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SubjectRe: [PATCH v2] xtensa: improve stack dumping
On Tue, Nov 12, 2019 at 1:49 AM Petr Mladek <pmladek@suse.com> wrote:
>
> On Thu 2019-11-07 16:44:48, Max Filippov wrote:
> > Calculate printable stack size and use print_hex_dump instead of
> > opencoding it.
> > Make size of stack dump configurable.
> > Drop extra newline output in show_trace as its output format does not
> > depend on CONFIG_KALLSYMS.
>
> > diff --git a/arch/xtensa/Kconfig.debug b/arch/xtensa/Kconfig.debug
> > index 39de98e20018..83cc8d12fa0e 100644
> > --- a/arch/xtensa/Kconfig.debug
> > +++ b/arch/xtensa/Kconfig.debug
> > @@ -31,3 +31,10 @@ config S32C1I_SELFTEST
> > It is easy to make wrong hardware configuration, this test should catch it early.
> >
> > Say 'N' on stable hardware.
> > +
> > +config PRINT_STACK_DEPTH
> > + int "Stack depth to print" if DEBUG_KERNEL
> > + default 64
> > + help
> > + This option allows you to set the stack depth that the kernel
> > + prints in stack traces.
>
> I would split this into separate patch.

Sure, I'll split it out.

> > diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
> > index 4a6c495ce9b6..fe090ab1cab8 100644
> > --- a/arch/xtensa/kernel/traps.c
> > +++ b/arch/xtensa/kernel/traps.c
> > @@ -491,32 +491,24 @@ void show_trace(struct task_struct *task, unsigned long *sp)
> >
> > pr_info("Call Trace:\n");
> > walk_stackframe(sp, show_trace_cb, NULL);
> > -#ifndef CONFIG_KALLSYMS
> > - pr_cont("\n");
> > -#endif
> > }
> >
> > -static int kstack_depth_to_print = 24;
> > +static int kstack_depth_to_print = CONFIG_PRINT_STACK_DEPTH;
> >
> > void show_stack(struct task_struct *task, unsigned long *sp)
> > {
> > - int i = 0;
> > - unsigned long *stack;
> > + size_t len;
> >
> > if (!sp)
> > sp = stack_pointer(task);
> > - stack = sp;
> >
> > - pr_info("Stack:\n");
> > + len = min((-(unsigned long)sp) & (THREAD_SIZE - 4),
> > + kstack_depth_to_print * 4ul);
>
> I would replace the hardcoded 4 with sizeof(void *).

It's not necessarily pointers, more like register-wide entries
on the stack. Ok, I guess I'll give it a name.

> > - for (i = 0; i < kstack_depth_to_print; i++) {
> > - if (kstack_end(sp))
> > - break;
> > - pr_cont(" %08lx", *sp++);
> > - if (i % 8 == 7)
> > - pr_cont("\n");
> > - }
> > - show_trace(task, stack);
> > + pr_info("Stack:\n");
> > + print_hex_dump(KERN_INFO, " ", DUMP_PREFIX_NONE, 32, 4,
> > + sp, len, false);
> > + show_trace(task, sp);
> > }
>
> The conversion looks fine to me. It is up to you (as a maintainer)
> what you do with the above proposal for two cosmetic changes ;-)
> Either way, feel free to use:
>
> Reviewed-by: Petr Mladek <pmladek@suse.com>

Thanks for the review.

-- Max

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