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From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org, Borislav Petkov <bp@alien8.de>,
	Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Andy Lutomirski <luto@kernel.org>
Subject: [PATCH v3 2/7] mm: Add a vm_special_mapping .fault method
Date: Tue, 29 Dec 2015 20:12:19 -0800	[thread overview]
Message-ID: <a26d1677c0bc7e774c33f469451a78ca31e9e6af.1451446564.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1451446564.git.luto@kernel.org>
In-Reply-To: <cover.1451446564.git.luto@kernel.org>

From: Andy Lutomirski <luto@amacapital.net>

Requiring special mappings to give a list of struct pages is
inflexible: it prevents sane use of IO memory in a special mapping,
it's inefficient (it requires arch code to initialize a list of
struct pages, and it requires the mm core to walk the entire list
just to figure out how long it is), and it prevents arch code from
doing anything fancy when a special mapping fault occurs.

Add a .fault method as an alternative to filling in a .pages array.

Looks-OK-to: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 include/linux/mm_types.h | 22 +++++++++++++++++++---
 mm/mmap.c                | 13 +++++++++----
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index f8d1492a114f..c88e48a3c155 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -568,10 +568,26 @@ static inline void clear_tlb_flush_pending(struct mm_struct *mm)
 }
 #endif
 
-struct vm_special_mapping
-{
-	const char *name;
+struct vm_fault;
+
+struct vm_special_mapping {
+	const char *name;	/* The name, e.g. "[vdso]". */
+
+	/*
+	 * If .fault is not provided, this points to a
+	 * NULL-terminated array of pages that back the special mapping.
+	 *
+	 * This must not be NULL unless .fault is provided.
+	 */
 	struct page **pages;
+
+	/*
+	 * If non-NULL, then this is called to resolve page faults
+	 * on the special mapping.  If used, .pages is not checked.
+	 */
+	int (*fault)(const struct vm_special_mapping *sm,
+		     struct vm_area_struct *vma,
+		     struct vm_fault *vmf);
 };
 
 enum tlb_flush_reason {
diff --git a/mm/mmap.c b/mm/mmap.c
index 2ce04a649f6b..f717453b1a57 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3030,11 +3030,16 @@ static int special_mapping_fault(struct vm_area_struct *vma,
 	pgoff_t pgoff;
 	struct page **pages;
 
-	if (vma->vm_ops == &legacy_special_mapping_vmops)
+	if (vma->vm_ops == &legacy_special_mapping_vmops) {
 		pages = vma->vm_private_data;
-	else
-		pages = ((struct vm_special_mapping *)vma->vm_private_data)->
-			pages;
+	} else {
+		struct vm_special_mapping *sm = vma->vm_private_data;
+
+		if (sm->fault)
+			return sm->fault(sm, vma, vmf);
+
+		pages = sm->pages;
+	}
 
 	for (pgoff = vmf->pgoff; pgoff && *pages; ++pages)
 		pgoff--;
-- 
2.5.0


  parent reply	other threads:[~2015-12-30  4:13 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-30  4:12 [PATCH v3 0/7] mm, x86/vdso: Special IO mapping improvements Andy Lutomirski
2015-12-30  4:12 ` [PATCH v3 1/7] x86/vsdo: Fix build on PARAVIRT_CLOCK=y, KVM_GUEST=n Andy Lutomirski
2016-01-05 19:21   ` Borislav Petkov
2016-01-06  9:54   ` [tip:x86/asm] x86/vsdo: Fix build on PARAVIRT_CLOCK=y, KVM_GUEST= n tip-bot for Andy Lutomirski
2015-12-30  4:12 ` Andy Lutomirski [this message]
2016-01-12 12:02   ` [tip:x86/asm] mm: Add a vm_special_mapping.fault() method tip-bot for Andy Lutomirski
2015-12-30  4:12 ` [PATCH v3 3/7] mm: Add vm_insert_pfn_prot Andy Lutomirski
2016-01-12 12:02   ` [tip:x86/asm] mm: Add vm_insert_pfn_prot() tip-bot for Andy Lutomirski
2015-12-30  4:12 ` [PATCH v3 4/7] x86/vdso: Track each mm's loaded vdso image as well as its base Andy Lutomirski
2016-01-12 12:03   ` [tip:x86/asm] x86/vdso: Track each mm' s loaded vDSO " tip-bot for Andy Lutomirski
2015-12-30  4:12 ` [PATCH v3 5/7] x86,vdso: Use .fault for the vdso text mapping Andy Lutomirski
2016-01-12 12:03   ` [tip:x86/asm] x86/vdso: Use .fault for the vDSO " tip-bot for Andy Lutomirski
2015-12-30  4:12 ` [PATCH v3 6/7] x86,vdso: Use .fault instead of remap_pfn_range for the vvar mapping Andy Lutomirski
2016-01-12 12:04   ` [tip:x86/asm] x86/vdso: Use ->fault() instead of remap_pfn_range( ) " tip-bot for Andy Lutomirski
2015-12-30  4:12 ` [PATCH v3 7/7] x86/vdso: Disallow vvar access to vclock IO for never-used vclocks Andy Lutomirski
2016-01-12 12:04   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2016-01-05  0:02 ` [PATCH v3 0/7] mm, x86/vdso: Special IO mapping improvements Kees Cook

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