The kgdb_single_step flag has the possibility to indefinitely
hang the system on an SMP system.
The x86 arch have the same problem, and that problem was fixed by
commit 8097551d9ab9b9e3630(kgdb,x86: do not set kgdb_single_step
on x86). This patch does the same behaviors as x86's patch.
Signed-off-by: Dongdong Deng <[email protected]>
Signed-off-by: Jason Wessel <[email protected]>
Signed-off-by: Tiejun Chen <[email protected]>
---
arch/powerpc/kernel/kgdb.c | 1 -
1 files changed, 0 insertions(+), 1 deletions(-)
diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
index 782bd0a..bbabc5a 100644
--- a/arch/powerpc/kernel/kgdb.c
+++ b/arch/powerpc/kernel/kgdb.c
@@ -410,7 +410,6 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
#else
linux_regs->msr |= MSR_SE;
#endif
- kgdb_single_step = 1;
atomic_set(&kgdb_cpu_doing_single_step,
raw_smp_processor_id());
}
--
1.5.6
For powerpc BooKE and e200, singlestep is handled on the critical/dbg
exception stack. This causes current_thread_info() to fail for kgdb
internal, so previously We work around this issue by copying
the thread_info from the kernel stack before calling kgdb_handle_exception,
and copying it back afterwards.
But actually we don't do this previously. We should backp current_thread_info
then restore that when exit.
CC: Jason Wessel <[email protected]>
Signed-off-by: Tiejun Chen <[email protected]>
---
arch/powerpc/kernel/kgdb.c | 11 +++++++++--
1 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
index e84252b..7dcdbe7 100644
--- a/arch/powerpc/kernel/kgdb.c
+++ b/arch/powerpc/kernel/kgdb.c
@@ -25,6 +25,7 @@
#include <asm/processor.h>
#include <asm/machdep.h>
#include <asm/debug.h>
+#include <linux/slab.h>
/*
* This table contains the mapping between PowerPC hardware trap types, and
@@ -156,6 +157,8 @@ static int kgdb_handle_breakpoint(struct pt_regs *regs)
static int kgdb_singlestep(struct pt_regs *regs)
{
struct thread_info *thread_info, *exception_thread_info;
+ struct thread_info *backup_current_thread_info = \
+ (struct thread_info *)kmalloc(sizeof(struct thread_info), GFP_KERNEL);
if (user_mode(regs))
return 0;
@@ -173,13 +176,17 @@ static int kgdb_singlestep(struct pt_regs *regs)
thread_info = (struct thread_info *)(regs->gpr[1] & ~(THREAD_SIZE-1));
exception_thread_info = current_thread_info();
- if (thread_info != exception_thread_info)
+ if (thread_info != exception_thread_info) {
+ /* Save the original current_thread_info. */
+ memcpy(backup_current_thread_info, exception_thread_info, sizeof *thread_info);
memcpy(exception_thread_info, thread_info, sizeof *thread_info);
+ }
kgdb_handle_exception(0, SIGTRAP, 0, regs);
if (thread_info != exception_thread_info)
- memcpy(thread_info, exception_thread_info, sizeof *thread_info);
+ /* Restore current_thread_info lastly. */
+ memcpy(exception_thread_info, backup_current_thread_info, sizeof *thread_info);
return 1;
}
--
1.5.6
We need to skip a breakpoint exception when it occurs after
a breakpoint has already been removed.
Signed-off-by: Tiejun Chen <[email protected]>
---
arch/powerpc/kernel/kgdb.c | 18 ++++++++++++++++++
1 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
index bbabc5a..e84252b 100644
--- a/arch/powerpc/kernel/kgdb.c
+++ b/arch/powerpc/kernel/kgdb.c
@@ -101,6 +101,24 @@ static int computeSignal(unsigned int tt)
return SIGHUP; /* default for things we don't know about */
}
+/**
+ *
+ * kgdb_skipexception - Bail out of KGDB when we've been triggered.
+ * @exception: Exception vector number
+ * @regs: Current &struct pt_regs.
+ *
+ * On some architectures we need to skip a breakpoint exception when
+ * it occurs after a breakpoint has been removed.
+ *
+ */
+int kgdb_skipexception(int exception, struct pt_regs *regs)
+{
+ if (kgdb_isremovedbreak(regs->nip))
+ return 1;
+
+ return 0;
+}
+
static int kgdb_call_nmi_hook(struct pt_regs *regs)
{
kgdb_nmicallback(raw_smp_processor_id(), regs);
--
1.5.6
On Wed, Aug 22, 2012 at 5:43 AM, Tiejun Chen <[email protected]> wrote:
> +int kgdb_skipexception(int exception, struct pt_regs *regs)
> +{
> + if (kgdb_isremovedbreak(regs->nip))
> + return 1;
> +
> + return 0;
> +}
int kgdb_skipexception(int exception, struct pt_regs *regs)
{
return !!kgdb_isremovedbreak(regs->nip));
}
If the caller only cares about zero vs. non-zero, you can drop the !!.
--
Timur Tabi
Linux kernel developer at Freescale
On 08/22/2012 11:07 PM, Tabi Timur-B04825 wrote:
> On Wed, Aug 22, 2012 at 5:43 AM, Tiejun Chen <[email protected]> wrote:
>
>> +int kgdb_skipexception(int exception, struct pt_regs *regs)
>> +{
>> + if (kgdb_isremovedbreak(regs->nip))
>> + return 1;
>> +
>> + return 0;
>> +}
>
> int kgdb_skipexception(int exception, struct pt_regs *regs)
> {
> return !!kgdb_isremovedbreak(regs->nip));
> }
>
> If the caller only cares about zero vs. non-zero, you can drop the !!.
Yes, so 'return kgdb_isremovedbreak(regs->nip);' is already fine and simple.
I'll update this as v2 so thanks your comment.
Tiejun