From patchwork Fri Sep 23 20:36:45 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tomislav Novak X-Patchwork-Id: 12987190 X-Patchwork-Delegate: bpf@iogearbox.net 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 CB05AC04A95 for ; Fri, 23 Sep 2022 20:44:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230421AbiIWUoj (ORCPT ); Fri, 23 Sep 2022 16:44:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45606 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232880AbiIWUnP (ORCPT ); Fri, 23 Sep 2022 16:43:15 -0400 Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com [67.231.145.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77F02E21E2 for ; Fri, 23 Sep 2022 13:37:43 -0700 (PDT) Received: from pps.filterd (m0109333.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 28NIGBkY012572 for ; Fri, 23 Sep 2022 13:37:16 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding : content-type; s=facebook; bh=uMW05ntqhTxnqydbjTlEBEZMb68OIqoNaDlQ3mavUhM=; b=PjvXvgInDOcO0zsYqAlpPNRgpxm75fc4q3PSV8XFhZR7cEr0BJWsL1nthv/Tgi9QLzJW jTwJ4dZo4J406ivdTkl012y0CFyogyKVNCLsgizDB6LM9wRn9wbA5zMUKhALn4n2PgBY 46G/U30j5sJW7+y9+DReAYOBGi+DXuewj7Y= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3jsb1nm5sw-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 23 Sep 2022 13:37:16 -0700 Received: from twshared22593.02.prn5.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::c) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Fri, 23 Sep 2022 13:37:14 -0700 Received: by devvm8797.prn0.facebook.com (Postfix, from userid 2982) id 94901B2B7691; Fri, 23 Sep 2022 13:37:02 -0700 (PDT) From: Tomislav Novak To: Alexei Starovoitov , Will Deacon , Catalin Marinas CC: , , , , Tomislav Novak , Samuel Gosselin Subject: [PATCH] hw_breakpoint: fix single-stepping when using bpf_overflow_handler Date: Fri, 23 Sep 2022 13:36:45 -0700 Message-ID: <20220923203644.2731604-1-tnovak@fb.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-ORIG-GUID: X8tLilDYzaUoOlwZsZyoBmOur0N3mdL_ X-Proofpoint-GUID: X8tLilDYzaUoOlwZsZyoBmOur0N3mdL_ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.528,FMLib:17.11.122.1 definitions=2022-09-23_09,2022-09-22_02,2022-06-22_01 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On ARM platforms is_default_overflow_handler() is used to determine if hw_breakpoint code should single-step over the watchpoint trigger or let the custom handler deal with it. Attaching a BPF program to a watchpoint replaces the handler with bpf_overflow_handler, which isn't recognized as a default handler so we never step over the instruction triggering the data abort exception (the watchpoint keeps firing): # bpftrace -e 'watchpoint:0x10000000:4:w { printf("hit\n"); }' ./wp_test Attaching 1 probe... hit hit hit [...] (wp_test performs a single 4-byte store to address 0x10000000) This patch replaces the check with uses_default_overflow_handler(), which accounts for the bpf_overflow_handler() case by also testing if the handler invokes one of the perf_event_output functions via orig_default_handler. Signed-off-by: Tomislav Novak Tested-by: Samuel Gosselin # arm64 Reviewed-by: Catalin Marinas --- arch/arm/kernel/hw_breakpoint.c | 8 ++++---- arch/arm64/kernel/hw_breakpoint.c | 4 ++-- include/linux/perf_event.h | 22 +++++++++++++++++++--- 3 files changed, 25 insertions(+), 9 deletions(-) diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c index 054e9199f30d..dc0fb7a81371 100644 --- a/arch/arm/kernel/hw_breakpoint.c +++ b/arch/arm/kernel/hw_breakpoint.c @@ -626,7 +626,7 @@ int hw_breakpoint_arch_parse(struct perf_event *bp, hw->address &= ~alignment_mask; hw->ctrl.len <<= offset; - if (is_default_overflow_handler(bp)) { + if (uses_default_overflow_handler(bp)) { /* * Mismatch breakpoints are required for single-stepping * breakpoints. @@ -798,7 +798,7 @@ static void watchpoint_handler(unsigned long addr, unsigned int fsr, * Otherwise, insert a temporary mismatch breakpoint so that * we can single-step over the watchpoint trigger. */ - if (!is_default_overflow_handler(wp)) + if (!uses_default_overflow_handler(wp)) continue; step: enable_single_step(wp, instruction_pointer(regs)); @@ -811,7 +811,7 @@ static void watchpoint_handler(unsigned long addr, unsigned int fsr, info->trigger = addr; pr_debug("watchpoint fired: address = 0x%x\n", info->trigger); perf_bp_event(wp, regs); - if (is_default_overflow_handler(wp)) + if (uses_default_overflow_handler(wp)) enable_single_step(wp, instruction_pointer(regs)); } @@ -886,7 +886,7 @@ static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs) info->trigger = addr; pr_debug("breakpoint fired: address = 0x%x\n", addr); perf_bp_event(bp, regs); - if (is_default_overflow_handler(bp)) + if (uses_default_overflow_handler(bp)) enable_single_step(bp, addr); goto unlock; } diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c index b29a311bb055..9659a9555c63 100644 --- a/arch/arm64/kernel/hw_breakpoint.c +++ b/arch/arm64/kernel/hw_breakpoint.c @@ -654,7 +654,7 @@ static int breakpoint_handler(unsigned long unused, unsigned long esr, perf_bp_event(bp, regs); /* Do we need to handle the stepping? */ - if (is_default_overflow_handler(bp)) + if (uses_default_overflow_handler(bp)) step = 1; unlock: rcu_read_unlock(); @@ -733,7 +733,7 @@ static u64 get_distance_from_watchpoint(unsigned long addr, u64 val, static int watchpoint_report(struct perf_event *wp, unsigned long addr, struct pt_regs *regs) { - int step = is_default_overflow_handler(wp); + int step = uses_default_overflow_handler(wp); struct arch_hw_breakpoint *info = counter_arch_bp(wp); info->trigger = addr; diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index ee8b9ecdc03b..f174b77437f5 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1105,15 +1105,31 @@ extern int perf_event_output(struct perf_event *event, struct pt_regs *regs); static inline bool -is_default_overflow_handler(struct perf_event *event) +__is_default_overflow_handler(perf_overflow_handler_t overflow_handler) { - if (likely(event->overflow_handler == perf_event_output_forward)) + if (likely(overflow_handler == perf_event_output_forward)) return true; - if (unlikely(event->overflow_handler == perf_event_output_backward)) + if (unlikely(overflow_handler == perf_event_output_backward)) return true; return false; } +#define is_default_overflow_handler(event) \ + __is_default_overflow_handler((event)->overflow_handler) + +#ifdef CONFIG_BPF_SYSCALL +static inline bool uses_default_overflow_handler(struct perf_event *event) +{ + if (likely(is_default_overflow_handler(event))) + return true; + + return __is_default_overflow_handler(event->orig_overflow_handler); +} +#else +#define uses_default_overflow_handler(event) \ + is_default_overflow_handler(event) +#endif + extern void perf_event_header__init_id(struct perf_event_header *header, struct perf_sample_data *data,