Re: [PATCHv3] mm: use stack_depot for recording kmemleak's backtrace

[Zhaoyang Huang]

This patchset fixes bellowing lkp report by having
CONFIG_DEBUG_KMEMLEAK select CONFIG_STACK_DEPOT by default and remove
unused function.

tree:   https://github.com/ammarfaizi2/linux-block akpm/mm/mm-unstable
head:   eecc1f68b7ae1e677dd01b728e58de61a2f8ae71
commit: a3ed421a1d5f0bea0bcd91a0d001428b2c42ecbe [216/244] mm: use
stack_depot for recording kmemleak's backtrace
config: s390-randconfig-r021-20221030
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project
791a7ae1ba3efd6bca96338e10ffde557ba83920)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross
-O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install s390 cross compiling tool for clang build
        # apt-get install binutils-s390x-linux-gnu
        # https://github.com/ammarfaizi2/linux-block/commit/a3ed421a1d5f0bea0bcd91a0d001428b2c42ecbe
        git remote add ammarfaizi2-block
https://github.com/ammarfaizi2/linux-block
        git fetch --no-tags ammarfaizi2-block akpm/mm/mm-unstable
        git checkout a3ed421a1d5f0bea0bcd91a0d001428b2c42ecbe
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1
O=build_dir ARCH=s390 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>

All errors (new ones prefixed by >>):

   s390x-linux-ld: DWARF error: could not find abbrev number 13221
   mm/kmemleak.o: in function `__create_object':
>> kmemleak.c:(.text+0x40a): undefined reference to `stack_depot_print'
   s390x-linux-ld: mm/kmemleak.o: in function `paint_ptr':
   kmemleak.c:(.text+0xaf8): undefined reference to `stack_depot_print'
   s390x-linux-ld: mm/kmemleak.o: in function `kmemleak_scan':
>> kmemleak.c:(.text+0x19ee): undefined reference to `stack_depot_fetch'
   s390x-linux-ld: mm/kmemleak.o: in function `dump_str_object_info':
   kmemleak.c:(.text+0x1bac): undefined reference to `stack_depot_print'
>> s390x-linux-ld: kmemleak.c:(.text+0x1c40): undefined reference to `stack_depot_print'
   s390x-linux-ld: mm/kmemleak.o: in function `scan_block':
   kmemleak.c:(.text+0x249a): undefined reference to `stack_depot_print'
   s390x-linux-ld: mm/kmemleak.o: in function `kmemleak_seq_show':
   kmemleak.c:(.text+0x2f28): undefined reference to `stack_depot_fetch'
   s390x-linux-ld: mm/kmemleak.o: in function `kmemleak_vmalloc':
>> kmemleak.c:(.ref.text+0x290): undefined reference to `stack_depot_print'
   s390x-linux-ld: mm/kmemleak.o: in function `kmemleak_free':
   kmemleak.c:(.ref.text+0x66c): undefined reference to `stack_depot_print'
   s390x-linux-ld: mm/kmemleak.o: in function `kmemleak_free_percpu':
   kmemleak.c:(.ref.text+0xb44): undefined reference to `stack_depot_print'
   s390x-linux-ld: mm/kmemleak.o: in function `kmemleak_scan_area':
   kmemleak.c:(.ref.text+0x1248): undefined reference to `stack_depot_print'
   s390x-linux-ld: mm/kmemleak.o: in function `kmemleak_no_scan':
   kmemleak.c:(.ref.text+0x1622): undefined reference to `stack_depot_print'

On Sun, Oct 30, 2022 at 11:43 AM zhaoyang.huang
<zhaoyang.huang@xxxxxxxxxx> wrote:
>
> From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
>
> Using stack_depot to record kmemleak's backtrace which has been implemented
> on slub for reducing redundant information.
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: ke.wang <ke.wang@xxxxxxxxxx>
> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Zhaoyang Huang <huangzhaoyang@xxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
> changes of v2: fix bugs of stack_depot_init related issue
> changes of v3: have DEBUG_KMEMLEAK select STACK_DEPOT by default
>                remove unuse functions
> ---
> ---
>  lib/Kconfig.debug |  1 +
>  mm/kmemleak.c     | 48 +++++++++++++++++++++++++++++-------------------
>  2 files changed, 30 insertions(+), 19 deletions(-)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index bcbe60d..0def8e0 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -717,6 +717,7 @@ config DEBUG_KMEMLEAK
>         select STACKTRACE if STACKTRACE_SUPPORT
>         select KALLSYMS
>         select CRC32
> +       select STACKDEPOT
>         help
>           Say Y here if you want to enable the memory leak
>           detector. The memory allocation/freeing is traced in a way
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> index 1eddc01..cedc6f3 100644
> --- a/mm/kmemleak.c
> +++ b/mm/kmemleak.c
> @@ -79,6 +79,7 @@
>  #include <linux/mutex.h>
>  #include <linux/rcupdate.h>
>  #include <linux/stacktrace.h>
> +#include <linux/stackdepot.h>
>  #include <linux/cache.h>
>  #include <linux/percpu.h>
>  #include <linux/memblock.h>
> @@ -159,8 +160,7 @@ struct kmemleak_object {
>         u32 checksum;
>         /* memory ranges to be scanned inside an object (empty for all) */
>         struct hlist_head area_list;
> -       unsigned long trace[MAX_TRACE];
> -       unsigned int trace_len;
> +       depot_stack_handle_t trace_handle;
>         unsigned long jiffies;          /* creation timestamp */
>         pid_t pid;                      /* pid of the current task */
>         char comm[TASK_COMM_LEN];       /* executable name */
> @@ -343,21 +343,24 @@ static bool unreferenced_object(struct kmemleak_object *object)
>   * print_unreferenced function must be called with the object->lock held.
>   */
>  static void print_unreferenced(struct seq_file *seq,
> -                              struct kmemleak_object *object)
> +               struct kmemleak_object *object)
>  {
>         int i;
> +       unsigned long *entries;
> +       unsigned int nr_entries;
>         unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);
>
> +       nr_entries = stack_depot_fetch(object->trace_handle, &entries);
>         warn_or_seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
> -                  object->pointer, object->size);
> +                       object->pointer, object->size);
>         warn_or_seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n",
> -                  object->comm, object->pid, object->jiffies,
> -                  msecs_age / 1000, msecs_age % 1000);
> +                       object->comm, object->pid, object->jiffies,
> +                       msecs_age / 1000, msecs_age % 1000);
>         hex_dump_object(seq, object);
>         warn_or_seq_printf(seq, "  backtrace:\n");
>
> -       for (i = 0; i < object->trace_len; i++) {
> -               void *ptr = (void *)object->trace[i];
> +       for (i = 0; i < nr_entries; i++) {
> +               void *ptr = (void *)entries[i];
>                 warn_or_seq_printf(seq, "    [<%p>] %pS\n", ptr, ptr);
>         }
>  }
> @@ -370,15 +373,16 @@ static void print_unreferenced(struct seq_file *seq,
>  static void dump_object_info(struct kmemleak_object *object)
>  {
>         pr_notice("Object 0x%08lx (size %zu):\n",
> -                 object->pointer, object->size);
> +                       object->pointer, object->size);
>         pr_notice("  comm \"%s\", pid %d, jiffies %lu\n",
> -                 object->comm, object->pid, object->jiffies);
> +                       object->comm, object->pid, object->jiffies);
>         pr_notice("  min_count = %d\n", object->min_count);
>         pr_notice("  count = %d\n", object->count);
>         pr_notice("  flags = 0x%x\n", object->flags);
>         pr_notice("  checksum = %u\n", object->checksum);
>         pr_notice("  backtrace:\n");
> -       stack_trace_print(object->trace, object->trace_len, 4);
> +       if (object->trace_handle)
> +               stack_depot_print(object->trace_handle);
>  }
>
>  /*
> @@ -591,12 +595,18 @@ static struct kmemleak_object *find_and_remove_object(unsigned long ptr, int ali
>         return object;
>  }
>
> -/*
> - * Save stack trace to the given array of MAX_TRACE size.
> - */
> -static int __save_stack_trace(unsigned long *trace)
> +static noinline depot_stack_handle_t set_track_prepare(void)
>  {
> -       return stack_trace_save(trace, MAX_TRACE, 2);
> +       depot_stack_handle_t trace_handle;
> +       unsigned long entries[MAX_TRACE];
> +       unsigned int nr_entries;
> +
> +       if (!kmemleak_initialized)
> +               return 0;
> +       nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
> +       trace_handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);
> +
> +       return trace_handle;
>  }
>
>  /*
> @@ -654,7 +664,7 @@ static struct kmemleak_object *__create_object(unsigned long ptr, size_t size,
>         }
>
>         /* kernel backtrace */
> -       object->trace_len = __save_stack_trace(object->trace);
> +       object->trace_handle = set_track_prepare();
>
>         raw_spin_lock_irqsave(&kmemleak_lock, flags);
>
> @@ -694,7 +704,6 @@ static struct kmemleak_object *__create_object(unsigned long ptr, size_t size,
>         rb_link_node(&object->rb_node, rb_parent, link);
>         rb_insert_color(&object->rb_node, is_phys ? &object_phys_tree_root :
>                                           &object_tree_root);
> -
>         list_add_tail_rcu(&object->object_list, &object_list);
>  out:
>         raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
> @@ -1094,7 +1103,7 @@ void __ref kmemleak_update_trace(const void *ptr)
>         }
>
>         raw_spin_lock_irqsave(&object->lock, flags);
> -       object->trace_len = __save_stack_trace(object->trace);
> +       object->trace_handle = set_track_prepare();
>         raw_spin_unlock_irqrestore(&object->lock, flags);
>
>         put_object(object);
> @@ -2064,6 +2073,7 @@ void __init kmemleak_init(void)
>         if (kmemleak_error)
>                 return;
>
> +       stack_depot_init();
>         jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
>         jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
>
> --
> 1.9.1
>