epoll: wire up syscall epoll_pwait2

Split off from prev patch in the series that implements the syscall.

Link: https://lkml.kernel.org/r/20201121144401.3727659-4-willemdebruijn.kernel@gmail.com
Sig

epoll: wire up syscall epoll_pwait2

Split off from prev patch in the series that implements the syscall.

Link: https://lkml.kernel.org/r/20201121144401.3727659-4-willemdebruijn.kernel@gmail.com
Signed-off-by: Willem de Bruijn <willemb@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

Merge branch 'for-5.11/elecom' into for-linus

- support for EX-G M-XGL20DLBK device, from YOSHIOKA Takuma

Merge branch 'next' into for-linus

Prepare input updates for 5.11 merge window.

Merge remote-tracking branch 'spi/for-5.10' into spi-linus

Merge remote-tracking branch 'asoc/for-5.10' into asoc-linus

Merge branches 'for-next/kvm-build-fix', 'for-next/va-refactor', 'for-next/lto', 'for-next/mem-hotplug', 'for-next/cppc-ffh', 'for-next/pad-image-header', 'for-next/zone-dma-default-32-bit', 'for-nex

Merge branches 'for-next/kvm-build-fix', 'for-next/va-refactor', 'for-next/lto', 'for-next/mem-hotplug', 'for-next/cppc-ffh', 'for-next/pad-image-header', 'for-next/zone-dma-default-32-bit', 'for-next/signal-tag-bits' and 'for-next/cmdline-extended' into for-next/core

* for-next/kvm-build-fix:
: Fix KVM build issues with 64K pages
KVM: arm64: Fix build error in user_mem_abort()

* for-next/va-refactor:
: VA layout changes
arm64: mm: don't assume struct page is always 64 bytes
Documentation/arm64: fix RST layout of memory.rst
arm64: mm: tidy up top of kernel VA space
arm64: mm: make vmemmap region a projection of the linear region
arm64: mm: extend linear region for 52-bit VA configurations

* for-next/lto:
: Upgrade READ_ONCE() to RCpc acquire on arm64 with LTO
arm64: lto: Strengthen READ_ONCE() to acquire when CONFIG_LTO=y
arm64: alternatives: Remove READ_ONCE() usage during patch operation
arm64: cpufeatures: Add capability for LDAPR instruction
arm64: alternatives: Split up alternative.h
arm64: uaccess: move uao_* alternatives to asm-uaccess.h

* for-next/mem-hotplug:
: Memory hotplug improvements
arm64/mm/hotplug: Ensure early memory sections are all online
arm64/mm/hotplug: Enable MEM_OFFLINE event handling
arm64/mm/hotplug: Register boot memory hot remove notifier earlier
arm64: mm: account for hotplug memory when randomizing the linear region

* for-next/cppc-ffh:
: Add CPPC FFH support using arm64 AMU counters
arm64: abort counter_read_on_cpu() when irqs_disabled()
arm64: implement CPPC FFH support using AMUs
arm64: split counter validation function
arm64: wrap and generalise counter read functions

* for-next/pad-image-header:
: Pad Image header to 64KB and unmap it
arm64: head: tidy up the Image header definition
arm64/head: avoid symbol names pointing into first 64 KB of kernel image
arm64: omit [_text, _stext) from permanent kernel mapping

* for-next/zone-dma-default-32-bit:
: Default to 32-bit wide ZONE_DMA (previously reduced to 1GB for RPi4)
of: unittest: Fix build on architectures without CONFIG_OF_ADDRESS
mm: Remove examples from enum zone_type comment
arm64: mm: Set ZONE_DMA size based on early IORT scan
arm64: mm: Set ZONE_DMA size based on devicetree's dma-ranges
of: unittest: Add test for of_dma_get_max_cpu_address()
of/address: Introduce of_dma_get_max_cpu_address()
arm64: mm: Move zone_dma_bits initialization into zone_sizes_init()
arm64: mm: Move reserve_crashkernel() into mem_init()
arm64: Force NO_BLOCK_MAPPINGS if crashkernel reservation is required
arm64: Ignore any DMA offsets in the max_zone_phys() calculation

* for-next/signal-tag-bits:
: Expose the FAR_EL1 tag bits in siginfo
arm64: expose FAR_EL1 tag bits in siginfo
signal: define the SA_EXPOSE_TAGBITS bit in sa_flags
signal: define the SA_UNSUPPORTED bit in sa_flags
arch: provide better documentation for the arch-specific SA_* flags
signal: clear non-uapi flag bits when passing/returning sa_flags
arch: move SA_* definitions to generic headers
parisc: start using signal-defs.h
parisc: Drop parisc special case for __sighandler_t

* for-next/cmdline-extended:
: Add support for CONFIG_CMDLINE_EXTENDED
arm64: Extend the kernel command line from the bootloader
arm64: kaslr: Refactor early init command line parsing

show more ...

Merge remote-tracking branch 'origin/master' into perf/core

Further perf/core patches will depend on:

d3f7b1bb2040 ("mm/gup: fix gup_fast with dynamic page table folding")

which is already in Li

Merge remote-tracking branch 'origin/master' into perf/core

Further perf/core patches will depend on:

d3f7b1bb2040 ("mm/gup: fix gup_fast with dynamic page table folding")

which is already in Linus' tree.

show more ...

Merge tag 'v5.9' into next

Sync up with mainline to bring in the latest DTS files.

Merge tag 'v5.10-rc1' into kvmarm-master/next

Linux 5.10-rc1

Signed-off-by: Marc Zyngier <maz@kernel.org>

Merge branch 'linus' into perf/kprobes

Conflicts:
include/asm-generic/atomic-instrumented.h
kernel/kprobes.c

Use the upstream atomic-instrumented.h checksum, and pick
the kprobes version of kerne

Merge branch 'linus' into perf/kprobes

Conflicts:
include/asm-generic/atomic-instrumented.h
kernel/kprobes.c

Use the upstream atomic-instrumented.h checksum, and pick
the kprobes version of kernel/kprobes.c, which effectively
reverts this upstream workaround:

645f224e7ba2: ("kprobes: Tell lockdep about kprobe nesting")

Since the new code *should* be fine without nesting.

Knock on wood ...

Signed-off-by: Ingo Molnar <mingo@kernel.org>

show more ...

Merge drm/drm-next into drm-intel-next-queued

Catch up with v5.10-rc2 and drm-misc-next.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Merge branch 'core/urgent' into core/entry

Pick up the entry fix before further modifications.

Merge drm/drm-next into drm-misc-next

Daniel needs -rc2 in drm-misc-next to merge some patches

Signed-off-by: Maxime Ripard <maxime@cerno.tech>

Merge tag 'drm-intel-fixes-2020-10-29' into gvt-fixes

Backmerge for 5.10-rc1 to apply one extra APL fix.

Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

Merge tag 'v5.10-rc1' into regulator-5.10

Linux 5.10-rc1

Merge tag 'v5.10-rc1' into spi-5.10

Linux 5.10-rc1

Merge tag 'v5.10-rc1' into asoc-5.10

Linux 5.10-rc1

Merge branch 'akpm' (patches from Andrew)

Merge yet more updates from Andrew Morton:
"Subsystems affected by this patch series: mm (memcg, migration,
pagemap, gup, madvise, vmalloc), ia64, and mi

Merge branch 'akpm' (patches from Andrew)

Merge yet more updates from Andrew Morton:
"Subsystems affected by this patch series: mm (memcg, migration,
pagemap, gup, madvise, vmalloc), ia64, and misc"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (31 commits)
mm: remove duplicate include statement in mmu.c
mm: remove the filename in the top of file comment in vmalloc.c
mm: cleanup the gfp_mask handling in __vmalloc_area_node
mm: remove alloc_vm_area
x86/xen: open code alloc_vm_area in arch_gnttab_valloc
xen/xenbus: use apply_to_page_range directly in xenbus_map_ring_pv
drm/i915: use vmap in i915_gem_object_map
drm/i915: stop using kmap in i915_gem_object_map
drm/i915: use vmap in shmem_pin_map
zsmalloc: switch from alloc_vm_area to get_vm_area
mm: allow a NULL fn callback in apply_to_page_range
mm: add a vmap_pfn function
mm: add a VM_MAP_PUT_PAGES flag for vmap
mm: update the documentation for vfree
mm/madvise: introduce process_madvise() syscall: an external memory hinting API
pid: move pidfd_get_pid() to pid.c
mm/madvise: pass mm to do_madvise
selftests/vm: 10x speedup for hmm-tests
binfmt_elf: take the mmap lock around find_extend_vma()
mm/gup_benchmark: take the mmap lock around GUP
...

show more ...

mm/madvise: introduce process_madvise() syscall: an external memory hinting API

There is usecase that System Management Software(SMS) want to give a
memory hint like MADV_[COLD|PAGEEOUT] to other pr

mm/madvise: introduce process_madvise() syscall: an external memory hinting API

There is usecase that System Management Software(SMS) want to give a
memory hint like MADV_[COLD|PAGEEOUT] to other processes and in the
case of Android, it is the ActivityManagerService.

The information required to make the reclaim decision is not known to the
app. Instead, it is known to the centralized userspace
daemon(ActivityManagerService), and that daemon must be able to initiate
reclaim on its own without any app involvement.

To solve the issue, this patch introduces a new syscall
process_madvise(2). It uses pidfd of an external process to give the
hint. It also supports vector address range because Android app has
thousands of vmas due to zygote so it's totally waste of CPU and power if
we should call the syscall one by one for each vma.(With testing 2000-vma
syscall vs 1-vector syscall, it showed 15% performance improvement. I
think it would be bigger in real practice because the testing ran very
cache friendly environment).

Another potential use case for the vector range is to amortize the cost
ofTLB shootdowns for multiple ranges when using MADV_DONTNEED; this could
benefit users like TCP receive zerocopy and malloc implementations. In
future, we could find more usecases for other advises so let's make it
happens as API since we introduce a new syscall at this moment. With
that, existing madvise(2) user could replace it with process_madvise(2)
with their own pid if they want to have batch address ranges support
feature.

ince it could affect other process's address range, only privileged
process(PTRACE_MODE_ATTACH_FSCREDS) or something else(e.g., being the same
UID) gives it the right to ptrace the process could use it successfully.
The flag argument is reserved for future use if we need to extend the API.

I think supporting all hints madvise has/will supported/support to
process_madvise is rather risky. Because we are not sure all hints make
sense from external process and implementation for the hint may rely on
the caller being in the current context so it could be error-prone. Thus,
I just limited hints as MADV_[COLD|PAGEOUT] in this patch.

If someone want to add other hints, we could hear the usecase and review
it for each hint. It's safer for maintenance rather than introducing a
buggy syscall but hard to fix it later.

So finally, the API is as follows,

ssize_t process_madvise(int pidfd, const struct iovec *iovec,
unsigned long vlen, int advice, unsigned int flags);

DESCRIPTION
The process_madvise() system call is used to give advice or directions
to the kernel about the address ranges from external process as well as
local process. It provides the advice to address ranges of process
described by iovec and vlen. The goal of such advice is to improve
system or application performance.

The pidfd selects the process referred to by the PID file descriptor
specified in pidfd. (See pidofd_open(2) for further information)

The pointer iovec points to an array of iovec structures, defined in
<sys/uio.h> as:

struct iovec {
void *iov_base; /* starting address */
size_t iov_len; /* number of bytes to be advised */
};

The iovec describes address ranges beginning at address(iov_base)
and with size length of bytes(iov_len).

The vlen represents the number of elements in iovec.

The advice is indicated in the advice argument, which is one of the
following at this moment if the target process specified by pidfd is
external.

MADV_COLD
MADV_PAGEOUT

Permission to provide a hint to external process is governed by a
ptrace access mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).

The process_madvise supports every advice madvise(2) has if target
process is in same thread group with calling process so user could
use process_madvise(2) to extend existing madvise(2) to support
vector address ranges.

RETURN VALUE
On success, process_madvise() returns the number of bytes advised.
This return value may be less than the total number of requested
bytes, if an error occurred. The caller should check return value
to determine whether a partial advice occurred.

FAQ:

Q.1 - Why does any external entity have better knowledge?

Quote from Sandeep

"For Android, every application (including the special SystemServer)
are forked from Zygote. The reason of course is to share as many
libraries and classes between the two as possible to benefit from the
preloading during boot.

After applications start, (almost) all of the APIs end up calling into
this SystemServer process over IPC (binder) and back to the
application.

In a fully running system, the SystemServer monitors every single
process periodically to calculate their PSS / RSS and also decides
which process is "important" to the user for interactivity.

So, because of how these processes start _and_ the fact that the
SystemServer is looping to monitor each process, it does tend to *know*
which address range of the application is not used / useful.

Besides, we can never rely on applications to clean things up
themselves. We've had the "hey app1, the system is low on memory,
please trim your memory usage down" notifications for a long time[1].
They rely on applications honoring the broadcasts and very few do.

So, if we want to avoid the inevitable killing of the application and
restarting it, some way to be able to tell the OS about unimportant
memory in these applications will be useful.

- ssp

Q.2 - How to guarantee the race(i.e., object validation) between when
giving a hint from an external process and get the hint from the target
process?

process_madvise operates on the target process's address space as it
exists at the instant that process_madvise is called. If the space
target process can run between the time the process_madvise process
inspects the target process address space and the time that
process_madvise is actually called, process_madvise may operate on
memory regions that the calling process does not expect. It's the
responsibility of the process calling process_madvise to close this
race condition. For example, the calling process can suspend the
target process with ptrace, SIGSTOP, or the freezer cgroup so that it
doesn't have an opportunity to change its own address space before
process_madvise is called. Another option is to operate on memory
regions that the caller knows a priori will be unchanged in the target
process. Yet another option is to accept the race for certain
process_madvise calls after reasoning that mistargeting will do no
harm. The suggested API itself does not provide synchronization. It
also apply other APIs like move_pages, process_vm_write.

The race isn't really a problem though. Why is it so wrong to require
that callers do their own synchronization in some manner? Nobody
objects to write(2) merely because it's possible for two processes to
open the same file and clobber each other's writes --- instead, we tell
people to use flock or something. Think about mmap. It never
guarantees newly allocated address space is still valid when the user
tries to access it because other threads could unmap the memory right
before. That's where we need synchronization by using other API or
design from userside. It shouldn't be part of API itself. If someone
needs more fine-grained synchronization rather than process level,
there were two ideas suggested - cookie[2] and anon-fd[3]. Both are
applicable via using last reserved argument of the API but I don't
think it's necessary right now since we have already ways to prevent
the race so don't want to add additional complexity with more
fine-grained optimization model.

To make the API extend, it reserved an unsigned long as last argument
so we could support it in future if someone really needs it.

Q.3 - Why doesn't ptrace work?

Injecting an madvise in the target process using ptrace would not work
for us because such injected madvise would have to be executed by the
target process, which means that process would have to be runnable and
that creates the risk of the abovementioned race and hinting a wrong
VMA. Furthermore, we want to act the hint in caller's context, not the
callee's, because the callee is usually limited in cpuset/cgroups or
even freezed state so they can't act by themselves quick enough, which
causes more thrashing/kill. It doesn't work if the target process are
ptraced(e.g., strace, debugger, minidump) because a process can have at
most one ptracer.

[1] https://developer.android.com/topic/performance/memory"

[2] process_getinfo for getting the cookie which is updated whenever
vma of process address layout are changed - Daniel Colascione -
https://lore.kernel.org/lkml/20190520035254.57579-1-minchan@kernel.org/T/#m7694416fd179b2066a2c62b5b139b14e3894e224

[3] anonymous fd which is used for the object(i.e., address range)
validation - Michal Hocko -
https://lore.kernel.org/lkml/20200120112722.GY18451@dhcp22.suse.cz/

[minchan@kernel.org: fix process_madvise build break for arm64]
Link: http://lkml.kernel.org/r/20200303145756.GA219683@google.com
[minchan@kernel.org: fix build error for mips of process_madvise]
Link: http://lkml.kernel.org/r/20200508052517.GA197378@google.com
[akpm@linux-foundation.org: fix patch ordering issue]
[akpm@linux-foundation.org: fix arm64 whoops]
[minchan@kernel.org: make process_madvise() vlen arg have type size_t, per Florian]
[akpm@linux-foundation.org: fix i386 build]
[sfr@canb.auug.org.au: fix syscall numbering]
Link: https://lkml.kernel.org/r/20200905142639.49fc3f1a@canb.auug.org.au
[sfr@canb.auug.org.au: madvise.c needs compat.h]
Link: https://lkml.kernel.org/r/20200908204547.285646b4@canb.auug.org.au
[minchan@kernel.org: fix mips build]
Link: https://lkml.kernel.org/r/20200909173655.GC2435453@google.com
[yuehaibing@huawei.com: remove duplicate header which is included twice]
Link: https://lkml.kernel.org/r/20200915121550.30584-1-yuehaibing@huawei.com
[minchan@kernel.org: do not use helper functions for process_madvise]
Link: https://lkml.kernel.org/r/20200921175539.GB387368@google.com
[akpm@linux-foundation.org: pidfd_get_pid() gained an argument]
[sfr@canb.auug.org.au: fix up for "iov_iter: transparently handle compat iovecs in import_iovec"]
Link: https://lkml.kernel.org/r/20200928212542.468e1fef@canb.auug.org.au

Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Christian Brauner <christian@brauner.io>
Cc: Daniel Colascione <dancol@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Dias <joaodias@google.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleksandr Natalenko <oleksandr@redhat.com>
Cc: Sandeep Patil <sspatil@google.com>
Cc: SeongJae Park <sj38.park@gmail.com>
Cc: SeongJae Park <sjpark@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Sonny Rao <sonnyrao@google.com>
Cc: Tim Murray <timmurray@google.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Florian Weimer <fw@deneb.enyo.de>
Cc: <linux-man@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200302193630.68771-3-minchan@kernel.org
Link: http://lkml.kernel.org/r/20200508183320.GA125527@google.com
Link: http://lkml.kernel.org/r/20200622192900.22757-4-minchan@kernel.org
Link: https://lkml.kernel.org/r/20200901000633.1920247-4-minchan@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

Merge branch 'for-5.10/core' into for-linus

- nonblocking read semantics fix for hid-debug

Merge branch 'compat.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull compat mount cleanups from Al Viro:
"The last remnants of mount(2) compat buried by Christoph.

Buried i

Merge branch 'compat.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull compat mount cleanups from Al Viro:
"The last remnants of mount(2) compat buried by Christoph.

Buried into NFS, that is.

Generally I'm less enthusiastic about "let's use in_compat_syscall()
deep in call chain" kind of approach than Christoph seems to be, but
in this case it's warranted - that had been an NFS-specific wart,
hopefully not to be repeated in any other filesystems (read: any new
filesystem introducing non-text mount options will get NAKed even if
it doesn't mess the layout up).

IOW, not worth trying to grow an infrastructure that would avoid that
use of in_compat_syscall()..."

* 'compat.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fs: remove compat_sys_mount
fs,nfs: lift compat nfs4 mount data handling into the nfs code
nfs: simplify nfs4_parse_monolithic

show more ...

Merge branch 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull compat iovec cleanups from Al Viro:
"Christoph's series around import_iovec() and compat variant thereof"

Merge branch 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull compat iovec cleanups from Al Viro:
"Christoph's series around import_iovec() and compat variant thereof"

* 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
security/keys: remove compat_keyctl_instantiate_key_iov
mm: remove compat_process_vm_{readv,writev}
fs: remove compat_sys_vmsplice
fs: remove the compat readv/writev syscalls
fs: remove various compat readv/writev helpers
iov_iter: transparently handle compat iovecs in import_iovec
iov_iter: refactor rw_copy_check_uvector and import_iovec
iov_iter: move rw_copy_check_uvector() into lib/iov_iter.c
compat.h: fix a spelling error in <linux/compat.h>

show more ...

mm: remove compat_process_vm_{readv,writev}

Now that import_iovec handles compat iovecs, the native syscalls
can be used for the compat case as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
S

mm: remove compat_process_vm_{readv,writev}

Now that import_iovec handles compat iovecs, the native syscalls
can be used for the compat case as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

show more ...

fs: remove compat_sys_vmsplice

Now that import_iovec handles compat iovecs, the native vmsplice syscall
can be used for the compat case as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed

fs: remove compat_sys_vmsplice

Now that import_iovec handles compat iovecs, the native vmsplice syscall
can be used for the compat case as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

show more ...

fs: remove the compat readv/writev syscalls

Now that import_iovec handles compat iovecs, the native readv and writev
syscalls can be used for the compat case as well.

Signed-off-by: Christoph Hellw

fs: remove the compat readv/writev syscalls

Now that import_iovec handles compat iovecs, the native readv and writev
syscalls can be used for the compat case as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

show more ...