Re: [PATCH v4 sl-b 0/6] Export return addresses etc. for better diagnostics

From: Paul E. McKenney
Date: Thu Jan 07 2021 - 19:27:40 EST

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On Wed, Jan 06, 2021 at 03:42:12PM -0800, Paul E. McKenney wrote:
> On Wed, Jan 06, 2021 at 01:48:43PM -0800, Andrew Morton wrote:
> > On Tue, 5 Jan 2021 17:16:03 -0800 "Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote:
> >
> > > This is v4 of the series the improves diagnostics by providing access
> > > to additional information including the return addresses, slab names,
> > > offsets, and sizes collected by the sl*b allocators and by vmalloc().
> >
> > Looks reasonable. And not as bloaty as I feared, but it does add ~300
> > bytes to my allnoconfig build. Is the CONFIG_ coverage as tight as it
> > could be?
>
> Glad I managed to exceed your expectations. ;-)
>
> Let's see... When I do an allnoconfig build, it has CONFIG_PRINTK=n.
> Given that this facility is based on printk(), I could create an
> additional patch that #ifdef'ed everything out in CONFIG_PRINTK=n kernels.
> This would uglify things a bit, but it would save ~300 bytes.
>
> If I don't hear otherwise from you, I will put something together,
> test it, and send it along.

And is a first draft, very lightly tested. Thoughts?

Thanx, Paul

------------------------------------------------------------------------

commit 4164efdca255093a423b55f44bd788b46d9c648f
Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
Date: Thu Jan 7 13:46:11 2021 -0800

mm: Don't build mm_dump_obj() on CONFIG_PRINTK=n kernels

The mem_dump_obj() functionality adds a few hundred bytes, which is a
small price to pay. Except on kernels built with CONFIG_PRINTK=n, in
which mem_dump_obj() messages will be suppressed. This commit therefore
makes mem_dump_obj() be a static inline empty function on kernels built
with CONFIG_PRINTK=n and excludes all of its support functions as well.
This avoids kernel bloat on systems that cannot use mem_dump_obj().

Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: <linux-mm@xxxxxxxxx>
Suggested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index af7d050..ed75a3a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3169,7 +3169,11 @@ unsigned long wp_shared_mapping_range(struct address_space *mapping,

extern int sysctl_nr_trim_pages;

+#ifdef CONFIG_PRINTK
void mem_dump_obj(void *object);
+#else
+static inline void mem_dump_obj(void *object) {}
+#endif

#endif /* __KERNEL__ */
#endif /* _LINUX_MM_H */
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 7ae6040..0c97d78 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -186,8 +186,10 @@ void kfree(const void *);
void kfree_sensitive(const void *);
size_t __ksize(const void *);
size_t ksize(const void *);
+#ifdef CONFIG_PRINTK
bool kmem_valid_obj(void *object);
void kmem_dump_obj(void *object);
+#endif

#ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR
void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index c18f475..3c8a765 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -246,7 +246,7 @@ pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
int register_vmap_purge_notifier(struct notifier_block *nb);
int unregister_vmap_purge_notifier(struct notifier_block *nb);

-#ifdef CONFIG_MMU
+#if defined(CONFIG_MMU) && defined(CONFIG_PRINTK)
bool vmalloc_dump_obj(void *object);
#else
static inline bool vmalloc_dump_obj(void *object) { return false; }
diff --git a/mm/slab.c b/mm/slab.c
index dcc55e7..965d277 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3635,6 +3635,7 @@ void *__kmalloc_node_track_caller(size_t size, gfp_t flags,
EXPORT_SYMBOL(__kmalloc_node_track_caller);
#endif /* CONFIG_NUMA */

+#ifdef CONFIG_PRINTK
void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page)
{
struct kmem_cache *cachep;
@@ -3654,6 +3655,7 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page)
if (DEBUG && cachep->flags & SLAB_STORE_USER)
kpp->kp_ret = *dbg_userword(cachep, objp);
}
+#endif

/**
* __do_kmalloc - allocate memory
diff --git a/mm/slab.h b/mm/slab.h
index ecad9b5..d2e39ab 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -615,6 +615,7 @@ static inline bool slab_want_init_on_free(struct kmem_cache *c)
return false;
}

+#ifdef CONFIG_PRINTK
#define KS_ADDRS_COUNT 16
struct kmem_obj_info {
void *kp_ptr;
@@ -626,5 +627,6 @@ struct kmem_obj_info {
void *kp_stack[KS_ADDRS_COUNT];
};
void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page);
+#endif

#endif /* MM_SLAB_H */
diff --git a/mm/slab_common.c b/mm/slab_common.c
index b594413..20b2cc6 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -537,6 +537,7 @@ bool slab_is_available(void)
return slab_state >= UP;
}

+#ifdef CONFIG_PRINTK
/**
* kmem_valid_obj - does the pointer reference a valid slab object?
* @object: pointer to query.
@@ -610,6 +611,7 @@ void kmem_dump_obj(void *object)
pr_info(" %pS\n", kp.kp_stack[i]);
}
}
+#endif

#ifndef CONFIG_SLOB
/* Create a cache during boot when no slab services are available yet */
diff --git a/mm/slob.c b/mm/slob.c
index ef87ada..8726931 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -461,11 +461,13 @@ static void slob_free(void *block, int size)
spin_unlock_irqrestore(&slob_lock, flags);
}

+#ifdef CONFIG_PRINTK
void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page)
{
kpp->kp_ptr = object;
kpp->kp_page = page;
}
+#endif

/*
* End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.
diff --git a/mm/slub.c b/mm/slub.c
index 3c1a843..9e205e4 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3919,6 +3919,7 @@ int __kmem_cache_shutdown(struct kmem_cache *s)
return 0;
}

+#ifdef CONFIG_PRINTK
void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page)
{
void *base;
@@ -3958,6 +3959,7 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page)
#endif
#endif
}
+#endif

/********************************************************************
* Kmalloc subsystem
diff --git a/mm/util.c b/mm/util.c
index 5487022..2d497fe 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -983,6 +983,7 @@ int __weak memcmp_pages(struct page *page1, struct page *page2)
return ret;
}

+#ifdef CONFIG_PRINTK
/**
* mem_dump_obj - Print available provenance information
* @object: object for which to find provenance information.
@@ -1013,3 +1014,4 @@ void mem_dump_obj(void *object)
}
pr_cont(" non-slab/vmalloc memory.\n");
}
+#endif
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index e3229ff..5002fd6 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3448,6 +3448,7 @@ void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
}
#endif /* CONFIG_SMP */

+#ifdef CONFIG_PRINTK
bool vmalloc_dump_obj(void *object)
{
struct vm_struct *vm;
@@ -3460,6 +3461,7 @@ bool vmalloc_dump_obj(void *object)
vm->nr_pages, (unsigned long)vm->addr, vm->caller);
return true;
}
+#endif

#ifdef CONFIG_PROC_FS
static void *s_start(struct seq_file *m, loff_t *pos)

Next message: Stephen Rothwell: "linux-next: manual merge of the net-next tree with the net tree"
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In reply to: Paul E. McKenney: "Re: [PATCH v4 sl-b 0/6] Export return addresses etc. for better diagnostics"
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