From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f50.google.com (mail-wr1-f50.google.com [209.85.221.50]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7DA8634105B for ; Mon, 12 Jan 2026 21:27:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.50 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768253278; cv=none; b=JOY9IJ0CSZdiHCkfU8Y5lBQs/GrPhb3Ms+3gmGliTw1Wm+e59T2fmGjr4BGbxWbjBYn0Z2+1xEk0+a672QqXAzUoCEDvAnfWhpbvOlbYuRXgNmzzWctwmH0FNE+vlOjnAikl5NxmDe8CZX0pg7qaVReK1bxC9tQsKx9G1FHUhWs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768253278; c=relaxed/simple; bh=2cfeRh/TqwL/Pv0ox/+JPyizCsTVyFt6ByQhjDKnX3E=; h=From:Date:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PMfnlScaMGwKjkQSs+4/CNn4jMjw7rRn1E71V3PnO27a0jaOxDzFc20aemKY6vOcSLCN9FSMa98Q4Vtp9deunitApLZeDKPdkjGcqBgqqNvM7MG8v5tn5mg8s/HG0bVaVlcHTnshg58TNkeEw4yk5AEQ6m/WwsQJrzwRM7oz/yA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=A/sh6hFR; arc=none smtp.client-ip=209.85.221.50 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="A/sh6hFR" Received: by mail-wr1-f50.google.com with SMTP id ffacd0b85a97d-432d2c7a8b9so3396667f8f.2 for ; Mon, 12 Jan 2026 13:27:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1768253275; x=1768858075; darn=vger.kernel.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:date:from:from:to :cc:subject:date:message-id:reply-to; bh=PQq++ScOu7vE0Lz/RtZKByNqj4pSUn78IDE7wyXt0WA=; b=A/sh6hFRnLJm/+CQmrimGB7Thd9dV9AWzSmNNZ5TuA208Vg2xYSwBkQyxlf7z3tywq 5RReQKE0asslxgwS+5qZvYG2pdmhiQjVmvkPwshrqUSTOCUaDD/YgiCAfYZhc+nLYciD Af5d1nFdsw7SfkcmH4I1XLTb8ApgFey54AIDDibsY4X5nc0JZFv0VjRJw/UfiiYrj2wU Ktm+VvAJy0a9SatISliYe0cM50/EgE0crTrNff9Df70428pXrwckIFkNhnGSODSMES94 0hw6X/gGUBl5ODUVvYUwgcPjfhvQJnC8kkZV5HhmZYnw0OONJErDNmNgVd4YgxTAjbLF JDeg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1768253275; x=1768858075; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:date:from:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=PQq++ScOu7vE0Lz/RtZKByNqj4pSUn78IDE7wyXt0WA=; b=UriDhefk/0KbiMHqWpJJ1LeQYQbAvYEgR/lei6tr5OWYjS+cGjxbs/3Gnc6bsn+Ztl +xBAWc9ZKnrcFsX6BSYwvAV5Ccp3z+e+eROzLejaC7vQwLrZTdLi9u43VOuwUqMLk3of 97HfF5ijl9Ixd4xYrRUNK6CC57k7AafgiQiyhB3zRBYKmpO8+Qs3+Ucy4OjPPu4+U1qX nsW4GUnNOQfs8WQ40S4VxXYvBO48edQxym+Wdy/bMc0A6cImtgwYYchMloigebJpgQq3 +ZMn/ebXNQfHxQlJ6YuOKmUC+tA0p4wmEu4YhKcUaWSkooUPsdCb1+ahlysAEPFZ5wBb h8OA== X-Forwarded-Encrypted: i=1; AJvYcCWI01l43tBpQpIflCyQHRdnlMCFY43L0q6OxruDuyzrAD03E7DB1mYuWArvqBSWGYi9jbbvM6pFLdYkH4s=@vger.kernel.org X-Gm-Message-State: AOJu0YxmEosYQ8yT9jgHhT+VcuO7dm73oFMy+opmCuHyupzxMm+SoY/C EZoRxt9bWSPKP7nCz30txNy6Ct1s3t0Jjt0grz4yRKbH4kEPacFGDlN/ X-Gm-Gg: AY/fxX7X/zwEhGSi26pG0e1cJdCF2w+986f2JHqkpO8X8JbBuQyyonJfzfTEwjVQw9x XeltAe2BtojhDRSCSVcv0vywBYd4LrJIDK8yu5M6HiL5benw6cxiMFEG3zdp2biKqXpFC1DR/UN 80AnVCRL9UtRuAyQXV26i+ewy70Hjsj6Akz3dfs4aNOPDQuoTiItj5IFTAF/B12BSkugCNgXmUe yCUWE3za5OcMg/oz1utjir8G21zw+SbOYoCdg5lIICq5MjWMbQ51Obd89kcmixJ6j/BXY5/UoPZ yTAhBbTqdpamwqPJ64ci3TW7fpvf/fs7Q82K7ctDMtCGbKvRpANdW9UCQV7aPBF5I4s5WRpsKB6 26fNOwTZ+trhVkIcaM7bCMGqd85+hN5hLm+dYHQQ7sV2B3NrdXwzvoF+Cym7vegE80ZykMTHKWJ A= X-Google-Smtp-Source: AGHT+IEaR0UW2C1CAn+Cjl3UGT4xxu7bcNb4qy4s5ukdVRcSA5IGeSTNKCNErEm4FMX6pr1j+2gIQA== X-Received: by 2002:a05:6000:290b:b0:431:369:e7b with SMTP id ffacd0b85a97d-432c3760c49mr22314037f8f.18.1768253274576; Mon, 12 Jan 2026 13:27:54 -0800 (PST) Received: from krava ([176.74.159.170]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-432bd0e199bsm40113986f8f.16.2026.01.12.13.27.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Jan 2026 13:27:54 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Mon, 12 Jan 2026 22:27:51 +0100 To: Andrii Nakryiko , Alan Maguire Cc: Steven Rostedt , Florent Revest , Mark Rutland , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Menglong Dong , Song Liu Subject: Re: [PATCHv6 bpf-next 7/9] bpf: Add trampoline ip hash table Message-ID: References: <20251230145010.103439-1-jolsa@kernel.org> <20251230145010.103439-8-jolsa@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Jan 09, 2026 at 04:36:41PM -0800, Andrii Nakryiko wrote: > On Tue, Dec 30, 2025 at 6:51 AM Jiri Olsa wrote: > > > > Following changes need to lookup trampoline based on its ip address, > > adding hash table for that. > > > > Signed-off-by: Jiri Olsa > > --- > > include/linux/bpf.h | 7 +++++-- > > kernel/bpf/trampoline.c | 30 +++++++++++++++++++----------- > > 2 files changed, 24 insertions(+), 13 deletions(-) > > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > > index 4e7d72dfbcd4..c85677aae865 100644 > > --- a/include/linux/bpf.h > > +++ b/include/linux/bpf.h > > @@ -1325,14 +1325,17 @@ struct bpf_tramp_image { > > }; > > > > struct bpf_trampoline { > > - /* hlist for trampoline_table */ > > - struct hlist_node hlist; > > + /* hlist for trampoline_key_table */ > > + struct hlist_node hlist_key; > > + /* hlist for trampoline_ip_table */ > > + struct hlist_node hlist_ip; > > struct ftrace_ops *fops; > > /* serializes access to fields of this trampoline */ > > struct mutex mutex; > > refcount_t refcnt; > > u32 flags; > > u64 key; > > + unsigned long ip; > > struct { > > struct btf_func_model model; > > void *addr; > > diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c > > index 789ff4e1f40b..bdac9d673776 100644 > > --- a/kernel/bpf/trampoline.c > > +++ b/kernel/bpf/trampoline.c > > @@ -24,9 +24,10 @@ const struct bpf_prog_ops bpf_extension_prog_ops = { > > #define TRAMPOLINE_HASH_BITS 10 > > #define TRAMPOLINE_TABLE_SIZE (1 << TRAMPOLINE_HASH_BITS) > > > > -static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE]; > > +static struct hlist_head trampoline_key_table[TRAMPOLINE_TABLE_SIZE]; > > +static struct hlist_head trampoline_ip_table[TRAMPOLINE_TABLE_SIZE]; > > > > -/* serializes access to trampoline_table */ > > +/* serializes access to trampoline tables */ > > static DEFINE_MUTEX(trampoline_mutex); > > > > #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > > @@ -135,15 +136,15 @@ void bpf_image_ksym_del(struct bpf_ksym *ksym) > > PAGE_SIZE, true, ksym->name); > > } > > > > -static struct bpf_trampoline *bpf_trampoline_lookup(u64 key) > > +static struct bpf_trampoline *bpf_trampoline_lookup(u64 key, unsigned long ip) > > { > > struct bpf_trampoline *tr; > > struct hlist_head *head; > > int i; > > > > mutex_lock(&trampoline_mutex); > > - head = &trampoline_table[hash_64(key, TRAMPOLINE_HASH_BITS)]; > > - hlist_for_each_entry(tr, head, hlist) { > > + head = &trampoline_key_table[hash_64(key, TRAMPOLINE_HASH_BITS)]; > > + hlist_for_each_entry(tr, head, hlist_key) { > > if (tr->key == key) { > > refcount_inc(&tr->refcnt); > > goto out; > > @@ -164,8 +165,12 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key) > > #endif > > > > tr->key = key; > > - INIT_HLIST_NODE(&tr->hlist); > > - hlist_add_head(&tr->hlist, head); > > + tr->ip = ftrace_location(ip); > > + INIT_HLIST_NODE(&tr->hlist_key); > > + INIT_HLIST_NODE(&tr->hlist_ip); > > + hlist_add_head(&tr->hlist_key, head); > > + head = &trampoline_ip_table[hash_64(tr->ip, TRAMPOLINE_HASH_BITS)]; > > For key lookups we check that there is no existing trampoline for the > given key. Can it happen that we have two trampolines at the same IP > but using two different keys? so multiple keys (different static functions with same name) resolving to the same ip happened in past and we should now be able to catch those in pahole, right? CC-ing Alan ;-) however, that should fail the attachment on ftrace/direct layer say we have already registered and attached trampoline key1-ip1, follow-up attachment of trampoline with key2-ip1 will fail on: bpf_trampoline_update register_fentry direct_ops_add update_ftrace_direct_add ... /* Make sure requested entries are not already registered. */ fails, because ip1 is already in direct_functions ... jirka > > > > > + hlist_add_head(&tr->hlist_ip, head); > > refcount_set(&tr->refcnt, 1); > > mutex_init(&tr->mutex); > > for (i = 0; i < BPF_TRAMP_MAX; i++) > > @@ -846,7 +851,7 @@ void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog) > > prog->aux->attach_btf_id); > > > > bpf_lsm_find_cgroup_shim(prog, &bpf_func); > > - tr = bpf_trampoline_lookup(key); > > + tr = bpf_trampoline_lookup(key, 0); > > if (WARN_ON_ONCE(!tr)) > > return; > > > > @@ -866,7 +871,7 @@ struct bpf_trampoline *bpf_trampoline_get(u64 key, > > { > > struct bpf_trampoline *tr; > > > > - tr = bpf_trampoline_lookup(key); > > + tr = bpf_trampoline_lookup(key, tgt_info->tgt_addr); > > if (!tr) > > return NULL; > > > > @@ -902,7 +907,8 @@ void bpf_trampoline_put(struct bpf_trampoline *tr) > > * fexit progs. The fentry-only trampoline will be freed via > > * multiple rcu callbacks. > > */ > > - hlist_del(&tr->hlist); > > + hlist_del(&tr->hlist_key); > > + hlist_del(&tr->hlist_ip); > > if (tr->fops) { > > ftrace_free_filter(tr->fops); > > kfree(tr->fops); > > @@ -1175,7 +1181,9 @@ static int __init init_trampolines(void) > > int i; > > > > for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++) > > - INIT_HLIST_HEAD(&trampoline_table[i]); > > + INIT_HLIST_HEAD(&trampoline_key_table[i]); > > + for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++) > > + INIT_HLIST_HEAD(&trampoline_ip_table[i]); > > return 0; > > } > > late_initcall(init_trampolines); > > -- > > 2.52.0 > >