Provide a generic helper for setting up an io_uring worker. Returns a
task_struct so that the caller can do whatever setup is needed, then call
wake_up_new_task() to kick it into gear.
Add a kernel_clone_args member, io_thread, which tells copy_process() to
mark the task with PF_IO_WORKER.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pull exec-update-lock update from Eric Biederman:
"The key point of this is to transform exec_update_mutex into a
rw_semaphore so readers can be separated from writers.
This makes it easier to understand what the holders of the lock are
doing, and makes it harder to contend or deadlock on the lock.
The real deadlock fix wound up in perf_event_open"
* 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
exec: Transform exec_update_mutex into a rw_semaphore
Pull execve updates from Eric Biederman:
"This set of changes ultimately fixes the interaction of posix file
lock and exec. Fundamentally most of the change is just moving where
unshare_files is called during exec, and tweaking the users of
files_struct so that the count of files_struct is not unnecessarily
played with.
Along the way fcheck and related helpers were renamed to more
accurately reflect what they do.
There were also many other small changes that fell out, as this is the
first time in a long time much of this code has been touched.
Benchmarks haven't turned up any practical issues but Al Viro has
observed a possibility for a lot of pounding on task_lock. So I have
some changes in progress to convert put_files_struct to always rcu
free files_struct. That wasn't ready for the merge window so that will
have to wait until next time"
* 'exec-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (27 commits)
exec: Move io_uring_task_cancel after the point of no return
coredump: Document coredump code exclusively used by cell spufs
file: Remove get_files_struct
file: Rename __close_fd_get_file close_fd_get_file
file: Replace ksys_close with close_fd
file: Rename __close_fd to close_fd and remove the files parameter
file: Merge __alloc_fd into alloc_fd
file: In f_dupfd read RLIMIT_NOFILE once.
file: Merge __fd_install into fd_install
proc/fd: In fdinfo seq_show don't use get_files_struct
bpf/task_iter: In task_file_seq_get_next use task_lookup_next_fd_rcu
proc/fd: In proc_readfd_common use task_lookup_next_fd_rcu
file: Implement task_lookup_next_fd_rcu
kcmp: In get_file_raw_ptr use task_lookup_fd_rcu
proc/fd: In tid_fd_mode use task_lookup_fd_rcu
file: Implement task_lookup_fd_rcu
file: Rename fcheck lookup_fd_rcu
file: Replace fcheck_files with files_lookup_fd_rcu
file: Factor files_lookup_fd_locked out of fcheck_files
file: Rename __fcheck_files to files_lookup_fd_raw
...
Core:
- support "prefer busy polling" NAPI operation mode, where we defer softirq
for some time expecting applications to periodically busy poll
- AF_XDP: improve efficiency by more batching and hindering
the adjacency cache prefetcher
- af_packet: make packet_fanout.arr size configurable up to 64K
- tcp: optimize TCP zero copy receive in presence of partial or unaligned
reads making zero copy a performance win for much smaller messages
- XDP: add bulk APIs for returning / freeing frames
- sched: support fragmenting IP packets as they come out of conntrack
- net: allow virtual netdevs to forward UDP L4 and fraglist GSO skbs
BPF:
- BPF switch from crude rlimit-based to memcg-based memory accounting
- BPF type format information for kernel modules and related tracing
enhancements
- BPF implement task local storage for BPF LSM
- allow the FENTRY/FEXIT/RAW_TP tracing programs to use bpf_sk_storage
Protocols:
- mptcp: improve multiple xmit streams support, memory accounting and
many smaller improvements
- TLS: support CHACHA20-POLY1305 cipher
- seg6: add support for SRv6 End.DT4/DT6 behavior
- sctp: Implement RFC 6951: UDP Encapsulation of SCTP
- ppp_generic: add ability to bridge channels directly
- bridge: Connectivity Fault Management (CFM) support as is defined in
IEEE 802.1Q section 12.14.
Drivers:
- mlx5: make use of the new auxiliary bus to organize the driver internals
- mlx5: more accurate port TX timestamping support
- mlxsw:
- improve the efficiency of offloaded next hop updates by using
the new nexthop object API
- support blackhole nexthops
- support IEEE 802.1ad (Q-in-Q) bridging
- rtw88: major bluetooth co-existance improvements
- iwlwifi: support new 6 GHz frequency band
- ath11k: Fast Initial Link Setup (FILS)
- mt7915: dual band concurrent (DBDC) support
- net: ipa: add basic support for IPA v4.5
Refactor:
- a few pieces of in_interrupt() cleanup work from Sebastian Andrzej Siewior
- phy: add support for shared interrupts; get rid of multiple driver
APIs and have the drivers write a full IRQ handler, slight growth
of driver code should be compensated by the simpler API which
also allows shared IRQs
- add common code for handling netdev per-cpu counters
- move TX packet re-allocation from Ethernet switch tag drivers to
a central place
- improve efficiency and rename nla_strlcpy
- number of W=1 warning cleanups as we now catch those in a patchwork
build bot
Old code removal:
- wan: delete the DLCI / SDLA drivers
- wimax: move to staging
- wifi: remove old WDS wifi bridging support
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Merge tag 'net-next-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next
Pull networking updates from Jakub Kicinski:
"Core:
- support "prefer busy polling" NAPI operation mode, where we defer
softirq for some time expecting applications to periodically busy
poll
- AF_XDP: improve efficiency by more batching and hindering the
adjacency cache prefetcher
- af_packet: make packet_fanout.arr size configurable up to 64K
- tcp: optimize TCP zero copy receive in presence of partial or
unaligned reads making zero copy a performance win for much smaller
messages
- XDP: add bulk APIs for returning / freeing frames
- sched: support fragmenting IP packets as they come out of conntrack
- net: allow virtual netdevs to forward UDP L4 and fraglist GSO skbs
BPF:
- BPF switch from crude rlimit-based to memcg-based memory accounting
- BPF type format information for kernel modules and related tracing
enhancements
- BPF implement task local storage for BPF LSM
- allow the FENTRY/FEXIT/RAW_TP tracing programs to use
bpf_sk_storage
Protocols:
- mptcp: improve multiple xmit streams support, memory accounting and
many smaller improvements
- TLS: support CHACHA20-POLY1305 cipher
- seg6: add support for SRv6 End.DT4/DT6 behavior
- sctp: Implement RFC 6951: UDP Encapsulation of SCTP
- ppp_generic: add ability to bridge channels directly
- bridge: Connectivity Fault Management (CFM) support as is defined
in IEEE 802.1Q section 12.14.
Drivers:
- mlx5: make use of the new auxiliary bus to organize the driver
internals
- mlx5: more accurate port TX timestamping support
- mlxsw:
- improve the efficiency of offloaded next hop updates by using
the new nexthop object API
- support blackhole nexthops
- support IEEE 802.1ad (Q-in-Q) bridging
- rtw88: major bluetooth co-existance improvements
- iwlwifi: support new 6 GHz frequency band
- ath11k: Fast Initial Link Setup (FILS)
- mt7915: dual band concurrent (DBDC) support
- net: ipa: add basic support for IPA v4.5
Refactor:
- a few pieces of in_interrupt() cleanup work from Sebastian Andrzej
Siewior
- phy: add support for shared interrupts; get rid of multiple driver
APIs and have the drivers write a full IRQ handler, slight growth
of driver code should be compensated by the simpler API which also
allows shared IRQs
- add common code for handling netdev per-cpu counters
- move TX packet re-allocation from Ethernet switch tag drivers to a
central place
- improve efficiency and rename nla_strlcpy
- number of W=1 warning cleanups as we now catch those in a patchwork
build bot
Old code removal:
- wan: delete the DLCI / SDLA drivers
- wimax: move to staging
- wifi: remove old WDS wifi bridging support"
* tag 'net-next-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1922 commits)
net: hns3: fix expression that is currently always true
net: fix proc_fs init handling in af_packet and tls
nfc: pn533: convert comma to semicolon
af_vsock: Assign the vsock transport considering the vsock address flags
af_vsock: Set VMADDR_FLAG_TO_HOST flag on the receive path
vsock_addr: Check for supported flag values
vm_sockets: Add VMADDR_FLAG_TO_HOST vsock flag
vm_sockets: Add flags field in the vsock address data structure
net: Disable NETIF_F_HW_TLS_TX when HW_CSUM is disabled
tcp: Add logic to check for SYN w/ data in tcp_simple_retransmit
net: mscc: ocelot: install MAC addresses in .ndo_set_rx_mode from process context
nfc: s3fwrn5: Release the nfc firmware
net: vxget: clean up sparse warnings
mlxsw: spectrum_router: Use eXtended mezzanine to offload IPv4 router
mlxsw: spectrum: Set KVH XLT cache mode for Spectrum2/3
mlxsw: spectrum_router_xm: Introduce basic XM cache flushing
mlxsw: reg: Add Router LPM Cache Enable Register
mlxsw: reg: Add Router LPM Cache ML Delete Register
mlxsw: spectrum_router_xm: Implement L-value tracking for M-index
mlxsw: reg: Add XM Router M Table Register
...
Merge misc updates from Andrew Morton:
- a few random little subsystems
- almost all of the MM patches which are staged ahead of linux-next
material. I'll trickle to post-linux-next work in as the dependents
get merged up.
Subsystems affected by this patch series: kthread, kbuild, ide, ntfs,
ocfs2, arch, and mm (slab-generic, slab, slub, dax, debug, pagecache,
gup, swap, shmem, memcg, pagemap, mremap, hmm, vmalloc, documentation,
kasan, pagealloc, memory-failure, hugetlb, vmscan, z3fold, compaction,
oom-kill, migration, cma, page-poison, userfaultfd, zswap, zsmalloc,
uaccess, zram, and cleanups).
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (200 commits)
mm: cleanup kstrto*() usage
mm: fix fall-through warnings for Clang
mm: slub: convert sysfs sprintf family to sysfs_emit/sysfs_emit_at
mm: shmem: convert shmem_enabled_show to use sysfs_emit_at
mm:backing-dev: use sysfs_emit in macro defining functions
mm: huge_memory: convert remaining use of sprintf to sysfs_emit and neatening
mm: use sysfs_emit for struct kobject * uses
mm: fix kernel-doc markups
zram: break the strict dependency from lzo
zram: add stat to gather incompressible pages since zram set up
zram: support page writeback
mm/process_vm_access: remove redundant initialization of iov_r
mm/zsmalloc.c: rework the list_add code in insert_zspage()
mm/zswap: move to use crypto_acomp API for hardware acceleration
mm/zswap: fix passing zero to 'PTR_ERR' warning
mm/zswap: make struct kernel_param_ops definitions const
userfaultfd/selftests: hint the test runner on required privilege
userfaultfd/selftests: fix retval check for userfaultfd_open()
userfaultfd/selftests: always dump something in modes
userfaultfd: selftests: make __{s,u}64 format specifiers portable
...
The *_lruvec_slab_state is also suitable for pages allocated from buddy,
not just for the slab objects. But the function name seems to tell us
that only slab object is applicable. So we can rename the keyword of slab
to kmem.
Link: https://lkml.kernel.org/r/20201117085249.24319-1-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since commit 70e806e4e6 ("mm: Do early cow for pinned pages during
fork() for ptes") pages under a FOLL_PIN will not be write protected
during COW for fork. This means that pages returned from
pin_user_pages(FOLL_WRITE) should not become write protected while the pin
is active.
However, there is a small race where get_user_pages_fast(FOLL_PIN) can
establish a FOLL_PIN at the same time copy_present_page() is write
protecting it:
CPU 0 CPU 1
get_user_pages_fast()
internal_get_user_pages_fast()
copy_page_range()
pte_alloc_map_lock()
copy_present_page()
atomic_read(has_pinned) == 0
page_maybe_dma_pinned() == false
atomic_set(has_pinned, 1);
gup_pgd_range()
gup_pte_range()
pte_t pte = gup_get_pte(ptep)
pte_access_permitted(pte)
try_grab_compound_head()
pte = pte_wrprotect(pte)
set_pte_at();
pte_unmap_unlock()
// GUP now returns with a write protected page
The first attempt to resolve this by using the write protect caused
problems (and was missing a barrrier), see commit f3c64eda3e ("mm: avoid
early COW write protect games during fork()")
Instead wrap copy_p4d_range() with the write side of a seqcount and check
the read side around gup_pgd_range(). If there is a collision then
get_user_pages_fast() fails and falls back to slow GUP.
Slow GUP is safe against this race because copy_page_range() is only
called while holding the exclusive side of the mmap_lock on the src
mm_struct.
[akpm@linux-foundation.org: coding style fixes]
Link: https://lore.kernel.org/r/CAHk-=wi=iCnYCARbPGjkVJu9eyYeZ13N64tZYLdOB8CP5Q_PLw@mail.gmail.com
Link: https://lkml.kernel.org/r/2-v4-908497cf359a+4782-gup_fork_jgg@nvidia.com
Fixes: f3c64eda3e ("mm: avoid early COW write protect games during fork()")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: "Ahmed S. Darwish" <a.darwish@linutronix.de> [seqcount_t parts]
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Leon Romanovsky <leonro@nvidia.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- Consolidate all kmap_atomic() internals into a generic implementation
which builds the base for the kmap_local() API and make the
kmap_atomic() interface wrappers which handle the disabling/enabling of
preemption and pagefaults.
- Switch the storage from per-CPU to per task and provide scheduler
support for clearing mapping when scheduling out and restoring them
when scheduling back in.
- Merge the migrate_disable/enable() code, which is also part of the
scheduler pull request. This was required to make the kmap_local()
interface available which does not disable preemption when a mapping
is established. It has to disable migration instead to guarantee that
the virtual address of the mapped slot is the same accross preemption.
- Provide better debug facilities: guard pages and enforced utilization
of the mapping mechanics on 64bit systems when the architecture allows
it.
- Provide the new kmap_local() API which can now be used to cleanup the
kmap_atomic() usage sites all over the place. Most of the usage sites
do not require the implicit disabling of preemption and pagefaults so
the penalty on 64bit and 32bit non-highmem systems is removed and quite
some of the code can be simplified. A wholesale conversion is not
possible because some usage depends on the implicit side effects and
some need to be cleaned up because they work around these side effects.
The migrate disable side effect is only effective on highmem systems
and when enforced debugging is enabled. On 64bit and 32bit non-highmem
systems the overhead is completely avoided.
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Merge tag 'core-mm-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull kmap updates from Thomas Gleixner:
"The new preemtible kmap_local() implementation:
- Consolidate all kmap_atomic() internals into a generic
implementation which builds the base for the kmap_local() API and
make the kmap_atomic() interface wrappers which handle the
disabling/enabling of preemption and pagefaults.
- Switch the storage from per-CPU to per task and provide scheduler
support for clearing mapping when scheduling out and restoring them
when scheduling back in.
- Merge the migrate_disable/enable() code, which is also part of the
scheduler pull request. This was required to make the kmap_local()
interface available which does not disable preemption when a
mapping is established. It has to disable migration instead to
guarantee that the virtual address of the mapped slot is the same
across preemption.
- Provide better debug facilities: guard pages and enforced
utilization of the mapping mechanics on 64bit systems when the
architecture allows it.
- Provide the new kmap_local() API which can now be used to cleanup
the kmap_atomic() usage sites all over the place. Most of the usage
sites do not require the implicit disabling of preemption and
pagefaults so the penalty on 64bit and 32bit non-highmem systems is
removed and quite some of the code can be simplified. A wholesale
conversion is not possible because some usage depends on the
implicit side effects and some need to be cleaned up because they
work around these side effects.
The migrate disable side effect is only effective on highmem
systems and when enforced debugging is enabled. On 64bit and 32bit
non-highmem systems the overhead is completely avoided"
* tag 'core-mm-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits)
ARM: highmem: Fix cache_is_vivt() reference
x86/crashdump/32: Simplify copy_oldmem_page()
io-mapping: Provide iomap_local variant
mm/highmem: Provide kmap_local*
sched: highmem: Store local kmaps in task struct
x86: Support kmap_local() forced debugging
mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP
mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL
microblaze/mm/highmem: Add dropped #ifdef back
xtensa/mm/highmem: Make generic kmap_atomic() work correctly
mm/highmem: Take kmap_high_get() properly into account
highmem: High implementation details and document API
Documentation/io-mapping: Remove outdated blurb
io-mapping: Cleanup atomic iomap
mm/highmem: Remove the old kmap_atomic cruft
highmem: Get rid of kmap_types.h
xtensa/mm/highmem: Switch to generic kmap atomic
sparc/mm/highmem: Switch to generic kmap atomic
powerpc/mm/highmem: Switch to generic kmap atomic
nds32/mm/highmem: Switch to generic kmap atomic
...
- More generalization of entry/exit functionality
- The consolidation work to reclaim TIF flags on x86 and also for non-x86
specific TIF flags which are solely relevant for syscall related work
and have been moved into their own storage space. The x86 specific part
had to be merged in to avoid a major conflict.
- The TIF_NOTIFY_SIGNAL work which replaces the inefficient signal
delivery mode of task work and results in an impressive performance
improvement for io_uring. The non-x86 consolidation of this is going to
come seperate via Jens.
- The selective syscall redirection facility which provides a clean and
efficient way to support the non-Linux syscalls of WINE by catching them
at syscall entry and redirecting them to the user space emulation. This
can be utilized for other purposes as well and has been designed
carefully to avoid overhead for the regular fastpath. This includes the
core changes and the x86 support code.
- Simplification of the context tracking entry/exit handling for the users
of the generic entry code which guarantee the proper ordering and
protection.
- Preparatory changes to make the generic entry code accomodate S390
specific requirements which are mostly related to their syscall restart
mechanism.
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Merge tag 'core-entry-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core entry/exit updates from Thomas Gleixner:
"A set of updates for entry/exit handling:
- More generalization of entry/exit functionality
- The consolidation work to reclaim TIF flags on x86 and also for
non-x86 specific TIF flags which are solely relevant for syscall
related work and have been moved into their own storage space. The
x86 specific part had to be merged in to avoid a major conflict.
- The TIF_NOTIFY_SIGNAL work which replaces the inefficient signal
delivery mode of task work and results in an impressive performance
improvement for io_uring. The non-x86 consolidation of this is
going to come seperate via Jens.
- The selective syscall redirection facility which provides a clean
and efficient way to support the non-Linux syscalls of WINE by
catching them at syscall entry and redirecting them to the user
space emulation. This can be utilized for other purposes as well
and has been designed carefully to avoid overhead for the regular
fastpath. This includes the core changes and the x86 support code.
- Simplification of the context tracking entry/exit handling for the
users of the generic entry code which guarantee the proper ordering
and protection.
- Preparatory changes to make the generic entry code accomodate S390
specific requirements which are mostly related to their syscall
restart mechanism"
* tag 'core-entry-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
entry: Add syscall_exit_to_user_mode_work()
entry: Add exit_to_user_mode() wrapper
entry_Add_enter_from_user_mode_wrapper
entry: Rename exit_to_user_mode()
entry: Rename enter_from_user_mode()
docs: Document Syscall User Dispatch
selftests: Add benchmark for syscall user dispatch
selftests: Add kselftest for syscall user dispatch
entry: Support Syscall User Dispatch on common syscall entry
kernel: Implement selective syscall userspace redirection
signal: Expose SYS_USER_DISPATCH si_code type
x86: vdso: Expose sigreturn address on vdso to the kernel
MAINTAINERS: Add entry for common entry code
entry: Fix boot for !CONFIG_GENERIC_ENTRY
x86: Support HAVE_CONTEXT_TRACKING_OFFSTACK
context_tracking: Only define schedule_user() on !HAVE_CONTEXT_TRACKING_OFFSTACK archs
sched: Detect call to schedule from critical entry code
context_tracking: Don't implement exception_enter/exit() on CONFIG_HAVE_CONTEXT_TRACKING_OFFSTACK
context_tracking: Introduce HAVE_CONTEXT_TRACKING_OFFSTACK
x86: Reclaim unused x86 TI flags
...
Recently syzbot reported[0] that there is a deadlock amongst the users
of exec_update_mutex. The problematic lock ordering found by lockdep
was:
perf_event_open (exec_update_mutex -> ovl_i_mutex)
chown (ovl_i_mutex -> sb_writes)
sendfile (sb_writes -> p->lock)
by reading from a proc file and writing to overlayfs
proc_pid_syscall (p->lock -> exec_update_mutex)
While looking at possible solutions it occured to me that all of the
users and possible users involved only wanted to state of the given
process to remain the same. They are all readers. The only writer is
exec.
There is no reason for readers to block on each other. So fix
this deadlock by transforming exec_update_mutex into a rw_semaphore
named exec_update_lock that only exec takes for writing.
Cc: Jann Horn <jannh@google.com>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Bernd Edlinger <bernd.edlinger@hotmail.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Christopher Yeoh <cyeoh@au1.ibm.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Fixes: eea9673250 ("exec: Add exec_update_mutex to replace cred_guard_mutex")
[0] https://lkml.kernel.org/r/00000000000063640c05ade8e3de@google.com
Reported-by: syzbot+db9cdf3dd1f64252c6ef@syzkaller.appspotmail.com
Link: https://lkml.kernel.org/r/87ft4mbqen.fsf@x220.int.ebiederm.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Patch series "mm: allow mapping accounted kernel pages to userspace", v6.
Currently a non-slab kernel page which has been charged to a memory cgroup
can't be mapped to userspace. The underlying reason is simple: PageKmemcg
flag is defined as a page type (like buddy, offline, etc), so it takes a
bit from a page->mapped counter. Pages with a type set can't be mapped to
userspace.
But in general the kmemcg flag has nothing to do with mapping to
userspace. It only means that the page has been accounted by the page
allocator, so it has to be properly uncharged on release.
Some bpf maps are mapping the vmalloc-based memory to userspace, and their
memory can't be accounted because of this implementation detail.
This patchset removes this limitation by moving the PageKmemcg flag into
one of the free bits of the page->mem_cgroup pointer. Also it formalizes
accesses to the page->mem_cgroup and page->obj_cgroups using new helpers,
adds several checks and removes a couple of obsolete functions. As the
result the code became more robust with fewer open-coded bit tricks.
This patch (of 4):
Currently there are many open-coded reads of the page->mem_cgroup pointer,
as well as a couple of read helpers, which are barely used.
It creates an obstacle on a way to reuse some bits of the pointer for
storing additional bits of information. In fact, we already do this for
slab pages, where the last bit indicates that a pointer has an attached
vector of objcg pointers instead of a regular memcg pointer.
This commits uses 2 existing helpers and introduces a new helper to
converts all read sides to calls of these helpers:
struct mem_cgroup *page_memcg(struct page *page);
struct mem_cgroup *page_memcg_rcu(struct page *page);
struct mem_cgroup *page_memcg_check(struct page *page);
page_memcg_check() is intended to be used in cases when the page can be a
slab page and have a memcg pointer pointing at objcg vector. It does
check the lowest bit, and if set, returns NULL. page_memcg() contains a
VM_BUG_ON_PAGE() check for the page not being a slab page.
To make sure nobody uses a direct access, struct page's
mem_cgroup/obj_cgroups is converted to unsigned long memcg_data.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Link: https://lkml.kernel.org/r/20201027001657.3398190-1-guro@fb.com
Link: https://lkml.kernel.org/r/20201027001657.3398190-2-guro@fb.com
Link: https://lore.kernel.org/bpf/20201201215900.3569844-2-guro@fb.com
Introduce a mechanism to quickly disable/enable syscall handling for a
specific process and redirect to userspace via SIGSYS. This is useful
for processes with parts that require syscall redirection and parts that
don't, but who need to perform this boundary crossing really fast,
without paying the cost of a system call to reconfigure syscall handling
on each boundary transition. This is particularly important for Windows
games running over Wine.
The proposed interface looks like this:
prctl(PR_SET_SYSCALL_USER_DISPATCH, <op>, <off>, <length>, [selector])
The range [<offset>,<offset>+<length>) is a part of the process memory
map that is allowed to by-pass the redirection code and dispatch
syscalls directly, such that in fast paths a process doesn't need to
disable the trap nor the kernel has to check the selector. This is
essential to return from SIGSYS to a blocked area without triggering
another SIGSYS from rt_sigreturn.
selector is an optional pointer to a char-sized userspace memory region
that has a key switch for the mechanism. This key switch is set to
either PR_SYS_DISPATCH_ON, PR_SYS_DISPATCH_OFF to enable and disable the
redirection without calling the kernel.
The feature is meant to be set per-thread and it is disabled on
fork/clone/execv.
Internally, this doesn't add overhead to the syscall hot path, and it
requires very little per-architecture support. I avoided using seccomp,
even though it duplicates some functionality, due to previous feedback
that maybe it shouldn't mix with seccomp since it is not a security
mechanism. And obviously, this should never be considered a security
mechanism, since any part of the program can by-pass it by using the
syscall dispatcher.
For the sysinfo benchmark, which measures the overhead added to
executing a native syscall that doesn't require interception, the
overhead using only the direct dispatcher region to issue syscalls is
pretty much irrelevant. The overhead of using the selector goes around
40ns for a native (unredirected) syscall in my system, and it is (as
expected) dominated by the supervisor-mode user-address access. In
fact, with SMAP off, the overhead is consistently less than 5ns on my
test box.
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201127193238.821364-4-krisman@collabora.com
Instead of storing the map per CPU provide and use per task storage. That
prepares for local kmaps which are preemptible.
The context switch code is preparatory and not yet in use because
kmap_atomic() runs with preemption disabled. Will be made usable in the
next step.
The context switch logic is safe even when an interrupt happens after
clearing or before restoring the kmaps. The kmap index in task struct is
not modified so any nesting kmap in an interrupt will use unused indices
and on return the counter is the same as before.
Also add an assert into the return to user space code. Going back to user
space with an active kmap local is a nono.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20201118204007.372935758@linutronix.de
On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.
Define SYSCALL_WORK_SYSCALL_EMU, use it in the generic entry code and
convert the code which uses the TIF specific helper functions to use the
new *_syscall_work() helpers which either resolve to the new mode for users
of the generic entry code or to the TIF based functions for the other
architectures.
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-8-krisman@collabora.com
On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.
Define SYSCALL_WORK_SYSCALL_TRACE, use it in the generic entry code and
convert the code which uses the TIF specific helper functions to use the
new *_syscall_work() helpers which either resolve to the new mode for users
of the generic entry code or to the TIF based functions for the other
architectures.
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-7-krisman@collabora.com
On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.
Define SYSCALL_WORK_SECCOMP, use it in the generic entry code and convert
the code which uses the TIF specific helper functions to use the new
*_syscall_work() helpers which either resolve to the new mode for users of
the generic entry code or to the TIF based functions for the other
architectures.
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-5-krisman@collabora.com
current->group_leader->exit_signal may change during copy_process() if
current->real_parent exits.
Move the assignment inside tasklist_lock to avoid the race.
Signed-off-by: Eddy Wu <eddy_wu@trendmicro.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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>
Fix multiple occurrences of duplicated words in kernel/.
Fix one typo/spello on the same line as a duplicate word. Change one
instance of "the the" to "that the". Otherwise just drop one of the
repeated words.
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/98202fa6-8919-ef63-9efe-c0fad5ca7af1@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In commit 1da177e4c3 ("Linux-2.6.12-rc2"), the helper put_write_access()
came with the atomic_dec operation of the i_writecount field. But it
forgot to use this helper in __vma_link_file() and dup_mmap().
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/20200924115235.5111-1-linmiaohe@huawei.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Merge tag 'kernel-clone-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull kernel_clone() updates from Christian Brauner:
"During the v5.9 merge window we reworked the process creation
codepaths across multiple architectures. After this work we were only
left with the _do_fork() helper based on the struct kernel_clone_args
calling convention. As was pointed out _do_fork() isn't valid
kernelese especially for a helper that isn't just static.
This series removes the _do_fork() helper and introduces the new
kernel_clone() helper. The process creation cleanup didn't change the
name to something more reasonable mainly because _do_fork() was used
in quite a few places. So sending this as a separate series seemed the
better strategy.
I originally intended to send this early in the v5.9 development cycle
after the merge window had closed but given that this was touching
quite a few places I decided to defer this until the v5.10 merge
window"
* tag 'kernel-clone-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
sched: remove _do_fork()
tracing: switch to kernel_clone()
kgdbts: switch to kernel_clone()
kprobes: switch to kernel_clone()
x86: switch to kernel_clone()
sparc: switch to kernel_clone()
nios2: switch to kernel_clone()
m68k: switch to kernel_clone()
ia64: switch to kernel_clone()
h8300: switch to kernel_clone()
fork: introduce kernel_clone()
Currently __set_oom_adj loops through all processes in the system to keep
oom_score_adj and oom_score_adj_min in sync between processes sharing
their mm. This is done for any task with more that one mm_users, which
includes processes with multiple threads (sharing mm and signals).
However for such processes the loop is unnecessary because their signal
structure is shared as well.
Android updates oom_score_adj whenever a tasks changes its role
(background/foreground/...) or binds to/unbinds from a service, making it
more/less important. Such operation can happen frequently. We noticed
that updates to oom_score_adj became more expensive and after further
investigation found out that the patch mentioned in "Fixes" introduced a
regression. Using Pixel 4 with a typical Android workload, write time to
oom_score_adj increased from ~3.57us to ~362us. Moreover this regression
linearly depends on the number of multi-threaded processes running on the
system.
Mark the mm with a new MMF_MULTIPROCESS flag bit when task is created with
(CLONE_VM && !CLONE_THREAD && !CLONE_VFORK). Change __set_oom_adj to use
MMF_MULTIPROCESS instead of mm_users to decide whether oom_score_adj
update should be synchronized between multiple processes. To prevent
races between clone() and __set_oom_adj(), when oom_score_adj of the
process being cloned might be modified from userspace, we use
oom_adj_mutex. Its scope is changed to global.
The combination of (CLONE_VM && !CLONE_THREAD) is rarely used except for
the case of vfork(). To prevent performance regressions of vfork(), we
skip taking oom_adj_mutex and setting MMF_MULTIPROCESS when CLONE_VFORK is
specified. Clearing the MMF_MULTIPROCESS flag (when the last process
sharing the mm exits) is left out of this patch to keep it simple and
because it is believed that this threading model is rare. Should there
ever be a need for optimizing that case as well, it can be done by hooking
into the exit path, likely following the mm_update_next_owner pattern.
With the combination of (CLONE_VM && !CLONE_THREAD && !CLONE_VFORK) being
quite rare, the regression is gone after the change is applied.
[surenb@google.com: v3]
Link: https://lkml.kernel.org/r/20200902012558.2335613-1-surenb@google.com
Fixes: 44a70adec9 ("mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj")
Reported-by: Tim Murray <timmurray@google.com>
Suggested-by: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Eugene Syromiatnikov <esyr@redhat.com>
Cc: Christian Kellner <christian@kellner.me>
Cc: Adrian Reber <areber@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alexey Gladkov <gladkov.alexey@gmail.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Bernd Edlinger <bernd.edlinger@hotmail.de>
Cc: John Johansen <john.johansen@canonical.com>
Cc: Yafang Shao <laoar.shao@gmail.com>
Link: https://lkml.kernel.org/r/20200824153036.3201505-1-surenb@google.com
Debugged-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Both of the mm pointers are not needed after commit 7a4830c380
("mm/fork: Pass new vma pointer into copy_page_range()").
Jason Gunthorpe also reported that the ordering of copy_page_range() is
odd. Since working at it, reorder the parameters to be logical, by (1)
always put the dst_* fields to be before src_* fields, and (2) keep the
same type of parameters together.
[peterx@redhat.com: further reorder some parameters and line format, per Jason]
Link: https://lkml.kernel.org/r/20201002192647.7161-1-peterx@redhat.com
[peterx@redhat.com: fix warnings]
Link: https://lkml.kernel.org/r/20201006200138.GA6026@xz-x1
Reported-by: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lkml.kernel.org/r/20200930204950.6668-1-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 4bb5f5d939 ("mm: allow drivers to prevent new writable mappings")
changed i_mmap_writable from unsigned int to atomic_t and add the helper
function mapping_allow_writable() to atomic_inc i_mmap_writable. But it
forgot to use this helper function in dup_mmap() and __vma_link_file().
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Christian Kellner <christian@kellner.me>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Adrian Reber <areber@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200917112736.7789-1-linmiaohe@huawei.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The kretprobe hash is mostly superfluous, replace it with a per-task
variable.
This gets rid of the task hash and it's related locking.
Note that this may change the kprobes module-exported API for kretprobe
handlers. If any out-of-tree kretprobe user uses ri->rp, use
get_kretprobe(ri) instead.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/159870620431.1229682.16325792502413731312.stgit@devnote2
Grab actual references to the files_struct. To avoid circular references
issues due to this, we add a per-task note that keeps track of what
io_uring contexts a task has used. When the tasks execs or exits its
assigned files, we cancel requests based on this tracking.
With that, we can grab proper references to the files table, and no
longer need to rely on stashing away ring_fd and ring_file to check
if the ring_fd may have been closed.
Cc: stable@vger.kernel.org # v5.5+
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This prepares for the future work to trigger early cow on pinned pages
during fork().
No functional change intended.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(Commit message majorly collected from Jason Gunthorpe)
Reduce the chance of false positive from page_maybe_dma_pinned() by
keeping track if the mm_struct has ever been used with pin_user_pages().
This allows cases that might drive up the page ref_count to avoid any
penalty from handling dma_pinned pages.
Future work is planned, to provide a more sophisticated solution, likely
to turn it into a real counter. For now, make it atomic_t but use it as
a boolean for simplicity.
Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 32927393dc ("sysctl: pass kernel pointers to ->proc_handler")
changed ctl_table.proc_handler to take a kernel pointer. Adjust the
definition of sysctl_max_threads to match its prototype in
linux/sysctl.h which fixes the following sparse error/warning:
kernel/fork.c:3050:47: warning: incorrect type in argument 3 (different address spaces)
kernel/fork.c:3050:47: expected void *
kernel/fork.c:3050:47: got void [noderef] __user *buffer
kernel/fork.c:3036:5: error: symbol 'sysctl_max_threads' redeclared with different type (incompatible argument 3 (different address spaces)):
kernel/fork.c:3036:5: int extern [addressable] [signed] [toplevel] sysctl_max_threads( ... )
kernel/fork.c: note: in included file (through include/linux/key.h, include/linux/cred.h, include/linux/sched/signal.h, include/linux/sched/cputime.h):
include/linux/sysctl.h:242:5: note: previously declared as:
include/linux/sysctl.h:242:5: int extern [addressable] [signed] [toplevel] sysctl_max_threads( ... )
Fixes: 32927393dc ("sysctl: pass kernel pointers to ->proc_handler")
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lkml.kernel.org/r/20200825093647.24263-1-tklauser@distanz.ch
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The old _do_fork() helper doesn't follow naming conventions of in-kernel
helpers for syscalls. The process creation cleanup in [1] didn't change the
name to something more reasonable mainly because _do_fork() was used in quite a
few places. So sending this as a separate series seemed the better strategy.
This commit does two things:
1. renames _do_fork() to kernel_clone() but keeps _do_fork() as a simple static
inline wrapper around kernel_clone().
2. Changes the return type from long to pid_t. This aligns kernel_thread() and
kernel_clone(). Also, the return value from kernel_clone that is surfaced in
fork(), vfork(), clone(), and clone3() is taken from pid_vrn() which returns
a pid_t too.
Follow-up patches will switch each caller of _do_fork() and each place where it
is referenced over to kernel_clone(). After all these changes are done, we can
remove _do_fork() completely and will only be left with kernel_clone().
[1]: 9ba27414f2 ("Merge tag 'fork-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux")
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200819104655.436656-2-christian.brauner@ubuntu.com
- Untangle the header spaghetti which causes build failures in various
situations caused by the lockdep additions to seqcount to validate that
the write side critical sections are non-preemptible.
- The seqcount associated lock debug addons which were blocked by the
above fallout.
seqcount writers contrary to seqlock writers must be externally
serialized, which usually happens via locking - except for strict per
CPU seqcounts. As the lock is not part of the seqcount, lockdep cannot
validate that the lock is held.
This new debug mechanism adds the concept of associated locks.
sequence count has now lock type variants and corresponding
initializers which take a pointer to the associated lock used for
writer serialization. If lockdep is enabled the pointer is stored and
write_seqcount_begin() has a lockdep assertion to validate that the
lock is held.
Aside of the type and the initializer no other code changes are
required at the seqcount usage sites. The rest of the seqcount API is
unchanged and determines the type at compile time with the help of
_Generic which is possible now that the minimal GCC version has been
moved up.
Adding this lockdep coverage unearthed a handful of seqcount bugs which
have been addressed already independent of this.
While generaly useful this comes with a Trojan Horse twist: On RT
kernels the write side critical section can become preemtible if the
writers are serialized by an associated lock, which leads to the well
known reader preempts writer livelock. RT prevents this by storing the
associated lock pointer independent of lockdep in the seqcount and
changing the reader side to block on the lock when a reader detects
that a writer is in the write side critical section.
- Conversion of seqcount usage sites to associated types and initializers.
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Merge tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Thomas Gleixner:
"A set of locking fixes and updates:
- Untangle the header spaghetti which causes build failures in
various situations caused by the lockdep additions to seqcount to
validate that the write side critical sections are non-preemptible.
- The seqcount associated lock debug addons which were blocked by the
above fallout.
seqcount writers contrary to seqlock writers must be externally
serialized, which usually happens via locking - except for strict
per CPU seqcounts. As the lock is not part of the seqcount, lockdep
cannot validate that the lock is held.
This new debug mechanism adds the concept of associated locks.
sequence count has now lock type variants and corresponding
initializers which take a pointer to the associated lock used for
writer serialization. If lockdep is enabled the pointer is stored
and write_seqcount_begin() has a lockdep assertion to validate that
the lock is held.
Aside of the type and the initializer no other code changes are
required at the seqcount usage sites. The rest of the seqcount API
is unchanged and determines the type at compile time with the help
of _Generic which is possible now that the minimal GCC version has
been moved up.
Adding this lockdep coverage unearthed a handful of seqcount bugs
which have been addressed already independent of this.
While generally useful this comes with a Trojan Horse twist: On RT
kernels the write side critical section can become preemtible if
the writers are serialized by an associated lock, which leads to
the well known reader preempts writer livelock. RT prevents this by
storing the associated lock pointer independent of lockdep in the
seqcount and changing the reader side to block on the lock when a
reader detects that a writer is in the write side critical section.
- Conversion of seqcount usage sites to associated types and
initializers"
* tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
locking/seqlock, headers: Untangle the spaghetti monster
locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header
x86/headers: Remove APIC headers from <asm/smp.h>
seqcount: More consistent seqprop names
seqcount: Compress SEQCNT_LOCKNAME_ZERO()
seqlock: Fold seqcount_LOCKNAME_init() definition
seqlock: Fold seqcount_LOCKNAME_t definition
seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g
hrtimer: Use sequence counter with associated raw spinlock
kvm/eventfd: Use sequence counter with associated spinlock
userfaultfd: Use sequence counter with associated spinlock
NFSv4: Use sequence counter with associated spinlock
iocost: Use sequence counter with associated spinlock
raid5: Use sequence counter with associated spinlock
vfs: Use sequence counter with associated spinlock
timekeeping: Use sequence counter with associated raw spinlock
xfrm: policy: Use sequence counters with associated lock
netfilter: nft_set_rbtree: Use sequence counter with associated rwlock
netfilter: conntrack: Use sequence counter with associated spinlock
sched: tasks: Use sequence counter with associated spinlock
...
Currently the kernel stack is being accounted per-zone. There is no need
to do that. In addition due to being per-zone, memcg has to keep a
separate MEMCG_KERNEL_STACK_KB. Make the stat per-node and deprecate
MEMCG_KERNEL_STACK_KB as memcg_stat_item is an extension of
node_stat_item. In addition localize the kernel stack stats updates to
account_kernel_stack().
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Roman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Link: http://lkml.kernel.org/r/20200630161539.1759185-1-shakeelb@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Merge tag 'close-range-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull close_range() implementation from Christian Brauner:
"This adds the close_range() syscall. It allows to efficiently close a
range of file descriptors up to all file descriptors of a calling
task.
This is coordinated with the FreeBSD folks which have copied our
version of this syscall and in the meantime have already merged it in
April 2019:
https://reviews.freebsd.org/D21627https://svnweb.freebsd.org/base?view=revision&revision=359836
The syscall originally came up in a discussion around the new mount
API and making new file descriptor types cloexec by default. During
this discussion, Al suggested the close_range() syscall.
First, it helps to close all file descriptors of an exec()ing task.
This can be done safely via (quoting Al's example from [1] verbatim):
/* that exec is sensitive */
unshare(CLONE_FILES);
/* we don't want anything past stderr here */
close_range(3, ~0U);
execve(....);
The code snippet above is one way of working around the problem that
file descriptors are not cloexec by default. This is aggravated by the
fact that we can't just switch them over without massively regressing
userspace. For a whole class of programs having an in-kernel method of
closing all file descriptors is very helpful (e.g. demons, service
managers, programming language standard libraries, container managers
etc.).
Second, it allows userspace to avoid implementing closing all file
descriptors by parsing through /proc/<pid>/fd/* and calling close() on
each file descriptor and other hacks. From looking at various
large(ish) userspace code bases this or similar patterns are very
common in service managers, container runtimes, and programming
language runtimes/standard libraries such as Python or Rust.
In addition, the syscall will also work for tasks that do not have
procfs mounted and on kernels that do not have procfs support compiled
in. In such situations the only way to make sure that all file
descriptors are closed is to call close() on each file descriptor up
to UINT_MAX or RLIMIT_NOFILE, OPEN_MAX trickery.
Based on Linus' suggestion close_range() also comes with a new flag
CLOSE_RANGE_UNSHARE to more elegantly handle file descriptor dropping
right before exec. This would usually be expressed in the sequence:
unshare(CLONE_FILES);
close_range(3, ~0U);
as pointed out by Linus it might be desirable to have this be a part
of close_range() itself under a new flag CLOSE_RANGE_UNSHARE which
gets especially handy when we're closing all file descriptors above a
certain threshold.
Test-suite as always included"
* tag 'close-range-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
tests: add CLOSE_RANGE_UNSHARE tests
close_range: add CLOSE_RANGE_UNSHARE
tests: add close_range() tests
arch: wire-up close_range()
open: add close_range()
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Merge tag 'fork-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull fork cleanups from Christian Brauner:
"This is cleanup series from when we reworked a chunk of the process
creation paths in the kernel and switched to struct
{kernel_}clone_args.
High-level this does two main things:
- Remove the double export of both do_fork() and _do_fork() where
do_fork() used the incosistent legacy clone calling convention.
Now we only export _do_fork() which is based on struct
kernel_clone_args.
- Remove the copy_thread_tls()/copy_thread() split making the
architecture specific HAVE_COYP_THREAD_TLS config option obsolete.
This switches all remaining architectures to select
HAVE_COPY_THREAD_TLS and thus to the copy_thread_tls() calling
convention. The current split makes the process creation codepaths
more convoluted than they need to be. Each architecture has their own
copy_thread() function unless it selects HAVE_COPY_THREAD_TLS then it
has a copy_thread_tls() function.
The split is not needed anymore nowadays, all architectures support
CLONE_SETTLS but quite a few of them never bothered to select
HAVE_COPY_THREAD_TLS and instead simply continued to use copy_thread()
and use the old calling convention. Removing this split cleans up the
process creation codepaths and paves the way for implementing clone3()
on such architectures since it requires the copy_thread_tls() calling
convention.
After having made each architectures support copy_thread_tls() this
series simply renames that function back to copy_thread(). It also
switches all architectures that call do_fork() directly over to
_do_fork() and the struct kernel_clone_args calling convention. This
is a corollary of switching the architectures that did not yet support
it over to copy_thread_tls() since do_fork() is conditional on not
supporting copy_thread_tls() (Mostly because it lacks a separate
argument for tls which is trivial to fix but there's no need for this
function to exist.).
The do_fork() removal is in itself already useful as it allows to to
remove the export of both do_fork() and _do_fork() we currently have
in favor of only _do_fork(). This has already been discussed back when
we added clone3(). The legacy clone() calling convention is - as is
probably well-known - somewhat odd:
#
# ABI hall of shame
#
config CLONE_BACKWARDS
config CLONE_BACKWARDS2
config CLONE_BACKWARDS3
that is aggravated by the fact that some architectures such as sparc
follow the CLONE_BACKWARDSx calling convention but don't really select
the corresponding config option since they call do_fork() directly.
So do_fork() enforces a somewhat arbitrary calling convention in the
first place that doesn't really help the individual architectures that
deviate from it. They can thus simply be switched to _do_fork()
enforcing a single calling convention. (I really hope that any new
architectures will __not__ try to implement their own calling
conventions...)
Most architectures already have made a similar switch (m68k comes to
mind).
Overall this removes more code than it adds even with a good portion
of added comments. It simplifies a chunk of arch specific assembly
either by moving the code into C or by simply rewriting the assembly.
Architectures that have been touched in non-trivial ways have all been
actually boot and stress tested: sparc and ia64 have been tested with
Debian 9 images. They are the two architectures which have been
touched the most. All non-trivial changes to architectures have seen
acks from the relevant maintainers. nios2 with a custom built
buildroot image. h8300 I couldn't get something bootable to test on
but the changes have been fairly automatic and I'm sure we'll hear
people yell if I broke something there.
All other architectures that have been touched in trivial ways have
been compile tested for each single patch of the series via git rebase
-x "make ..." v5.8-rc2. arm{64} and x86{_64} have been boot tested
even though they have just been trivially touched (removal of the
HAVE_COPY_THREAD_TLS macro from their Kconfig) because well they are
basically "core architectures" and since it is trivial to get your
hands on a useable image"
* tag 'fork-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
arch: rename copy_thread_tls() back to copy_thread()
arch: remove HAVE_COPY_THREAD_TLS
unicore: switch to copy_thread_tls()
sh: switch to copy_thread_tls()
nds32: switch to copy_thread_tls()
microblaze: switch to copy_thread_tls()
hexagon: switch to copy_thread_tls()
c6x: switch to copy_thread_tls()
alpha: switch to copy_thread_tls()
fork: remove do_fork()
h8300: select HAVE_COPY_THREAD_TLS, switch to kernel_clone_args
nios2: enable HAVE_COPY_THREAD_TLS, switch to kernel_clone_args
ia64: enable HAVE_COPY_THREAD_TLS, switch to kernel_clone_args
sparc: unconditionally enable HAVE_COPY_THREAD_TLS
sparc: share process creation helpers between sparc and sparc64
sparc64: enable HAVE_COPY_THREAD_TLS
fork: fold legacy_clone_args_valid() into _do_fork()
Pull execve updates from Eric Biederman:
"During the development of v5.7 I ran into bugs and quality of
implementation issues related to exec that could not be easily fixed
because of the way exec is implemented. So I have been diggin into
exec and cleaning up what I can.
This cycle I have been looking at different ideas and different
implementations to see what is possible to improve exec, and cleaning
the way exec interfaces with in kernel users. Only cleaning up the
interfaces of exec with rest of the kernel has managed to stabalize
and make it through review in time for v5.9-rc1 resulting in 2 sets of
changes this cycle.
- Implement kernel_execve
- Make the user mode driver code a better citizen
With kernel_execve the code size got a little larger as the copying of
parameters from userspace and copying of parameters from userspace is
now separate. The good news is kernel threads no longer need to play
games with set_fs to use exec. Which when combined with the rest of
Christophs set_fs changes should security bugs with set_fs much more
difficult"
* 'exec-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (23 commits)
exec: Implement kernel_execve
exec: Factor bprm_stack_limits out of prepare_arg_pages
exec: Factor bprm_execve out of do_execve_common
exec: Move bprm_mm_init into alloc_bprm
exec: Move initialization of bprm->filename into alloc_bprm
exec: Factor out alloc_bprm
exec: Remove unnecessary spaces from binfmts.h
umd: Stop using split_argv
umd: Remove exit_umh
bpfilter: Take advantage of the facilities of struct pid
exit: Factor thread_group_exited out of pidfd_poll
umd: Track user space drivers with struct pid
bpfilter: Move bpfilter_umh back into init data
exec: Remove do_execve_file
umh: Stop calling do_execve_file
umd: Transform fork_usermode_blob into fork_usermode_driver
umd: Rename umd_info.cmdline umd_info.driver_name
umd: For clarity rename umh_info umd_info
umh: Separate the user mode driver and the user mode helper support
umh: Remove call_usermodehelper_setup_file.
...
- Improved selftest coverage, timeouts, and reporting
- Add EPOLLHUP support for SECCOMP_RET_USER_NOTIF (Christian Brauner)
- Refactor __scm_install_fd() into __receive_fd() and fix buggy callers
- Introduce "addfd" command for SECCOMP_RET_USER_NOTIF (Sargun Dhillon)
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Merge tag 'seccomp-v5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull seccomp updates from Kees Cook:
"There are a bunch of clean ups and selftest improvements along with
two major updates to the SECCOMP_RET_USER_NOTIF filter return:
EPOLLHUP support to more easily detect the death of a monitored
process, and being able to inject fds when intercepting syscalls that
expect an fd-opening side-effect (needed by both container folks and
Chrome). The latter continued the refactoring of __scm_install_fd()
started by Christoph, and in the process found and fixed a handful of
bugs in various callers.
- Improved selftest coverage, timeouts, and reporting
- Add EPOLLHUP support for SECCOMP_RET_USER_NOTIF (Christian Brauner)
- Refactor __scm_install_fd() into __receive_fd() and fix buggy
callers
- Introduce 'addfd' command for SECCOMP_RET_USER_NOTIF (Sargun
Dhillon)"
* tag 'seccomp-v5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (30 commits)
selftests/seccomp: Test SECCOMP_IOCTL_NOTIF_ADDFD
seccomp: Introduce addfd ioctl to seccomp user notifier
fs: Expand __receive_fd() to accept existing fd
pidfd: Replace open-coded receive_fd()
fs: Add receive_fd() wrapper for __receive_fd()
fs: Move __scm_install_fd() to __receive_fd()
net/scm: Regularize compat handling of scm_detach_fds()
pidfd: Add missing sock updates for pidfd_getfd()
net/compat: Add missing sock updates for SCM_RIGHTS
selftests/seccomp: Check ENOSYS under tracing
selftests/seccomp: Refactor to use fixture variants
selftests/harness: Clean up kern-doc for fixtures
seccomp: Use -1 marker for end of mode 1 syscall list
seccomp: Fix ioctl number for SECCOMP_IOCTL_NOTIF_ID_VALID
selftests/seccomp: Rename user_trap_syscall() to user_notif_syscall()
selftests/seccomp: Make kcmp() less required
seccomp: Use pr_fmt
selftests/seccomp: Improve calibration loop
selftests/seccomp: use 90s as timeout
selftests/seccomp: Expand benchmark to per-filter measurements
...
- Improve uclamp performance by using a static key for the fast path
- Add the "sched_util_clamp_min_rt_default" sysctl, to optimize for
better power efficiency of RT tasks on battery powered devices.
(The default is to maximize performance & reduce RT latencies.)
- Improve utime and stime tracking accuracy, which had a fixed boundary
of error, which created larger and larger relative errors as the values
become larger. This is now replaced with more precise arithmetics,
using the new mul_u64_u64_div_u64() helper in math64.h.
- Improve the deadline scheduler, such as making it capacity aware
- Improve frequency-invariant scheduling
- Misc cleanups in energy/power aware scheduling
- Add sched_update_nr_running tracepoint to track changes to nr_running
- Documentation additions and updates
- Misc cleanups and smaller fixes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
- Improve uclamp performance by using a static key for the fast path
- Add the "sched_util_clamp_min_rt_default" sysctl, to optimize for
better power efficiency of RT tasks on battery powered devices.
(The default is to maximize performance & reduce RT latencies.)
- Improve utime and stime tracking accuracy, which had a fixed boundary
of error, which created larger and larger relative errors as the
values become larger. This is now replaced with more precise
arithmetics, using the new mul_u64_u64_div_u64() helper in math64.h.
- Improve the deadline scheduler, such as making it capacity aware
- Improve frequency-invariant scheduling
- Misc cleanups in energy/power aware scheduling
- Add sched_update_nr_running tracepoint to track changes to nr_running
- Documentation additions and updates
- Misc cleanups and smaller fixes
* tag 'sched-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
sched/doc: Factorize bits between sched-energy.rst & sched-capacity.rst
sched/doc: Document capacity aware scheduling
sched: Document arch_scale_*_capacity()
arm, arm64: Fix selection of CONFIG_SCHED_THERMAL_PRESSURE
Documentation/sysctl: Document uclamp sysctl knobs
sched/uclamp: Add a new sysctl to control RT default boost value
sched/uclamp: Fix a deadlock when enabling uclamp static key
sched: Remove duplicated tick_nohz_full_enabled() check
sched: Fix a typo in a comment
sched/uclamp: Remove unnecessary mutex_init()
arm, arm64: Select CONFIG_SCHED_THERMAL_PRESSURE
sched: Cleanup SCHED_THERMAL_PRESSURE kconfig entry
arch_topology, sched/core: Cleanup thermal pressure definition
trace/events/sched.h: fix duplicated word
linux/sched/mm.h: drop duplicated words in comments
smp: Fix a potential usage of stale nr_cpus
sched/fair: update_pick_idlest() Select group with lowest group_util when idle_cpus are equal
sched: nohz: stop passing around unused "ticks" parameter.
sched: Better document ttwu()
sched: Add a tracepoint to track rq->nr_running
...
Pull v5.9 KCSAN bits from Paul E. McKenney.
Perhaps the most important change is that GCC 11 now has all fixes in place
to support KCSAN, so GCC support can be enabled again.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Refactor the IRQ trace events fields, used for printing information
about the IRQ trace events, into a separate struct 'irqtrace_events'.
This improves readability by separating the information only used in
reporting, as well as enables (simplified) storing/restoring of
irqtrace_events snapshots.
No functional change intended.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200729110916.3920464-1-elver@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.
Use the new seqcount_spinlock_t data type, which allows to associate a
spinlock with the sequence counter. This enables lockdep to verify that
the spinlock used for writer serialization is held when the write side
critical section is entered.
If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-14-a.darwish@linutronix.de
RT tasks by default run at the highest capacity/performance level. When
uclamp is selected this default behavior is retained by enforcing the
requested uclamp.min (p->uclamp_req[UCLAMP_MIN]) of the RT tasks to be
uclamp_none(UCLAMP_MAX), which is SCHED_CAPACITY_SCALE; the maximum
value.
This is also referred to as 'the default boost value of RT tasks'.
See commit 1a00d99997 ("sched/uclamp: Set default clamps for RT tasks").
On battery powered devices, it is desired to control this default
(currently hardcoded) behavior at runtime to reduce energy consumed by
RT tasks.
For example, a mobile device manufacturer where big.LITTLE architecture
is dominant, the performance of the little cores varies across SoCs, and
on high end ones the big cores could be too power hungry.
Given the diversity of SoCs, the new knob allows manufactures to tune
the best performance/power for RT tasks for the particular hardware they
run on.
They could opt to further tune the value when the user selects
a different power saving mode or when the device is actively charging.
The runtime aspect of it further helps in creating a single kernel image
that can be run on multiple devices that require different tuning.
Keep in mind that a lot of RT tasks in the system are created by the
kernel. On Android for instance I can see over 50 RT tasks, only
a handful of which created by the Android framework.
To control the default behavior globally by system admins and device
integrator, introduce the new sysctl_sched_uclamp_util_min_rt_default
to change the default boost value of the RT tasks.
I anticipate this to be mostly in the form of modifying the init script
of a particular device.
To avoid polluting the fast path with unnecessary code, the approach
taken is to synchronously do the update by traversing all the existing
tasks in the system. This could race with a concurrent fork(), which is
dealt with by introducing sched_post_fork() function which will ensure
the racy fork will get the right update applied.
Tested on Juno-r2 in combination with the RT capacity awareness [1].
By default an RT task will go to the highest capacity CPU and run at the
maximum frequency, which is particularly energy inefficient on high end
mobile devices because the biggest core[s] are 'huge' and power hungry.
With this patch the RT task can be controlled to run anywhere by
default, and doesn't cause the frequency to be maximum all the time.
Yet any task that really needs to be boosted can easily escape this
default behavior by modifying its requested uclamp.min value
(p->uclamp_req[UCLAMP_MIN]) via sched_setattr() syscall.
[1] 804d402fb6f6: ("sched/rt: Make RT capacity-aware")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200716110347.19553-2-qais.yousef@arm.com
The seccomp filter used to be released in free_task() which is called
asynchronously via call_rcu() and assorted mechanisms. Since we need
to inform tasks waiting on the seccomp notifier when a filter goes empty
we will notify them as soon as a task has been marked fully dead in
release_task(). To not split seccomp cleanup into two parts, move
filter release out of free_task() and into release_task() after we've
unhashed struct task from struct pid, exited signals, and unlinked it
from the threadgroups' thread list. We'll put the empty filter
notification infrastructure into it in a follow up patch.
This also renames put_seccomp_filter() to seccomp_filter_release() which
is a more descriptive name of what we're doing here especially once
we've added the empty filter notification mechanism in there.
We're also NULL-ing the task's filter tree entrypoint which seems
cleaner than leaving a dangling pointer in there. Note that this shouldn't
need any memory barriers since we're calling this when the task is in
release_task() which means it's EXIT_DEAD. So it can't modify its seccomp
filters anymore. You can also see this from the point where we're calling
seccomp_filter_release(). It's after __exit_signal() and at this point,
tsk->sighand will already have been NULLed which is required for
thread-sync and filter installation alike.
Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Kees Cook <keescook@chromium.org>
Cc: Matt Denton <mpdenton@google.com>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Jann Horn <jannh@google.com>
Cc: Chris Palmer <palmer@google.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Robert Sesek <rsesek@google.com>
Cc: Jeffrey Vander Stoep <jeffv@google.com>
Cc: Linux Containers <containers@lists.linux-foundation.org>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20200531115031.391515-2-christian.brauner@ubuntu.com
Signed-off-by: Kees Cook <keescook@chromium.org>
Currently all IRQ-tracking state is in task_struct, this means that
task_struct needs to be defined before we use it.
Especially for lockdep_assert_irq*() this can lead to header-hell.
Move the hardirq state into per-cpu variables to avoid the task_struct
dependency.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200623083721.512673481@infradead.org
Create an independent helper thread_group_exited which returns true
when all threads have passed exit_notify in do_exit. AKA all of the
threads are at least zombies and might be dead or completely gone.
Create this helper by taking the logic out of pidfd_poll where it is
already tested, and adding a READ_ONCE on the read of
task->exit_state.
I will be changing the user mode driver code to use this same logic
to know when a user mode driver needs to be restarted.
Place the new helper thread_group_exited in kernel/exit.c and
EXPORT it so it can be used by modules.
Link: https://lkml.kernel.org/r/20200702164140.4468-13-ebiederm@xmission.com
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Now that HAVE_COPY_THREAD_TLS has been removed, rename copy_thread_tls()
back simply copy_thread(). It's a simpler name, and doesn't imply that only
tls is copied here. This finishes an outstanding chunk of internal process
creation work since we've added clone3().
Cc: linux-arch@vger.kernel.org
Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>A
Acked-by: Stafford Horne <shorne@gmail.com>
Acked-by: Greentime Hu <green.hu@gmail.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>A
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Jens Axboe