Commit 1e987790 authored by Dave Hansen's avatar Dave Hansen Committed by Ingo Molnar
Browse files

mm/gup: Introduce get_user_pages_remote() 



For protection keys, we need to understand whether protections
should be enforced in software or not.  In general, we enforce
protections when working on our own task, but not when on others.
We call these "current" and "remote" operations.

This patch introduces a new get_user_pages() variant:

        get_user_pages_remote()

Which is a replacement for when get_user_pages() is called on
non-current tsk/mm.

We also introduce a new gup flag: FOLL_REMOTE which can be used
for the "__" gup variants to get this new behavior.

The uprobes is_trap_at_addr() location holds mmap_sem and
calls get_user_pages(current->mm) on an instruction address.  This
makes it a pretty unique gup caller.  Being an instruction access
and also really originating from the kernel (vs. the app), I opted
to consider this a 'remote' access where protection keys will not
be enforced.

Without protection keys, this patch should not change any behavior.

Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: jack@suse.cz
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20160212210154.3F0E51EA@viggo.jf.intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 1fe3f29e

drivers/gpu/drm/etnaviv/etnaviv_gem.c

+3 −3
Original line number Diff line number Diff line
@@ -753,7 +753,7 @@ static struct page **etnaviv_gem_userptr_do_get_pages( 


	down_read(&mm->mmap_sem);

	while (pinned < npages) {

		ret = get_user_pages(task, mm, ptr, npages - pinned,

		ret = get_user_pages_remote(task, mm, ptr, npages - pinned,

					    !etnaviv_obj->userptr.ro, 0,

					    pvec + pinned, NULL);

		if (ret < 0)

drivers/gpu/drm/i915/i915_gem_userptr.c

+5 −5
Original line number Diff line number Diff line
@@ -584,7 +584,7 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work) 


		down_read(&mm->mmap_sem);

		while (pinned < npages) {

			ret = get_user_pages(work->task, mm,

			ret = get_user_pages_remote(work->task, mm,

					obj->userptr.ptr + pinned * PAGE_SIZE,

					npages - pinned,

					!obj->userptr.read_only, 0,

drivers/infiniband/core/umem_odp.c

+4 −4
Original line number Diff line number Diff line
@@ -572,10 +572,10 @@ int ib_umem_odp_map_dma_pages(struct ib_umem *umem, u64 user_virt, u64 bcnt, 
		 * complex (and doesn't gain us much performance in most use

		 * cases).

		 */

		npages = get_user_pages(owning_process, owning_mm, user_virt,

					gup_num_pages,

					access_mask & ODP_WRITE_ALLOWED_BIT, 0,

					local_page_list, NULL);

		npages = get_user_pages_remote(owning_process, owning_mm,

				user_virt, gup_num_pages,

				access_mask & ODP_WRITE_ALLOWED_BIT,

				0, local_page_list, NULL);

		up_read(&owning_mm->mmap_sem);



		if (npages < 0)

fs/exec.c

+6 −2
Original line number Diff line number Diff line
@@ -198,8 +198,12 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 
			return NULL;

	}

#endif

	ret = get_user_pages(current, bprm->mm, pos,

			1, write, 1, &page, NULL);

	/*

	 * We are doing an exec().  'current' is the process

	 * doing the exec and bprm->mm is the new process's mm.

	 */

	ret = get_user_pages_remote(current, bprm->mm, pos, 1, write,

			1, &page, NULL);

	if (ret <= 0)

		return NULL;

include/linux/mm.h

+5 −0
Original line number Diff line number Diff line
@@ -1225,6 +1225,10 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 
		      unsigned long start, unsigned long nr_pages,

		      unsigned int foll_flags, struct page **pages,

		      struct vm_area_struct **vmas, int *nonblocking);

long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,

			    unsigned long start, unsigned long nr_pages,

			    int write, int force, struct page **pages,

			    struct vm_area_struct **vmas);

long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,

		    unsigned long start, unsigned long nr_pages,

		    int write, int force, struct page **pages,
@@ -2170,6 +2174,7 @@ static inline struct page *follow_page(struct vm_area_struct *vma, 
#define FOLL_MIGRATION	0x400	/* wait for page to replace migration entry */

#define FOLL_TRIED	0x800	/* a retry, previous pass started an IO */

#define FOLL_MLOCK	0x1000	/* lock present pages */

#define FOLL_REMOTE	0x2000	/* we are working on non-current tsk/mm */



typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,

			void *data);

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