On Tue, Feb 27, 2024 at 5:07 AM Vlastimil Babka [off-list ref] wrote:

On 2/21/24 20:40, Suren Baghdasaryan wrote:

quoted

Account slab allocations using codetag reference embedded into slabobj_ext.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Co-developed-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Reviewed-by: Kees Cook <redacted>
---
 mm/slab.h | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 mm/slub.c |  9 ++++++++
 2 files changed, 75 insertions(+)

diff --git a/mm/slab.h b/mm/slab.h
index 13b6ba2abd74..c4bd0d5348cb 100644
--- a/mm/slab.h
+++ b/mm/slab.h

@@ -567,6 +567,46 @@ static inline struct slabobj_ext *slab_obj_exts(struct slab *slab)
 int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
                      gfp_t gfp, bool new_slab);

+static inline bool need_slab_obj_ext(void)
+{
+#ifdef CONFIG_MEM_ALLOC_PROFILING
+     if (mem_alloc_profiling_enabled())
+             return true;
+#endif
+     /*
+      * CONFIG_MEMCG_KMEM creates vector of obj_cgroup objects conditionally
+      * inside memcg_slab_post_alloc_hook. No other users for now.
+      */
+     return false;
+}
+
+static inline struct slabobj_ext *
+prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
+{
+     struct slab *slab;
+
+     if (!p)
+             return NULL;
+
+     if (!need_slab_obj_ext())
+             return NULL;
+
+     if (s->flags & SLAB_NO_OBJ_EXT)
+             return NULL;
+
+     if (flags & __GFP_NO_OBJ_EXT)
+             return NULL;
+
+     slab = virt_to_slab(p);
+     if (!slab_obj_exts(slab) &&
+         WARN(alloc_slab_obj_exts(slab, s, flags, false),
+              "%s, %s: Failed to create slab extension vector!\n",
+              __func__, s->name))
+             return NULL;
+
+     return slab_obj_exts(slab) + obj_to_index(s, slab, p);
+}
+
 #else /* CONFIG_SLAB_OBJ_EXT */

 static inline struct slabobj_ext *slab_obj_exts(struct slab *slab)

@@ -589,6 +629,32 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)

 #endif /* CONFIG_SLAB_OBJ_EXT */

+#ifdef CONFIG_MEM_ALLOC_PROFILING
+
+static inline void alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab,
+                                     void **p, int objects)

Only used from mm/slub.c so could move?

Ack.

quoted

+{
+     struct slabobj_ext *obj_exts;
+     int i;
+
+     obj_exts = slab_obj_exts(slab);
+     if (!obj_exts)
+             return;
+
+     for (i = 0; i < objects; i++) {
+             unsigned int off = obj_to_index(s, slab, p[i]);
+
+             alloc_tag_sub(&obj_exts[off].ref, s->size);
+     }
+}
+
+#else
+
+static inline void alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab,
+                                     void **p, int objects) {}
+
+#endif /* CONFIG_MEM_ALLOC_PROFILING */
+
 #ifdef CONFIG_MEMCG_KMEM
 void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
                   enum node_stat_item idx, int nr);

diff --git a/mm/slub.c b/mm/slub.c
index 5dc7beda6c0d..a69b6b4c8df6 100644
--- a/mm/slub.c
+++ b/mm/slub.c

@@ -3826,6 +3826,7 @@ void slab_post_alloc_hook(struct kmem_cache *s, struct obj_cgroup *objcg,
                        unsigned int orig_size)
 {
      unsigned int zero_size = s->object_size;
+     struct slabobj_ext *obj_exts;
      bool kasan_init = init;
      size_t i;
      gfp_t init_flags = flags & gfp_allowed_mask;

@@ -3868,6 +3869,12 @@ void slab_post_alloc_hook(struct kmem_cache *s,        struct obj_cgroup *objcg,
              kmemleak_alloc_recursive(p[i], s->object_size, 1,
                                       s->flags, init_flags);
              kmsan_slab_alloc(s, p[i], init_flags);
+             obj_exts = prepare_slab_obj_exts_hook(s, flags, p[i]);
+#ifdef CONFIG_MEM_ALLOC_PROFILING
+             /* obj_exts can be allocated for other reasons */
+             if (likely(obj_exts) && mem_alloc_profiling_enabled())
+                     alloc_tag_add(&obj_exts->ref, current->alloc_tag, s->size);
+#endif

I think that like in the page allocator, this could be better guarded by
mem_alloc_profiling_enabled() as the outermost thing.

Oops, missed it. Will fix.

quoted

      }

      memcg_slab_post_alloc_hook(s, objcg, flags, size, p);

@@ -4346,6 +4353,7 @@ void slab_free(struct kmem_cache *s, struct slab *slab, void *object,
             unsigned long addr)
 {
      memcg_slab_free_hook(s, slab, &object, 1);
+     alloc_tagging_slab_free_hook(s, slab, &object, 1);

Same here, the static key is not even inside of this?

Ack.

quoted

      if (likely(slab_free_hook(s, object, slab_want_init_on_free(s))))
              do_slab_free(s, slab, object, object, 1, addr);

@@ -4356,6 +4364,7 @@ void slab_free_bulk(struct kmem_cache *s, struct slab *slab, void *head,
                  void *tail, void **p, int cnt, unsigned long addr)
 {
      memcg_slab_free_hook(s, slab, p, cnt);
+     alloc_tagging_slab_free_hook(s, slab, p, cnt);

Ditto.

Ack.

quoted

      /*
       * With KASAN enabled slab_free_freelist_hook modifies the freelist
       * to remove objects, whose reuse must be delayed.

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