From patchwork Tue Jan 24 08:43:22 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Muhammad Usama Anjum X-Patchwork-Id: 13113659 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 F2D1EC25B4E for ; Tue, 24 Jan 2023 08:45:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233220AbjAXIpP (ORCPT ); Tue, 24 Jan 2023 03:45:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59948 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233206AbjAXIpM (ORCPT ); Tue, 24 Jan 2023 03:45:12 -0500 Received: from madras.collabora.co.uk (madras.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e5ab]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1FA9A3526B; Tue, 24 Jan 2023 00:44:55 -0800 (PST) Received: from localhost.localdomain (unknown [39.45.186.163]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: usama.anjum) by madras.collabora.co.uk (Postfix) with ESMTPSA id 048456602E29; Tue, 24 Jan 2023 08:44:46 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1674549893; bh=zvQOHS4OemOKK7s48q0sdRpUgCuoq0sXZit8P7U09v4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CT6Qcs3PFg1hQgBAjLmZpL5L8hUr+0JqmM4ZAb7UMef59QT/cKbAU4cw0yk/01BzY G1L4Obs7KFMX9tbQIwpkN2nkjIRka4qjaX97nYAsItgeEbjWVmIpf1dpV8a3mPRx4y 2054pvdSp6g9x6kF4PI4oN6wyx2HcpWeCSy8dbx9IXVHYhA+rWqH09RGqL7P7+sBTh p9pmaNuool/lSNj/8E+XjZOBUMxUH5/WjwMlO5LEcdAaHTZJ17LiGsmtIrswkti7v2 ncSjA+cKp8/H7qPjp26wr4VrJIS8++i+DbfpCth2NqZQ+eZSUd/Dl5taOoN4/DeNkJ LbJwhEw1O0DVQ== From: Muhammad Usama Anjum To: Peter Xu , David Hildenbrand , Andrew Morton , =?utf-8?b?TWljaGHFgiBNaXJvc8WC?= =?utf-8?b?YXc=?= , Andrei Vagin , Danylo Mocherniuk , Paul Gofman , Cyrill Gorcunov Cc: Alexander Viro , Shuah Khan , Christian Brauner , Yang Shi , Vlastimil Babka , "Liam R . Howlett" , Yun Zhou , Suren Baghdasaryan , Alex Sierra , Muhammad Usama Anjum , Matthew Wilcox , Pasha Tatashin , Mike Rapoport , Nadav Amit , Axel Rasmussen , "Gustavo A . R . Silva" , Dan Williams , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Greg KH , kernel@collabora.com Subject: [PATCH v8 3/4] fs/proc/task_mmu: Implement IOCTL to get and/or the clear info about PTEs Date: Tue, 24 Jan 2023 13:43:22 +0500 Message-Id: <20230124084323.1363825-4-usama.anjum@collabora.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20230124084323.1363825-1-usama.anjum@collabora.com> References: <20230124084323.1363825-1-usama.anjum@collabora.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear the info about page table entries. The following operations are supported in this ioctl: - Get the information if the pages have been written-to (PAGE_IS_WT), file mapped (PAGE_IS_FILE), present (PAGE_IS_PRESENT) or swapped (PAGE_IS_SWAPPED). - Write-protect the pages (PAGEMAP_WP_ENGAGE) to start finding which pages have been written-to. - Find pages which have been written-to and write protect the pages (atomic PAGE_IS_WT + PAGEMAP_WP_ENGAGE) The uffd should have been registered on the memory range before performing any WP/WT (Write Protect/Writtern-To) related operations with the IOCTL. struct pagemap_scan_args is used as the argument of the IOCTL. In this struct: - The range is specified through start and len. - The output buffer of struct page_region array and size is specified as vec and vec_len. - The optional maximum requested pages are specified in the max_pages. - The flags can be specified in the flags field. The PAGEMAP_WP_ENGAGE is the only added flag at this time. - The masks are specified in required_mask, anyof_mask, excluded_ mask and return_mask. This IOCTL can be extended to get information about more PTE bits. This IOCTL doesn't support hugetlbs at the moment. No information about hugetlb can be obtained. This patch has evolved from a basic patch from Gabriel Krisman Bertazi. Signed-off-by: Muhammad Usama Anjum --- Change in v8: - Correct is_pte_uffd_wp() - Improve readability and error checks - Remove some un-needed code Changes in v7: - Rebase on top of latest next - Fix some corner cases - Base soft-dirty on the uffd wp async - Update the terminologies - Optimize the memory usage inside the ioctl Changes in v6: - Rename variables and update comments - Make IOCTL independent of soft_dirty config - Change masks and bitmap type to _u64 - Improve code quality Changes in v5: - Remove tlb flushing even for clear operation Changes in v4: - Update the interface and implementation Changes in v3: - Tighten the user-kernel interface by using explicit types and add more error checking Changes in v2: - Convert the interface from syscall to ioctl - Remove pidfd support as it doesn't make sense in ioctl --- fs/proc/task_mmu.c | 294 ++++++++++++++++++++++++++++++++++ include/uapi/linux/fs.h | 50 ++++++ tools/include/uapi/linux/fs.h | 50 ++++++ 3 files changed, 394 insertions(+) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index e35a0398db63..f9fbda00eb5c 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include @@ -1135,6 +1136,22 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma, } #endif +static inline bool is_pte_uffd_wp(pte_t pte) +{ + if ((pte_present(pte) && pte_uffd_wp(pte)) || + (is_swap_pte(pte) && pte_swp_uffd_wp_any(pte))) + return true; + return false; +} + +static inline bool is_pmd_uffd_wp(pmd_t pmd) +{ + if ((pmd_present(pmd) && pmd_uffd_wp(pmd)) || + (is_swap_pmd(pmd) && pmd_swp_uffd_wp(pmd))) + return true; + return false; +} + #if defined(CONFIG_MEM_SOFT_DIRTY) && defined(CONFIG_TRANSPARENT_HUGEPAGE) static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmdp) @@ -1763,11 +1780,288 @@ static int pagemap_release(struct inode *inode, struct file *file) return 0; } +#define PAGEMAP_OP_MASK (PAGE_IS_WT | PAGE_IS_FILE | \ + PAGE_IS_PRESENT | PAGE_IS_SWAPPED) +#define PAGEMAP_NONWT_OP_MASK (PAGE_IS_FILE | PAGE_IS_PRESENT | PAGE_IS_SWAPPED) +#define IS_WP_ENGAGE_OP(a) (a->flags & PAGEMAP_WP_ENGAGE) +#define IS_GET_OP(a) (a->vec) +#define PAGEMAP_SCAN_BITMAP(wt, file, present, swap) \ + (wt | file << 1 | present << 2 | swap << 3) +#define IS_WT_REQUIRED(a) \ + ((a->required_mask & PAGE_IS_WT) || \ + (a->anyof_mask & PAGE_IS_WT)) +#define HAS_NO_SPACE(p) (p->max_pages && (p->found_pages == p->max_pages)) + +struct pagemap_scan_private { + struct page_region *vec; + struct page_region prev; + unsigned long vec_len, vec_index; + unsigned int max_pages, found_pages, flags; + unsigned long required_mask, anyof_mask, excluded_mask, return_mask; +}; + +static int pagemap_scan_test_walk(unsigned long start, unsigned long end, struct mm_walk *walk) +{ + struct pagemap_scan_private *p = walk->private; + struct vm_area_struct *vma = walk->vma; + + if (IS_WT_REQUIRED(p) && !userfaultfd_wp(vma) && !userfaultfd_wp_async(vma)) + return -EPERM; + if (IS_GET_OP(p) && HAS_NO_SPACE(p)) + return -ENOSPC; + if (vma->vm_flags & VM_PFNMAP) + return 1; + return 0; +} + +static inline int add_to_out(bool wt, bool file, bool pres, bool swap, + struct pagemap_scan_private *p, unsigned long addr, unsigned int len) +{ + unsigned long bitmap, cur = PAGEMAP_SCAN_BITMAP(wt, file, pres, swap); + bool cpy = true; + struct page_region *prev = &p->prev; + + if (HAS_NO_SPACE(p)) + return -ENOSPC; + + if (p->required_mask) + cpy = ((p->required_mask & cur) == p->required_mask); + if (cpy && p->anyof_mask) + cpy = (p->anyof_mask & cur); + if (cpy && p->excluded_mask) + cpy = !(p->excluded_mask & cur); + bitmap = cur & p->return_mask; + if (cpy && bitmap) { + if ((prev->len) && (prev->bitmap == bitmap) && + (prev->start + prev->len * PAGE_SIZE == addr)) { + prev->len += len; + p->found_pages += len; + } else if (p->vec_index < p->vec_len) { + if (prev->len) { + memcpy(&p->vec[p->vec_index], prev, sizeof(struct page_region)); + p->vec_index++; + } + prev->start = addr; + prev->len = len; + prev->bitmap = bitmap; + p->found_pages += len; + } else { + return -ENOSPC; + } + } + return 0; +} + +static inline int export_prev_to_out(struct pagemap_scan_private *p, struct page_region __user *vec, + unsigned long *vec_index) +{ + struct page_region *prev = &p->prev; + + if (prev->len) { + if (copy_to_user(&vec[*vec_index], prev, sizeof(struct page_region))) + return -EFAULT; + p->vec_index++; + (*vec_index)++; + prev->len = 0; + } + return 0; +} + +static inline int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start, + unsigned long end, struct mm_walk *walk) +{ + struct pagemap_scan_private *p = walk->private; + struct vm_area_struct *vma = walk->vma; + unsigned long addr = end; + unsigned int len; + spinlock_t *ptl; + int ret = 0; + pte_t *pte; + bool pmd_wt; + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + ptl = pmd_trans_huge_lock(pmd, vma); + if (ptl) { + pmd_wt = !is_pmd_uffd_wp(*pmd); + /* + * Break huge page into small pages if operation needs to be performed is + * on a portion of the huge page or the return buffer cannot store complete + * data. + */ + if (pmd_wt && (IS_WP_ENGAGE_OP(p) && (end - start < HPAGE_SIZE))) { + spin_unlock(ptl); + split_huge_pmd(vma, pmd, start); + goto process_smaller_pages; + } + if (IS_GET_OP(p)) { + len = (end - start)/PAGE_SIZE; + if (p->max_pages && p->found_pages + len > p->max_pages) + len = p->max_pages - p->found_pages; + + ret = add_to_out(pmd_wt, vma->vm_file, pmd_present(*pmd), + is_swap_pmd(*pmd), p, start, len); + if (ret) { + spin_unlock(ptl); + return ret; + } + } + spin_unlock(ptl); + if (IS_WP_ENGAGE_OP(p) && pmd_wt) + ret = wp_range_async(vma, start, HPAGE_SIZE); + return ret; + } +process_smaller_pages: + if (pmd_trans_unstable(pmd)) + return 0; +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ + + pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl); + if (IS_GET_OP(p)) { + for (addr = start; + addr < end && !ret && (!p->max_pages || (p->found_pages < p->max_pages)); + pte++, addr += PAGE_SIZE) { + ret = add_to_out(!is_pte_uffd_wp(*pte), vma->vm_file, pte_present(*pte), + is_swap_pte(*pte), p, addr, 1); + if (ret) + break; + } + } + pte_unmap_unlock(pte - 1, ptl); + if (!ret && IS_WP_ENGAGE_OP(p)) + ret = wp_range_async(vma, start, addr - start); + + cond_resched(); + return ret; +} + +static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end, int depth, + struct mm_walk *walk) +{ + struct pagemap_scan_private *p = walk->private; + struct vm_area_struct *vma = walk->vma; + unsigned int len; + int ret = 0; + + if (vma) { + len = (end - addr)/PAGE_SIZE; + if (p->max_pages && p->found_pages + len > p->max_pages) + len = p->max_pages - p->found_pages; + ret = add_to_out(false, vma->vm_file, false, false, p, addr, len); + } + return ret; +} + +/* No hugetlb support is present. */ +static const struct mm_walk_ops pagemap_scan_ops = { + .test_walk = pagemap_scan_test_walk, + .pmd_entry = pagemap_scan_pmd_entry, + .pte_hole = pagemap_scan_pte_hole, +}; + +static long do_pagemap_cmd(struct mm_struct *mm, struct pagemap_scan_arg *arg) +{ + unsigned long empty_slots, vec_index = 0; + unsigned long __user start, end; + unsigned long __start, __end; + struct page_region __user *vec; + struct pagemap_scan_private p; + int ret; + + start = (unsigned long)untagged_addr(arg->start); + vec = (struct page_region *)untagged_addr(arg->vec); + if ((!IS_ALIGNED(start, PAGE_SIZE)) || (!access_ok((void __user *)start, arg->len))) + return -EINVAL; + if (IS_GET_OP(arg) && ((arg->vec_len == 0) || + (!access_ok((void __user *)vec, arg->vec_len * sizeof(struct page_region))))) + return -ENOMEM; + if ((arg->flags & ~PAGEMAP_WP_ENGAGE) || (arg->required_mask & ~PAGEMAP_OP_MASK) || + (arg->anyof_mask & ~PAGEMAP_OP_MASK) || (arg->excluded_mask & ~PAGEMAP_OP_MASK) || + (arg->return_mask & ~PAGEMAP_OP_MASK)) + return -EINVAL; + if (IS_GET_OP(arg) && ((!arg->required_mask && !arg->anyof_mask && !arg->excluded_mask) || + !arg->return_mask)) + return -EINVAL; + /* The non-WT flags cannot be obtained if PAGEMAP_WP_ENGAGE is also specified. */ + if (IS_WP_ENGAGE_OP(arg) && ((arg->required_mask & PAGEMAP_NONWT_OP_MASK) || + (arg->anyof_mask & PAGEMAP_NONWT_OP_MASK))) + return -EINVAL; + + end = start + arg->len; + p.max_pages = arg->max_pages; + p.found_pages = 0; + p.flags = arg->flags; + p.required_mask = arg->required_mask; + p.anyof_mask = arg->anyof_mask; + p.excluded_mask = arg->excluded_mask; + p.return_mask = arg->return_mask; + p.prev.len = 0; + p.vec_len = (PAGEMAP_WALK_SIZE >> PAGE_SHIFT); + + if (IS_GET_OP(arg)) { + p.vec = kmalloc_array(p.vec_len, sizeof(struct page_region), GFP_KERNEL); + if (!p.vec) + return -ENOMEM; + } else { + p.vec = NULL; + } + __start = __end = start; + while (__end < end) { + p.vec_index = 0; + empty_slots = arg->vec_len - vec_index; + if (p.vec_len > empty_slots) + p.vec_len = empty_slots; + + __end = (__start + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK; + if (__end > end) + __end = end; + + mmap_read_lock(mm); + ret = walk_page_range(mm, __start, __end, &pagemap_scan_ops, &p); + mmap_read_unlock(mm); + if (!(!ret || ret == -ENOSPC)) + goto free_data; + + __start = __end; + if (IS_GET_OP(arg) && p.vec_index) { + if (copy_to_user(&vec[vec_index], p.vec, + p.vec_index * sizeof(struct page_region))) { + ret = -EFAULT; + goto free_data; + } + vec_index += p.vec_index; + } + } + ret = export_prev_to_out(&p, vec, &vec_index); + if (!ret) + ret = vec_index; +free_data: + if (IS_GET_OP(arg)) + kfree(p.vec); + + return ret; +} + +static long pagemap_scan_ioctl(struct file *file, unsigned int cmd, unsigned long arg) +{ + struct pagemap_scan_arg __user *uarg = (struct pagemap_scan_arg __user *)arg; + struct mm_struct *mm = file->private_data; + struct pagemap_scan_arg argument; + + if (cmd == PAGEMAP_SCAN) { + if (copy_from_user(&argument, uarg, sizeof(struct pagemap_scan_arg))) + return -EFAULT; + return do_pagemap_cmd(mm, &argument); + } + return -EINVAL; +} + const struct file_operations proc_pagemap_operations = { .llseek = mem_lseek, /* borrow this */ .read = pagemap_read, .open = pagemap_open, .release = pagemap_release, + .unlocked_ioctl = pagemap_scan_ioctl, + .compat_ioctl = pagemap_scan_ioctl, }; #endif /* CONFIG_PROC_PAGE_MONITOR */ diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index b7b56871029c..6d03a903a745 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -305,4 +305,54 @@ typedef int __bitwise __kernel_rwf_t; #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ RWF_APPEND) +/* Pagemap ioctl */ +#define PAGEMAP_SCAN _IOWR('f', 16, struct pagemap_scan_arg) + +/* Bits are set in the bitmap of the page_region and masks in pagemap_scan_args */ +#define PAGE_IS_WT (1 << 0) +#define PAGE_IS_FILE (1 << 1) +#define PAGE_IS_PRESENT (1 << 2) +#define PAGE_IS_SWAPPED (1 << 3) + +/* + * struct page_region - Page region with bitmap flags + * @start: Start of the region + * @len: Length of the region + * bitmap: Bits sets for the region + */ +struct page_region { + __u64 start; + __u64 len; + __u64 bitmap; +}; + +/* + * struct pagemap_scan_arg - Pagemap ioctl argument + * @start: Starting address of the region + * @len: Length of the region (All the pages in this length are included) + * @vec: Address of page_region struct array for output + * @vec_len: Length of the page_region struct array + * @max_pages: Optional max return pages + * @flags: Flags for the IOCTL + * @required_mask: Required mask - All of these bits have to be set in the PTE + * @anyof_mask: Any mask - Any of these bits are set in the PTE + * @excluded_mask: Exclude mask - None of these bits are set in the PTE + * @return_mask: Bits that are to be reported in page_region + */ +struct pagemap_scan_arg { + __u64 start; + __u64 len; + __u64 vec; + __u64 vec_len; + __u32 max_pages; + __u32 flags; + __u64 required_mask; + __u64 anyof_mask; + __u64 excluded_mask; + __u64 return_mask; +}; + +/* Special flags */ +#define PAGEMAP_WP_ENGAGE (1 << 0) + #endif /* _UAPI_LINUX_FS_H */ diff --git a/tools/include/uapi/linux/fs.h b/tools/include/uapi/linux/fs.h index b7b56871029c..6d03a903a745 100644 --- a/tools/include/uapi/linux/fs.h +++ b/tools/include/uapi/linux/fs.h @@ -305,4 +305,54 @@ typedef int __bitwise __kernel_rwf_t; #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ RWF_APPEND) +/* Pagemap ioctl */ +#define PAGEMAP_SCAN _IOWR('f', 16, struct pagemap_scan_arg) + +/* Bits are set in the bitmap of the page_region and masks in pagemap_scan_args */ +#define PAGE_IS_WT (1 << 0) +#define PAGE_IS_FILE (1 << 1) +#define PAGE_IS_PRESENT (1 << 2) +#define PAGE_IS_SWAPPED (1 << 3) + +/* + * struct page_region - Page region with bitmap flags + * @start: Start of the region + * @len: Length of the region + * bitmap: Bits sets for the region + */ +struct page_region { + __u64 start; + __u64 len; + __u64 bitmap; +}; + +/* + * struct pagemap_scan_arg - Pagemap ioctl argument + * @start: Starting address of the region + * @len: Length of the region (All the pages in this length are included) + * @vec: Address of page_region struct array for output + * @vec_len: Length of the page_region struct array + * @max_pages: Optional max return pages + * @flags: Flags for the IOCTL + * @required_mask: Required mask - All of these bits have to be set in the PTE + * @anyof_mask: Any mask - Any of these bits are set in the PTE + * @excluded_mask: Exclude mask - None of these bits are set in the PTE + * @return_mask: Bits that are to be reported in page_region + */ +struct pagemap_scan_arg { + __u64 start; + __u64 len; + __u64 vec; + __u64 vec_len; + __u32 max_pages; + __u32 flags; + __u64 required_mask; + __u64 anyof_mask; + __u64 excluded_mask; + __u64 return_mask; +}; + +/* Special flags */ +#define PAGEMAP_WP_ENGAGE (1 << 0) + #endif /* _UAPI_LINUX_FS_H */