linux-kernel - [PATCH v7 1/5] mm/page_ext: Add page_ext_get

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20260114164322.787125-2-smostafa@google.com>
Date: Wed, 14 Jan 2026 16:43:18 +0000
From: Mostafa Saleh <smostafa@...gle.com>
To: linux-mm@...ck.org, iommu@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	linux-doc@...r.kernel.org
Cc: corbet@....net, joro@...tes.org, will@...nel.org, robin.murphy@....com, 
	akpm@...ux-foundation.org, vbabka@...e.cz, surenb@...gle.com, mhocko@...e.com, 
	jackmanb@...gle.com, hannes@...xchg.org, ziy@...dia.com, david@...hat.com, 
	lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, rppt@...nel.org, 
	xiaqinxin@...wei.com, baolu.lu@...ux.intel.com, rdunlap@...radead.org, 
	Mostafa Saleh <smostafa@...gle.com>
Subject: [PATCH v7 1/5] mm/page_ext: Add page_ext_get_phys()

In the next patches, IOMMU code will add data to page_ext.
The IOMMU code would operate on physical addresses which
can be outside of system RAM.

Add a new function page_ext_get_phys() to abstract the logic of
checking the address and returning the page_ext.

Signed-off-by: Mostafa Saleh <smostafa@...gle.com>
---
 include/linux/page_ext.h |  6 ++++++
 mm/page_ext.c            | 23 +++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
index 76c817162d2f..bd373496e166 100644
--- a/include/linux/page_ext.h
+++ b/include/linux/page_ext.h
@@ -93,6 +93,7 @@ static inline bool page_ext_iter_next_fast_possible(unsigned long next_pfn)
 #endif
 
 extern struct page_ext *page_ext_get(const struct page *page);
+extern struct page_ext *page_ext_get_phys(phys_addr_t phys);
 extern void page_ext_put(struct page_ext *page_ext);
 extern struct page_ext *page_ext_lookup(unsigned long pfn);
 
@@ -215,6 +216,11 @@ static inline struct page_ext *page_ext_get(const struct page *page)
 	return NULL;
 }
 
+static inline struct page_ext *page_ext_get_phys(phys_addr_t phys)
+{
+	return NULL;
+}
+
 static inline void page_ext_put(struct page_ext *page_ext)
 {
 }
diff --git a/mm/page_ext.c b/mm/page_ext.c
index d7396a8970e5..95e8c40131b7 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -534,6 +534,29 @@ struct page_ext *page_ext_get(const struct page *page)
 	return page_ext;
 }
 
+/**
+ * page_ext_get_phys() - Get the page_ext structure for a physical address.
+ * @phys: The physical address to query.
+ *
+ * This function safely gets the `struct page_ext` associated with a given
+ * physical address. It performs validation to ensure the address corresponds
+ * to a valid, online struct page before attempting to access it.
+ * It should return NULL for (MMIO, ZONE_DEVICE, holes, offline memory)
+ *
+ * Return: NULL if no page_ext exists for this physical address.
+ * Context: Any context.  Caller may not sleep until they have called
+ * page_ext_put().
+ */
+struct page_ext *page_ext_get_phys(phys_addr_t phys)
+{
+	struct page *page = pfn_to_online_page(__phys_to_pfn(phys));
+
+	if (!page)
+		return NULL;
+
+	return page_ext_get(page);
+}
+
 /**
  * page_ext_put() - Working with page extended information is done.
  * @page_ext: Page extended information received from page_ext_get().
-- 
2.52.0.457.g6b5491de43-goog