user: What would the C source look like for the assembly code provided here?

```asm
<multiplication>:
  endbr64
  push   %r15
  movslq %esi,%r15
  mov    $0x4,%esi
  push   %r14
  lea    (%r15,%rcx,1),%eax
  push   %r13
  mov    %rdi,%r13
  push   %r12
  mov    %ecx,%r12d
  push   %rbp
  mov    %rdx,%rbp
  push   %rbx
  sub    $0xf8,%rsp
  mov    %eax,0x48(%rsp)
  add    $0x1,%eax
  mov    %eax,%edi
  mov    %r8,0x98(%rsp)
  mov    %eax,0x74(%rsp)
  call   <calloc@plt>
  mov    %rax,%rbx
  test   %r15d,%r15d
  js     L117
  test   %r12d,%r12d
  js     L117
  lea    0x4(%rax),%r10
  lea    0x1(%r12),%eax
  pxor   %xmm6,%xmm6
  mov    %eax,%edx
  mov    %rax,%rdi
  lea    0x1(%r13,%r15,1),%rsi
  mov    %eax,0x1c(%rsp)
  shr    $0x4,%edx
  and    $0xfffffff0,%edi
  lea    0x4(%rbx,%rax,4),%r14
  add    %rbp,%rax
  sub    $0x1,%edx
  mov    %rax,0x10(%rsp)
  mov    $0x1,%eax
  pxor   %xmm2,%xmm2
  mov    %rdx,%rcx
  movslq %edi,%rdx
  sub    %r13d,%eax
  mov    %rsi,0x8(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdx,%r15
  shl    $0x6,%rcx
  mov    %rdi,0x28(%rsp)
  lea    0x1(%rdx),%edi
  movslq %edi,%rdx
  mov    %edi,0x30(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0x38(%rsp)
  lea    0x2(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0x34(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0x40(%rsp)
  lea    0x3(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0x4c(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0x50(%rsp)
  lea    0x4(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0x60(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0x58(%rsp)
  lea    0x5(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0x64(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0x68(%rsp)
  lea    0x6(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0x70(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0x78(%rsp)
  lea    0x7(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0x88(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0x80(%rsp)
  lea    0x8(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0x8c(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0x90(%rsp)
  lea    0x9(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0xa8(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0xa0(%rsp)
  lea    0xa(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0xac(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0xb0(%rsp)
  lea    0xb(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0xc0(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0xb8(%rsp)
  lea    0xc(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0xc4(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0xd0(%rsp)
  lea    0xd(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0xe0(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0xd8(%rsp)
  lea    0xe(%r15),%edi
  movslq %edi,%rdx
  mov    %edi,0xe4(%rsp)
  lea    0x0(%rbp,%rdx,1),%rdi
  mov    %rdi,0xe8(%rsp)
  mov    %eax,0x18(%rsp)
  movslq %r12d,%rax
  lea    0x1(%rbp,%rax,1),%rax
  mov    %rax,0xc8(%rsp)
  lea    0x44(%rcx),%rax
  mov    %rax,0x20(%rsp)
  nopl   0x0(%rax)
L23:
  mov    0x18(%rsp),%eax
  mov    %r13,%r9
  lea    -0x4(%r10),%r11
  lea    (%rax,%r13,1),%edi
  add    $0x1,%r13
  cmp    0x10(%rsp),%r10
  setae  %dl
  cmp    %r14,%rbp
  setae  %al
  or     %edx,%eax
  cmp    $0xe,%r12d
  seta   %dl
  test   %dl,%al
  je     L118
  cmp    %r9,%r14
  setbe  %dl
  cmp    %r13,%r10
  setae  %al
  or     %dl,%al
  je     L118
  movzbl (%r9),%eax
  mov    %rbp,%r8
  lea    0x10(%r10),%rsi
  lea    0x20(%r10),%rcx
  lea    0x30(%r10),%rdx
  add    0x20(%rsp),%r11
  movd   %eax,%xmm5
  mov    %r10,%rax
  punpcklbw %xmm5,%xmm5
  punpcklwd %xmm5,%xmm5
  pshufd $0x0,%xmm5,%xmm5
  movdqa %xmm5,%xmm7
  punpckhbw %xmm6,%xmm5
  punpcklbw %xmm6,%xmm7
  cs nopw 0x0(%rax,%rax,1)
L71:
  movdqu (%r8),%xmm0
  movdqu (%rsi),%xmm4
  add    $0x40,%rax
  add    $0x10,%r8
  movdqu -0x40(%rax),%xmm10
  add    $0x40,%rsi
  add    $0x40,%rcx
  add    $0x40,%rdx
  movdqa %xmm0,%xmm1
  punpckhbw %xmm6,%xmm0
  movdqu -0x40(%rcx),%xmm8
  movdqu -0x40(%rdx),%xmm9
  punpcklbw %xmm6,%xmm1
  pmullw %xmm5,%xmm0
  pmullw %xmm7,%xmm1
  movdqa %xmm1,%xmm3
  punpcklwd %xmm2,%xmm1
  punpckhwd %xmm2,%xmm3
  paddd  %xmm10,%xmm1
  paddd  %xmm3,%xmm4
  movdqa %xmm0,%xmm3
  punpckhwd %xmm2,%xmm0
  movups %xmm1,-0x40(%rax)
  punpcklwd %xmm2,%xmm3
  paddd  %xmm9,%xmm0
  movups %xmm4,-0x40(%rsi)
  paddd  %xmm8,%xmm3
  movups %xmm3,-0x40(%rcx)
  movups %xmm0,-0x40(%rdx)
  cmp    %r11,%rax
  jne    L71
  add    %r15d,%edi
  cmp    0x1c(%rsp),%r15d
  je     L252
  mov    0x28(%rsp),%rsi
  movzbl (%r9),%eax
  movslq %edi,%rdx
  add    $0x1,%edi
  movzbl (%rsi),%ecx
  imul   %ecx,%eax
  add    %eax,(%rbx,%rdx,4)
  cmp    0x30(%rsp),%r12d
  jl     L252
  mov    0x38(%rsp),%rax
  movzbl (%r9),%edx
  movslq %edi,%rdi
  shl    $0x2,%rdi
  movzbl (%rax),%eax
  imul   %edx,%eax
  add    %eax,(%rbx,%rdi,1)
  cmp    0x34(%rsp),%r12d
  jl     L252
  mov    0x40(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0x4(%rbx,%rdi,1)
  cmp    0x4c(%rsp),%r12d
  jl     L252
  mov    0x50(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0x8(%rbx,%rdi,1)
  cmp    0x60(%rsp),%r12d
  jl     L252
  mov    0x58(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0xc(%rbx,%rdi,1)
  cmp    0x64(%rsp),%r12d
  jl     L252
  mov    0x68(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0x10(%rbx,%rdi,1)
  cmp    0x70(%rsp),%r12d
  jl     L252
  mov    0x78(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0x14(%rbx,%rdi,1)
  cmp    0x88(%rsp),%r12d
  jl     L252
  mov    0x80(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0x18(%rbx,%rdi,1)
  cmp    0x8c(%rsp),%r12d
  jl     L252
  mov    0x90(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0x1c(%rbx,%rdi,1)
  cmp    0xa8(%rsp),%r12d
  jl     L252
  mov    0xa0(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0x20(%rbx,%rdi,1)
  cmp    0xac(%rsp),%r12d
  jl     L252
  mov    0xb0(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0x24(%rbx,%rdi,1)
  cmp    0xc0(%rsp),%r12d
  jl     L252
  mov    0xb8(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0x28(%rbx,%rdi,1)
  cmp    0xc4(%rsp),%r12d
  jl     L252
  mov    0xd0(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0x2c(%rbx,%rdi,1)
  cmp    0xe0(%rsp),%r12d
  jl     L252
  mov    0xd8(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0x30(%rbx,%rdi,1)
  cmp    0xe4(%rsp),%r12d
  jl     L252
  mov    0xe8(%rsp),%rsi
  movzbl (%r9),%eax
  movzbl (%rsi),%edx
  imul   %edx,%eax
  add    %eax,0x34(%rbx,%rdi,1)
  nopw   0x0(%rax,%rax,1)
L252:
  add    $0x4,%r10
  add    $0x4,%r14
  cmp    0x8(%rsp),%r13
  jne    L23
L117:
  mov    0x74(%rsp),%esi
  test   %esi,%esi
  js     L205
  movslq 0x74(%rsp),%rax
  movslq 0x48(%rsp),%rdx
  mov    %rax,%rdi
  lea    (%rbx,%rax,4),%rax
  mov    %edi,%ecx
  sub    %rcx,%rdx
  xor    %ecx,%ecx
  lea    (%rbx,%rdx,4),%rsi
  nopl   0x0(%rax,%rax,1)
L280:
  add    (%rax),%ecx
  sub    $0x4,%rax
  mov    %ecx,%edx
  shr    $0x8,%ecx
  and    $0xff,%edx
  mov    %edx,0x4(%rax)
  cmp    %rax,%rsi
  jne    L280
  mov    (%rbx),%edx
  test   %edx,%edx
  jne    L215
  mov    0x74(%rsp),%ecx
  test   %ecx,%ecx
  je     L163
  mov    0x48(%rsp),%eax
  lea    0x4(%rbx),%rsi
  mov    %rbx,%rdi
  lea    0x4(,%rax,4),%rdx
  call   <memmove@plt>
L163:
  mov    0x48(%rsp),%r14d
  mov    0x98(%rsp),%rdi
  mov    %r14d,%esi
  call   <realloc@plt>
  test   %r14d,%r14d
  jns    L90
L142:
  mov    0x48(%rsp),%eax
  add    $0xf8,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nop
L118:
  mov    0xc8(%rsp),%rdi
  mov    %rbp,%rdx
  mov    %r10,%rax
  xchg   %ax,%ax
L85:
  movzbl (%rdx),%esi
  movzbl (%r9),%ecx
  add    $0x1,%rdx
  imul   %esi,%ecx
  add    %ecx,(%rax)
  add    $0x4,%rax
  cmp    %rdi,%rdx
  jne    L85
  jmp    L252
L215:
  mov    0x74(%rsp),%r14d
  mov    0x98(%rsp),%rdi
  mov    %r14d,%esi
  call   <realloc@plt>
  mov    %r14d,0x48(%rsp)
L90:
  movslq 0x48(%rsp),%rax
  mov    0x98(%rsp),%rsi
  lea    (%rbx,%rax,4),%rdx
  nopl   0x0(%rax)
L291:
  mov    (%rdx),%ecx
  sub    $0x4,%rdx
  mov    %cl,(%rsi,%rax,1)
  sub    $0x1,%rax
  test   %eax,%eax
  jns    L291
  jmp    L142
L205:
  mov    (%rbx),%eax
  test   %eax,%eax
  je     L163
  mov    0x74(%rsp),%ebx
  mov    0x98(%rsp),%rdi
  mov    %ebx,%esi
  call   <realloc@plt>
  mov    %ebx,0x48(%rsp)
  jmp    L142
```

assistant: ```c
int multiplication(unsigned char *a, int a_len, unsigned char *b, int b_len, unsigned char *multires) {
  int i, j, k, m = 0;
  unsigned int *cross = (unsigned int *)calloc(a_len + b_len + 1, sizeof(unsigned int));
  for (i = 0; i <= a_len; i++)
    for (j = 0, k = i + 1; j <= b_len; j++, k++)
      cross[k] += a[i] * b[j];
  k = a_len + b_len + 1;
  for (i = k; i >= 0; i--) {
    cross[i] += m;
    m = cross[i] >> 8;
    cross[i] &= 0xff;
  }
  if (cross[0] == 0) {
    for (i = 0; i < k; i++)
      cross[i] = cross[i + 1];
    k--;
  }
  realloc(multires, k);
  for (i = k; i >= 0; i--)
    multires[i] = cross[i];
  return k;
}
```