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author | Linus Torvalds <torvalds@linux-foundation.org> | 2015-09-08 17:52:23 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-09-08 17:52:23 -0700 |
commit | f6f7a6369203fa3e07efb7f35cfd81efe9f25b07 (patch) | |
tree | 97bec9ddd999040822acf314647eaf4208213589 /Documentation/vm/pagemap.txt | |
parent | 839fe9156fbe89c3157aa6146d22090f8cffddd8 (diff) | |
parent | df69f52d990bd85159727bd26e819d3a6e49c666 (diff) | |
download | blackbird-op-linux-f6f7a6369203fa3e07efb7f35cfd81efe9f25b07.tar.gz blackbird-op-linux-f6f7a6369203fa3e07efb7f35cfd81efe9f25b07.zip |
Merge branch 'akpm' (patches from Andrew)
Merge second patch-bomb from Andrew Morton:
"Almost all of the rest of MM. There was an unusually large amount of
MM material this time"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (141 commits)
zpool: remove no-op module init/exit
mm: zbud: constify the zbud_ops
mm: zpool: constify the zpool_ops
mm: swap: zswap: maybe_preload & refactoring
zram: unify error reporting
zsmalloc: remove null check from destroy_handle_cache()
zsmalloc: do not take class lock in zs_shrinker_count()
zsmalloc: use class->pages_per_zspage
zsmalloc: consider ZS_ALMOST_FULL as migrate source
zsmalloc: partial page ordering within a fullness_list
zsmalloc: use shrinker to trigger auto-compaction
zsmalloc: account the number of compacted pages
zsmalloc/zram: introduce zs_pool_stats api
zsmalloc: cosmetic compaction code adjustments
zsmalloc: introduce zs_can_compact() function
zsmalloc: always keep per-class stats
zsmalloc: drop unused variable `nr_to_migrate'
mm/memblock.c: fix comment in __next_mem_range()
mm/page_alloc.c: fix type information of memoryless node
memory-hotplug: fix comments in zone_spanned_pages_in_node() and zone_spanned_pages_in_node()
...
Diffstat (limited to 'Documentation/vm/pagemap.txt')
-rw-r--r-- | Documentation/vm/pagemap.txt | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/Documentation/vm/pagemap.txt b/Documentation/vm/pagemap.txt index 6bfbc172cdb9..3cd38438242a 100644 --- a/Documentation/vm/pagemap.txt +++ b/Documentation/vm/pagemap.txt @@ -16,11 +16,17 @@ There are three components to pagemap: * Bits 0-4 swap type if swapped * Bits 5-54 swap offset if swapped * Bit 55 pte is soft-dirty (see Documentation/vm/soft-dirty.txt) - * Bits 56-60 zero - * Bit 61 page is file-page or shared-anon + * Bit 56 page exclusively mapped (since 4.2) + * Bits 57-60 zero + * Bit 61 page is file-page or shared-anon (since 3.5) * Bit 62 page swapped * Bit 63 page present + Since Linux 4.0 only users with the CAP_SYS_ADMIN capability can get PFNs. + In 4.0 and 4.1 opens by unprivileged fail with -EPERM. Starting from + 4.2 the PFN field is zeroed if the user does not have CAP_SYS_ADMIN. + Reason: information about PFNs helps in exploiting Rowhammer vulnerability. + If the page is not present but in swap, then the PFN contains an encoding of the swap file number and the page's offset into the swap. Unmapped pages return a null PFN. This allows determining @@ -159,3 +165,8 @@ Other notes: Reading from any of the files will return -EINVAL if you are not starting the read on an 8-byte boundary (e.g., if you sought an odd number of bytes into the file), or if the size of the read is not a multiple of 8 bytes. + +Before Linux 3.11 pagemap bits 55-60 were used for "page-shift" (which is +always 12 at most architectures). Since Linux 3.11 their meaning changes +after first clear of soft-dirty bits. Since Linux 4.2 they are used for +flags unconditionally. |