| From 46b0567c851cf85d6ba6f23eef385ec9111d09bc Mon Sep 17 00:00:00 2001 |
| From: Mark Rutland <mark.rutland@arm.com> |
| Date: Mon, 15 Jun 2015 16:40:27 +0100 |
| Subject: arm64: entry: fix context tracking for el0_sp_pc |
| |
| 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 |
