linux-toradex.git/include/linux/highmem.h, branch v6.3-rc1

mm: fix memcpy_from_file_folio() integer underflow

2023-02-10T00:51:30+00:00

If we have a HIGHMEM system with a large folio, 'offset' may be larger
than PAGE_SIZE, and so min_t will cap at 'len' instead of the intended
end-of-page.  That can overflow into the next page which is likely to be
unmapped and fault, but could theoretically copy the wrong data.

Link: https://lkml.kernel.org/r/Y919vmSrtAgsf6K3@casper.infradead.org
Fixes: 00cdf76012ab ("mm: add memcpy_from_file_folio()")
Signed-off-by: Matthew Wilcox (Oracle) 
Cc: "Fabio M. De Francesco" 
Cc: Ira Weiny 
Signed-off-by: Andrew Morton

mm: add memcpy_from_file_folio()

2023-02-03T06:33:34+00:00

This is the equivalent of memcpy_from_page().  It differs in that it takes
the position in a file instead of offset in a folio, it accepts the total
number of bytes to be copied (instead of the number of bytes to be copied
from this folio) and it returns how many bytes were copied from the folio,
rather than making the caller calculate that and then checking if the
caller got it right.

[akpm@linux-foundation.org: fix typo in comment]
Link: https://lkml.kernel.org/r/20230126201552.1681588-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Cc: "Fabio M. De Francesco" 
Cc: Ira Weiny 
Signed-off-by: Andrew Morton

mm: add vma_alloc_zeroed_movable_folio()

2023-02-03T06:33:18+00:00

Replace alloc_zeroed_user_highpage_movable().  The main difference is
returning a folio containing a single page instead of returning the page,
but take the opportunity to rename the function to match other allocation
functions a little better and rewrite the documentation to place more
emphasis on the zeroing rather than the highmem aspect.

Link: https://lkml.kernel.org/r/20230116191813.2145215-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: Zi Yan 
Signed-off-by: Andrew Morton

mm: fix spelling mistake in highmem.h

2023-01-19T01:12:54+00:00

Substitute "higmem" with "highmem" in highmem.h.

Link: https://lkml.kernel.org/r/20230105121305.30714-1-fmdefrancesco@gmail.com
Signed-off-by: Fabio M. De Francesco 
Suggested-by: "Matthew Wilcox (Oracle)" 
Reviewed-by: Ira Weiny 
Signed-off-by: Andrew Morton

mm: remove an ambiguous sentence from kmap_local_folio() kdocs

2023-01-19T01:12:54+00:00

In the kdocs of kmap_local_folio() there is a an ambiguous sentence which
suggests to use this API "only when really necessary".

On the contrary, since kmap() and kmap_atomic() are deprecated, both
kmap_local_folio(), as well as kmap_local_page(), must be preferred to the
previous ones.

Therefore, remove the above-mentioned sentence exactly how it has
previously been done for the kmap_local_page() kdocs in commit
72f1c55adf70 ("highmem: delete a sentence from kmap_local_page() kdocs").

Link: https://lkml.kernel.org/r/20230105120424.30055-1-fmdefrancesco@gmail.com
Signed-off-by: Fabio M. De Francesco 
Reviewed-by: Ira Weiny 
Cc: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton

mm, hwpoison: try to recover from copy-on write faults

2022-11-30T23:58:40+00:00

Patch series "Copy-on-write poison recovery", v3.

Part 1 deals with the process that triggered the copy on write fault with
a store to a shared read-only page.  That process is send a SIGBUS with
the usual machine check decoration to specify the virtual address of the
lost page, together with the scope.

Part 2 sets up to asynchronously take the page with the uncorrected error
offline to prevent additional machine check faults.  H/t to Miaohe Lin
 and Shuai Xue  for
pointing me to the existing function to queue a call to memory_failure().

On x86 there is some duplicate reporting (because the error is also
signalled by the memory controller as well as by the core that triggered
the machine check).  Console logs look like this:


This patch (of 2):

If the kernel is copying a page as the result of a copy-on-write
fault and runs into an uncorrectable error, Linux will crash because
it does not have recovery code for this case where poison is consumed
by the kernel.

It is easy to set up a test case. Just inject an error into a private
page, fork(2), and have the child process write to the page.

I wrapped that neatly into a test at:

  git://git.kernel.org/pub/scm/linux/kernel/git/aegl/ras-tools.git

just enable ACPI error injection and run:

  # ./einj_mem-uc -f copy-on-write

Add a new copy_user_highpage_mc() function that uses copy_mc_to_kernel()
on architectures where that is available (currently x86 and powerpc).
When an error is detected during the page copy, return VM_FAULT_HWPOISON
to caller of wp_page_copy(). This propagates up the call stack. Both x86
and powerpc have code in their fault handler to deal with this code by
sending a SIGBUS to the application.

Note that this patch avoids a system crash and signals the process that
triggered the copy-on-write action. It does not take any action for the
memory error that is still in the shared page. To handle that a call to
memory_failure() is needed. But this cannot be done from wp_page_copy()
because it holds mmap_lock(). Perhaps the architecture fault handlers
can deal with this loose end in a subsequent patch?

On Intel/x86 this loose end will often be handled automatically because
the memory controller provides an additional notification of the h/w
poison in memory, the handler for this will call memory_failure(). This
isn't a 100% solution. If there are multiple errors, not all may be
logged in this way.

[tony.luck@intel.com: add call to kmsan_unpoison_memory(), per Miaohe Lin]
  Link: https://lkml.kernel.org/r/20221031201029.102123-2-tony.luck@intel.com
Link: https://lkml.kernel.org/r/20221021200120.175753-1-tony.luck@intel.com
Link: https://lkml.kernel.org/r/20221021200120.175753-2-tony.luck@intel.com
Signed-off-by: Tony Luck 
Reviewed-by: Dan Williams 
Reviewed-by: Naoya Horiguchi 
Reviewed-by: Miaohe Lin 
Reviewed-by: Alexander Potapenko 
Tested-by: Shuai Xue 
Cc: Christophe Leroy 
Cc: Matthew Wilcox (Oracle) 
Cc: Michael Ellerman 
Cc: Nicholas Piggin 
Signed-off-by: Andrew Morton

mm: kmsan: maintain KMSAN metadata for page operations

2022-10-03T21:03:20+00:00

Insert KMSAN hooks that make the necessary bookkeeping changes:
 - poison page shadow and origins in alloc_pages()/free_page();
 - clear page shadow and origins in clear_page(), copy_user_highpage();
 - copy page metadata in copy_highpage(), wp_page_copy();
 - handle vmap()/vunmap()/iounmap();

Link: https://lkml.kernel.org/r/20220915150417.722975-15-glider@google.com
Signed-off-by: Alexander Potapenko 
Cc: Alexander Viro 
Cc: Alexei Starovoitov 
Cc: Andrey Konovalov 
Cc: Andrey Konovalov 
Cc: Andy Lutomirski 
Cc: Arnd Bergmann 
Cc: Borislav Petkov 
Cc: Christoph Hellwig 
Cc: Christoph Lameter 
Cc: David Rientjes 
Cc: Dmitry Vyukov 
Cc: Eric Biggers 
Cc: Eric Biggers 
Cc: Eric Dumazet 
Cc: Greg Kroah-Hartman 
Cc: Herbert Xu 
Cc: Ilya Leoshkevich 
Cc: Ingo Molnar 
Cc: Jens Axboe 
Cc: Joonsoo Kim 
Cc: Kees Cook 
Cc: Marco Elver 
Cc: Mark Rutland 
Cc: Matthew Wilcox 
Cc: Michael S. Tsirkin 
Cc: Pekka Enberg 
Cc: Peter Zijlstra 
Cc: Petr Mladek 
Cc: Stephen Rothwell 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Cc: Vasily Gorbik 
Cc: Vegard Nossum 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

highmem: delete a sentence from kmap_local_page() kdocs

2022-08-09T01:06:46+00:00

kmap_local_page() should always be preferred in place of kmap() and
kmap_atomic().  "Only use when really necessary." is not consistent with
the Documentation/mm/highmem.rst and these kdocs it embeds.

Therefore, delete the above-mentioned sentence from kdocs.

Link: https://lkml.kernel.org/r/20220728154844.10874-7-fmdefrancesco@gmail.com
Signed-off-by: Fabio M. De Francesco 
Suggested-by: Ira Weiny 
Reviewed-by: Ira Weiny 
Cc: Matthew Wilcox (Oracle) 
Cc: Mike Rapoport 
Cc: Sebastian Andrzej Siewior 
Cc: Thomas Gleixner 
Cc: Catalin Marinas 
Cc: Jonathan Corbet 
Cc: Peter Collingbourne 
Cc: Vlastimil Babka 
Cc: Will Deacon 
Signed-off-by: Andrew Morton

highmem: specify that kmap_local_page() is callable from interrupts

2022-08-09T01:06:45+00:00

In a recent thread about converting kmap() to kmap_local_page(), the
safety of calling kmap_local_page() was questioned.[1]

"any context" should probably be enough detail for users who want to know
whether or not kmap_local_page() can be called from interrupts.  However,
Linux still has kmap_atomic() which might make users think they must use
the latter in interrupts.

Add "including interrupts" for better clarity.

[1] https://lore.kernel.org/lkml/3187836.aeNJFYEL58@opensuse/

Link: https://lkml.kernel.org/r/20220728154844.10874-3-fmdefrancesco@gmail.com
Signed-off-by: Fabio M. De Francesco 
Suggested-by: Ira Weiny 
Cc: Matthew Wilcox (Oracle) 
Cc: Mike Rapoport 
Cc: Sebastian Andrzej Siewior 
Cc: Thomas Gleixner 
Cc: Catalin Marinas 
Cc: Jonathan Corbet 
Cc: Peter Collingbourne 
Cc: Vlastimil Babka 
Cc: Will Deacon 
Signed-off-by: Andrew Morton

highmem: remove unneeded spaces in kmap_local_page() kdocs

2022-08-09T01:06:45+00:00

Patch series "highmem: Extend kmap_local_page() documentation", v2.

The Highmem interface is evolving and the current documentation does not
reflect the intended uses of each of the calls.  Furthermore, after a
recent series of reworks, the differences of the calls can still be
confusing and may lead to the expanded use of calls which are deprecated.

This series is the second round of changes towards an enhanced
documentation of the Highmem's interface; at this stage the patches are
only focused to kmap_local_page().

In addition it also contains some minor clean ups.


This patch (of 7):

In the kdocs of kmap_local_page(), the description of @page starts after
several unnecessary spaces.

Therefore, remove those spaces.

Link: https://lkml.kernel.org/r/20220728154844.10874-1-fmdefrancesco@gmail.com
Link: https://lkml.kernel.org/r/20220728154844.10874-2-fmdefrancesco@gmail.com
Signed-off-by: Fabio M. De Francesco 
Suggested-by: Ira Weiny 
Reviewed-by: Ira Weiny 
Cc: Matthew Wilcox (Oracle) 
Cc: Mike Rapoport 
Cc: Sebastian Andrzej Siewior 
Cc: Thomas Gleixner 
Cc: Catalin Marinas 
Cc: Will Deacon 
Cc: Peter Collingbourne 
Cc: Vlastimil Babka 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton