Re: [PATCH 1/1] mm/page_owner: ignore everything below the IRQ entry point

[Alexander Potapenko <glider@google.com>]

On Mon, Dec 4, 2017 at 5:43 AM, Maninder Singh <maninder1.s@samsung.com> wrote:
> Check whether the allocation happens in an IRQ handler.
> This lets us strip everything below the IRQ entry point to reduce the
> number of unique stack traces needed to be stored.
>
> so moved code of KASAN in generic file so that page_owner can also
> do same filteration.
>
> Initial KASAN commit
> id=be7635e7287e0e8013af3c89a6354a9e0182594c
>
> Signed-off-by: Vaneet Narang <v.narang@samsung.com>
> Signed-off-by: Maninder Singh <maninder1.s@samsung.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
> ---
>  include/linux/stacktrace.h | 25 +++++++++++++++++++++++++
>  mm/kasan/kasan.c           | 22 ----------------------
>  mm/page_owner.c            |  1 +
>  3 files changed, 26 insertions(+), 22 deletions(-)
>
> diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
> index ba29a06..2c1a562 100644
> --- a/include/linux/stacktrace.h
> +++ b/include/linux/stacktrace.h
> @@ -3,6 +3,7 @@
>  #define __LINUX_STACKTRACE_H
>
>  #include <linux/types.h>
> +#include <asm-generic/sections.h>
>
>  struct task_struct;
>  struct pt_regs;
> @@ -26,6 +27,28 @@ extern int save_stack_trace_tsk_reliable(struct task_struct *tsk,
>  extern int snprint_stack_trace(char *buf, size_t size,
>                         struct stack_trace *trace, int spaces);
>
> +static inline int in_irqentry_text(unsigned long ptr)
> +{
> +       return (ptr >= (unsigned long)&__irqentry_text_start &&
> +               ptr < (unsigned long)&__irqentry_text_end) ||
> +               (ptr >= (unsigned long)&__softirqentry_text_start &&
> +                ptr < (unsigned long)&__softirqentry_text_end);
> +}
> +
> +static inline void filter_irq_stacks(struct stack_trace *trace)
> +{
> +       int i;
> +
> +       if (!trace->nr_entries)
> +               return;
> +       for (i = 0; i < trace->nr_entries; i++)
> +               if (in_irqentry_text(trace->entries[i])) {
> +                       /* Include the irqentry function into the stack. */
> +                       trace->nr_entries = i + 1;
> +                       break;
> +               }
> +}
> +
>  #ifdef CONFIG_USER_STACKTRACE_SUPPORT
>  extern void save_stack_trace_user(struct stack_trace *trace);
>  #else
> @@ -38,6 +61,8 @@ extern int snprint_stack_trace(char *buf, size_t size,
>  # define save_stack_trace_user(trace)                  do { } while (0)
>  # define print_stack_trace(trace, spaces)              do { } while (0)
>  # define snprint_stack_trace(buf, size, trace, spaces) do { } while (0)
> +# define filter_irq_stacks(trace)                      do { } while (0)
> +# define in_irqentry_text(ptr)                         do { } while (0)
>  # define save_stack_trace_tsk_reliable(tsk, trace)     ({ -ENOSYS; })
>  #endif /* CONFIG_STACKTRACE */
>
> diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
> index 405bba4..129e7b8 100644
> --- a/mm/kasan/kasan.c
> +++ b/mm/kasan/kasan.c
> @@ -412,28 +412,6 @@ void kasan_poison_object_data(struct kmem_cache *cache, void *object)
>                         KASAN_KMALLOC_REDZONE);
>  }
>
> -static inline int in_irqentry_text(unsigned long ptr)
> -{
> -       return (ptr >= (unsigned long)&__irqentry_text_start &&
> -               ptr < (unsigned long)&__irqentry_text_end) ||
> -               (ptr >= (unsigned long)&__softirqentry_text_start &&
> -                ptr < (unsigned long)&__softirqentry_text_end);
> -}
> -
> -static inline void filter_irq_stacks(struct stack_trace *trace)
> -{
> -       int i;
> -
> -       if (!trace->nr_entries)
> -               return;
> -       for (i = 0; i < trace->nr_entries; i++)
> -               if (in_irqentry_text(trace->entries[i])) {
> -                       /* Include the irqentry function into the stack. */
> -                       trace->nr_entries = i + 1;
> -                       break;
> -               }
> -}
> -
>  static inline depot_stack_handle_t save_stack(gfp_t flags)
>  {
>         unsigned long entries[KASAN_STACK_DEPTH];
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 8602fb4..30e9cb2 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -148,6 +148,7 @@ static noinline depot_stack_handle_t save_stack(gfp_t flags)
>         depot_stack_handle_t handle;
>
>         save_stack_trace(&trace);
> +       filter_irq_stacks(&trace);
>         if (trace.nr_entries != 0 &&
>             trace.entries[trace.nr_entries-1] == ULONG_MAX)
>                 trace.nr_entries--;
> --
> 1.9.1
>



-- 
Alexander Potapenko
Software Engineer

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