Arithmetic functions written in Inline asm in C program cause Segmentation Fault

Got the following functions for doing multiplication, division and finding a remainder:

#define IS_EQUAL(var_, const_)          ((INT32)(var_) == (INT32)(const_))

// all these functions must use hexadecimals as constants according to syllabus
static inline INT32
math_qmultiply (INT32 num1, INT32 num2)
{
  INT32 retval = 0x0,
        count =  0x0;
  while (num2)
    {
      if (IS_EQUAL ((num2 & 0x1), 0x1))
        {
          retval += num1 << count;
        }
      count++;
      num2 = num2 >> 1;
    }
  return retval;
}

static inline INT32
math_qdivide (INT32 num1, INT32 num2)
{
  if (!num1)
    {
      return 0x0;
    }
  if (!num2)
    {
      return INT_MAX;
    }
  INT32 neg_result = FALSE;
  if (num1 < 0x0)
    {
      num1 = -num1;
      if (num2 < 0x0)
        {
          num2 = -num2;
        }
      else
        {
          neg_result = TRUE;
        }
    }
  else if (num2 < 0x0)
    {
      num2 = -num2;
      neg_result = TRUE;
    }
  INT32 quotient = 0x0;
  while (num1 >= num2)
    {
      num1 -= num2;
      quotient++;
    }
  if (neg_result)
    {
      quotient = -quotient;
    }
  return quotient;
}

static inline INT32
math_qmod (INT32 n1, INT32 n2)
{
  INT32 q = math_qdivide (n1, n2);
  INT32 p = math_qmultiply (q, n2);
  return n1 - p;
}

These three functions are used in the below function:

static inline INT32
find_actual_x_for_char_idx (const INT32 char_idx)
{
  INT32 t1 = math_qdivide (char_idx, FRAME_COLS_COUNT);
  register INT32 divisor = math_qmultiply (FRAME_COLS_COUNT, t1);
  INT32 t2 = math_qmod(char_idx, FRAME_COLS_COUNT);
  register INT32 x = !t2 ? 0x0 : char_idx - divisor;
  return FRAME_TOP_LEFT_X + x;
}

This function produces correct output and works OK.

The problem begins when I change the code of the previous functions to have them like this:

INLINE_ATTRIB INT32
math_qmultiply (INT32 n1, INT32 n2)
{
  INT32 res = 0x0;
  asm volatile(
      "mov eax, %1;""mov ebx, %2;""mul ebx;""mov %0, eax;"
      : "=r" (res)
      : "g" (n1),
      "g" (n2)
      );
  return res;
}

INLINE_ATTRIB INT32
math_qdivide (INT32 n1, INT32 n2)
{
  INT32 res = 0;
  asm volatile(
      "mov eax, %1;""mov ebx, %2;""xor edx, edx;""div ebx;""mov %0, eax;"
      : "=r" (res)
      : "g" (n1),
      "g" (n2)
      );
  return res;
}

INLINE_ATTRIB INT32
math_qmod (INT32 n1, INT32 n2)
{
  INT32 res = 0;
  asm volatile
    ("mov eax, %1;""mov ebx, %2;""xor edx, edx;""div ebx;""mov %0, edx;"
     : "=r" (res)
     : "g" (n1), "g" (n2)
     );
  return res;
}

Now I always SEGMENTATION FAULT, though when I check these functions separately they do division, multiplication and finding the remainder correctly. Can you show me what causes SEGMENTATION FAULT?