From patchwork Sun Sep 29 20:57:06 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiri Olsa X-Patchwork-Id: 13815228 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 5D38513C3EE; Sun, 29 Sep 2024 20:57:50 +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=1727643470; cv=none; b=bdYJ2dSJQ3/lPwvS6CA5fxqssmopeht9iD4j3iFknGg6TKnfcQued6LeYJbx5RVjp/K1OT2jCJ6bpVk9F1EAUNu1XWyF/mvcTq7jJAidSv+64f0FuYE9aGMNpo21eIISpVTbl9VAmunFIvajSVTZIzOXmi3CUjlTpsfKOrThP24= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727643470; c=relaxed/simple; bh=ubdVoXUcNMJ32NluaZK9m/9+tu736MJgye8617L0U/E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JC/ceMwfoiK3Xn4wvr2oyy62lwNK1RIfmNQihiWlu4J+0+qUbHa7sU0O6cpBJh8bwstr/ffbTXdXT+YFvEUULa5eO7+QXfrCvAey09AttAJ8ZTL7eN+q3R/SKacMS/9Dlt6fZxscP3JSiHH0niS0SQInmjxDPmtzqsPxf3FeS3U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=L57En9IH; 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="L57En9IH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 35823C4CEC5; Sun, 29 Sep 2024 20:57:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1727643470; bh=ubdVoXUcNMJ32NluaZK9m/9+tu736MJgye8617L0U/E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=L57En9IHYq/YOXo9OrvIrnVyAy8Xf0RJg2QEraitCSqMKehwy3cjycV4vgkJyD8Wi owtmHsOIslRDchFgTQ8jBHqc3aSCDhMRC3+BHGhCe5QgPCIGz5RNLWckt6ZULLWvAB KLhFjwRd9kwZwlYS8w6UAXfepBqhIdLMLKiptqoaTizy68rqNCdm60u51gdvIrQkbn CInony/Fdjn87LoaLIE/tkIZHP0dDDqC0xSFl1kbOQo4j6s9RrhNHxNRqZAoWZeR9H 71w29UVJozRq5nYRxmTLqZSbG3V5fHxh0M3ZbD1sIk3dYBF/AlFevGbXDC47pV4qMT 05BfASbXtEHqQ== From: Jiri Olsa To: Oleg Nesterov , Peter Zijlstra , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Steven Rostedt , Masami Hiramatsu , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: [PATCHv5 bpf-next 02/13] uprobe: Add support for session consumer Date: Sun, 29 Sep 2024 22:57:06 +0200 Message-ID: <20240929205717.3813648-3-jolsa@kernel.org> X-Mailer: git-send-email 2.46.1 In-Reply-To: <20240929205717.3813648-1-jolsa@kernel.org> References: <20240929205717.3813648-1-jolsa@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 This change allows the uprobe consumer to behave as session which means that 'handler' and 'ret_handler' callbacks are connected in a way that allows to: - control execution of 'ret_handler' from 'handler' callback - share data between 'handler' and 'ret_handler' callbacks The session concept fits to our common use case where we do filtering on entry uprobe and based on the result we decide to run the return uprobe (or not). It's also convenient to share the data between session callbacks. To achive this we are adding new return value the uprobe consumer can return from 'handler' callback: UPROBE_HANDLER_IGNORE - Ignore 'ret_handler' callback for this consumer. And store cookie and pass it to 'ret_handler' when consumer has both 'handler' and 'ret_handler' callbacks defined. We store shared data in the return_consumer object array as part of the return_instance object. This way the handle_uretprobe_chain can find related return_consumer and its shared data. We also store entry handler return value, for cases when there are multiple consumers on single uprobe and some of them are ignored and some of them not, in which case the return probe gets installed and we need to have a way to find out which consumer needs to be ignored. The tricky part is when consumer is registered 'after' the uprobe entry handler is hit. In such case this consumer's 'ret_handler' gets executed as well, but it won't have the proper data pointer set, so we can filter it out. Suggested-by: Oleg Nesterov Signed-off-by: Jiri Olsa Acked-by: Andrii Nakryiko --- include/linux/uprobes.h | 21 +++++- kernel/events/uprobes.c | 148 +++++++++++++++++++++++++++++++--------- 2 files changed, 137 insertions(+), 32 deletions(-) diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h index bb265a632b91..dbaf04189548 100644 --- a/include/linux/uprobes.h +++ b/include/linux/uprobes.h @@ -23,8 +23,17 @@ struct inode; struct notifier_block; struct page; +/* + * Allowed return values from uprobe consumer's handler callback + * with following meaning: + * + * UPROBE_HANDLER_REMOVE + * - Remove the uprobe breakpoint from current->mm. + * UPROBE_HANDLER_IGNORE + * - Ignore ret_handler callback for this consumer. + */ #define UPROBE_HANDLER_REMOVE 1 -#define UPROBE_HANDLER_MASK 1 +#define UPROBE_HANDLER_IGNORE 2 #define MAX_URETPROBE_DEPTH 64 @@ -44,6 +53,8 @@ struct uprobe_consumer { bool (*filter)(struct uprobe_consumer *self, struct mm_struct *mm); struct list_head cons_node; + + __u64 id; /* set when uprobe_consumer is registered */ }; #ifdef CONFIG_UPROBES @@ -83,14 +94,22 @@ struct uprobe_task { unsigned int depth; }; +struct return_consumer { + __u64 cookie; + __u64 id; +}; + struct return_instance { struct uprobe *uprobe; unsigned long func; unsigned long stack; /* stack pointer */ unsigned long orig_ret_vaddr; /* original return address */ bool chained; /* true, if instance is nested */ + int consumers_cnt; struct return_instance *next; /* keep as stack */ + + struct return_consumer consumers[] __counted_by(consumers_cnt); }; enum rp_check { diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 2ba93f8a31aa..76fe535c9b3c 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -65,7 +65,7 @@ struct uprobe { struct rcu_head rcu; loff_t offset; loff_t ref_ctr_offset; - unsigned long flags; + unsigned long flags; /* "unsigned long" so bitops work */ /* * The generic code assumes that it has two members of unknown type @@ -825,8 +825,11 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset, static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc) { + static atomic64_t id; + down_write(&uprobe->consumer_rwsem); list_add_rcu(&uc->cons_node, &uprobe->consumers); + uc->id = (__u64) atomic64_inc_return(&id); up_write(&uprobe->consumer_rwsem); } @@ -1797,6 +1800,34 @@ static struct uprobe_task *get_utask(void) return current->utask; } +static size_t ri_size(int consumers_cnt) +{ + struct return_instance *ri; + + return sizeof(*ri) + sizeof(ri->consumers[0]) * consumers_cnt; +} + +#define DEF_CNT 4 + +static struct return_instance *alloc_return_instance(void) +{ + struct return_instance *ri; + + ri = kzalloc(ri_size(DEF_CNT), GFP_KERNEL); + if (!ri) + return ZERO_SIZE_PTR; + + ri->consumers_cnt = DEF_CNT; + return ri; +} + +static struct return_instance *dup_return_instance(struct return_instance *old) +{ + size_t size = ri_size(old->consumers_cnt); + + return kmemdup(old, size, GFP_KERNEL); +} + static int dup_utask(struct task_struct *t, struct uprobe_task *o_utask) { struct uprobe_task *n_utask; @@ -1809,11 +1840,10 @@ static int dup_utask(struct task_struct *t, struct uprobe_task *o_utask) p = &n_utask->return_instances; for (o = o_utask->return_instances; o; o = o->next) { - n = kmalloc(sizeof(struct return_instance), GFP_KERNEL); + n = dup_return_instance(o); if (!n) return -ENOMEM; - *n = *o; /* * uprobe's refcnt has to be positive at this point, kept by * utask->return_instances items; return_instances can't be @@ -1906,39 +1936,35 @@ static void cleanup_return_instances(struct uprobe_task *utask, bool chained, utask->return_instances = ri; } -static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs) +static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs, + struct return_instance *ri) { - struct return_instance *ri; struct uprobe_task *utask; unsigned long orig_ret_vaddr, trampoline_vaddr; bool chained; if (!get_xol_area()) - return; + goto free; utask = get_utask(); if (!utask) - return; + goto free; if (utask->depth >= MAX_URETPROBE_DEPTH) { printk_ratelimited(KERN_INFO "uprobe: omit uretprobe due to" " nestedness limit pid/tgid=%d/%d\n", current->pid, current->tgid); - return; + goto free; } /* we need to bump refcount to store uprobe in utask */ if (!try_get_uprobe(uprobe)) - return; - - ri = kmalloc(sizeof(struct return_instance), GFP_KERNEL); - if (!ri) - goto fail; + goto free; trampoline_vaddr = uprobe_get_trampoline_vaddr(); orig_ret_vaddr = arch_uretprobe_hijack_return_addr(trampoline_vaddr, regs); if (orig_ret_vaddr == -1) - goto fail; + goto put; /* drop the entries invalidated by longjmp() */ chained = (orig_ret_vaddr == trampoline_vaddr); @@ -1956,7 +1982,7 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs) * attack from user-space. */ uprobe_warn(current, "handle tail call"); - goto fail; + goto put; } orig_ret_vaddr = utask->return_instances->orig_ret_vaddr; } @@ -1971,9 +1997,10 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs) utask->return_instances = ri; return; -fail: - kfree(ri); +put: put_uprobe(uprobe); +free: + kfree(ri); } /* Prepare to single-step probed instruction out of line. */ @@ -2125,35 +2152,91 @@ static struct uprobe *find_active_uprobe_rcu(unsigned long bp_vaddr, int *is_swb return uprobe; } +static struct return_instance* +push_consumer(struct return_instance *ri, int idx, __u64 id, __u64 cookie) +{ + if (unlikely(ri == ZERO_SIZE_PTR)) + return ri; + + if (unlikely(idx >= ri->consumers_cnt)) { + struct return_instance *old_ri = ri; + + ri->consumers_cnt += DEF_CNT; + ri = krealloc(old_ri, ri_size(old_ri->consumers_cnt), GFP_KERNEL); + if (!ri) { + kfree(old_ri); + return ZERO_SIZE_PTR; + } + } + + ri->consumers[idx].id = id; + ri->consumers[idx].cookie = cookie; + return ri; +} + +static struct return_consumer * +return_consumer_find(struct return_instance *ri, int *iter, int id) +{ + struct return_consumer *ric; + int idx = *iter; + + for (ric = &ri->consumers[idx]; idx < ri->consumers_cnt; idx++, ric++) { + if (ric->id == id) { + *iter = idx + 1; + return ric; + } + } + return NULL; +} + +static bool ignore_ret_handler(int rc) +{ + return rc == UPROBE_HANDLER_REMOVE || rc == UPROBE_HANDLER_IGNORE; +} + static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs) { struct uprobe_consumer *uc; - int remove = UPROBE_HANDLER_REMOVE; - bool need_prep = false; /* prepare return uprobe, when needed */ - bool has_consumers = false; + bool has_consumers = false, remove = true; + struct return_instance *ri = NULL; + int push_idx = 0; current->utask->auprobe = &uprobe->arch; list_for_each_entry_srcu(uc, &uprobe->consumers, cons_node, srcu_read_lock_held(&uprobes_srcu)) { + bool session = uc->handler && uc->ret_handler; + __u64 cookie = 0; int rc = 0; if (uc->handler) { - rc = uc->handler(uc, regs, NULL); - WARN(rc & ~UPROBE_HANDLER_MASK, + rc = uc->handler(uc, regs, &cookie); + WARN(rc < 0 || rc > 2, "bad rc=0x%x from %ps()\n", rc, uc->handler); } - if (uc->ret_handler) - need_prep = true; - - remove &= rc; + remove &= rc == UPROBE_HANDLER_REMOVE; has_consumers = true; + + if (!uc->ret_handler || ignore_ret_handler(rc)) + continue; + + if (!ri) + ri = alloc_return_instance(); + + if (session) + ri = push_consumer(ri, push_idx++, uc->id, cookie); } current->utask->auprobe = NULL; - if (need_prep && !remove) - prepare_uretprobe(uprobe, regs); /* put bp at return */ + if (!ZERO_OR_NULL_PTR(ri)) { + /* + * The push_idx value has the final number of return consumers, + * and ri->consumers_cnt has number of allocated consumers. + */ + ri->consumers_cnt = push_idx; + prepare_uretprobe(uprobe, regs, ri); + } if (remove && has_consumers) { down_read(&uprobe->register_rwsem); @@ -2172,14 +2255,17 @@ static void handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs) { struct uprobe *uprobe = ri->uprobe; + struct return_consumer *ric; struct uprobe_consumer *uc; - int srcu_idx; + int srcu_idx, ric_idx = 0; srcu_idx = srcu_read_lock(&uprobes_srcu); list_for_each_entry_srcu(uc, &uprobe->consumers, cons_node, srcu_read_lock_held(&uprobes_srcu)) { - if (uc->ret_handler) - uc->ret_handler(uc, ri->func, regs, NULL); + if (uc->ret_handler) { + ric = return_consumer_find(ri, &ric_idx, uc->id); + uc->ret_handler(uc, ri->func, regs, ric ? &ric->cookie : NULL); + } } srcu_read_unlock(&uprobes_srcu, srcu_idx); }