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 X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0252BC2B9F7 for ; Wed, 26 May 2021 08:07:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF3D1613E1 for ; Wed, 26 May 2021 08:07:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232473AbhEZIJS (ORCPT ); Wed, 26 May 2021 04:09:18 -0400 Received: from outbound-smtp15.blacknight.com ([46.22.139.232]:38163 "EHLO outbound-smtp15.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229594AbhEZIJR (ORCPT ); Wed, 26 May 2021 04:09:17 -0400 Received: from mail.blacknight.com (pemlinmail03.blacknight.ie [81.17.254.16]) by outbound-smtp15.blacknight.com (Postfix) with ESMTPS id 4A7B41C3FDB for ; Wed, 26 May 2021 09:07:45 +0100 (IST) Received: (qmail 9993 invoked from network); 26 May 2021 08:07:45 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.23.168]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 26 May 2021 08:07:45 -0000 Date: Wed, 26 May 2021 09:07:41 +0100 From: Mel Gorman To: Andrew Morton Cc: Andrii Nakryiko , Michal Suchanek , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , open list , Arnaldo Carvalho de Melo , Jiri Olsa , Hritik Vijay , bpf , Linux-Net , Linux-MM Subject: [PATCH] mm/page_alloc: Work around a pahole limitation with zero-sized struct pagesets Message-ID: <20210526080741.GW30378@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Michal Suchanek reported the following problem with linux-next [ 0.000000] Linux version 5.13.0-rc2-next-20210519-1.g3455ff8-vanilla (geeko@buildhost) (gcc (SUSE Linux) 10.3.0, GNU ld (GNU Binutils; openSUSE Tumbleweed) 2.36.1.20210326-3) #1 SMP Wed May 19 10:05:10 UTC 2021 (3455ff8) [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.13.0-rc2-next-20210519-1.g3455ff8-vanilla root=UUID=ec42c33e-a2c2-4c61-afcc-93e9527 8f687 plymouth.enable=0 resume=/dev/disk/by-uuid/f1fe4560-a801-4faf-a638-834c407027c7 mitigations=auto earlyprintk initcall_debug nomodeset earlycon ignore_loglevel console=ttyS0,115200 ... [ 26.093364] calling tracing_set_default_clock+0x0/0x62 @ 1 [ 26.098937] initcall tracing_set_default_clock+0x0/0x62 returned 0 after 0 usecs [ 26.106330] calling acpi_gpio_handle_deferred_request_irqs+0x0/0x7c @ 1 [ 26.113033] initcall acpi_gpio_handle_deferred_request_irqs+0x0/0x7c returned 0 after 3 usecs [ 26.121559] calling clk_disable_unused+0x0/0x102 @ 1 [ 26.126620] initcall clk_disable_unused+0x0/0x102 returned 0 after 0 usecs [ 26.133491] calling regulator_init_complete+0x0/0x25 @ 1 [ 26.138890] initcall regulator_init_complete+0x0/0x25 returned 0 after 0 usecs [ 26.147816] Freeing unused decrypted memory: 2036K [ 26.153682] Freeing unused kernel image (initmem) memory: 2308K [ 26.165776] Write protecting the kernel read-only data: 26624k [ 26.173067] Freeing unused kernel image (text/rodata gap) memory: 2036K [ 26.180416] Freeing unused kernel image (rodata/data gap) memory: 1184K [ 26.187031] Run /init as init process [ 26.190693] with arguments: [ 26.193661] /init [ 26.195933] with environment: [ 26.199079] HOME=/ [ 26.201444] TERM=linux [ 26.204152] BOOT_IMAGE=/boot/vmlinuz-5.13.0-rc2-next-20210519-1.g3455ff8-vanilla [ 26.254154] BPF: type_id=35503 offset=178440 size=4 [ 26.259125] BPF: [ 26.261054] BPF:Invalid offset [ 26.264119] BPF: [ 26.264119] [ 26.267437] failed to validate module [efivarfs] BTF: -22 Andrii Nakryiko bisected the problem to the commit "mm/page_alloc: convert per-cpu list protection to local_lock" currently staged in mmotm. In his own words The immediate problem is two different definitions of numa_node per-cpu variable. They both are at the same offset within .data..percpu ELF section, they both have the same name, but one of them is marked as static and another as global. And one is int variable, while another is struct pagesets. I'll look some more tomorrow, but adding Jiri and Arnaldo for visibility. [110907] DATASEC '.data..percpu' size=178904 vlen=303 ... type_id=27753 offset=163976 size=4 (VAR 'numa_node') type_id=27754 offset=163976 size=4 (VAR 'numa_node') [27753] VAR 'numa_node' type_id=27556, linkage=static [27754] VAR 'numa_node' type_id=20, linkage=global [20] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED [27556] STRUCT 'pagesets' size=0 vlen=1 'lock' type_id=507 bits_offset=0 [506] STRUCT '(anon)' size=0 vlen=0 [507] TYPEDEF 'local_lock_t' type_id=506 The patch in question introduces a zero-sized per-cpu struct and while this is not wrong, versions of pahole prior to 1.22 (unreleased) get confused during BTF generation with two separate variables occupying the same address. This patch checks for older versions of pahole and forces struct pagesets to be non-zero sized as a workaround when CONFIG_DEBUG_INFO_BTF is set. A warning is omitted so that distributions can update pahole when 1.22 is released. Reported-by: Michal Suchanek Reported-by: Hritik Vijay Debugged-by: Andrii Nakryiko Signed-off-by: Mel Gorman --- lib/Kconfig.debug | 3 +++ mm/page_alloc.c | 11 +++++++++++ 2 files changed, 14 insertions(+) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 678c13967580..f88a155b80a9 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -313,6 +313,9 @@ config DEBUG_INFO_BTF config PAHOLE_HAS_SPLIT_BTF def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "119") +config PAHOLE_HAS_ZEROSIZE_PERCPU_SUPPORT + def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "122") + config DEBUG_INFO_BTF_MODULES def_bool y depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ff8f706839ea..1d56d3de8e08 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -124,6 +124,17 @@ static DEFINE_MUTEX(pcp_batch_high_lock); struct pagesets { local_lock_t lock; +#if defined(CONFIG_DEBUG_INFO_BTF) && \ + !defined(CONFIG_DEBUG_LOCK_ALLOC) && \ + !defined(CONFIG_PAHOLE_HAS_ZEROSIZE_PERCPU_SUPPORT) + /* + * pahole 1.21 and earlier gets confused by zero-sized per-CPU + * variables and produces invalid BTF. Ensure that + * sizeof(struct pagesets) != 0 for older versions of pahole. + */ + char __pahole_hack; + #warning "pahole too old to support zero-sized struct pagesets" +#endif }; static DEFINE_PER_CPU(struct pagesets, pagesets) = { .lock = INIT_LOCAL_LOCK(lock),