[PATCH 1/2] powerpc/kgdb: Fix a single stgep case of lazy IRQ

[PATCH 1/2] powerpc/kgdb: Fix a single stgep case of lazy IRQ

[Tiejun Chen]

When we're in kgdb_singlestep(), we have to work around to get
thread_info by copying from the kernel stack before calling
kgdb_handle_exception(), then copying it back afterwards.

But for PPC64, we have a lazy interrupt implementation. So after
copying thread info frome kernle stack, if we need to replay an
interrupt, we shouldn't restore that previous backup thread info
to make sure we can replay an interrupt lately with a proper
thread info.

This patch use __check_irq_replay() to guarantee this process.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
---
 arch/powerpc/kernel/irq.c  |   12 +++++++++++-
 arch/powerpc/kernel/kgdb.c |    7 ++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 71413f4..a773789 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -332,7 +332,17 @@ bool prep_irq_for_idle(void)
 	return true;
 }
 
-#endif /* CONFIG_PPC64 */
+notrace unsigned int check_irq_replay(void)
+{
+	return __check_irq_replay();
+}
+#else /* CONFIG_PPC64 */
+notrace unsigned int check_irq_replay(void)
+{
+	return 0;
+}
+#endif /* !CONFIG_PPC64 */
+EXPORT_SYMBOL(check_irq_replay);
 
 int arch_show_interrupts(struct seq_file *p, int prec)
 {
diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
index c470a40..c4af341 100644
--- a/arch/powerpc/kernel/kgdb.c
+++ b/arch/powerpc/kernel/kgdb.c
@@ -151,6 +151,7 @@ static int kgdb_handle_breakpoint(struct pt_regs *regs)
 	return 1;
 }
 
+extern notrace unsigned int check_irq_replay(void);
 static int kgdb_singlestep(struct pt_regs *regs)
 {
 	struct thread_info *thread_info, *exception_thread_info;
@@ -181,9 +182,9 @@ static int kgdb_singlestep(struct pt_regs *regs)
 
 	kgdb_handle_exception(0, SIGTRAP, 0, regs);
 
-	if (thread_info != exception_thread_info)
-		/* Restore current_thread_info lastly. */
-		memcpy(exception_thread_info, backup_current_thread_info, sizeof *thread_info);
+	if ((thread_info != exception_thread_info) && (!check_irq_replay()))
+		/* Restore current_thread_info lastly only if we don't replay interrupt. */
+			memcpy(exception_thread_info, backup_current_thread_info, sizeof *thread_info);
 
 	return 1;
 }
-- 
1.7.9.5

[PATCH 2/2] PPC_BOOK3E/KGDB: support kgdb kernel space

[Tiejun Chen]

We can support KGDB with current debug exception for BOOK3E, so we
should initial specific dbg_kstack to avoid overwriting other thing.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
---
 arch/powerpc/kernel/exceptions-64e.S |    4 ++++
 arch/powerpc/kernel/paca.c           |   10 ++++++++++
 2 files changed, 14 insertions(+)

diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index 4684e33..ed5862d 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -539,11 +539,15 @@ kernel_dbg_exc:
 	rfdi
 
 	/* Normal debug exception */
+#ifndef CONFIG_KGDB
 	/* XXX We only handle coming from userspace for now since we can't
 	 *     quite save properly an interrupted kernel state yet
 	 */
 1:	andi.	r14,r11,MSR_PR;		/* check for userspace again */
 	beq	kernel_dbg_exc;		/* if from kernel mode */
+#else
+1:
+#endif
 
 	/* Now we mash up things to make it look like we are coming on a
 	 * normal exception
diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
index cd6da85..28a5141 100644
--- a/arch/powerpc/kernel/paca.c
+++ b/arch/powerpc/kernel/paca.c
@@ -122,6 +122,13 @@ EXPORT_SYMBOL(paca);
 
 struct paca_struct boot_paca;
 
+void *debug_kstack;
+static void allocate_dbg_kstack(unsigned long limit)
+{
+	debug_kstack = __va(memblock_alloc_base(THREAD_SIZE,
+					THREAD_SIZE, limit));
+}
+
 void __init initialise_paca(struct paca_struct *new_paca, int cpu)
 {
        /* The TOC register (GPR2) points 32kB into the TOC, so that 64kB
@@ -133,6 +140,7 @@ void __init initialise_paca(struct paca_struct *new_paca, int cpu)
 	new_paca->lppaca_ptr = new_lppaca(cpu);
 #else
 	new_paca->kernel_pgd = swapper_pg_dir;
+	new_paca->dbg_kstack = debug_kstack;
 #endif
 	new_paca->lock_token = 0x8000;
 	new_paca->paca_index = cpu;
@@ -192,6 +200,8 @@ void __init allocate_pacas(void)
 
 	allocate_lppacas(nr_cpu_ids, limit);
 
+	allocate_dbg_kstack(limit);
+
 	/* Can't use for_each_*_cpu, as they aren't functional yet */
 	for (cpu = 0; cpu < nr_cpu_ids; cpu++)
 		initialise_paca(&paca[cpu], cpu);
-- 
1.7.9.5

Re: [PATCH 2/2] PPC_BOOK3E/KGDB: support kgdb kernel space

[Andreas Schwab]

Tiejun Chen <tiejun.chen@windriver.com> writes:

> diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
> index 4684e33..ed5862d 100644
> --- a/arch/powerpc/kernel/exceptions-64e.S
> +++ b/arch/powerpc/kernel/exceptions-64e.S
> @@ -539,11 +539,15 @@ kernel_dbg_exc:
>  	rfdi
>  
>  	/* Normal debug exception */
> +#ifndef CONFIG_KGDB
>  	/* XXX We only handle coming from userspace for now since we can't
>  	 *     quite save properly an interrupted kernel state yet
>  	 */
>  1:	andi.	r14,r11,MSR_PR;		/* check for userspace again */
>  	beq	kernel_dbg_exc;		/* if from kernel mode */
> +#else
> +1:
> +#endif

You could move the label before the conditional.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: [PATCH 2/2] PPC_BOOK3E/KGDB: support kgdb kernel space

[tiejun.chen]

On 10/17/2012 08:07 PM, Andreas Schwab wrote:
> Tiejun Chen <tiejun.chen@windriver.com> writes:
>
>> diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
>> index 4684e33..ed5862d 100644
>> --- a/arch/powerpc/kernel/exceptions-64e.S
>> +++ b/arch/powerpc/kernel/exceptions-64e.S
>> @@ -539,11 +539,15 @@ kernel_dbg_exc:
>>   	rfdi
>>
>>   	/* Normal debug exception */
>> +#ifndef CONFIG_KGDB
>>   	/* XXX We only handle coming from userspace for now since we can't
>>   	 *     quite save properly an interrupted kernel state yet
>>   	 */
>>   1:	andi.	r14,r11,MSR_PR;		/* check for userspace again */
>>   	beq	kernel_dbg_exc;		/* if from kernel mode */
>> +#else
>> +1:
>> +#endif
>
> You could move the label before the conditional.

Okay.

diff --git a/arch/powerpc/kernel/exceptions-64e.S 
b/arch/powerpc/kernel/exceptions-64e.S
index 4684e33..73ce1a7 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -538,12 +538,15 @@ kernel_dbg_exc:
         mfspr   r13,SPRN_SPRG_DBG_SCRATCH
         rfdi

+1:
         /* Normal debug exception */
+#ifndef CONFIG_KGDB
         /* XXX We only handle coming from userspace for now since we can't
          *     quite save properly an interrupted kernel state yet
          */
-1:     andi.   r14,r11,MSR_PR;         /* check for userspace again */
+       andi.   r14,r11,MSR_PR;         /* check for userspace again */
         beq     kernel_dbg_exc;         /* if from kernel mode */
+#endif

         /* Now we mash up things to make it look like we are coming on a
          * normal exception
...

Tiejun