From: Richard Weinberger <richard@nod.at>
To: linux-mm@kvack.org
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, upstream+pagemap@sigma-star.at,
adobriyan@gmail.com, wangkefeng.wang@huawei.com,
ryan.roberts@arm.com, hughd@google.com, peterx@redhat.com,
david@redhat.com, avagin@google.com, lstoakes@gmail.com,
vbabka@suse.cz, akpm@linux-foundation.org,
usama.anjum@collabora.com, corbet@lwn.net,
Richard Weinberger <richard@nod.at>
Subject: [PATCH 1/2] [RFC] proc: pagemap: Expose whether a PTE is writable
Date: Thu, 7 Mar 2024 00:23:38 +0100 [thread overview]
Message-ID: <20240306232339.29659-1-richard@nod.at> (raw)
Is a PTE present and writable, bit 58 will be set.
This allows detecting CoW memory mappings and other mappings
where a write access will cause a page fault.
Signed-off-by: Richard Weinberger <richard@nod.at>
---
fs/proc/task_mmu.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 3f78ebbb795f..7c7e0e954c02 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1341,6 +1341,7 @@ struct pagemapread {
#define PM_SOFT_DIRTY BIT_ULL(55)
#define PM_MMAP_EXCLUSIVE BIT_ULL(56)
#define PM_UFFD_WP BIT_ULL(57)
+#define PM_WRITE BIT_ULL(58)
#define PM_FILE BIT_ULL(61)
#define PM_SWAP BIT_ULL(62)
#define PM_PRESENT BIT_ULL(63)
@@ -1417,6 +1418,8 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
flags |= PM_SOFT_DIRTY;
if (pte_uffd_wp(pte))
flags |= PM_UFFD_WP;
+ if (pte_write(pte))
+ flags |= PM_WRITE;
} else if (is_swap_pte(pte)) {
swp_entry_t entry;
if (pte_swp_soft_dirty(pte))
@@ -1483,6 +1486,8 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
flags |= PM_SOFT_DIRTY;
if (pmd_uffd_wp(pmd))
flags |= PM_UFFD_WP;
+ if (pmd_write(pmd))
+ flags |= PM_WRITE;
if (pm->show_pfn)
frame = pmd_pfn(pmd) +
((addr & ~PMD_MASK) >> PAGE_SHIFT);
@@ -1586,6 +1591,9 @@ static int pagemap_hugetlb_range(pte_t *ptep, unsigned long hmask,
if (huge_pte_uffd_wp(pte))
flags |= PM_UFFD_WP;
+ if (pte_write(pte))
+ flags |= PM_WRITE;
+
flags |= PM_PRESENT;
if (pm->show_pfn)
frame = pte_pfn(pte) +
--
2.35.3
next reply other threads:[~2024-03-06 23:24 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-06 23:23 Richard Weinberger [this message]
2024-03-06 23:23 ` [PATCH 2/2] [RFC] pagemap.rst: Document write bit Richard Weinberger
2024-03-07 10:52 ` David Hildenbrand
2024-03-07 11:10 ` Richard Weinberger
2024-03-07 11:15 ` David Hildenbrand
2024-03-10 22:14 ` Lorenzo Stoakes
2024-03-07 10:44 ` [PATCH 1/2] [RFC] proc: pagemap: Expose whether a PTE is writable Muhammad Usama Anjum
2024-03-07 10:52 ` David Hildenbrand
2024-03-07 11:10 ` Richard Weinberger
2024-03-07 11:20 ` David Hildenbrand
2024-03-07 11:51 ` Richard Weinberger
2024-03-07 11:59 ` David Hildenbrand
2024-03-07 12:09 ` David Hildenbrand
2024-03-07 14:42 ` Richard Weinberger
2024-03-10 21:55 ` Lorenzo Stoakes
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