Re: [PATCH v10 21/40] arm64/gcs: Implement shadow stack prctl() interface

On Thu, Aug 01, 2024 at 01:06:48PM +0100, Mark Brown wrote:

Implement the architecture neutral prtctl() interface for setting the

s/prtctl/prctl/

+int arch_set_shadow_stack_status(struct task_struct *task, unsigned long arg) +{

• unsigned long gcs, size;
• int ret;
• if (!system_supports_gcs())

• return -EINVAL;
  

• if (is_compat_thread(task_thread_info(task)))

• return -EINVAL;
  

• /* Reject unknown flags */
• if (arg & ~PR_SHADOW_STACK_SUPPORTED_STATUS_MASK)

• return -EINVAL;
  

• ret = gcs_check_locked(task, arg);
• if (ret != 0)

• return ret;
  

• /* If we are enabling GCS then make sure we have a stack */
• if (arg & PR_SHADOW_STACK_ENABLE) {

• if (!task_gcs_el0_enabled(task)) {
  

• 	/* Do not allow GCS to be reenabled */
  

• 	if (task->thread.gcs_base)
  

• 		return -EINVAL;
  

• 	if (task != current)
  

• 		return -EBUSY;
  

• 	size = gcs_size(0);
  

• 	gcs = alloc_gcs(0, size);
  

• 	if (!gcs)
  

• 		return -ENOMEM;
  

• 	task->thread.gcspr_el0 = gcs + size - sizeof(u64);
  

• 	task->thread.gcs_base = gcs;
  

• 	task->thread.gcs_size = size;
  

• 	if (task == current)
  

• 		write_sysreg_s(task->thread.gcspr_el0,
  

• 			       SYS_GCSPR_EL0);
  

• }
  

• }

Nitpick: use a single 'if' instead of nesting (unless subsequent patches add more to the first block).

Otherwise it looks fine.

Reviewed-by: Catalin Marinas catalin.marinas@arm.com