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[PATCH 4.0 28/58] arm64: entry: fix context tracking for el0_sp_pc

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4.0-stable review patch.  If anyone has any objections, please let me know.

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

From: Mark Rutland <mark.rutland@arm.com>

commit 46b0567c851cf85d6ba6f23eef385ec9111d09bc upstream.

Commit 6c81fe7925cc4c42 ("arm64: enable context tracking") did not
update el0_sp_pc to use ct_user_exit, but this appears to have been
unintentional. In commit 6ab6463aeb5fbc75 ("arm64: adjust el0_sync so
that a function can be called") we made x0 available, and in the return
to userspace we call ct_user_enter in the kernel_exit macro.

Due to this, we currently don't correctly inform RCU of the user->kernel
transition, and may erroneously account for time spent in the kernel as
if we were in an extended quiescent state when CONFIG_CONTEXT_TRACKING
is enabled.

As we do record the kernel->user transition, a userspace application
making accesses from an unaligned stack pointer can demonstrate the
imbalance, provoking the following warning:

------------[ cut here ]------------
WARNING: CPU: 2 PID: 3660 at kernel/context_tracking.c:75 context_tracking_enter+0xd8/0xe4()
Modules linked in:
CPU: 2 PID: 3660 Comm: a.out Not tainted 4.1.0-rc7+ #8
Hardware name: ARM Juno development board (r0) (DT)
Call trace:
[<ffffffc000089914>] dump_backtrace+0x0/0x124
[<ffffffc000089a48>] show_stack+0x10/0x1c
[<ffffffc0005b3cbc>] dump_stack+0x84/0xc8
[<ffffffc0000b3214>] warn_slowpath_common+0x98/0xd0
[<ffffffc0000b330c>] warn_slowpath_null+0x14/0x20
[<ffffffc00013ada4>] context_tracking_enter+0xd4/0xe4
[<ffffffc0005b534c>] preempt_schedule_irq+0xd4/0x114
[<ffffffc00008561c>] el1_preempt+0x4/0x28
[<ffffffc0001b8040>] exit_files+0x38/0x4c
[<ffffffc0000b5b94>] do_exit+0x430/0x978
[<ffffffc0000b614c>] do_group_exit+0x40/0xd4
[<ffffffc0000c0208>] get_signal+0x23c/0x4f4
[<ffffffc0000890b4>] do_signal+0x1ac/0x518
[<ffffffc000089650>] do_notify_resume+0x5c/0x68
---[ end trace 963c192600337066 ]---

This patch adds the missing ct_user_exit to the el0_sp_pc entry path,
correcting the context tracking for this case.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Fixes: 6c81fe7925cc ("arm64: enable context tracking")
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -517,6 +517,7 @@ el0_sp_pc:
 	mrs	x26, far_el1
 	// enable interrupts before calling the main handler
 	enable_dbg_and_irq
+	ct_user_exit
 	mov	x0, x26
 	mov	x1, x25
 	mov	x2, sp


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[PATCH 4.0 00/58] 4.0.9-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 36/58] regmap: Fix possible shift overflow in regmap_field_init() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 57/58] of/pci: Fix pci_address_to_pio() conversion of CPU address to I/O port Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 35/58] regmap: Fix regmap_bulk_read in BE mode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 22/58] tools selftests: Fix clean target with make 3.81 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 09/58] sysfs: Create mountpoints with sysfs_create_mount_point Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 20/58] ACPI / PM: Add missing pm_generic_complete() invocation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 33/58] mm, thp: respect MPOL_PREFERRED policy with non-local node Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 24/58] ARC: add compiler barrier to LLSC based cmpxchg Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 44/58] scsi_transport_srp: Fix a race condition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 19/58] ACPI / init: Switch over platform to the ACPI mode later Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 32/58] mm: kmemleak_alloc_percpu() should follow the gfp from per_alloc() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 31/58] mm: kmemleak: allow safe memory scanning during kmemleak disabling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 18/58] ALSA: hda - Fix the dock headphone output on Fujitsu Lifebook E780 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 23/58] ARC: add smp barriers around atomics per Documentation/atomic_ops.txt Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 07/58] mnt: Refactor the logic for mounting sysfs and proc in a user namespace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 26/58] mei: txe: reduce suspend/resume time Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 15/58] ALSA: hda - Fix Dock Headphone on Thinkpad X250 seen as a Line Out Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 29/58] arm64: mm: Fix freeing of the wrong memmap entries with !SPARSEMEM_VMEMMAP Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 30/58] arm64: vdso: work-around broken ELF toolchains in Makefile Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 25/58] mei: me: wait for power gating exit confirmation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 27/58] arm64: Do not attempt to use init_mm in reset_context() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 28/58] arm64: entry: fix context tracking for el0_sp_pc Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 21/58] iio: accel: kxcjk-1013: add the "KXCJ9000" ACPI id Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 17/58] ALSA: hda - Add headset support to Acer Aspire V5 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 08/58] mnt: Modify fs_fully_visible to deal with locked ro nodev and atime Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 16/58] ALSA: hda - set proper caps for newer AMD hda audio in KB/KV Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 58/58] Input: pixcir_i2c_ts - fix receive error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 02/58] sysctl: Allow creating permanently empty directories that serve as mountpoints. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 39/58] livepatch: add module locking around kallsyms calls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 55/58] PCI: Add pci_bus_addr_t Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 41/58] spi: orion: Fix maximum baud rates for Armada 370/XP Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 52/58] mtd: fix: avoid race condition when accessing mtd->usecount Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 14/58] ALSA: pcm: Fix pcm_class sysfs output Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 38/58] regulator: core: fix constraints output buffer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 05/58] sysfs: Add support for permanently empty directories to serve as mount points. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 12/58] ipr: Increase default adapter init stage change timeout Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 37/58] regulator: max77686: fix gpio_enabled shift wrapping bug Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 47/58] IB/srp: Fix connection state tracking Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 56/58] PCI: pciehp: Wait for hotplug command completion where necessary Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 42/58] spi: pl022: Specify num-cs property as required in devicetree binding Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 43/58] scsi_transport_srp: Introduce srp_wait_for_queuecommand() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 48/58] IB/srp: Fix reconnection failure handling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 45/58] IB/srp: Remove an extraneous scsi_host_put() from an error path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 03/58] proc: Allow creating permanently empty directories that serve as mount points Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 13/58] Disable write buffering on Toshiba ToPIC95 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 46/58] IB/srp: Fix a connection setup race Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 54/58] PCI: Propagate the "ignore hotplug" setting to parent Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 04/58] kernfs: Add support for always empty directories. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 50/58] video: mxsfb: Make sure axi clock is enabled when accessing registers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 06/58] mnt: Update fs_fully_visible to test for permanently empty directories Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 01/58] fs: Add helper functions for permanently empty directories. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 49/58] genirq: devres: Fix testing return value of request_any_context_irq() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 10/58] gpio: crystalcove: set IRQCHIP_SKIP_SET_WAKE for the irqchip Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 51/58] leds / PM: fix hibernation on arm when gpio-led used with CPU led trigger Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  Re: [PATCH 4.0 00/58] 4.0.9-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2015-07-20 19:20 +0200

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