From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0AF06C433EF for ; Thu, 3 Mar 2022 15:59:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234656AbiCCQA0 (ORCPT ); Thu, 3 Mar 2022 11:00:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60174 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234487AbiCCQAX (ORCPT ); Thu, 3 Mar 2022 11:00:23 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 077D618F21C for ; Thu, 3 Mar 2022 07:59:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=lmKm34gjsT5RKmkMNGJuz66nZitqN3EkUdufPgE1EqY=; b=RG2xqR1pwGB1xg2w4P6vt85GbB buRzpHu/9KZ3e2ilalq/4PlHTHaqkuxdwIeSkroXc3mNTGLHINRfrizZGHcj8J/SHJDefO9TgWO7A XeiDEyu+ftuWkvGIPEjxy9agQmhE4c+R65jVaTTdYgBjdzvLbn66Sw09Wah6kc0lXAlnT0xUDZuqq nEql1jOCKRnCVSgQjpx59+Q3GiOdwaLFf4zb5RMSGLBx4AnnHHxdNjqoFw++RPSdzG3DAHNZzyG/Y Yal8DxyI5EKMSf2szOtNoMi4qBdq7sWxptjIrwdUIM3JTsbhqDH2ucYde2LwEcFwJ4s5UUwyNIlwJ kKht/vFQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nPnr8-00BmOS-5U; Thu, 03 Mar 2022 15:59:06 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id DA0DF300230; Thu, 3 Mar 2022 16:59:03 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 9463620790218; Thu, 3 Mar 2022 16:59:03 +0100 (CET) Date: Thu, 3 Mar 2022 16:59:03 +0100 From: Peter Zijlstra To: Steven Rostedt Cc: "Naveen N. Rao" , alexei.starovoitov@gmail.com, alyssa.milburn@intel.com, andrew.cooper3@citrix.com, hjl.tools@gmail.com, joao@overdrivepizza.com, jpoimboe@redhat.com, keescook@chromium.org, linux-kernel@vger.kernel.org, mark.rutland@arm.com, mbenes@suse.cz, Masami Hiramatsu , ndesaulniers@google.com, samitolvanen@google.com, x86@kernel.org Subject: Re: [PATCH v2 12/39] x86/ibt,ftrace: Search for __fentry__ location Message-ID: References: <20220225083647.12ceb54b@gandalf.local.home> <1646159447.ngbqgzj71t.naveen@linux.ibm.com> <20220301142016.22e787fb@gandalf.local.home> <20220302110138.6d2abcec@gandalf.local.home> <20220302144716.1772020c@gandalf.local.home> <1646300416.yyrqygami4.naveen@linux.ibm.com> <20220303093413.387ee6f1@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220303093413.387ee6f1@gandalf.local.home> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 03, 2022 at 09:34:13AM -0500, Steven Rostedt wrote: > On Thu, 3 Mar 2022 14:04:52 +0100 > Peter Zijlstra wrote: > > > > @@ -1596,7 +1596,7 @@ static int check_ftrace_location(struct kprobe *p) > > > { > > > unsigned long ftrace_addr; > > > > > > - ftrace_addr = ftrace_location((unsigned long)p->addr); > > > + ftrace_addr = ftrace_location_range((unsigned long)p->addr, (unsigned long)p->addr); > > > > Yes, although perhaps a new helper. I'll go ponder during lunch. > > Is there more places to add that to make it worth creating a helper? This is what I ended up with, I've looked at all ftrace_location() sites there are, seems to work too, both the built-in boot time ftrace tests and the selftests work splat-less. I should update the Changelog some though. Naveen also mentioned register_ftrace_direct() could be further cleaned up, but I didn't want to do too much in once go. --- Subject: x86/ibt,ftrace: Search for __fentry__ location From: Peter Zijlstra Date: Wed Feb 23 10:01:38 CET 2022 Have ftrace_location() search the symbol for the __fentry__ location when it isn't at func+0 and use this for {,un}register_ftrace_direct(). This avoids a whole bunch of assumptions about __fentry__ being at func+0. Suggested-by: Steven Rostedt Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/kernel/kprobes/core.c | 11 +--------- kernel/bpf/trampoline.c | 20 +++---------------- kernel/kprobes.c | 8 +------ kernel/trace/ftrace.c | 43 +++++++++++++++++++++++++++++++++-------- 4 files changed, 43 insertions(+), 39 deletions(-) --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -193,17 +193,10 @@ static unsigned long __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr) { struct kprobe *kp; - unsigned long faddr; + bool faddr; kp = get_kprobe((void *)addr); - faddr = ftrace_location(addr); - /* - * Addresses inside the ftrace location are refused by - * arch_check_ftrace_location(). Something went terribly wrong - * if such an address is checked here. - */ - if (WARN_ON(faddr && faddr != addr)) - return 0UL; + faddr = ftrace_location(addr) == addr; /* * Use the current code if it is not modified by Kprobe * and it cannot be modified by ftrace. --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -117,18 +117,6 @@ static void bpf_trampoline_module_put(st tr->mod = NULL; } -static int is_ftrace_location(void *ip) -{ - long addr; - - addr = ftrace_location((long)ip); - if (!addr) - return 0; - if (WARN_ON_ONCE(addr != (long)ip)) - return -EFAULT; - return 1; -} - static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr) { void *ip = tr->func.addr; @@ -160,12 +148,12 @@ static int modify_fentry(struct bpf_tram static int register_fentry(struct bpf_trampoline *tr, void *new_addr) { void *ip = tr->func.addr; + unsigned long faddr; int ret; - ret = is_ftrace_location(ip); - if (ret < 0) - return ret; - tr->func.ftrace_managed = ret; + faddr = ftrace_location((unsigned long)ip); + if (faddr) + tr->func.ftrace_managed = true; if (bpf_trampoline_module_get(tr)) return -ENOENT; --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1562,14 +1562,10 @@ static inline int warn_kprobe_rereg(stru static int check_ftrace_location(struct kprobe *p) { - unsigned long ftrace_addr; + unsigned long addr = (unsigned long)p->addr; - ftrace_addr = ftrace_location((unsigned long)p->addr); - if (ftrace_addr) { + if (ftrace_location(addr) == addr) { #ifdef CONFIG_KPROBES_ON_FTRACE - /* Given address is not on the instruction boundary */ - if ((unsigned long)p->addr != ftrace_addr) - return -EILSEQ; p->flags |= KPROBE_FLAG_FTRACE; #else /* !CONFIG_KPROBES_ON_FTRACE */ return -EINVAL; --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -1568,17 +1568,34 @@ unsigned long ftrace_location_range(unsi } /** - * ftrace_location - return true if the ip giving is a traced location + * ftrace_location - return the ftrace location * @ip: the instruction pointer to check * - * Returns rec->ip if @ip given is a pointer to a ftrace location. - * That is, the instruction that is either a NOP or call to - * the function tracer. It checks the ftrace internal tables to - * determine if the address belongs or not. + * If @ip matches the ftrace location, return @ip. + * If @ip matches sym+0, return sym's ftrace location. + * Otherwise, return 0. */ unsigned long ftrace_location(unsigned long ip) { - return ftrace_location_range(ip, ip); + struct dyn_ftrace *rec; + unsigned long offset; + unsigned long size; + + rec = lookup_rec(ip, ip); + if (!rec) { + if (!kallsyms_lookup_size_offset(ip, &size, &offset)) + goto out; + + /* map sym+0 to __fentry__ */ + if (!offset) + rec = lookup_rec(ip, ip + size - 1); + } + + if (rec) + return rec->ip; + +out: + return 0; } /** @@ -4962,7 +4979,8 @@ ftrace_match_addr(struct ftrace_hash *ha { struct ftrace_func_entry *entry; - if (!ftrace_location(ip)) + ip = ftrace_location(ip); + if (!ip) return -EINVAL; if (remove) { @@ -5110,11 +5128,16 @@ int register_ftrace_direct(unsigned long struct ftrace_func_entry *entry; struct ftrace_hash *free_hash = NULL; struct dyn_ftrace *rec; - int ret = -EBUSY; + int ret = -ENODEV; mutex_lock(&direct_mutex); + ip = ftrace_location(ip); + if (!ip) + goto out_unlock; + /* See if there's a direct function at @ip already */ + ret = -EBUSY; if (ftrace_find_rec_direct(ip)) goto out_unlock; @@ -5222,6 +5245,10 @@ int unregister_ftrace_direct(unsigned lo mutex_lock(&direct_mutex); + ip = ftrace_location(ip); + if (!ip) + goto out_unlock; + entry = find_direct_entry(&ip, NULL); if (!entry) goto out_unlock;