Re: [PATCH v2] arm64/debug: Fix registers on sleeping tasks

From: Doug Anderson
Date: Thu Mar 08 2018 - 11:42:07 EST

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Hi,

On Thu, Mar 8, 2018 at 8:19 AM, Daniel Thompson
<daniel.thompson@xxxxxxxxxx> wrote:
> On 05/03/18 23:43, Douglas Anderson wrote:
>>
>> This is the equivalent of commit 001bf455d206 ("ARM: 8428/1: kgdb: Fix
>> registers on sleeping tasks") but for arm64. Nuff said.
>>
>> ...well, perhaps I could also add that task_pt_regs are userspace
>> registers and that's not what kgdb is supposed to be reporting. We're
>> supposed to be reporting kernel registers.
>>
>> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
>
>
> I hacked together a (still very immature) kgdb test suite[1] around the turn
> of the year. Whilst its not quite solid enough for me to recommend others
> deploy it except out of curiosity... so I haven't yet started yelling about
> test suite failures except in the privacy of my own head.
>
> However I can confirm that this patch fixes one of the test suite failures I
> haven't had time to blame allocate yet!
>
> So...
> Tested-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>

Thanks for your testing! ...I'll have to check out your test suite soon.

> BTW is this something that should Cc: stable?

It wouldn't hurt if this made it back to stable on a best-effort
approach. The problem has been there since the beginning, so it's not
like it's fixing a regression that cropped up in a specific version.
...but it does fix a bug, so probably Cc stable makes sense. I guess
I'd leave it up to the maintainer that applies the patch?

-Doug<div class="gmail_extra"> <div class="gmail_quote">On Thu, Mar
8, 2018 at 8:19 AM, Daniel Thompson <<a
href="mailto:daniel.thompson@xxxxxxxxxx";
target="_blank">daniel.thompson@xxxxxxxxxx</a>>
wrote: <blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">On
05/03/18 23:43, Douglas Anderson wrote: 
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
This is the equivalent of commit 001bf455d206 ("ARM: 8428/1: kgdb: Fix 
registers on sleeping tasks") but for arm64.  Nuff said. 
 
...well, perhaps I could also add that task_pt_regs are userspace 
registers and that's not what kgdb is supposed to be reporting.  We're 
supposed to be reporting kernel registers. 
 
Signed-off-by: Douglas Anderson <<a
href="mailto:dianders@xxxxxxxxxxxx";
target="_blank">dianders@xxxxxxxxxxxx</a>> 
</blockquote>
 
I hacked together a (still very immature) kgdb test suite[1] around
the turn of the year. Whilst its not quite solid enough for me to
recommend others deploy it except out of curiosity... so I haven't yet
started yelling about test suite failures except in the privacy of my
own head. 
 
However I can confirm that this patch fixes one of the test suite
failures I haven't had time to blame allocate yet! 
 
So... 
Tested-by: Daniel Thompson <<a
href="mailto:daniel.thompson@xxxxxxxxxx";
target="_blank">daniel.thompson@xxxxxxxxxx</a>> 
 
BTW is this something that should Cc: stable? 
 
 
Daniel. 
 
[1] <a href="https://github.com/daniel-thompson/kgdbtest";
rel="noreferrer" target="_blank"
data-saferedirecturl="https://www.google.com/url?hl=en&q=https://github.com/daniel-thompson/kgdbtest&source=gmail&ust=1520613443900000&usg=AFQjCNHzh_tGdP65DdFEQo-ofF_LCI5XBQ";>https://github.com/daniel-thompson/kgdbtest</a><div
class="HOEnZb"><div class="h5"> 
 
 
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
--- 
 
Changes in v2: 
- Init cpu_context in one line 
- Explain that task_pt_regs are userspace 
 
  arch/arm64/kernel/kgdb.c | 21 ++++++++++++++++----- 
  1 file changed, 16 insertions(+), 5 deletions(-) 
 
diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c 
index 2122cd187f19..a20de58061a8 100644 
--- a/arch/arm64/kernel/kgdb.c 
+++ b/arch/arm64/kernel/kgdb.c 
@@ -138,14 +138,25 @@ int dbg_set_reg(int regno, void *mem, struct
pt_regs *regs) 
  void 
  sleeping_thread_to_gdb_regs(unsigned long *gdb_regs,
struct task_struct *task) 
  { 
-       struct pt_regs *thread_regs; 
+       struct cpu_context *cpu_context =
&task->thread.cpu_context; 
        /* Initialize to zero */ 
        memset((char *)gdb_regs, 0, NUMREGBYTES); 
-       thread_regs = task_pt_regs(task); 
-       memcpy((void *)gdb_regs, (void
*)thread_regs->regs, GP_REG_BYTES); 
-       /* Special case for PSTATE (check comments
in asm/kgdb.h for details) */ 
-       dbg_get_reg(33, gdb_regs + GP_REG_BYTES,
thread_regs); 
+ 
+       gdb_regs[19] = cpu_context->x19; 
+       gdb_regs[20] = cpu_context->x20; 
+       gdb_regs[21] = cpu_context->x21; 
+       gdb_regs[22] = cpu_context->x22; 
+       gdb_regs[23] = cpu_context->x23; 
+       gdb_regs[24] = cpu_context->x24; 
+       gdb_regs[25] = cpu_context->x25; 
+       gdb_regs[26] = cpu_context->x26; 
+       gdb_regs[27] = cpu_context->x27; 
+       gdb_regs[28] = cpu_context->x28; 
+       gdb_regs[29] = cpu_context->fp; 
+ 
+       gdb_regs[31] = cpu_context->sp; 
+       gdb_regs[32] = cpu_context->pc; 
  } 
    void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc) 
 
</blockquote>
 
</div></div></blockquote></div> </div>

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