From patchwork Fri Sep 27 18:41:31 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Namhyung Kim X-Patchwork-Id: 13814480 X-Patchwork-Delegate: bpf@iogearbox.net Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 01D031C1ADE; Fri, 27 Sep 2024 18:41:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727462497; cv=none; b=LukHl5AEemvsQ/78bcpJL+rofoSxND0SrbyFtVsZ8Uo5riWQ9jHnqCNsFN1wKUrompnXoxhRa7W8PZ+XyXMwJXXePKTIYedUTtH7zsHCtA74Uk2FrG0l/810aRwIWXAPhpIbaH3FVmutimJAtOafVE0oRqOm/HL+oO+vzhrU3E0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727462497; c=relaxed/simple; bh=kkigyrBYeiWFl3tgn2/scYgLndEN9wtat/LKpQKHAbM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mw2ZXS/s3PboHQaP1igDBtnQS7EBfuY4cqYOcv89F6ClP3BntcwrM+AFE/Z3xZcvNL+YrTH1GTCU1MRqkXRVg2FQkY/g8ghqEzQRlVBMe8246l0IfwFqp+OzPb6cdSAYZ0eeVqYRMX1fEU3oV3a5YUmUjitvXq/btQmWR3jFHRs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mpN/lLFl; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mpN/lLFl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C852AC4CED0; Fri, 27 Sep 2024 18:41:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1727462496; bh=kkigyrBYeiWFl3tgn2/scYgLndEN9wtat/LKpQKHAbM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mpN/lLFlB1Vb1cprdBgZpMgvY7xKvVW4ERpyob0A4VD5ETjBfYgXi5tR6/8EAF+Jb 1EcA81jZSJ7KmCVBP9+6vc4aJqOy0eKwdD33fngUqmVFPrTLgpSkQBX2RIByycMYrN 5RgnokD2ZNhl5Xm/6BhI1KIMqHOa2Uwa7EAyGs1C6KwXVpJRC0tK4z+gDiUrguKvv2 iu1kuFDjSJ3ZhR8zEhurS21hnyht5jvxNxGc0Xy5KrRNGCJ38g8ll1FATQLjDFHUt+ r/SzBZ81vAKbFt3VbIB1dg77XaUGQrKBFfP6uXPYmU7m+/B5ecq6z7mVufBXloKQuj nnTrTYVsUKbWw== From: Namhyung Kim To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , LKML , bpf@vger.kernel.org, Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, Arnaldo Carvalho de Melo Subject: [RFC/PATCH bpf-next 1/3] bpf: Add kmem_cache iterator Date: Fri, 27 Sep 2024 11:41:31 -0700 Message-ID: <20240927184133.968283-2-namhyung@kernel.org> X-Mailer: git-send-email 2.46.1.824.gd892dcdcdd-goog In-Reply-To: <20240927184133.968283-1-namhyung@kernel.org> References: <20240927184133.968283-1-namhyung@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net X-Patchwork-State: RFC The new "kmem_cache" iterator will traverse the list of slab caches and call attached BPF programs for each entry. It should check the argument (ctx.s) if it's NULL before using it. The iteration will be done with slab_mutex held but it'd break and return to user if the BPF program emits data to seq buffer more than the buffer size given by the user. IOW the whole iteration would be protected by the slab_mutex as long as it won't emit anything. It includes the internal "mm/slab.h" header to access kmem_cache, slab_caches and slab_mutex. Hope it's ok to mm folks. Acked-by: Roman Gushchin (mm/*) Acked-by: Vlastimil Babka #mm/slab Signed-off-by: Namhyung Kim --- include/linux/btf_ids.h | 1 + kernel/bpf/Makefile | 1 + kernel/bpf/kmem_cache_iter.c | 131 +++++++++++++++++++++++++++++++++++ 3 files changed, 133 insertions(+) create mode 100644 kernel/bpf/kmem_cache_iter.c diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h index c0e3e1426a82f5c4..139bdececdcfaefb 100644 --- a/include/linux/btf_ids.h +++ b/include/linux/btf_ids.h @@ -283,5 +283,6 @@ extern u32 btf_tracing_ids[]; extern u32 bpf_cgroup_btf_id[]; extern u32 bpf_local_storage_map_btf_id[]; extern u32 btf_bpf_map_id[]; +extern u32 bpf_kmem_cache_btf_id[]; #endif diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile index 9b9c151b5c826b31..105328f0b9c04e37 100644 --- a/kernel/bpf/Makefile +++ b/kernel/bpf/Makefile @@ -52,3 +52,4 @@ obj-$(CONFIG_BPF_PRELOAD) += preload/ obj-$(CONFIG_BPF_SYSCALL) += relo_core.o obj-$(CONFIG_BPF_SYSCALL) += btf_iter.o obj-$(CONFIG_BPF_SYSCALL) += btf_relocate.o +obj-$(CONFIG_BPF_SYSCALL) += kmem_cache_iter.o diff --git a/kernel/bpf/kmem_cache_iter.c b/kernel/bpf/kmem_cache_iter.c new file mode 100644 index 0000000000000000..5f7436b52f2e6b06 --- /dev/null +++ b/kernel/bpf/kmem_cache_iter.c @@ -0,0 +1,131 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2024 Google */ +#include +#include +#include +#include +#include + +#include "../../mm/slab.h" /* kmem_cache, slab_caches and slab_mutex */ + +struct bpf_iter__kmem_cache { + __bpf_md_ptr(struct bpf_iter_meta *, meta); + __bpf_md_ptr(struct kmem_cache *, s); +}; + +static void *kmem_cache_iter_seq_start(struct seq_file *seq, loff_t *pos) +{ + loff_t cnt = 0; + struct kmem_cache *s = NULL; + + mutex_lock(&slab_mutex); + + /* + * Find an entry at the given position in the slab_caches list instead + * of keeping a reference (of the last visited entry, if any) out of + * slab_mutex. It might miss something if one is deleted in the middle + * while it releases the lock. But it should be rare and there's not + * much we can do about it. + */ + list_for_each_entry(s, &slab_caches, list) { + if (cnt == *pos) + break; + + cnt++; + } + + if (cnt != *pos) + return NULL; + + ++*pos; + return s; +} + +static void kmem_cache_iter_seq_stop(struct seq_file *seq, void *v) +{ + struct bpf_iter_meta meta; + struct bpf_iter__kmem_cache ctx = { + .meta = &meta, + .s = v, + }; + struct bpf_prog *prog; + + meta.seq = seq; + prog = bpf_iter_get_info(&meta, true); + if (prog) + bpf_iter_run_prog(prog, &ctx); + + mutex_unlock(&slab_mutex); +} + +static void *kmem_cache_iter_seq_next(struct seq_file *seq, void *v, loff_t *pos) +{ + struct kmem_cache *s = v; + + ++*pos; + + if (list_last_entry(&slab_caches, struct kmem_cache, list) == s) + return NULL; + + return list_next_entry(s, list); +} + +static int kmem_cache_iter_seq_show(struct seq_file *seq, void *v) +{ + struct bpf_iter_meta meta; + struct bpf_iter__kmem_cache ctx = { + .meta = &meta, + .s = v, + }; + struct bpf_prog *prog; + int ret = 0; + + meta.seq = seq; + prog = bpf_iter_get_info(&meta, false); + if (prog) + ret = bpf_iter_run_prog(prog, &ctx); + + return ret; +} + +static const struct seq_operations kmem_cache_iter_seq_ops = { + .start = kmem_cache_iter_seq_start, + .next = kmem_cache_iter_seq_next, + .stop = kmem_cache_iter_seq_stop, + .show = kmem_cache_iter_seq_show, +}; + +BTF_ID_LIST_GLOBAL_SINGLE(bpf_kmem_cache_btf_id, struct, kmem_cache) + +static const struct bpf_iter_seq_info kmem_cache_iter_seq_info = { + .seq_ops = &kmem_cache_iter_seq_ops, +}; + +static void bpf_iter_kmem_cache_show_fdinfo(const struct bpf_iter_aux_info *aux, + struct seq_file *seq) +{ + seq_puts(seq, "kmem_cache iter\n"); +} + +DEFINE_BPF_ITER_FUNC(kmem_cache, struct bpf_iter_meta *meta, + struct kmem_cache *s) + +static struct bpf_iter_reg bpf_kmem_cache_reg_info = { + .target = "kmem_cache", + .feature = BPF_ITER_RESCHED, + .show_fdinfo = bpf_iter_kmem_cache_show_fdinfo, + .ctx_arg_info_size = 1, + .ctx_arg_info = { + { offsetof(struct bpf_iter__kmem_cache, s), + PTR_TO_BTF_ID_OR_NULL | PTR_TRUSTED }, + }, + .seq_info = &kmem_cache_iter_seq_info, +}; + +static int __init bpf_kmem_cache_iter_init(void) +{ + bpf_kmem_cache_reg_info.ctx_arg_info[0].btf_id = bpf_kmem_cache_btf_id[0]; + return bpf_iter_reg_target(&bpf_kmem_cache_reg_info); +} + +late_initcall(bpf_kmem_cache_iter_init);