From patchwork Mon Nov 20 10:55:24 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Valentin Schneider X-Patchwork-Id: 13461021 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="TRXbUREp" Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 73A5C9C for ; Mon, 20 Nov 2023 02:55:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1700477756; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hYWM4is6LVmFMNo5dpMFH0Wy9yxc8y0LNuURzC8Srcg=; b=TRXbUREpF24hnJ4/Mc4F4lMUdPbm+E6hxJBTrzxF1ADBCMmSeViKzLZBSkN39xzYowNrg2 NKCErmHElaYxIolgPwaEgYskODV+2I8YvkJ7L0SJ6uvGHmfnfLNMiHUUXVlXZVsObLMn4p rmMFquA1mp9/bYOtzXcz3cO3C3JLYbk= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-554--kwMc0T6P4mJ0OpNhhuLlA-1; Mon, 20 Nov 2023 05:55:53 -0500 X-MC-Unique: -kwMc0T6P4mJ0OpNhhuLlA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 33059101A529; Mon, 20 Nov 2023 10:55:52 +0000 (UTC) Received: from vschneid-thinkpadt14sgen2i.remote.csb (unknown [10.39.195.45]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B77642026D4C; Mon, 20 Nov 2023 10:55:46 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-arch@vger.kernel.org, x86@kernel.org Cc: Peter Zijlstra , Thomas Gleixner , Borislav Petkov , Josh Poimboeuf , Pawan Gupta , Ingo Molnar , Dave Hansen , "H. Peter Anvin" , Paolo Bonzini , Wanpeng Li , Vitaly Kuznetsov , Arnd Bergmann , Jason Baron , Steven Rostedt , Ard Biesheuvel , Frederic Weisbecker , "Paul E. McKenney" , Feng Tang , Andrew Morton , "Mike Rapoport (IBM)" , Vlastimil Babka , David Hildenbrand , "ndesaulniers@google.com" , Michael Kelley , "Masami Hiramatsu (Google)" Subject: [PATCH 1/5] jump_label,module: Don't alloc static_key_mod for __ro_after_init keys Date: Mon, 20 Nov 2023 11:55:24 +0100 Message-ID: <20231120105528.760306-2-vschneid@redhat.com> In-Reply-To: <20231120105528.760306-1-vschneid@redhat.com> References: <20231120105528.760306-1-vschneid@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.4 From: Peter Zijlstra When a static_key is marked ro_after_init, its state will never change (after init), therefore jump_label_update() will never need to iterate the entries, and thus module load won't actually need to track this -- avoiding the static_key::next write. Therefore, mark these keys such that jump_label_add_module() might recognise them and avoid the modification. Use the special state: 'static_key_linked(key) && !static_key_mod(key)' to denote such keys. Link: http://lore.kernel.org/r/20230705204142.GB2813335@hirez.programming.kicks-ass.net Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Valentin Schneider --- include/asm-generic/sections.h | 5 ++++ include/linux/jump_label.h | 1 + init/main.c | 1 + kernel/jump_label.c | 49 ++++++++++++++++++++++++++++++++++ 4 files changed, 56 insertions(+) diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index db13bb620f527..c768de6f19a9a 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -180,6 +180,11 @@ static inline bool is_kernel_rodata(unsigned long addr) addr < (unsigned long)__end_rodata; } +static inline bool is_kernel_ro_after_init(unsigned long addr) +{ + return addr >= (unsigned long)__start_ro_after_init && + addr < (unsigned long)__end_ro_after_init; +} /** * is_kernel_inittext - checks if the pointer address is located in the * .init.text section diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h index f0a949b7c9733..88ef9e776af8d 100644 --- a/include/linux/jump_label.h +++ b/include/linux/jump_label.h @@ -216,6 +216,7 @@ extern struct jump_entry __start___jump_table[]; extern struct jump_entry __stop___jump_table[]; extern void jump_label_init(void); +extern void jump_label_ro(void); extern void jump_label_lock(void); extern void jump_label_unlock(void); extern void arch_jump_label_transform(struct jump_entry *entry, diff --git a/init/main.c b/init/main.c index e24b0780fdff7..5f51d8b910dc1 100644 --- a/init/main.c +++ b/init/main.c @@ -1407,6 +1407,7 @@ static void mark_readonly(void) * insecure pages which are W+X. */ rcu_barrier(); + jump_label_ro(); mark_rodata_ro(); rodata_test(); } else diff --git a/kernel/jump_label.c b/kernel/jump_label.c index d9c822bbffb8d..661ef74dee9b7 100644 --- a/kernel/jump_label.c +++ b/kernel/jump_label.c @@ -530,6 +530,45 @@ void __init jump_label_init(void) cpus_read_unlock(); } +static inline bool static_key_sealed(struct static_key *key) +{ + return (key->type & JUMP_TYPE_LINKED) && !(key->type & ~JUMP_TYPE_MASK); +} + +static inline void static_key_seal(struct static_key *key) +{ + unsigned long type = key->type & JUMP_TYPE_TRUE; + key->type = JUMP_TYPE_LINKED | type; +} + +void jump_label_ro(void) +{ + struct jump_entry *iter_start = __start___jump_table; + struct jump_entry *iter_stop = __stop___jump_table; + struct jump_entry *iter; + + if (WARN_ON_ONCE(!static_key_initialized)) + return; + + cpus_read_lock(); + jump_label_lock(); + + for (iter = iter_start; iter < iter_stop; iter++) { + struct static_key *iterk = jump_entry_key(iter); + + if (!is_kernel_ro_after_init((unsigned long)iterk)) + continue; + + if (static_key_sealed(iterk)) + continue; + + static_key_seal(iterk); + } + + jump_label_unlock(); + cpus_read_unlock(); +} + #ifdef CONFIG_MODULES enum jump_label_type jump_label_init_type(struct jump_entry *entry) @@ -650,6 +689,15 @@ static int jump_label_add_module(struct module *mod) static_key_set_entries(key, iter); continue; } + + /* + * If the key was sealed at init, then there's no need to keep a + * a reference to its module entries - just patch them now and + * be done with it. + */ + if (static_key_sealed(key)) + goto do_poke; + jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL); if (!jlm) return -ENOMEM; @@ -675,6 +723,7 @@ static int jump_label_add_module(struct module *mod) static_key_set_linked(key); /* Only update if we've changed from our initial state */ +do_poke: if (jump_label_type(iter) != jump_label_init_type(iter)) __jump_label_update(key, iter, iter_stop, true); }