linux-stable.git/arch/sh, branch v4.9.321

gup: document and work around "COW can break either way" issue

2022-01-27T07:47:42+00:00

commit 9bbd42e79720122334226afad9ddcac1c3e6d373 upstream.

Doing a "get_user_pages()" on a copy-on-write page for reading can be
ambiguous: the page can be COW'ed at any time afterwards, and the
direction of a COW event isn't defined.

Yes, whoever writes to it will generally do the COW, but if the thread
that did the get_user_pages() unmapped the page before the write (and
that could happen due to memory pressure in addition to any outright
action), the writer could also just take over the old page instead.

End result: the get_user_pages() call might result in a page pointer
that is no longer associated with the original VM, and is associated
with - and controlled by - another VM having taken it over instead.

So when doing a get_user_pages() on a COW mapping, the only really safe
thing to do would be to break the COW when getting the page, even when
only getting it for reading.

At the same time, some users simply don't even care.

For example, the perf code wants to look up the page not because it
cares about the page, but because the code simply wants to look up the
physical address of the access for informational purposes, and doesn't
really care about races when a page might be unmapped and remapped
elsewhere.

This adds logic to force a COW event by setting FOLL_WRITE on any
copy-on-write mapping when FOLL_GET (or FOLL_PIN) is used to get a page
pointer as a result.

The current semantics end up being:

 - __get_user_pages_fast(): no change. If you don't ask for a write,
   you won't break COW. You'd better know what you're doing.

 - get_user_pages_fast(): the fast-case "look it up in the page tables
   without anything getting mmap_sem" now refuses to follow a read-only
   page, since it might need COW breaking.  Which happens in the slow
   path - the fast path doesn't know if the memory might be COW or not.

 - get_user_pages() (including the slow-path fallback for gup_fast()):
   for a COW mapping, turn on FOLL_WRITE for FOLL_GET/FOLL_PIN, with
   very similar semantics to FOLL_FORCE.

If it turns out that we want finer granularity (ie "only break COW when
it might actually matter" - things like the zero page are special and
don't need to be broken) we might need to push these semantics deeper
into the lookup fault path.  So if people care enough, it's possible
that we might end up adding a new internal FOLL_BREAK_COW flag to go
with the internal FOLL_COW flag we already have for tracking "I had a
COW".

Alternatively, if it turns out that different callers might want to
explicitly control the forced COW break behavior, we might even want to
make such a flag visible to the users of get_user_pages() instead of
using the above default semantics.

But for now, this is mostly commentary on the issue (this commit message
being a lot bigger than the patch, and that patch in turn is almost all
comments), with that minimal "enable COW breaking early" logic using the
existing FOLL_WRITE behavior.

[ It might be worth noting that we've always had this ambiguity, and it
  could arguably be seen as a user-space issue.

  You only get private COW mappings that could break either way in
  situations where user space is doing cooperative things (ie fork()
  before an execve() etc), but it _is_ surprising and very subtle, and
  fork() is supposed to give you independent address spaces.

  So let's treat this as a kernel issue and make the semantics of
  get_user_pages() easier to understand. Note that obviously a true
  shared mapping will still get a page that can change under us, so this
  does _not_ mean that get_user_pages() somehow returns any "stable"
  page ]

[surenb: backport notes
	Replaced (gup_flags | FOLL_WRITE) with write=1 in gup_pgd_range.
	Removed FOLL_PIN usage in should_force_cow_break since it's missing in
	the earlier kernels.]

Reported-by: Jann Horn 
Tested-by: Christoph Hellwig 
Acked-by: Oleg Nesterov 
Acked-by: Kirill Shutemov 
Acked-by: Jan Kara 
Cc: Andrea Arcangeli 
Cc: Matthew Wilcox 
Signed-off-by: Linus Torvalds 
[surenb: backport to 4.19 kernel]
Cc: stable@vger.kernel.org # 4.19.x
Signed-off-by: Suren Baghdasaryan 
Signed-off-by: Greg Kroah-Hartman 
[bwh: Backported to 4.9:
 - Generic get_user_pages_fast() calls __get_user_pages_fast() here,
   so make it pass write=1
 - Various architectures have their own implementations of
   get_user_pages_fast(), so apply the corresponding change there
 - Adjust context]
Signed-off-by: Ben Hutchings 
Signed-off-by: Greg Kroah-Hartman

hugetlbfs: flush TLBs correctly after huge_pmd_unshare

2021-12-08T07:45:03+00:00

commit a4a118f2eead1d6c49e00765de89878288d4b890 upstream.

When __unmap_hugepage_range() calls to huge_pmd_unshare() succeed, a TLB
flush is missing.  This TLB flush must be performed before releasing the
i_mmap_rwsem, in order to prevent an unshared PMDs page from being
released and reused before the TLB flush took place.

Arguably, a comprehensive solution would use mmu_gather interface to
batch the TLB flushes and the PMDs page release, however it is not an
easy solution: (1) try_to_unmap_one() and try_to_migrate_one() also call
huge_pmd_unshare() and they cannot use the mmu_gather interface; and (2)
deferring the release of the page reference for the PMDs page until
after i_mmap_rwsem is dropeed can confuse huge_pmd_unshare() into
thinking PMDs are shared when they are not.

Fix __unmap_hugepage_range() by adding the missing TLB flush, and
forcing a flush when unshare is successful.

Fixes: 24669e58477e ("hugetlb: use mmu_gather instead of a temporary linked list for accumulating pages)" # 3.6
Signed-off-by: Nadav Amit 
Reviewed-by: Mike Kravetz 
Cc: Aneesh Kumar K.V 
Cc: KAMEZAWA Hiroyuki 
Cc: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

sh: define __BIG_ENDIAN for math-emu

2021-11-26T10:48:41+00:00

[ Upstream commit b929926f01f2d14635345d22eafcf60feed1085e ]

Fix this by defining both ENDIAN macros in
 so that they can be utilized in
 according to the latter's comment:
/* Allow sfp-machine to have its own byte order definitions. */

(This is what is done in arch/nds32/include/asm/sfp-machine.h.)

This placates these build warnings:

In file included from ../arch/sh/math-emu/math.c:23:
.../include/math-emu/single.h:50:21: warning: "__BIG_ENDIAN" is not defined, evaluates to 0 [-Wundef]
   50 | #if __BYTE_ORDER == __BIG_ENDIAN
In file included from ../arch/sh/math-emu/math.c:24:
.../include/math-emu/double.h:59:21: warning: "__BIG_ENDIAN" is not defined, evaluates to 0 [-Wundef]
   59 | #if __BYTE_ORDER == __BIG_ENDIAN

Fixes: 4b565680d163 ("sh: math-emu support")
Signed-off-by: Randy Dunlap 
Cc: Yoshinori Sato 
Cc: John Paul Adrian Glaubitz 
Reviewed-by: Geert Uytterhoeven 
Tested-by: John Paul Adrian Glaubitz 
Signed-off-by: Rich Felker 
Signed-off-by: Sasha Levin

sh: fix kconfig unmet dependency warning for FRAME_POINTER

2021-11-26T10:48:41+00:00

[ Upstream commit fda1bc533094a7db68b11e7503d2c6c73993d12a ]

FRAME_POINTER depends on DEBUG_KERNEL so DWARF_UNWINDER should
depend on DEBUG_KERNEL before selecting FRAME_POINTER.

WARNING: unmet direct dependencies detected for FRAME_POINTER
  Depends on [n]: DEBUG_KERNEL [=n] && (M68K || UML || SUPERH [=y]) || ARCH_WANT_FRAME_POINTERS [=n]
  Selected by [y]:
  - DWARF_UNWINDER [=y]

Fixes: bd353861c735 ("sh: dwarf unwinder support.")
Signed-off-by: Randy Dunlap 
Cc: Matt Fleming 
Cc: Matt Fleming 
Cc: Yoshinori Sato 
Cc: John Paul Adrian Glaubitz 
Cc: Geert Uytterhoeven 
Reviewed-by: Geert Uytterhoeven 
Tested-by: John Paul Adrian Glaubitz 
Signed-off-by: Rich Felker 
Signed-off-by: Sasha Levin

sh: check return code of request_irq

2021-11-26T10:48:41+00:00

[ Upstream commit 0e38225c92c7964482a8bb6b3e37fde4319e965c ]

request_irq is marked __must_check, but the call in shx3_prepare_cpus
has a void return type, so it can't propagate failure to the caller.
Follow cues from hexagon and just print an error.

Fixes: c7936b9abcf5 ("sh: smp: Hook in to the generic IPI handler for SH-X3 SMP.")
Cc: Miguel Ojeda 
Cc: Paul Mundt 
Reported-by: Guenter Roeck 
Signed-off-by: Nick Desaulniers 
Tested-by: John Paul Adrian Glaubitz 
Reviewed-by: Miguel Ojeda 
Signed-off-by: Rich Felker 
Signed-off-by: Sasha Levin

sh: dma: fix kconfig dependency for G2_DMA

2021-01-30T12:27:15+00:00

commit f477a538c14d07f8c45e554c8c5208d588514e98 upstream.

When G2_DMA is enabled and SH_DMA is disabled, it results in the following
Kbuild warning:

WARNING: unmet direct dependencies detected for SH_DMA_API
  Depends on [n]: SH_DMA [=n]
  Selected by [y]:
  - G2_DMA [=y] && SH_DREAMCAST [=y]

The reason is that G2_DMA selects SH_DMA_API without depending on or
selecting SH_DMA while SH_DMA_API depends on SH_DMA.

When G2_DMA was first introduced with commit 40f49e7ed77f
("sh: dma: Make G2 DMA configurable."), this wasn't an issue since
SH_DMA_API didn't have such dependency, and this way was the only way to
enable it since SH_DMA_API was non-visible. However, later SH_DMA_API was
made visible and dependent on SH_DMA with commit d8902adcc1a9
("dmaengine: sh: Add Support SuperH DMA Engine driver").

Let G2_DMA depend on SH_DMA_API instead to avoid Kbuild issues.

Fixes: d8902adcc1a9 ("dmaengine: sh: Add Support SuperH DMA Engine driver")
Signed-off-by: Necip Fazil Yildiran 
Signed-off-by: Rich Felker 
Signed-off-by: Greg Kroah-Hartman

sh: landisk: Add missing initialization of sh_io_port_base

2020-08-21T09:02:11+00:00

[ Upstream commit 0c64a0dce51faa9c706fdf1f957d6f19878f4b81 ]

The Landisk setup code maps the CF IDE area using ioremap_prot(), and
passes the resulting virtual addresses to the pata_platform driver,
disguising them as I/O port addresses.  Hence the pata_platform driver
translates them again using ioport_map().
As CONFIG_GENERIC_IOMAP=n, and CONFIG_HAS_IOPORT_MAP=y, the
SuperH-specific mapping code in arch/sh/kernel/ioport.c translates
I/O port addresses to virtual addresses by adding sh_io_port_base, which
defaults to -1, thus breaking the assumption of an identity mapping.

Fix this by setting sh_io_port_base to zero.

Fixes: 37b7a97884ba64bf ("sh: machvec IO death.")
Signed-off-by: Geert Uytterhoeven 
Signed-off-by: Rich Felker 
Signed-off-by: Sasha Levin

sh: Fix validation of system call number

2020-08-21T09:01:50+00:00

[ Upstream commit 04a8a3d0a73f51c7c2da84f494db7ec1df230e69 ]

The slow path for traced system call entries accessed a wrong memory
location to get the number of the maximum allowed system call number.
Renumber the numbered "local" label for the correct location to avoid
collisions with actual local labels.

Signed-off-by: Michael Karcher 
Tested-by: John Paul Adrian Glaubitz 
Fixes: f3a8308864f920d2 ("sh: Add a few missing irqflags tracing markers.")
Signed-off-by: Rich Felker 
Signed-off-by: Sasha Levin

pinctrl: sh-pfc: sh7269: Fix CAN function GPIOs

2020-02-28T14:42:28+00:00

[ Upstream commit 02aeb2f21530c98fc3ca51028eda742a3fafbd9f ]

pinmux_func_gpios[] contains a hole due to the missing function GPIO
definition for the "CTX0&CTX1" signal, which is the logical "AND" of the
first two CAN outputs.

A closer look reveals other issues:
  - Some functionality is available on alternative pins, but the
    PINMUX_DATA() entries is using the wrong marks,
  - Several configurations are missing.

Fix this by:
  - Renaming CTX0CTX1CTX2_MARK, CRX0CRX1_PJ22_MARK, and
    CRX0CRX1CRX2_PJ20_MARK to CTX0_CTX1_CTX2_MARK, CRX0_CRX1_PJ22_MARK,
    resp. CRX0_CRX1_CRX2_PJ20_MARK for consistency with the
    corresponding enum IDs,
  - Adding all missing enum IDs and marks,
  - Use the right (*_PJ2x) variants for alternative pins,
  - Adding all missing configurations to pinmux_data[],
  - Adding all missing function GPIO definitions to pinmux_func_gpios[].

See SH7268 Group, SH7269 Group User’s Manual: Hardware, Rev. 2.00:
  [1] Table 1.4 List of Pins
  [2] Figure 23.29 Connection Example when Using Channels 0 and 1 as One
      Channel (64 Mailboxes × 1 Channel) and Channel 2 as One Channel
      (32 Mailboxes × 1 Channel),
  [3] Figure 23.30 Connection Example when Using Channels 0, 1, and 2 as
      One Channel (96 Mailboxes × 1 Channel),
  [4] Table 48.3 Multiplexed Pins (Port B),
  [5] Table 48.4 Multiplexed Pins (Port C),
  [6] Table 48.10 Multiplexed Pins (Port J),
  [7] Section 48.2.4 Port B Control Registers 0 to 5 (PBCR0 to PBCR5).

Signed-off-by: Geert Uytterhoeven 
Link: https://lore.kernel.org/r/20191218194812.12741-5-geert+renesas@glider.be
Signed-off-by: Sasha Levin

pinctrl: sh-pfc: sh7734: Fix duplicate TCLK1_B

2020-01-04T12:39:31+00:00

[ Upstream commit 884caadad128efad8e00c1cdc3177bc8912ee8ec ]

The definitions for bit field [19:18] of the Peripheral Function Select
Register 3 were accidentally copied from bit field [20], leading to
duplicates for the TCLK1_B function, and missing TCLK0, CAN_CLK_B, and
ET0_ETXD4 functions.

Fix this by adding the missing GPIO_FN_CAN_CLK_B and GPIO_FN_ET0_ETXD4
enum values, and correcting the functions.

Reported-by: Ben Dooks 
Signed-off-by: Geert Uytterhoeven 
Link: https://lore.kernel.org/r/20191024131308.16659-1-geert+renesas@glider.be
Signed-off-by: Sasha Levin