On Fri, Apr 23, 2021 at 12:50 AM Christophe Leroy
[off-list ref] wrote:

Le 22/04/2021 à 17:29, Christophe Leroy a écrit :

quoted

Le 22/04/2021 à 17:10, Xiongwei Song a écrit :

quoted

From: Xiongwei Song <redacted>

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

Signed-off-by: Xiongwei Song <redacted>
---
  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