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Subject[PATCH 3.18 017/120] arm64: Add trace_hardirqs_off annotation in ret_to_user
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Catalin Marinas <catalin.marinas@arm.com>

commit db3899a6477a4dccd26cbfb7f408b6be2cc068e0 upstream.

When a kernel is built with CONFIG_TRACE_IRQFLAGS the following warning
is produced when entering userspace for the first time:

WARNING: at /work/Linux/linux-2.6-aarch64/kernel/locking/lockdep.c:3519
Modules linked in:
CPU: 1 PID: 1 Comm: systemd Not tainted 4.4.0-rc3+ #639
Hardware name: Juno (DT)
task: ffffffc9768a0000 ti: ffffffc9768a8000 task.ti: ffffffc9768a8000
PC is at check_flags.part.22+0x19c/0x1a8
LR is at check_flags.part.22+0x19c/0x1a8
pc : [<ffffffc0000fba6c>] lr : [<ffffffc0000fba6c>] pstate: 600001c5
sp : ffffffc9768abe10
x29: ffffffc9768abe10 x28: ffffffc9768a8000
x27: 0000000000000000 x26: 0000000000000001
x25: 00000000000000a6 x24: ffffffc00064be6c
x23: ffffffc0009f249e x22: ffffffc9768a0000
x21: ffffffc97fea5480 x20: 00000000000001c0
x19: ffffffc00169a000 x18: 0000005558cc7b58
x17: 0000007fb78e3180 x16: 0000005558d2e238
x15: ffffffffffffffff x14: 0ffffffffffffffd
x13: 0000000000000008 x12: 0101010101010101
x11: 7f7f7f7f7f7f7f7f x10: fefefefefefeff63
x9 : 7f7f7f7f7f7f7f7f x8 : 6e655f7371726964
x7 : 0000000000000001 x6 : ffffffc0001079c4
x5 : 0000000000000000 x4 : 0000000000000001
x3 : ffffffc001698438 x2 : 0000000000000000
x1 : ffffffc9768a0000 x0 : 000000000000002e
Call trace:
[<ffffffc0000fba6c>] check_flags.part.22+0x19c/0x1a8
[<ffffffc0000fc440>] lock_is_held+0x80/0x98
[<ffffffc00064bafc>] __schedule+0x404/0x730
[<ffffffc00064be6c>] schedule+0x44/0xb8
[<ffffffc000085bb0>] ret_to_user+0x0/0x24
possible reason: unannotated irqs-off.
irq event stamp: 502169
hardirqs last enabled at (502169): [<ffffffc000085a98>] el0_irq_naked+0x1c/0x24
hardirqs last disabled at (502167): [<ffffffc0000bb3bc>] __do_softirq+0x17c/0x298
softirqs last enabled at (502168): [<ffffffc0000bb43c>] __do_softirq+0x1fc/0x298
softirqs last disabled at (502143): [<ffffffc0000bb830>] irq_exit+0xa0/0xf0

This happens because we disable interrupts in ret_to_user before calling
schedule() in work_resched. This patch adds the necessary
trace_hardirqs_off annotation.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


---
arch/arm64/kernel/entry.S | 3 +++
1 file changed, 3 insertions(+)

--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -633,6 +633,9 @@ work_pending:
bl do_notify_resume
b ret_to_user
work_resched:
+#ifdef CONFIG_TRACE_IRQFLAGS
+ bl trace_hardirqs_off // the IRQs are off here, inform the tracing code
+#endif
bl schedule

/*

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