mm: Add a vm_special_mapping.fault() method (f872f540) · Commits · 戴 / test

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> Reviewed-by:

Kees Cook <keescook@chromium.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/a26d1677c0bc7e774c33f469451a78ca31e9e6af.1451446564.git.luto@kernel.org Signed-off-by:

Ingo Molnar <mingo@kernel.org>

include/linux/mm_types.h

+19 −3

Original line number	Diff line number	Diff line
		@@ -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 {

mm/mmap.c

+9 −4

Original line number	Diff line number	Diff line
		@@ -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--;

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