Unverified Commit b0f4c74e authored by Andrew Bresticker's avatar Andrew Bresticker Committed by Palmer Dabbelt
Browse files

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



The return to userspace path in entry.S may enable interrupts without the
corresponding lockdep annotation, producing a splat[0] when DEBUG_LOCKDEP
is enabled. Simply calling __trace_hardirqs_on() here gets a bit messy
due to the use of RA to point back to ret_from_exception, so just move
the whole slow-path loop into C. It's more readable and it lets us use
local_irq_{enable,disable}(), avoiding the need for manual annotations
altogether.

[0]:
  ------------[ cut here ]------------
  DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())
  WARNING: CPU: 2 PID: 1 at kernel/locking/lockdep.c:5512 check_flags+0x10a/0x1e0
  Modules linked in:
  CPU: 2 PID: 1 Comm: init Not tainted 6.1.0-rc4-00160-gb56b6e2b4f31 #53
  Hardware name: riscv-virtio,qemu (DT)
  epc : check_flags+0x10a/0x1e0
  ra : check_flags+0x10a/0x1e0
  <snip>
   status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003
  [<ffffffff808edb90>] lock_is_held_type+0x78/0x14e
  [<ffffffff8003dae2>] __might_resched+0x26/0x22c
  [<ffffffff8003dd24>] __might_sleep+0x3c/0x66
  [<ffffffff80022c60>] get_signal+0x9e/0xa70
  [<ffffffff800054a2>] do_notify_resume+0x6e/0x422
  [<ffffffff80003c68>] ret_from_exception+0x0/0x10
  irq event stamp: 44512
  hardirqs last  enabled at (44511): [<ffffffff808f901c>] _raw_spin_unlock_irqrestore+0x54/0x62
  hardirqs last disabled at (44512): [<ffffffff80008200>] __trace_hardirqs_off+0xc/0x14
  softirqs last  enabled at (44472): [<ffffffff808f9fbe>] __do_softirq+0x3de/0x51e
  softirqs last disabled at (44467): [<ffffffff80017760>] irq_exit+0xd6/0x104
  ---[ end trace 0000000000000000 ]---
  possible reason: unannotated irqs-on.

Signed-off-by: default avatarAndrew Bresticker <abrestic@rivosinc.com>
Fixes: 3c469798 ("riscv: Enable LOCKDEP_SUPPORT & fixup TRACE_IRQFLAGS_SUPPORT")
Link: https://lore.kernel.org/r/20221111223108.1976562-1-abrestic@rivosinc.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 9abf2313

arch/riscv/kernel/entry.S

+5 −13
Original line number Diff line number Diff line
@@ -263,12 +263,11 @@ ret_from_exception: 
#endif

	bnez s0, resume_kernel



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
@@ -368,19 +367,12 @@ 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

+21 −13
Original line number Diff line number Diff line
@@ -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,

asmlinkage __visible void do_work_pending(struct pt_regs *regs,

					  unsigned long thread_info_flags)

{

	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))

			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);

}