Support custom stack guard size

[no1wudi]

Add a new option WAMR_BUILD_STACK_GUARD_SIZE to use custom stack guard size, for most RTOS port, we use stack base as check boundry which may not safety as POSIX based system (like linux).

[lum1n0us]

Just a little confused about the meaning of when exec_env->native_stack_boundary is NULL. Does it mean one of the below?

• be easy, there is no stack boundary at all.
• or, be panic, there is something wrong. There should always be value.

[no1wudi]

@lum1n0us In current implementation, I think NULL means there is no stack boundary at all.

[wenyongh]

@lum1n0us In current implementation, I think NULL means there is no stack boundary at all.

Some platforms doesn't provide the related API to get native stack boundary, so we return NULL in API os_thread_get_stack_boundary, e.g. alios.

[lum1n0us]

in that case, such a comparison looks a little wired. It will be passed but ...

    //  if (&module_inst < NULL)
    if ((uint8 *)&module_inst < exec_env->native_stack_boundary) {
        aot_set_exception_with_id(module_inst, EXCE_NATIVE_STACK_OVERFLOW);
        return false;
    }

Would one of the below be better?

• if (!exec_env->native_stack_boundary && &moudle_inst < exec_env->native_stack_bounbdary)
• Or use UINT64_MAX instead of NULL if native_stack_boundary isn't provided.

[wenyongh]

in that case, such a comparison looks a little wired. It will be passed but ...

    //  if (&module_inst < NULL)
    if ((uint8 *)&module_inst < exec_env->native_stack_boundary) {
        aot_set_exception_with_id(module_inst, EXCE_NATIVE_STACK_OVERFLOW);
        return false;
    }

Would one of the below be better?

• if (!exec_env->native_stack_boundary && &moudle_inst < exec_env->native_stack_bounbdary)
• Or use UINT64_MAX instead of NULL if native_stack_boundary isn't provided.

No need to do that, if exec_env->native_stack_boundary is NULL, this condition if ((uint8 *)&module_inst < exec_env->native_stack_boundary) will be always false, here the check is OK. The issue is in the platform API itself.