deposit 8 of%ESP in the stack

Call calls G (0X80483DB)

? Execute g function, g initialize stack pointer

? g Allocation Stack space

? PUSHL 0x8 (%EBP) to deposit 8 of%ESP in the stack

? Add%eax to immediate number 19

? pop%EBP the stack before G ends

RET returns the call position in G, ending the G function

? Add%esp to immediate number 4

? Leave back to prep stack

RET returns the call position in F, ending the F function

Enter the main function to add the%ESP to the immediate number 4

? Add%eax to immediate number 19

? Leave back to prep stack

? RET End Main function

GDB stack trace and assembly debugging