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Message-ID: <20240927184133.968283-3-namhyung@kernel.org>
Date: Fri, 27 Sep 2024 11:41:32 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>,
Eduard Zingerman <eddyz87@...il.com>,
Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...ichev.me>,
Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
bpf@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Christoph Lameter <cl@...ux.com>,
Pekka Enberg <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Vlastimil Babka <vbabka@...e.cz>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Hyeonggon Yoo <42.hyeyoo@...il.com>,
linux-mm@...ck.org,
Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: [RFC/PATCH bpf-next 2/3] mm/bpf: Add bpf_get_kmem_cache() kfunc
The bpf_get_kmem_cache() is to get a slab cache information from a
virtual address like virt_to_cache(). If the address is a pointer
to a slab object, it'd return a valid kmem_cache pointer, otherwise
NULL is returned.
It doesn't grab a reference count of the kmem_cache so the caller is
responsible to manage the access. The intended use case for now is to
symbolize locks in slab objects from the lock contention tracepoints.
Suggested-by: Vlastimil Babka <vbabka@...e.cz>
Acked-by: Roman Gushchin <roman.gushchin@...ux.dev> (mm/*)
Acked-by: Vlastimil Babka <vbabka@...e.cz> #mm/slab
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
kernel/bpf/helpers.c | 1 +
mm/slab_common.c | 16 ++++++++++++++++
2 files changed, 17 insertions(+)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 1a43d06eab286c26..bbc5800ec3afc899 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -3090,6 +3090,7 @@ BTF_ID_FLAGS(func, bpf_iter_bits_new, KF_ITER_NEW)
BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_copy_from_user_str, KF_SLEEPABLE)
+BTF_ID_FLAGS(func, bpf_get_kmem_cache, KF_RET_NULL)
BTF_KFUNCS_END(common_btf_ids)
static const struct btf_kfunc_id_set common_kfunc_set = {
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 7443244656150325..e648b05a635b94bf 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1322,6 +1322,22 @@ size_t ksize(const void *objp)
}
EXPORT_SYMBOL(ksize);
+#ifdef CONFIG_BPF_SYSCALL
+#include <linux/btf.h>
+
+__bpf_kfunc_start_defs();
+
+__bpf_kfunc struct kmem_cache *bpf_get_kmem_cache(u64 addr)
+{
+ struct slab *slab;
+
+ slab = virt_to_slab((void *)(long)addr);
+ return slab ? slab->slab_cache : NULL;
+}
+
+__bpf_kfunc_end_defs();
+#endif /* CONFIG_BPF_SYSCALL */
+
/* Tracepoints definitions. */
EXPORT_TRACEPOINT_SYMBOL(kmalloc);
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
--
2.46.1.824.gd892dcdcdd-goog
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