[PATCH 1/2] powerpc: Make the code in __show_regs nice-looking

[PATCH 1/2] powerpc: Make the code in __show_regs nice-looking

[Xiongwei Song]

From: Xiongwei Song <sxwjean@gmail.com>

Create a new function named interrupt_detail_printable to judge which
interrupts can print esr/dsisr register.

Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
---
 arch/powerpc/kernel/process.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 89e34aa273e2..5c3830837f3a 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1453,9 +1453,23 @@ static void print_msr_bits(unsigned long val)
 #define REGS_PER_LINE	8
 #endif
 
+static bool interrupt_detail_printable(int trap)
+{
+	switch (trap) {
+	case INTERRUPT_MACHINE_CHECK:
+	case INTERRUPT_DATA_STORAGE:
+	case INTERRUPT_ALIGNMENT:
+		return true;
+	default:
+		return false;
+	}
+
+	return false;
+}
+
 static void __show_regs(struct pt_regs *regs)
 {
-	int i, trap;
+	int i;
 
 	printk("NIP:  "REG" LR: "REG" CTR: "REG"\n",
 	       regs->nip, regs->link, regs->ctr);
@@ -1464,12 +1478,9 @@ static void __show_regs(struct pt_regs *regs)
 	printk("MSR:  "REG" ", regs->msr);
 	print_msr_bits(regs->msr);
 	pr_cont("  CR: %08lx  XER: %08lx\n", regs->ccr, regs->xer);
-	trap = TRAP(regs);
 	if (!trap_is_syscall(regs) && cpu_has_feature(CPU_FTR_CFAR))
 		pr_cont("CFAR: "REG" ", regs->orig_gpr3);
-	if (trap == INTERRUPT_MACHINE_CHECK ||
-	    trap == INTERRUPT_DATA_STORAGE ||
-	    trap == INTERRUPT_ALIGNMENT) {
+	if (interrupt_detail_printable(TRAP(regs))) {
 		if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE))
 			pr_cont("DEAR: "REG" ESR: "REG" ", regs->dar, regs->dsisr);
 		else
-- 
2.17.1

[PATCH 2/2] powerpc: Print esr register when hitting Program Interrupt

[Xiongwei Song]

From: Xiongwei Song <sxwjean@gmail.com>

The esr register has the details of Program Interrupt on BookE/4xx cpus,
printing its value is helpful.

Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
---
 arch/powerpc/kernel/process.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 5c3830837f3a..664aecf8ee2e 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1459,6 +1459,7 @@ static bool interrupt_detail_printable(int trap)
 	case INTERRUPT_MACHINE_CHECK:
 	case INTERRUPT_DATA_STORAGE:
 	case INTERRUPT_ALIGNMENT:
+	case INTERRUPT_PROGRAM:
 		return true;
 	default:
 		return false;
-- 
2.17.1

Re: [PATCH 1/2] powerpc: Make the code in __show_regs nice-looking

[Christophe Leroy]

Le 22/04/2021 à 17:10, Xiongwei Song a écrit :
> From: Xiongwei Song <sxwjean@gmail.com>
> 
> Create a new function named interrupt_detail_printable to judge which
> interrupts can print esr/dsisr register.

What is the benefit of that function ? It may be interesting if the test was done at several places, 
but as it is done at only one place, I don't thing it is an improvement.

Until know, you new immediately what was the traps that would print it. Now you have to go and look 
into a sub-function.

And the name is not nice either. All other functions testing anything on the trap type are called 
trap_is_something()

Here your function would be better called something like trap_sets_dsisr()

> 
> Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
> ---
>   arch/powerpc/kernel/process.c | 21 ++++++++++++++++-----
>   1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 89e34aa273e2..5c3830837f3a 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1453,9 +1453,23 @@ static void print_msr_bits(unsigned long val)
>   #define REGS_PER_LINE	8
>   #endif
>   
> +static bool interrupt_detail_printable(int trap)
> +{
> +	switch (trap) {
> +	case INTERRUPT_MACHINE_CHECK:
> +	case INTERRUPT_DATA_STORAGE:
> +	case INTERRUPT_ALIGNMENT:
> +		return true;
> +	default:
> +		return false;
> +	}
> +
> +	return false;

That's redundant with the default case inside the switch.

> +}
> +
>   static void __show_regs(struct pt_regs *regs)
>   {
> -	int i, trap;
> +	int i;
>   
>   	printk("NIP:  "REG" LR: "REG" CTR: "REG"\n",
>   	       regs->nip, regs->link, regs->ctr);
> @@ -1464,12 +1478,9 @@ static void __show_regs(struct pt_regs *regs)
>   	printk("MSR:  "REG" ", regs->msr);
>   	print_msr_bits(regs->msr);
>   	pr_cont("  CR: %08lx  XER: %08lx\n", regs->ccr, regs->xer);
> -	trap = TRAP(regs);
>   	if (!trap_is_syscall(regs) && cpu_has_feature(CPU_FTR_CFAR))
>   		pr_cont("CFAR: "REG" ", regs->orig_gpr3);
> -	if (trap == INTERRUPT_MACHINE_CHECK ||
> -	    trap == INTERRUPT_DATA_STORAGE ||
> -	    trap == INTERRUPT_ALIGNMENT) {
> +	if (interrupt_detail_printable(TRAP(regs))) {
>   		if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE))
>   			pr_cont("DEAR: "REG" ESR: "REG" ", regs->dar, regs->dsisr);
>   		else
> 

Re: [PATCH 2/2] powerpc: Print esr register when hitting Program Interrupt

[Christophe Leroy]

Le 22/04/2021 à 17:10, Xiongwei Song a écrit :
> From: Xiongwei Song <sxwjean@gmail.com>
> 
> The esr register has the details of Program Interrupt on BookE/4xx cpus,
> printing its value is helpful.
> 
> Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
> ---
>   arch/powerpc/kernel/process.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 5c3830837f3a..664aecf8ee2e 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1459,6 +1459,7 @@ static bool interrupt_detail_printable(int trap)
>   	case INTERRUPT_MACHINE_CHECK:
>   	case INTERRUPT_DATA_STORAGE:
>   	case INTERRUPT_ALIGNMENT:
> +	case INTERRUPT_PROGRAM:

With this, it will also print the DSISR on 8xx/6xx so it will print garbage.

8xx/6xx provide the information in SRR1. If you want to proceed, you have to do the same as in ISI: 
Copy the content of SRR1 into regs->dsisr in the assembly handler in head_book3s_32.S and in the 
instruction TLB error handler in head_8xx.S

>   		return true;
>   	default:
>   		return false;
> 

Re: [PATCH 2/2] powerpc: Print esr register when hitting Program Interrupt

[Christophe Leroy]

Le 22/04/2021 à 17:29, Christophe Leroy a écrit :
> 
> 
> Le 22/04/2021 à 17:10, Xiongwei Song a écrit :
>> From: Xiongwei Song <sxwjean@gmail.com>
>>
>> The esr register has the details of Program Interrupt on BookE/4xx cpus,
>> printing its value is helpful.
>>
>> Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
>> ---
>>   arch/powerpc/kernel/process.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
>> index 5c3830837f3a..664aecf8ee2e 100644
>> --- a/arch/powerpc/kernel/process.c
>> +++ b/arch/powerpc/kernel/process.c
>> @@ -1459,6 +1459,7 @@ static bool interrupt_detail_printable(int trap)
>>       case INTERRUPT_MACHINE_CHECK:
>>       case INTERRUPT_DATA_STORAGE:
>>       case INTERRUPT_ALIGNMENT:
>> +    case INTERRUPT_PROGRAM:
> 
> With this, it will also print the DSISR on 8xx/6xx so it will print garbage.
> 
> 8xx/6xx provide the information in SRR1. If you want to proceed, you have to do the same as in ISI: 
> Copy the content of SRR1 into regs->dsisr in the assembly handler in head_book3s_32.S and in the 
> instruction TLB error handler in head_8xx.S

In fact, we already have get_reason() called by do_program_check() to retrieve the reason of the 
program check exception. Maybe it could be used to print usefull information instead of starting 
doing almost the same is another way.

Or we do as I suggested above, and we remove that get_reason() stuff. But get_reason() is also used 
by the alignment exception. So that doesn't look easy.

I don't know what the best approach is.


> 
>>           return true;
>>       default:
>>           return false;
>>

Re: [PATCH 2/2] powerpc: Print esr register when hitting Program Interrupt

[Xiongwei Song]

On Thu, Apr 22, 2021 at 11:29 PM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
>
>
> Le 22/04/2021 à 17:10, Xiongwei Song a écrit :
> > From: Xiongwei Song <sxwjean@gmail.com>
> >
> > The esr register has the details of Program Interrupt on BookE/4xx cpus,
> > printing its value is helpful.
> >
> > Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
> > ---
> >   arch/powerpc/kernel/process.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> > index 5c3830837f3a..664aecf8ee2e 100644
> > --- a/arch/powerpc/kernel/process.c
> > +++ b/arch/powerpc/kernel/process.c
> > @@ -1459,6 +1459,7 @@ static bool interrupt_detail_printable(int trap)
> >       case INTERRUPT_MACHINE_CHECK:
> >       case INTERRUPT_DATA_STORAGE:
> >       case INTERRUPT_ALIGNMENT:
> > +     case INTERRUPT_PROGRAM:
>
> With this, it will also print the DSISR on 8xx/6xx so it will print garbage.
>
> 8xx/6xx provide the information in SRR1. If you want to proceed, you have to do the same as in ISI:
> Copy the content of SRR1 into regs->dsisr in the assembly handler in head_book3s_32.S and in the
> instruction TLB error handler in head_8xx.S

Good point.

Re: [PATCH 2/2] powerpc: Print esr register when hitting Program Interrupt

[Xiongwei Song]

On Fri, Apr 23, 2021 at 12:50 AM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
>
>
> Le 22/04/2021 à 17:29, Christophe Leroy a écrit :
> >
> >
> > Le 22/04/2021 à 17:10, Xiongwei Song a écrit :
> >> From: Xiongwei Song <sxwjean@gmail.com>
> >>
> >> The esr register has the details of Program Interrupt on BookE/4xx cpus,
> >> printing its value is helpful.
> >>
> >> Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
> >> ---
> >>   arch/powerpc/kernel/process.c | 1 +
> >>   1 file changed, 1 insertion(+)
> >>
> >> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> >> index 5c3830837f3a..664aecf8ee2e 100644
> >> --- a/arch/powerpc/kernel/process.c
> >> +++ b/arch/powerpc/kernel/process.c
> >> @@ -1459,6 +1459,7 @@ static bool interrupt_detail_printable(int trap)
> >>       case INTERRUPT_MACHINE_CHECK:
> >>       case INTERRUPT_DATA_STORAGE:
> >>       case INTERRUPT_ALIGNMENT:
> >> +    case INTERRUPT_PROGRAM:
> >
> > With this, it will also print the DSISR on 8xx/6xx so it will print garbage.
> >
> > 8xx/6xx provide the information in SRR1. If you want to proceed, you have to do the same as in ISI:
> > Copy the content of SRR1 into regs->dsisr in the assembly handler in head_book3s_32.S and in the
> > instruction TLB error handler in head_8xx.S
>
> In fact, we already have get_reason() called by do_program_check() to retrieve the reason of the
> program check exception. Maybe it could be used to print usefull information instead of starting
> doing almost the same is another way.

Yes, there is the get_reason() function. But if the program interrupt
is triggered in kernel mode,
the reason can be lost , see the code below:

335 static bool exception_common(int signr, struct pt_regs *regs, int code,
 336                               unsigned long addr)
 337 {
 338         if (!user_mode(regs)) {
 339                 die("Exception in kernel mode", regs, signr);
 340                 return false;
 341         }

The third parameter(int code) of exception_common is to pass the
reason, when in kernel
mode, the "code" parameter is lost, hence I append INTERRUPT_PROGRAM here.

This is for __show_regs(), so just printing the content of the
register is fine I think.

>
> Or we do as I suggested above, and we remove that get_reason() stuff. But get_reason() is also used
> by the alignment exception. So that doesn't look easy.
>
> I don't know what the best approach is.

Is it acceptable to print the interrupt reason before invoking die()
in exception_common()?

Regards,
Xiongwei

Re: [PATCH 1/2] powerpc: Make the code in __show_regs nice-looking

[Xiongwei Song]

On Thu, Apr 22, 2021 at 11:27 PM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
>
>
> Le 22/04/2021 à 17:10, Xiongwei Song a écrit :
> > From: Xiongwei Song <sxwjean@gmail.com>
> >
> > Create a new function named interrupt_detail_printable to judge which
> > interrupts can print esr/dsisr register.
>
> What is the benefit of that function ? It may be interesting if the test was done at several places,
> but as it is done at only one place, I don't thing it is an improvement.
>
> Until know, you new immediately what was the traps that would print it. Now you have to go and look
> into a sub-function.

How about replace if statement with switch statement directly, like
the changes below:

@@ -1467,13 +1481,17 @@ static void __show_regs(struct pt_regs *regs)
        trap = TRAP(regs);
        if (!trap_is_syscall(regs) && cpu_has_feature(CPU_FTR_CFAR))
                pr_cont("CFAR: "REG" ", regs->orig_gpr3);
-       if (trap == INTERRUPT_MACHINE_CHECK ||
-           trap == INTERRUPT_DATA_STORAGE ||
-           trap == INTERRUPT_ALIGNMENT) {
+       switch(trap){
+       case INTERRUPT_MACHINE_CHECK:
+       case INTERRUPT_DATA_STORAGE:
+       case INTERRUPT_ALIGNMENT:
                if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE))
                        pr_cont("DEAR: "REG" ESR: "REG" ", regs->dar,
regs->dsisr);
                else
                        pr_cont("DAR: "REG" DSISR: %08lx ", regs->dar,
regs->dsisr);
+               break;
+       default:
+               break;
        }

Thanks,
Xiongwei