[PATCH] mips: Fix crash registers on non-crashing CPUs

[PATCH] mips: Fix crash registers on non-crashing CPUs

[minyard]

From: Corey Minyard <cminyard@mvista.com>

As part of handling a crash on an SMP system, an IPI is send to
all other CPUs to save their current registers and stop.  It was
using task_pt_regs(current) to get the registers, but that will
only be accurate if the CPU was interrupted running in userland.
Instead allow the architecture to pass in the registers (all
pass NULL now, but allow for the future) and then use get_irq_regs()
which should be accurate as we are in an interrupt.  Fall back to
task_pt_regs(current) if nothing else is available.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
---
 arch/mips/kernel/crash.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/mips/kernel/crash.c b/arch/mips/kernel/crash.c
index d434d5d..610f0f3 100644
--- a/arch/mips/kernel/crash.c
+++ b/arch/mips/kernel/crash.c
@@ -14,12 +14,22 @@ static int crashing_cpu = -1;
 static cpumask_t cpus_in_crash = CPU_MASK_NONE;
 
 #ifdef CONFIG_SMP
-static void crash_shutdown_secondary(void *ignore)
+static void crash_shutdown_secondary(void *passed_regs)
 {
-	struct pt_regs *regs;
+	struct pt_regs *regs = passed_regs;
 	int cpu = smp_processor_id();
 
-	regs = task_pt_regs(current);
+	/*
+	 * If we are passed registers, use those.  Otherwise get the
+	 * regs from the last interrupt, which should be correct, as
+	 * we are in an interrupt.  But if the regs are not there,
+	 * pull them from the top of the stack.  They are probably
+	 * wrong, but we need something to keep from crashing again.
+	 */
+	if (!regs)
+		regs = get_irq_regs();
+	if (!regs)
+		regs = task_pt_regs(current);
 
 	if (!cpu_online(cpu))
 		return;
-- 
2.5.0

Re: [PATCH] mips: Fix crash registers on non-crashing CPUs

[Corey Minyard]

Anything on this?

-corey

On 04/11/2016 09:10 AM, minyard@acm.org wrote:
> From: Corey Minyard <cminyard@mvista.com>
>
> As part of handling a crash on an SMP system, an IPI is send to
> all other CPUs to save their current registers and stop.  It was
> using task_pt_regs(current) to get the registers, but that will
> only be accurate if the CPU was interrupted running in userland.
> Instead allow the architecture to pass in the registers (all
> pass NULL now, but allow for the future) and then use get_irq_regs()
> which should be accurate as we are in an interrupt.  Fall back to
> task_pt_regs(current) if nothing else is available.
>
> Signed-off-by: Corey Minyard <cminyard@mvista.com>
> ---
>   arch/mips/kernel/crash.c | 16 +++++++++++++---
>   1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/arch/mips/kernel/crash.c b/arch/mips/kernel/crash.c
> index d434d5d..610f0f3 100644
> --- a/arch/mips/kernel/crash.c
> +++ b/arch/mips/kernel/crash.c
> @@ -14,12 +14,22 @@ static int crashing_cpu = -1;
>   static cpumask_t cpus_in_crash = CPU_MASK_NONE;
>   
>   #ifdef CONFIG_SMP
> -static void crash_shutdown_secondary(void *ignore)
> +static void crash_shutdown_secondary(void *passed_regs)
>   {
> -	struct pt_regs *regs;
> +	struct pt_regs *regs = passed_regs;
>   	int cpu = smp_processor_id();
>   
> -	regs = task_pt_regs(current);
> +	/*
> +	 * If we are passed registers, use those.  Otherwise get the
> +	 * regs from the last interrupt, which should be correct, as
> +	 * we are in an interrupt.  But if the regs are not there,
> +	 * pull them from the top of the stack.  They are probably
> +	 * wrong, but we need something to keep from crashing again.
> +	 */
> +	if (!regs)
> +		regs = get_irq_regs();
> +	if (!regs)
> +		regs = task_pt_regs(current);
>   
>   	if (!cpu_online(cpu))
>   		return;

Re: [PATCH] mips: Fix crash registers on non-crashing CPUs

[Ralf Baechle]

On Wed, Apr 20, 2016 at 08:24:54AM -0500, Corey Minyard wrote:

> Anything on this?

Applied a few days ago and waiting to be pulled by Linus.

  Ralf

Re: [PATCH] mips: Fix crash registers on non-crashing CPUs

[Corey Minyard]

On 04/20/2016 08:33 AM, Ralf Baechle wrote:
> On Wed, Apr 20, 2016 at 08:24:54AM -0500, Corey Minyard wrote:
>
>> Anything on this?
> Applied a few days ago and waiting to be pulled by Linus.
>
>    Ralf
Thanks a bunch.

-corey