From patchwork Wed Jan 8 14:57:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Price X-Patchwork-Id: 11323833 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 678181871 for ; Wed, 8 Jan 2020 14:57:21 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 39F29206F0 for ; Wed, 8 Jan 2020 14:57:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 39F29206F0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 36C098E0005; Wed, 8 Jan 2020 09:57:20 -0500 (EST) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 31C5E8E0001; Wed, 8 Jan 2020 09:57:20 -0500 (EST) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 234288E0005; Wed, 8 Jan 2020 09:57:20 -0500 (EST) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0004.hostedemail.com [216.40.44.4]) by kanga.kvack.org (Postfix) with ESMTP id 0AE218E0001 for ; Wed, 8 Jan 2020 09:57:20 -0500 (EST) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id A46D0181AC9CC for ; Wed, 8 Jan 2020 14:57:19 +0000 (UTC) X-FDA: 76354770198.19.bird24_3fe1730cb1444 X-Spam-Summary: 2,0,0,c71dc9ba0edcf786,d41d8cd98f00b204,steven.price@arm.com,:akpm@linux-foundation.org:x86@kernel.org:sfr@canb.auug.org.au:linux-next@vger.kernel.org:linux-kernel@vger.kernel.org::linux-arm-kernel@lists.infradead.org:steven.price@arm.com,RULES_HIT:2:41:69:355:379:541:800:960:973:988:989:1260:1261:1311:1314:1345:1359:1437:1515:1535:1605:1730:1747:1777:1792:1801:2393:2553:2559:2562:2693:2730:3138:3139:3140:3141:3142:3865:3866:3867:3868:3870:3871:3872:3874:4050:4120:4321:4605:5007:6119:6261:7875:7903:8603:8634:8660:9592:10004:11026:11473:11658:11914:12043:12296:12297:12438:12517:12519:12555:12895:12986:13148:13230:13894:14096:14394:21080:21451:21627:21795:21796:21990:30036:30051:30054:30056:30060:30070:30075:30090,0,RBL:217.140.110.172:@arm.com:.lbl8.mailshell.net-62.2.0.100 64.100.201.201,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:28,LUA_SUMMARY:none X-HE-Tag: bird24_3fe1730cb1444 X-Filterd-Recvd-Size: 9219 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf27.hostedemail.com (Postfix) with ESMTP for ; Wed, 8 Jan 2020 14:57:18 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 08D7531B; Wed, 8 Jan 2020 06:57:18 -0800 (PST) Received: from e112269-lin.cambridge.arm.com (e112269-lin.cambridge.arm.com [10.1.194.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E1BE13F703; Wed, 8 Jan 2020 06:57:16 -0800 (PST) From: Steven Price To: Andrew Morton , x86@kernel.org Cc: Stephen Rothwell , Linux Next Mailing List , Linux Kernel Mailing List , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, Steven Price Subject: [PATCH] x86: mm: Avoid allocating struct mm_struct on the stack Date: Wed, 8 Jan 2020 14:57:10 +0000 Message-Id: <20200108145710.34314-1-steven.price@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200108145248.GA2584@arm.com> References: <20200108145248.GA2584@arm.com> MIME-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: struct mm_struct is quite large (~1664 bytes) and so allocating on the stack may cause problems as the kernel stack size is small. Since ptdump_walk_pgd_level_core() was only allocating the structure so that it could modify the pgd argument we can instead introduce a pgd override in struct mm_walk and pass this down the call stack to where it is needed. Since the correct mm_struct is now being passed down, it is now also unnecessary to take the mmap_sem semaphore because ptdump_walk_pgd() will now take the semaphore on the real mm. Signed-off-by: Steven Price --- arch/arm64/mm/dump.c | 4 ++-- arch/x86/mm/debug_pagetables.c | 10 ++-------- arch/x86/mm/dump_pagetables.c | 18 +++++++----------- include/linux/pagewalk.h | 3 +++ include/linux/ptdump.h | 2 +- mm/pagewalk.c | 7 ++++++- mm/ptdump.c | 4 ++-- 7 files changed, 23 insertions(+), 25 deletions(-) diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c index ef4b3ca1e058..860c00ec8bd3 100644 --- a/arch/arm64/mm/dump.c +++ b/arch/arm64/mm/dump.c @@ -323,7 +323,7 @@ void ptdump_walk(struct seq_file *s, struct ptdump_info *info) } }; - ptdump_walk_pgd(&st.ptdump, info->mm); + ptdump_walk_pgd(&st.ptdump, info->mm, NULL); } static void ptdump_initialize(void) @@ -361,7 +361,7 @@ void ptdump_check_wx(void) } }; - ptdump_walk_pgd(&st.ptdump, &init_mm); + ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); if (st.wx_pages || st.uxn_pages) pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found, %lu non-UXN pages found\n", diff --git a/arch/x86/mm/debug_pagetables.c b/arch/x86/mm/debug_pagetables.c index d0efec713c6c..4a3b62f780b4 100644 --- a/arch/x86/mm/debug_pagetables.c +++ b/arch/x86/mm/debug_pagetables.c @@ -15,11 +15,8 @@ DEFINE_SHOW_ATTRIBUTE(ptdump); static int ptdump_curknl_show(struct seq_file *m, void *v) { - if (current->mm->pgd) { - down_read(¤t->mm->mmap_sem); + if (current->mm->pgd) ptdump_walk_pgd_level_debugfs(m, current->mm, false); - up_read(¤t->mm->mmap_sem); - } return 0; } @@ -28,11 +25,8 @@ DEFINE_SHOW_ATTRIBUTE(ptdump_curknl); #ifdef CONFIG_PAGE_TABLE_ISOLATION static int ptdump_curusr_show(struct seq_file *m, void *v) { - if (current->mm->pgd) { - down_read(¤t->mm->mmap_sem); + if (current->mm->pgd) ptdump_walk_pgd_level_debugfs(m, current->mm, true); - up_read(¤t->mm->mmap_sem); - } return 0; } diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c index 411f6a758998..64229dad7eab 100644 --- a/arch/x86/mm/dump_pagetables.c +++ b/arch/x86/mm/dump_pagetables.c @@ -357,7 +357,8 @@ static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, } } -static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd, +static void ptdump_walk_pgd_level_core(struct seq_file *m, + struct mm_struct *mm, pgd_t *pgd, bool checkwx, bool dmesg) { const struct ptdump_range ptdump_ranges[] = { @@ -386,12 +387,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd, .seq = m }; - struct mm_struct fake_mm = { - .pgd = pgd - }; - init_rwsem(&fake_mm.mmap_sem); - - ptdump_walk_pgd(&st.ptdump, &fake_mm); + ptdump_walk_pgd(&st.ptdump, mm, pgd); if (!checkwx) return; @@ -404,7 +400,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd, void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm) { - ptdump_walk_pgd_level_core(m, mm->pgd, false, true); + ptdump_walk_pgd_level_core(m, mm, mm->pgd, false, true); } void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm, @@ -415,7 +411,7 @@ void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm, if (user && boot_cpu_has(X86_FEATURE_PTI)) pgd = kernel_to_user_pgdp(pgd); #endif - ptdump_walk_pgd_level_core(m, pgd, false, false); + ptdump_walk_pgd_level_core(m, mm, pgd, false, false); } EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level_debugfs); @@ -430,13 +426,13 @@ void ptdump_walk_user_pgd_level_checkwx(void) pr_info("x86/mm: Checking user space page tables\n"); pgd = kernel_to_user_pgdp(pgd); - ptdump_walk_pgd_level_core(NULL, pgd, true, false); + ptdump_walk_pgd_level_core(NULL, &init_mm, pgd, true, false); #endif } void ptdump_walk_pgd_level_checkwx(void) { - ptdump_walk_pgd_level_core(NULL, INIT_PGD, true, false); + ptdump_walk_pgd_level_core(NULL, &init_mm, INIT_PGD, true, false); } static int __init pt_dump_init(void) diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h index 745a654c6ea7..b1cb6b753abb 100644 --- a/include/linux/pagewalk.h +++ b/include/linux/pagewalk.h @@ -74,6 +74,7 @@ enum page_walk_action { * mm_walk - walk_page_range data * @ops: operation to call during the walk * @mm: mm_struct representing the target process of page table walk + * @pgd: pointer to PGD; only valid with no_vma (otherwise set to NULL) * @vma: vma currently walked (NULL if walking outside vmas) * @action: next action to perform (see enum page_walk_action) * @no_vma: walk ignoring vmas (vma will always be NULL) @@ -84,6 +85,7 @@ enum page_walk_action { struct mm_walk { const struct mm_walk_ops *ops; struct mm_struct *mm; + pgd_t *pgd; struct vm_area_struct *vma; enum page_walk_action action; bool no_vma; @@ -95,6 +97,7 @@ int walk_page_range(struct mm_struct *mm, unsigned long start, void *private); int walk_page_range_novma(struct mm_struct *mm, unsigned long start, unsigned long end, const struct mm_walk_ops *ops, + pgd_t *pgd, void *private); int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops, void *private); diff --git a/include/linux/ptdump.h b/include/linux/ptdump.h index b28f3f2acf90..a67065c403c3 100644 --- a/include/linux/ptdump.h +++ b/include/linux/ptdump.h @@ -17,6 +17,6 @@ struct ptdump_state { const struct ptdump_range *range; }; -void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm); +void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd); #endif /* _LINUX_PTDUMP_H */ diff --git a/mm/pagewalk.c b/mm/pagewalk.c index 5895ce4f1a85..928df1638c30 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -206,7 +206,10 @@ static int walk_pgd_range(unsigned long addr, unsigned long end, const struct mm_walk_ops *ops = walk->ops; int err = 0; - pgd = pgd_offset(walk->mm, addr); + if (walk->pgd) + pgd = walk->pgd + pgd_index(addr); + else + pgd = pgd_offset(walk->mm, addr); do { next = pgd_addr_end(addr, end); if (pgd_none_or_clear_bad(pgd)) { @@ -436,11 +439,13 @@ int walk_page_range(struct mm_struct *mm, unsigned long start, */ int walk_page_range_novma(struct mm_struct *mm, unsigned long start, unsigned long end, const struct mm_walk_ops *ops, + pgd_t *pgd, void *private) { struct mm_walk walk = { .ops = ops, .mm = mm, + .pgd = pgd, .private = private, .no_vma = true }; diff --git a/mm/ptdump.c b/mm/ptdump.c index ad18a9839d6f..26208d0d03b7 100644 --- a/mm/ptdump.c +++ b/mm/ptdump.c @@ -122,14 +122,14 @@ static const struct mm_walk_ops ptdump_ops = { .pte_hole = ptdump_hole, }; -void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm) +void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd) { const struct ptdump_range *range = st->range; down_read(&mm->mmap_sem); while (range->start != range->end) { walk_page_range_novma(mm, range->start, range->end, - &ptdump_ops, st); + &ptdump_ops, pgd, st); range++; } up_read(&mm->mmap_sem);