`Threads` tutorial's `printf` doesn't work.

[jwnhy]

int new_thread(void *arg1, void *arg2, void *arg3) {
  puts("HELLO");
  printf("Hello2: arg1 %p, arg2 %p, arg3 %p\n", arg1, arg2, arg3);
  //  void (*func)(int) = arg1;
  //  func(*(int *)arg2);
  while (1)
    ;
}

int main(int c, char *arbv[]) {

  printf("Hello, World!\n");

  seL4_DebugDumpScheduler();

  // TODO fix the parameters in this invocation
  seL4_Error result =
      seL4_Untyped_Retype(tcb_untyped, seL4_TCBObject, seL4_TCBBits, root_cnode,
                          0, 0, tcb_cap_slot, 1);
  ZF_LOGF_IF(result, "Failed to retype thread: %d", result);
  seL4_DebugDumpScheduler();

  // TODO fix the parameters in this invocation
  result = seL4_TCB_Configure(tcb_cap_slot, 0, root_cnode, 0, root_vspace, 0,
                              (seL4_Word)thread_ipc_buff_sym, tcb_ipc_frame);
  ZF_LOGF_IF(result, "Failed to configure thread: %d", result);

  // TODO fix the call to set priority using the authority of the current thread
  // and change the priority to 254
  result = seL4_TCB_SetPriority(tcb_cap_slot, root_tcb, 254);
  ZF_LOGF_IF(result, "Failed to set the priority for the new TCB object.\n");
  seL4_DebugDumpScheduler();

  seL4_UserContext regs = {0};
  int error = seL4_TCB_ReadRegisters(tcb_cap_slot, 0, 0,
                                     sizeof(regs) / sizeof(seL4_Word), &regs);
  ZF_LOGF_IFERR(error, "Failed to read the new thread's register set.\n");

  // TODO use valid instruction pointer
  sel4utils_set_instruction_pointer(&regs, (seL4_Word)new_thread);
  // TODO use valid stack pointer
  sel4utils_set_stack_pointer(&regs, tcb_stack_top);
  // TODO fix parameters to this invocation
  error = seL4_TCB_WriteRegisters(tcb_cap_slot, 0, 0,
                                  sizeof(regs) / sizeof(seL4_Word), &regs);
  ZF_LOGF_IFERR(error,
                "Failed to write the new thread's register set.\n"
                "\tDid you write the correct number of registers? See arg4.\n");
  seL4_DebugDumpScheduler();

  // TODO resume the new thread
  error = seL4_TCB_Resume(tcb_cap_slot);
  ZF_LOGF_IFERR(error, "Failed to start new thread.\n");
  while (1)
    ;
  return 0;
}

I followed the tutorial and completed the task as above.
However, if new_thread function contains a printf invocation, it will fail before it prints out anything.

I originally thought it's an issue with my solution to the tutorial, but I tried puts, which outputs content.
This means new_thread indeed started but failed at printf.

As I am new to seL4, I am not sure what's going on here. I have tested replacing every piece of my code with the solution code but the error remains.

Thank you in advance for your kind help.

[jwnhy]

The fault is as follows.
0xd on x86 means #GP, not entirely sure what makes printf differs from puts...

HELLO
Caught cap fault in send phase at address 0
while trying to handle:
user exception 0xd code 0
in thread 0xffffff800814cc00 "child of: 'tcb_threads'" at address 0x410654

[jwnhy]

After trying sel4utils_arch_init_local_context, I found that one must use sel4utils_set_stack_pointer(&regs, tcb_stack_top - 8); instead of tcb_stack_top, which is indicated in the solution...

I can only guess that printf did some unusual things that occupies the 8 bytes...

Anyway, there is an issue in the solution..