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Commit ecba20dd authored by Kalesh Singh's avatar Kalesh Singh
Browse files

ANDROID: 16K: Handle pad VMA splits and merges 



In some cases a VMA with padding representation may be split, and
therefore the padding flags must be updated accordingly.

There are 3 cases to handle:

Given:
    | DDDDPPPP |

where:
    - D represents 1 page of data;
    - P represents 1 page of padding;
    - | represents the boundaries (start/end) of the VMA

1) Split exactly at the padding boundary

    | DDDDPPPP | --> | DDDD | PPPP |

    - Remove padding flags from the first VMA.
    - The second VMA is all padding

2) Split within the padding area

    | DDDDPPPP | --> | DDDDPP | PP |

    - Subtract the length of the second VMA from the first VMA's
      padding.
    - The second VMA is all padding, adjust its padding length (flags)

3) Split within the data area

    | DDDDPPPP | --> | DD | DDPPPP |

    - Remove padding flags from the first VMA.
    - The second VMA is has the same padding as from before the split.

To simplify the semantics merging of padding VMAs is not allowed.

If a split produces a VMA that is entirely padding, show_[s]maps()
only outputs the padding VMA entry (as the data entry is of length 0).

Bug: 330117029
Bug: 327600007
Bug: 330767927
Bug: 328266487
Bug: 329803029
Change-Id: Ie2628ced5512e2c7f8af25fabae1f38730c8bb1a
Signed-off-by: default avatarKalesh Singh <kaleshsingh@google.com>
parent 7231bbf0

fs/proc/task_mmu.c

+4 −3
Original line number Diff line number Diff line
@@ -423,6 +423,7 @@ static int show_map(struct seq_file *m, void *v) 
	struct vm_area_struct *pad_vma = get_pad_vma(v);

	struct vm_area_struct *vma = get_data_vma(v);



	if (vma_pages(vma))

		show_map_vma(m, vma);



	show_map_pad_vma(vma, pad_vma, m, show_map_vma);
@@ -913,7 +914,6 @@ static void show_smap_vma(struct seq_file *m, void *v) 
	if (arch_pkeys_enabled())

		seq_printf(m, "ProtectionKey:  %8u\n", vma_pkey(vma));

	show_smap_vma_flags(m, vma);



}



static int show_smap(struct seq_file *m, void *v)
@@ -921,6 +921,7 @@ static int show_smap(struct seq_file *m, void *v) 
	struct vm_area_struct *pad_vma = get_pad_vma(v);

	struct vm_area_struct *vma = get_data_vma(v);



	if (vma_pages(vma))

		show_smap_vma(m, vma);



	show_map_pad_vma(vma, pad_vma, m, (show_pad_vma_fn)show_smap_vma);

include/linux/pgsize_migration.h

+34 −0
Original line number Diff line number Diff line
@@ -61,6 +61,9 @@ extern struct vm_area_struct *get_data_vma(struct vm_area_struct *vma); 
extern void show_map_pad_vma(struct vm_area_struct *vma,

			     struct vm_area_struct *pad,

			     struct seq_file *m, show_pad_vma_fn func);



extern void split_pad_vma(struct vm_area_struct *vma, struct vm_area_struct *new,

			  unsigned long addr, int new_below);

#else /* PAGE_SIZE != SZ_4K || !defined(CONFIG_64BIT) */

static inline void vma_set_pad_pages(struct vm_area_struct *vma,

				     unsigned long nr_pages)
@@ -92,10 +95,41 @@ static inline void show_map_pad_vma(struct vm_area_struct *vma, 
				    struct seq_file *m, show_pad_vma_fn func)

{

}



static inline void split_pad_vma(struct vm_area_struct *vma, struct vm_area_struct *new,

				 unsigned long addr, int new_below)

{

}

#endif /* PAGE_SIZE == SZ_4K && defined(CONFIG_64BIT) */



static inline unsigned long vma_data_pages(struct vm_area_struct *vma)

{

	return vma_pages(vma) - vma_pad_pages(vma);

}



/*

 * Sets the correct padding bits / flags for a VMA split.

 */

static inline unsigned long vma_pad_fixup_flags(struct vm_area_struct *vma,

						unsigned long newflags)

{

	if (newflags & VM_PAD_MASK)

		return (newflags & ~VM_PAD_MASK) | (vma->vm_flags & VM_PAD_MASK);

	else

		return newflags;

}



/*

 * Merging of padding VMAs is uncommon, as padding is only allowed

 * from the linker context.

 *

 * To simplify the semantics, adjacent VMAs with padding are not

 * allowed to merge.

 */

static inline bool is_mergable_pad_vma(struct vm_area_struct *vma,

				       unsigned long vm_flags)

{

	/* Padding VMAs cannot be merged with other padding or real VMAs */

	return !((vma->vm_flags | vm_flags) & VM_PAD_MASK);

}

#endif /* _LINUX_PAGE_SIZE_MIGRATION_H */

mm/mlock.c

+2 −1
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include <linux/swap.h>

#include <linux/swapops.h>

#include <linux/pagemap.h>

#include <linux/pgsize_migration.h>

#include <linux/pagevec.h>

#include <linux/mempolicy.h>

#include <linux/syscalls.h>
@@ -571,7 +572,7 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev, 
	 */



	if (lock)

		vma->vm_flags = newflags;

		vma->vm_flags = vma_pad_fixup_flags(vma, newflags);

	else

		munlock_vma_pages_range(vma, start, end);

mm/mmap.c

+6 −1
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <linux/init.h>

#include <linux/file.h>

#include <linux/fs.h>

#include <linux/pgsize_migration.h>

#include <linux/personality.h>

#include <linux/security.h>

#include <linux/hugetlb.h>
@@ -1030,6 +1031,8 @@ static inline int is_mergeable_vma(struct vm_area_struct *vma, 
		return 0;

	if (vma_get_anon_name(vma) != anon_name)

		return 0;

	if (!is_mergable_pad_vma(vma, vm_flags))

		return 0;

	return 1;

}
@@ -2731,8 +2734,10 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma, 
		err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);



	/* Success. */

	if (!err)

	if (!err) {

		split_pad_vma(vma, new, addr, new_below);

		return 0;

	}



	/* Clean everything up if vma_adjust failed. */

	if (new->vm_ops && new->vm_ops->close)

mm/mprotect.c

+2 −1
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <linux/highmem.h>

#include <linux/security.h>

#include <linux/mempolicy.h>

#include <linux/pgsize_migration.h>

#include <linux/personality.h>

#include <linux/syscalls.h>

#include <linux/swap.h>
@@ -454,7 +455,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, 
	 * vm_flags and vm_page_prot are protected by the mmap_sem

	 * held in write mode.

	 */

	vma->vm_flags = newflags;

	vma->vm_flags = vma_pad_fixup_flags(vma, newflags);

	dirty_accountable = vma_wants_writenotify(vma, vma->vm_page_prot);

	vma_set_page_prot(vma);