Re: [RFC v4 9/9] Add S390 support for linux-kernel target

[Yao Qi <qiyaoltc@gmail.com>]

Philipp Rudo <prudo@linux.vnet.ibm.com> writes:

> +/* S390s kernel stack is split up on several memory locations:
> +
> +   - kernel stack (per task)
> +   - async aka. interrupt stack (per cpu)
> +   - panic stack (per cpu)
> +   - restart stack (unique, global)
> +
> +   Each memory location is page aligned and has a size of four consecutive
> +   pages (except the panic stack with only one page).  */
> +
> +enum s390_lk_stack_location
> +{
> +  S390_LK_STACK_INVALID = -1,
> +  S390_LK_STACK_USER,
> +  S390_LK_STACK_KERNEL,
> +  S390_LK_STACK_ASYNC,
> +  S390_LK_STACK_PANIC,
> +  S390_LK_STACK_RESTART
> +};
> +

Did you consider adding different frame unwinders for frames on
different memory locations?  Your patches only adds two, but IMO, we
need more unwinders for different frames,

> +
> +/* Helper macro for s390_lk_get_stack_location to check for stacks which
> +   locations are stored in the lowcore.
> +
> +      _addr	address to be checked for
> +      _lc	address of the corresponding lowcore
> +      _stack	field name of stack in lowcore
> +      _type	type to be returned if _addr is on _stack
> +      _size	size of _stack
> +*/
> +
> +#define s390_lk_check_lowcore_stack(_addr, _lc, _stack, _type, _size)	\
> +  do									\
> +    {									\
> +      CORE_ADDR _##_stack, _##_stack##_top, _##_stack##_bottom;		\
> +      _##_stack = lk_read_addr ((_lc) + LK_OFFSET (lowcore, _stack));	\
> +      _##_stack##_top = S390_LK_ROUNDUP (_##_stack, S390_LK_PAGESIZE);	\
> +      _##_stack##_bottom = _##_stack##_top - (_size);			\
> +      if ((_addr) <= _##_stack##_top && (_addr) >= _##_stack##_bottom)	\
> +	return (_type);							\
> +    }									\
> +  while (0)
> +
> +/* Find and return the stack location of ADDR belonging to TASK.  */
> +
> +static enum s390_lk_stack_location
> +s390_lk_get_stack_location (CORE_ADDR task, CORE_ADDR addr)
> +{
> +  CORE_ADDR lowcore, top, bottom;
> +  unsigned int cpu = lk_task_running (task);
> +
> +
> +  /* Kernel stack.  */
> +  bottom = lk_read_addr (task + LK_OFFSET (task_struct, stack));
> +  top = bottom + S390_LK_STACKSIZE;
> +  if (addr <= top && addr >= bottom)
> +    return S390_LK_STACK_KERNEL;
> +
> +  /* A sleeping task only has the kernel stack.  If a sleeping task reaches
> +     this point ADDR isn't on the stack.  */
> +  if (cpu == LK_CPU_INVAL)
> +    return S390_LK_STACK_INVALID;
> +
> +  lowcore = s390_lk_get_lowcore (cpu);
> +
> +  /* Async aka. interrupt stack.  */
> +  s390_lk_check_lowcore_stack (addr, lowcore, async_stack,
> +			       S390_LK_STACK_ASYNC, S390_LK_ASYNCSIZE);
> +
> +  /* Panic stack.
> +     Note: The panic stack only has a size of one page.  */
> +  s390_lk_check_lowcore_stack (addr, lowcore, panic_stack,
> +			       S390_LK_STACK_PANIC, S390_LK_PAGESIZE);
> +
> +  /* Restart stack.  */
> +  s390_lk_check_lowcore_stack (addr, lowcore, restart_stack,
> +			       S390_LK_STACK_RESTART, S390_LK_ASYNCSIZE);
> +
> +  return S390_LK_STACK_INVALID;
> +}

The unwinders for different frames should be chained in this order.

-- 
Yao (齐尧)