Merge patch "RISC-V: Fix unannoted hardirqs-on in return to userspace slow-path"

I'm merging this in as a single patch to make it easier to handle the
backports.

* b4-shazam-merge:
  RISC-V: Fix unannoted hardirqs-on in return to userspace slow-path

Link: https://lore.kernel.org/r/20221111223108.1976562-1-abrestic@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/entry.S

@@ -264,12 +264,11 @@ SYM_CODE_START_NOALIGN(ret_from_exception)
 	bnez s0, resume_kernel
 SYM_CODE_END(ret_from_exception)
 
-resume_userspace:
 	/* Interrupts must be disabled here so flags are checked atomically */
 	REG_L s0, TASK_TI_FLAGS(tp) /* current_thread_info->flags */
 	andi s1, s0, _TIF_WORK_MASK
-	bnez s1, work_pending
-
+	bnez s1, resume_userspace_slow
+resume_userspace:
 #ifdef CONFIG_CONTEXT_TRACKING_USER
 	call user_enter_callable
 #endif
@@ -369,19 +368,12 @@ resume_kernel:
 	j restore_all
 #endif
 
-work_pending:
+resume_userspace_slow:
 	/* Enter slow path for supplementary processing */
-	la ra, ret_from_exception
-	andi s1, s0, _TIF_NEED_RESCHED
-	bnez s1, work_resched
-work_notifysig:
-	/* Handle pending signals and notify-resume requests */
-	csrs CSR_STATUS, SR_IE /* Enable interrupts for do_notify_resume() */
 	move a0, sp /* pt_regs */
 	move a1, s0 /* current_thread_info->flags */
-	tail do_notify_resume
-work_resched:
-	tail schedule
+	call do_work_pending
+	j resume_userspace
 
 /* Slow paths for ptrace. */
 handle_syscall_trace_enter:

arch/riscv/kernel/signal.c

@@ -313,19 +313,27 @@ static void do_signal(struct pt_regs *regs)
 }
 
 /*
- * notification of userspace execution resumption
- * - triggered by the _TIF_WORK_MASK flags
+ * Handle any pending work on the resume-to-userspace path, as indicated by
+ * _TIF_WORK_MASK. Entered from assembly with IRQs off.
  */
-asmlinkage __visible void do_notify_resume(struct pt_regs *regs,
-					   unsigned long thread_info_flags)
+asmlinkage __visible void do_work_pending(struct pt_regs *regs,
+					  unsigned long thread_info_flags)
 {
-	if (thread_info_flags & _TIF_UPROBE)
-		uprobe_notify_resume(regs);
-
-	/* Handle pending signal delivery */
-	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
-		do_signal(regs);
-
-	if (thread_info_flags & _TIF_NOTIFY_RESUME)
-		resume_user_mode_work(regs);
+	do {
+		if (thread_info_flags & _TIF_NEED_RESCHED) {
+			schedule();
+		} else {
+			local_irq_enable();
+			if (thread_info_flags & _TIF_UPROBE)
+				uprobe_notify_resume(regs);
+			/* Handle pending signal delivery */
+			if (thread_info_flags & (_TIF_SIGPENDING |
+						 _TIF_NOTIFY_SIGNAL))
+				do_signal(regs);
+			if (thread_info_flags & _TIF_NOTIFY_RESUME)
+				resume_user_mode_work(regs);
+		}
+		local_irq_disable();
+		thread_info_flags = read_thread_flags();
+	} while (thread_info_flags & _TIF_WORK_MASK);
 }