ret_to_user代码详解

1.主要代码

SYM_CODE_START_LOCAL(ret_to_user)
	disable_daif 
	gic_prio_kentry_setup tmp=x3
#ifdef CONFIG_TRACE_IRQFLAGS
	bl	trace_hardirqs_off
#endif
	ldr	x19, [tsk, #TSK_TI_FLAGS]
	and	x2, x19, #_TIF_WORK_MASK
	cbnz	x2, work_pending
finish_ret_to_user:
	user_enter_irqoff
	/* Ignore asynchronous tag check faults in the uaccess routines */
	clear_mte_async_tcf
	enable_step_tsk x19, x2
#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
	bl	stackleak_erase
#endif
	kernel_exit 0

/*
 * Ok, we need to do extra processing, enter the slow path.
 */
work_pending: //work_pending主要做pending的信号处理，做完后返回用户态。
	mov	x0, sp				// 'regs'
	mov	x1, x19
	bl	do_notify_resume
	ldr	x19, [tsk, #TSK_TI_FLAGS]	// re-check for single-step
	b	finish_ret_to_user
SYM_CODE_EN