[PATCH 6.1 0677/1146] RISC-V: Fix unannoted hardirqs-on in return to userspace slow-path

Greg Kroah-Hartman
2022-12-28T16:25:40Z

From: Andrew Bresticker <abrestic@rivosinc.com>

[ Upstream commit b0f4c74eadbf69a3298f38566bfaa2e202541f2f ]

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: Andrew Bresticker <abrestic@rivosinc.com>
Fixes: 3c4697982982 ("riscv: Enable LOCKDEP_SUPPORT & fixup TRACE_IRQFLAGS_SUPPORT")
Link: https://lore.kernel.org/r/20221111223108.1976562-1-abrestic@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/riscv/kernel/entry.S | 18 +++++-------------
arch/riscv/kernel/signal.c | 34 +++++++++++++++++++++-------------
2 files changed, 26 insertions(+), 26 deletions(-)

diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 186abd146eaf..3221a9e5f372 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -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:
diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index 5c591123c440..bfb2afa4135f 100644
--- a/arch/riscv/kernel/signal.c
+++ b/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);
}
--
2.35.1