From nobody Sun Oct 5 03:36:01 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass(p=quarantine dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1754911640; cv=none; d=zohomail.com; s=zohoarc; b=H8JdViXpdzyvSPraT6ugZYEXlzNRGyduKDQjSAcMUbCDb+rFIKSsu2jcSO4A0No5om+mZGiu39xG8Mviq+w0PY0J5yp/sfoFZR/8DkBX2cPMB9k4Vuqycw21SdMOj4KaoOKRuOrLEk5oKZQvDFcMZ82eI5bxxY/RoyJQJv88Eww= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1754911640; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=cAxz8wtEYwnzSbLFT0UZ22FzefKNNzcleMeX5Ma3lWM=; b=KeJ75cFWPlh0vhQbCTSE9sg+4HEkdGYUPiS7MZF2KHvZYuuqq2CA1Hzo46W4pNIi7kV1gBB3Z+UxjQx2ODwqzaV48neXJ6jgD/gO5o0cdjxehCkJe1cC1Cc6+Ce7Tper0iwHPE8ALJGzlyg5zZ6iZAz2mWHZ1kdXXsctwjoGmyc= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass header.from= (p=quarantine dis=none) Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1754911640732988.5614177595929; Mon, 11 Aug 2025 04:27:20 -0700 (PDT) Received: from list by lists.xenproject.org with outflank-mailman.1077389.1438512 (Exim 4.92) (envelope-from ) id 1ulQg9-000883-D9; Mon, 11 Aug 2025 11:27:01 +0000 Received: by outflank-mailman (output) from mailman id 1077389.1438512; Mon, 11 Aug 2025 11:27:01 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ulQg9-00087F-8d; Mon, 11 Aug 2025 11:27:01 +0000 Received: by outflank-mailman (input) for mailman id 1077389; Mon, 11 Aug 2025 11:26:59 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ulQg7-0005jI-PO for xen-devel@lists.xenproject.org; Mon, 11 Aug 2025 11:26:59 +0000 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 17885278-76a6-11f0-a325-13f23c93f187; Mon, 11 Aug 2025 13:26:59 +0200 (CEST) Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-617-NsEbjSgrMgSL9TmYbqp4vQ-1; Mon, 11 Aug 2025 07:26:56 -0400 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-451d30992bcso40949665e9.2 for ; Mon, 11 Aug 2025 04:26:56 -0700 (PDT) Received: from localhost (p200300d82f06a600a397de1d2f8bb66f.dip0.t-ipconnect.de. [2003:d8:2f06:a600:a397:de1d:2f8b:b66f]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3b79c4530b3sm41080102f8f.34.2025.08.11.04.26.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 Aug 2025 04:26:54 -0700 (PDT) X-Outflank-Mailman: Message body and most headers restored to incoming version X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 17885278-76a6-11f0-a325-13f23c93f187 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754911617; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=cAxz8wtEYwnzSbLFT0UZ22FzefKNNzcleMeX5Ma3lWM=; b=iR1WrxDNbGUaAIjQeyLPXO0TEnwD5+xxqMDcuc7O+LhPclkuMwNCMJUr5DLu23HcfKk6+I T3N36B3f73fwPbaQWASTnvAhDwAMOdzgJu/TgvtBLhKjmGILGXnjlfj/WWT2oDt8Y/xj0H iwyCyXPSyo+hJpjJx/NaB3J2xXRESoE= X-MC-Unique: NsEbjSgrMgSL9TmYbqp4vQ-1 X-Mimecast-MFC-AGG-ID: NsEbjSgrMgSL9TmYbqp4vQ_1754911615 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1754911615; x=1755516415; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=cAxz8wtEYwnzSbLFT0UZ22FzefKNNzcleMeX5Ma3lWM=; b=Uz+9jiyJ4Qi1/qP3l8fRQdY7aOZ7AmcLDCIJU8SjYwJowFGrBV6B0r9Nn2s1uTDu7j 4WcQgi7nXbVLECgbm1MyAGKik806ufuWbbSbXvu7vDYTXAfRklkm+cccMeXi7RzyPtfj odx1rZqcfDLPDHIwEFSjdmLrr+/PLCLino2qJukcEr9UbANbYt0mghy/2Cw8qeE/Ht2I obqgmBh1Z2/89IkG7+vTCdlb0hDTXLqZ3JSi8u97KEd7h+kIaTJJhaH2+nRFQicCqaVN yh2OpmeRdHoo5Xla3CJQKOrjDUyb0HlyCOSJfiGWOUfSBKbg1voZs1+OWfiAFM8FwHjw gP7g== X-Forwarded-Encrypted: i=1; AJvYcCWAevMYpY4Sda8k1BzIZj6XAZexcnAHIc7zwYak9O3K+3DogjUhwDZEVXW3uoW9V+5nvqlB9vkm940=@lists.xenproject.org X-Gm-Message-State: AOJu0YwH5wg25iFZ7rT40qoC7ppFsU8UmqroZtZLDvcvJRfc6g4T7eRq UXzauvH/3IpLfm+7oQFBhoNsfgmG1rJKxt5Nkv7RmbANKVfz5n2SfZqjKWmwUdttnjlrlSzsyOa 8y5mQdlrwf2saugDCL0ry5W/tBhDks1AhhAnbCYFq/f3DDyIds0/m7AUfqeoiP1ZNLpZ+ X-Gm-Gg: ASbGncuU4OugYHl6+x9pr04Xw4dFaCpJ2yjoevIk7oEn1e3QUa0BFC714X1yPknegal 0mLtOR96GW4cpIiczmUWfeAwI2HiquceN6dguhcDwh+BWjfSy0DOQc+5HNpLB6++MiuS+E7Kk/C G4ubxc6YlnURlnAqBc/mNXcW4vF6mZwq/0FUEzET4gYu14+MEV2NFJJ2bWpS8tgXZKV7dVnK74g PoKmgSQSvodCpV2lREFizxMNNLj2YHAW4gwpn+ICYjWmjcI5pQT9sK7IAk6fvgHUwg3nS/s8tU+ 4jxYb2NG1BF8MWtAZibSYK033obeZtlHq6PoddpYG56b3wdS0vH+YCiVImlwB7ekc6oirD6PU+Q Sp2pmVcMbDT1VRcWK2+0852g1 X-Received: by 2002:a05:600c:350f:b0:456:1560:7c63 with SMTP id 5b1f17b1804b1-459f4f3dde5mr124071065e9.3.1754911615200; Mon, 11 Aug 2025 04:26:55 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHKs8kYesKmGWPRfo05vS75I0Yn/yE7Pq2L/J4XRbC28zXbi7Rocgkv1+OCyQd3aXR+1J2h1Q== X-Received: by 2002:a05:600c:350f:b0:456:1560:7c63 with SMTP id 5b1f17b1804b1-459f4f3dde5mr124070425e9.3.1754911614678; Mon, 11 Aug 2025 04:26:54 -0700 (PDT) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, xen-devel@lists.xenproject.org, linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, David Hildenbrand , Andrew Morton , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Dan Williams , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Jann Horn , Pedro Falcato , Hugh Dickins , Oscar Salvador , Lance Yang Subject: [PATCH v3 08/11] mm/memory: convert print_bad_pte() to print_bad_page_map() Date: Mon, 11 Aug 2025 13:26:28 +0200 Message-ID: <20250811112631.759341-9-david@redhat.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250811112631.759341-1-david@redhat.com> References: <20250811112631.759341-1-david@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 1v7BmQgpxPNvKRzGkXypQ5jUwCR6YCDHTDRpB1rcqzI_1754911615 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1754911643988116600 Content-Type: text/plain; charset="utf-8"; x-default="true" print_bad_pte() looks like something that should actually be a WARN or similar, but historically it apparently has proven to be useful to detect corruption of page tables even on production systems -- report the issue and keep the system running to make it easier to actually detect what is going wrong (e.g., multiple such messages might shed a light). As we want to unify vm_normal_page_*() handling for PTE/PMD/PUD, we'll have to take care of print_bad_pte() as well. Let's prepare for using print_bad_pte() also for non-PTEs by adjusting the implementation and renaming the function to print_bad_page_map(). Provide print_bad_pte() as a simple wrapper. Document the implicit locking requirements for the page table re-walk. To make the function a bit more readable, factor out the ratelimit check into is_bad_page_map_ratelimited() and place the printing of page table content into __print_bad_page_map_pgtable(). We'll now dump information from each level in a single line, and just stop the table walk once we hit something that is not a present page table. The report will now look something like (dumping pgd to pmd values): [ 77.943408] BUG: Bad page map in process XXX pte:80000001233f5867 [ 77.944077] addr:00007fd84bb1c000 vm_flags:08100071 anon_vma: ... [ 77.945186] pgd:10a89f067 p4d:10a89f067 pud:10e5a2067 pmd:105327067 Not using pgdp_get(), because that does not work properly on some arm configs where pgd_t is an array. Note that we are dumping all levels even when levels are folded for simplicity. Signed-off-by: David Hildenbrand Reviewed-by: Lorenzo Stoakes --- include/linux/pgtable.h | 19 ++++++++ mm/memory.c | 104 ++++++++++++++++++++++++++++++++-------- 2 files changed, 103 insertions(+), 20 deletions(-) diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index bff5c4241bf2e..33c84b38b7ec6 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -1966,6 +1966,25 @@ enum pgtable_level { PGTABLE_LEVEL_PGD, }; =20 +static inline const char *pgtable_level_to_str(enum pgtable_level level) +{ + switch (level) { + case PGTABLE_LEVEL_PTE: + return "pte"; + case PGTABLE_LEVEL_PMD: + return "pmd"; + case PGTABLE_LEVEL_PUD: + return "pud"; + case PGTABLE_LEVEL_P4D: + return "p4d"; + case PGTABLE_LEVEL_PGD: + return "pgd"; + default: + VM_WARN_ON_ONCE(1); + return "unknown"; + } +} + #endif /* !__ASSEMBLY__ */ =20 #if !defined(MAX_POSSIBLE_PHYSMEM_BITS) && !defined(CONFIG_64BIT) diff --git a/mm/memory.c b/mm/memory.c index 626caedce35e0..dc0107354d37b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -491,22 +491,8 @@ static inline void add_mm_rss_vec(struct mm_struct *mm= , int *rss) add_mm_counter(mm, i, rss[i]); } =20 -/* - * This function is called to print an error when a bad pte - * is found. For example, we might have a PFN-mapped pte in - * a region that doesn't allow it. - * - * The calling function must still handle the error. - */ -static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr, - pte_t pte, struct page *page) +static bool is_bad_page_map_ratelimited(void) { - pgd_t *pgd =3D pgd_offset(vma->vm_mm, addr); - p4d_t *p4d =3D p4d_offset(pgd, addr); - pud_t *pud =3D pud_offset(p4d, addr); - pmd_t *pmd =3D pmd_offset(pud, addr); - struct address_space *mapping; - pgoff_t index; static unsigned long resume; static unsigned long nr_shown; static unsigned long nr_unshown; @@ -518,7 +504,7 @@ static void print_bad_pte(struct vm_area_struct *vma, u= nsigned long addr, if (nr_shown =3D=3D 60) { if (time_before(jiffies, resume)) { nr_unshown++; - return; + return true; } if (nr_unshown) { pr_alert("BUG: Bad page map: %lu messages suppressed\n", @@ -529,15 +515,91 @@ static void print_bad_pte(struct vm_area_struct *vma,= unsigned long addr, } if (nr_shown++ =3D=3D 0) resume =3D jiffies + 60 * HZ; + return false; +} + +static void __print_bad_page_map_pgtable(struct mm_struct *mm, unsigned lo= ng addr) +{ + unsigned long long pgdv, p4dv, pudv, pmdv; + p4d_t p4d, *p4dp; + pud_t pud, *pudp; + pmd_t pmd, *pmdp; + pgd_t *pgdp; + + /* + * Although this looks like a fully lockless pgtable walk, it is not: + * see locking requirements for print_bad_page_map(). + */ + pgdp =3D pgd_offset(mm, addr); + pgdv =3D pgd_val(*pgdp); + + if (!pgd_present(*pgdp) || pgd_leaf(*pgdp)) { + pr_alert("pgd:%08llx\n", pgdv); + return; + } + + p4dp =3D p4d_offset(pgdp, addr); + p4d =3D p4dp_get(p4dp); + p4dv =3D p4d_val(p4d); + + if (!p4d_present(p4d) || p4d_leaf(p4d)) { + pr_alert("pgd:%08llx p4d:%08llx\n", pgdv, p4dv); + return; + } + + pudp =3D pud_offset(p4dp, addr); + pud =3D pudp_get(pudp); + pudv =3D pud_val(pud); + + if (!pud_present(pud) || pud_leaf(pud)) { + pr_alert("pgd:%08llx p4d:%08llx pud:%08llx\n", pgdv, p4dv, pudv); + return; + } + + pmdp =3D pmd_offset(pudp, addr); + pmd =3D pmdp_get(pmdp); + pmdv =3D pmd_val(pmd); + + /* + * Dumping the PTE would be nice, but it's tricky with CONFIG_HIGHPTE, + * because the table should already be mapped by the caller and + * doing another map would be bad. print_bad_page_map() should + * already take care of printing the PTE. + */ + pr_alert("pgd:%08llx p4d:%08llx pud:%08llx pmd:%08llx\n", pgdv, + p4dv, pudv, pmdv); +} + +/* + * This function is called to print an error when a bad page table entry (= e.g., + * corrupted page table entry) is found. For example, we might have a + * PFN-mapped pte in a region that doesn't allow it. + * + * The calling function must still handle the error. + * + * This function must be called during a proper page table walk, as it will + * re-walk the page table to dump information: the caller MUST prevent page + * table teardown (by holding mmap, vma or rmap lock) and MUST hold the le= af + * page table lock. + */ +static void print_bad_page_map(struct vm_area_struct *vma, + unsigned long addr, unsigned long long entry, struct page *page, + enum pgtable_level level) +{ + struct address_space *mapping; + pgoff_t index; + + if (is_bad_page_map_ratelimited()) + return; =20 mapping =3D vma->vm_file ? vma->vm_file->f_mapping : NULL; index =3D linear_page_index(vma, addr); =20 - pr_alert("BUG: Bad page map in process %s pte:%08llx pmd:%08llx\n", - current->comm, - (long long)pte_val(pte), (long long)pmd_val(*pmd)); + pr_alert("BUG: Bad page map in process %s %s:%08llx", current->comm, + pgtable_level_to_str(level), entry); + __print_bad_page_map_pgtable(vma->vm_mm, addr); if (page) - dump_page(page, "bad pte"); + dump_page(page, "bad page map"); pr_alert("addr:%px vm_flags:%08lx anon_vma:%px mapping:%px index:%lx\n", (void *)addr, vma->vm_flags, vma->anon_vma, mapping, index); pr_alert("file:%pD fault:%ps mmap:%ps mmap_prepare: %ps read_folio:%ps\n", @@ -549,6 +611,8 @@ static void print_bad_pte(struct vm_area_struct *vma, u= nsigned long addr, dump_stack(); add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); } +#define print_bad_pte(vma, addr, pte, page) \ + print_bad_page_map(vma, addr, pte_val(pte), page, PGTABLE_LEVEL_PTE) =20 /* * vm_normal_page -- This function gets the "struct page" associated with = a pte. --=20 2.50.1