.globl main

main:
        sub $0x16, %esp

        // our signal handler
        // -----------------
        // pop %ebp
        // add $6, %esp
        // inc %eax
        // ret
        mov %esp, %ebx
        //movb $0xb3, (%ebx)
        //inc %ebx
        //movb $0x01, (%ebx)
        //inc %ebx
        //movb $0xc3, (%ebx)
        movb $0x83, (%ebx)
        inc %ebx
        movb $0xc4, (%ebx)
        inc %ebx
        movb $0x40, (%ebx)
        inc %ebx
        movb $0x8b, (%ebx)
        inc %ebx
        movb $0x1c, (%ebx)
        inc %ebx
        movb $0x24, (%ebx)
        inc %ebx
        movb $0x83, (%ebx)
        inc %ebx
        movb $0xec, (%ebx)
        inc %ebx
        movb $0x40, (%ebx)
        inc %ebx
        movb $0x83, (%ebx)
        inc %ebx
        movb $0xc3, (%ebx)
        inc %ebx
        movb $0x04, (%ebx)
        inc %ebx
        movb $0x53, (%ebx)
        inc %ebx
        //movb $0xff, (%ebx)
        //inc %ebx
        //movb $0xe3, (%ebx)
        //inc %ebx
        movb $0xc3, (%ebx)

        // install signal handler
        mov %esp, %ecx
        xor %eax, %eax
        movb $48, %al
        xor %ebx, %ebx
        movb $11, %bl
        int $0x80

        // prepare vars for loop and save ebp for later ret
        mov %esp, %edi
        mov %esp, %edx
        mov %esp, %esi
        xor %ecx, %ecx
        inc %ecx
        xor %ebx, %ebx

calculate_stack_start:
        cmp %cl, %bl
        je calculate_stack_end
        inc %edi
        mov (%edi), %edx
        jmp calculate_stack_start

calculate_stack_end:
        // at this point, esi holds the original esp
        // and edi holds the start of the stack
        // re-install signal handler
        mov %esi, %ecx
        xor %eax, %eax
        movb $48, %al
        xor %ebx, %ebx
        movb $11, %bl
        int $0x80

        // reset variables
        // mov %esp, %edi
        mov %esi, %esp
        xor %ebx, %ebx
        xor %ecx, %ecx
        inc %ecx

        // save for later use
        push %edi

cse_loop:
        cmp %cl, %bl
        je munmap_stack
        dec %edi
        mov (%edi), %edx
        jmp cse_loop

munmap_stack:
        add $1, %edi
        mov %esi, %esp
        // restore end of stack
        sub $4, %esp
        pop %esi

        // at this point - edi = end of stack, esi = start of stack
        // edi holds the end of the stack
        sub %edi, %esi
        // we stopped short in our loops by 2 bytes each time
        add $2, %esi
        // ebx is the memory to munmap
        mov %edi, %ebx
        // ecx is the size to munmap
        mov %esi, %ecx
        // perform munmap
        xor %eax, %eax
        mov $91, %al
        int $0x80

my_exit:
        xor %eax, %eax
        xor %ebx, %ebx
        inc %eax
        int $0x80