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There is currently no good way to query the page cache state of large file
sets and directory trees. There is mincore(), but it scales poorly: the
kernel writes out a lot of bitmap data that userspace has to aggregate,
when the user really doesn not care about per-page information in that
case. The user also needs to mmap and unmap each file as it goes along,
which can be quite slow as well.
Some use cases where this information could come in handy:
* Allowing database to decide whether to perform an index scan or
direct table queries based on the in-memory cache state of the
index.
* Visibility into the writeback algorithm, for performance issues
diagnostic.
* Workload-aware writeback pacing: estimating IO fulfilled by page
cache (and IO to be done) within a range of a file, allowing for
more frequent syncing when and where there is IO capacity, and
batching when there is not.
* Computing memory usage of large files/directory trees, analogous to
the du tool for disk usage.
More information about these use cases could be found in the following
thread:
https://lore.kernel.org/lkml/20230315170934.GA97793@cmpxchg.org/
This patch implements a new syscall that queries cache state of a file and
summarizes the number of cached pages, number of dirty pages, number of
pages marked for writeback, number of (recently) evicted pages, etc. in a
given range. Currently, the syscall is only wired in for x86
architecture.
NAME
cachestat - query the page cache statistics of a file.
SYNOPSIS
#include <sys/mman.h>
struct cachestat_range {
__u64 off;
__u64 len;
};
struct cachestat {
__u64 nr_cache;
__u64 nr_dirty;
__u64 nr_writeback;
__u64 nr_evicted;
__u64 nr_recently_evicted;
};
int cachestat(unsigned int fd, struct cachestat_range *cstat_range,
struct cachestat *cstat, unsigned int flags);
DESCRIPTION
cachestat() queries the number of cached pages, number of dirty
pages, number of pages marked for writeback, number of evicted
pages, number of recently evicted pages, in the bytes range given by
`off` and `len`.
An evicted page is a page that is previously in the page cache but
has been evicted since. A page is recently evicted if its last
eviction was recent enough that its reentry to the cache would
indicate that it is actively being used by the system, and that
there is memory pressure on the system.
These values are returned in a cachestat struct, whose address is
given by the `cstat` argument.
The `off` and `len` arguments must be non-negative integers. If
`len` > 0, the queried range is [`off`, `off` + `len`]. If `len` ==
0, we will query in the range from `off` to the end of the file.
The `flags` argument is unused for now, but is included for future
extensibility. User should pass 0 (i.e no flag specified).
Currently, hugetlbfs is not supported.
Because the status of a page can change after cachestat() checks it
but before it returns to the application, the returned values may
contain stale information.
RETURN VALUE
On success, cachestat returns 0. On error, -1 is returned, and errno
is set to indicate the error.
ERRORS
EFAULT cstat or cstat_args points to an invalid address.
EINVAL invalid flags.
EBADF invalid file descriptor.
EOPNOTSUPP file descriptor is of a hugetlbfs file
[nphamcs@gmail.com: replace rounddown logic with the existing helper]
Link: https://lkml.kernel.org/r/20230504022044.3675469-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20230503013608.2431726-3-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Brian Foster <bfoster@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Link: https://lkml.kernel.org/r/20211202123810.267175-4-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Ben Widawsky <ben.widawsky@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: <linux-api@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Wire up syscall entry point for x86 arch, for both i386 and x86_64.
Signed-off-by: André Almeida <andrealmeid@collabora.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210923171111.300673-18-andrealmeid@collabora.com
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These are all handled correctly when calling the native system call entry
point, so remove the special cases.
Link: https://lkml.kernel.org/r/20210727144859.4150043-6-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Merge misc updates from Andrew Morton:
"173 patches.
Subsystems affected by this series: ia64, ocfs2, block, and mm (debug,
pagecache, gup, swap, shmem, memcg, selftests, pagemap, mremap,
bootmem, sparsemem, vmalloc, kasan, pagealloc, memory-failure,
hugetlb, userfaultfd, vmscan, compaction, mempolicy, memblock,
oom-kill, migration, ksm, percpu, vmstat, and madvise)"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (173 commits)
mm/madvise: add MADV_WILLNEED to process_madvise()
mm/vmstat: remove unneeded return value
mm/vmstat: simplify the array size calculation
mm/vmstat: correct some wrong comments
mm/percpu,c: remove obsolete comments of pcpu_chunk_populated()
selftests: vm: add COW time test for KSM pages
selftests: vm: add KSM merging time test
mm: KSM: fix data type
selftests: vm: add KSM merging across nodes test
selftests: vm: add KSM zero page merging test
selftests: vm: add KSM unmerge test
selftests: vm: add KSM merge test
mm/migrate: correct kernel-doc notation
mm: wire up syscall process_mrelease
mm: introduce process_mrelease system call
memblock: make memblock_find_in_range method private
mm/mempolicy.c: use in_task() in mempolicy_slab_node()
mm/mempolicy: unify the create() func for bind/interleave/prefer-many policies
mm/mempolicy: advertise new MPOL_PREFERRED_MANY
mm/hugetlb: add support for mempolicy MPOL_PREFERRED_MANY
...
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Split off from prev patch in the series that implements the syscall.
Link: https://lkml.kernel.org/r/20210809185259.405936-2-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Jan Engelhardt <jengelh@inai.de>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tim Murray <timmurray@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The bdflush system call has been deprecated for a very long time.
Recently Michael Schmitz tested[1] and found that the last known
caller of of the bdflush system call is unaffected by it's removal.
Since the code is not needed delete it.
[1] https://lkml.kernel.org/r/36123b5d-daa0-6c2b-f2d4-a942f069fd54@gmail.com
Link: https://lkml.kernel.org/r/87sg10quue.fsf_-_@disp2133
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Cyril Hrubis <chrubis@suse.cz>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Wire up memfd_secret system call on architectures that define
ARCH_HAS_SET_DIRECT_MAP, namely arm64, risc-v and x86.
Link: https://lkml.kernel.org/r/20210518072034.31572-7-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Will Deacon <will@kernel.org>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Wire up the quotactl_fd syscall.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
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In commit fa8b90070a80 ("quota: wire up quotactl_path") we have wired up
new quotactl_path syscall. However some people in LWN discussion have
objected that the path based syscall is missing dirfd and flags argument
which is mostly standard for contemporary path based syscalls. Indeed
they have a point and after a discussion with Christian Brauner and
Sascha Hauer I've decided to disable the syscall for now and update its
API. Since there is no userspace currently using that syscall and it
hasn't been released in any major release, we should be fine.
CC: Christian Brauner <christian.brauner@ubuntu.com>
CC: Sascha Hauer <s.hauer@pengutronix.de>
Link: https://lore.kernel.org/lkml/20210512153621.n5u43jsytbik4yze@wittgenstein
Signed-off-by: Jan Kara <jack@suse.cz>
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git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
Pull Landlock LSM from James Morris:
"Add Landlock, a new LSM from Mickaël Salaün.
Briefly, Landlock provides for unprivileged application sandboxing.
From Mickaël's cover letter:
"The goal of Landlock is to enable to restrict ambient rights (e.g.
global filesystem access) for a set of processes. Because Landlock
is a stackable LSM [1], it makes possible to create safe security
sandboxes as new security layers in addition to the existing
system-wide access-controls. This kind of sandbox is expected to
help mitigate the security impact of bugs or unexpected/malicious
behaviors in user-space applications. Landlock empowers any
process, including unprivileged ones, to securely restrict
themselves.
Landlock is inspired by seccomp-bpf but instead of filtering
syscalls and their raw arguments, a Landlock rule can restrict the
use of kernel objects like file hierarchies, according to the
kernel semantic. Landlock also takes inspiration from other OS
sandbox mechanisms: XNU Sandbox, FreeBSD Capsicum or OpenBSD
Pledge/Unveil.
In this current form, Landlock misses some access-control features.
This enables to minimize this patch series and ease review. This
series still addresses multiple use cases, especially with the
combined use of seccomp-bpf: applications with built-in sandboxing,
init systems, security sandbox tools and security-oriented APIs [2]"
The cover letter and v34 posting is here:
https://lore.kernel.org/linux-security-module/20210422154123.13086-1-mic@digikod.net/
See also:
https://landlock.io/
This code has had extensive design discussion and review over several
years"
Link: https://lore.kernel.org/lkml/50db058a-7dde-441b-a7f9-f6837fe8b69f@schaufler-ca.com/ [1]
Link: https://lore.kernel.org/lkml/f646e1c7-33cf-333f-070c-0a40ad0468cd@digikod.net/ [2]
* tag 'landlock_v34' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
landlock: Enable user space to infer supported features
landlock: Add user and kernel documentation
samples/landlock: Add a sandbox manager example
selftests/landlock: Add user space tests
landlock: Add syscall implementations
arch: Wire up Landlock syscalls
fs,security: Add sb_delete hook
landlock: Support filesystem access-control
LSM: Infrastructure management of the superblock
landlock: Add ptrace restrictions
landlock: Set up the security framework and manage credentials
landlock: Add ruleset and domain management
landlock: Add object management
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Wire up the following system calls for all architectures:
* landlock_create_ruleset(2)
* landlock_add_rule(2)
* landlock_restrict_self(2)
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: James Morris <jmorris@namei.org>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Serge E. Hallyn <serge@hallyn.com>
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Link: https://lore.kernel.org/r/20210422154123.13086-10-mic@digikod.net
Signed-off-by: James Morris <jamorris@linux.microsoft.com>
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Wire up the quotactl_path syscall added in the previous patch.
Link: https://lore.kernel.org/r/20210304123541.30749-3-s.hauer@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
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This implements the missing mount_setattr() syscall. While the new mount
api allows to change the properties of a superblock there is currently
no way to change the properties of a mount or a mount tree using file
descriptors which the new mount api is based on. In addition the old
mount api has the restriction that mount options cannot be applied
recursively. This hasn't changed since changing mount options on a
per-mount basis was implemented in [1] and has been a frequent request
not just for convenience but also for security reasons. The legacy
mount syscall is unable to accommodate this behavior without introducing
a whole new set of flags because MS_REC | MS_REMOUNT | MS_BIND |
MS_RDONLY | MS_NOEXEC | [...] only apply the mount option to the topmost
mount. Changing MS_REC to apply to the whole mount tree would mean
introducing a significant uapi change and would likely cause significant
regressions.
The new mount_setattr() syscall allows to recursively clear and set
mount options in one shot. Multiple calls to change mount options
requesting the same changes are idempotent:
int mount_setattr(int dfd, const char *path, unsigned flags,
struct mount_attr *uattr, size_t usize);
Flags to modify path resolution behavior are specified in the @flags
argument. Currently, AT_EMPTY_PATH, AT_RECURSIVE, AT_SYMLINK_NOFOLLOW,
and AT_NO_AUTOMOUNT are supported. If useful, additional lookup flags to
restrict path resolution as introduced with openat2() might be supported
in the future.
The mount_setattr() syscall can be expected to grow over time and is
designed with extensibility in mind. It follows the extensible syscall
pattern we have used with other syscalls such as openat2(), clone3(),
sched_{set,get}attr(), and others.
The set of mount options is passed in the uapi struct mount_attr which
currently has the following layout:
struct mount_attr {
__u64 attr_set;
__u64 attr_clr;
__u64 propagation;
__u64 userns_fd;
};
The @attr_set and @attr_clr members are used to clear and set mount
options. This way a user can e.g. request that a set of flags is to be
raised such as turning mounts readonly by raising MOUNT_ATTR_RDONLY in
@attr_set while at the same time requesting that another set of flags is
to be lowered such as removing noexec from a mount tree by specifying
MOUNT_ATTR_NOEXEC in @attr_clr.
Note, since the MOUNT_ATTR_<atime> values are an enum starting from 0,
not a bitmap, users wanting to transition to a different atime setting
cannot simply specify the atime setting in @attr_set, but must also
specify MOUNT_ATTR__ATIME in the @attr_clr field. So we ensure that
MOUNT_ATTR__ATIME can't be partially set in @attr_clr and that @attr_set
can't have any atime bits set if MOUNT_ATTR__ATIME isn't set in
@attr_clr.
The @propagation field lets callers specify the propagation type of a
mount tree. Propagation is a single property that has four different
settings and as such is not really a flag argument but an enum.
Specifically, it would be unclear what setting and clearing propagation
settings in combination would amount to. The legacy mount() syscall thus
forbids the combination of multiple propagation settings too. The goal
is to keep the semantics of mount propagation somewhat simple as they
are overly complex as it is.
The @userns_fd field lets user specify a user namespace whose idmapping
becomes the idmapping of the mount. This is implemented and explained in
detail in the next patch.
[1]: commit 2e4b7fcd9260 ("[PATCH] r/o bind mounts: honor mount writer counts at remount")
Link: https://lore.kernel.org/r/20210121131959.646623-35-christian.brauner@ubuntu.com
Cc: David Howells <dhowells@redhat.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-api@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
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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>
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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>
|
|
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
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull compat quotactl cleanups from Al Viro:
"More Christoph's compat cleanups: quotactl(2)"
* 'work.quota-compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
quota: simplify the quotactl compat handling
compat: add a compat_need_64bit_alignment_fixup() helper
compat: lift compat_s64 and compat_u64 to <asm-generic/compat.h>
|
|
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>
|
|
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>
|
|
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>
|
|
compat_sys_mount is identical to the regular sys_mount now, so remove it
and use the native version everywhere.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Fold the misaligned u64 workarounds into the main quotactl flow instead
of implementing a separate compat syscall handler.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Since commit 61a47c1ad3a4dc ("sysctl: Remove the sysctl system call"),
sys_sysctl is actually unavailable: any input can only return an error.
We have been warning about people using the sysctl system call for years
and believe there are no more users. Even if there are users of this
interface if they have not complained or fixed their code by now they
probably are not going to, so there is no point in warning them any
longer.
So completely remove sys_sysctl on all architectures.
[nixiaoming@huawei.com: s390: fix build error for sys_call_table_emu]
Link: http://lkml.kernel.org/r/20200618141426.16884-1-nixiaoming@huawei.com
Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Will Deacon <will@kernel.org> [arm/arm64]
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Bin Meng <bin.meng@windriver.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: chenzefeng <chenzefeng2@huawei.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christian Brauner <christian@brauner.io>
Cc: Chris Zankel <chris@zankel.net>
Cc: David Howells <dhowells@redhat.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Diego Elio Pettenò <flameeyes@flameeyes.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kars de Jong <jongk@linux-m68k.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Nick Piggin <npiggin@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Paul Burton <paulburton@kernel.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Sven Schnelle <svens@stackframe.org>
Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Zhou Yanjie <zhouyanjie@wanyeetech.com>
Link: http://lkml.kernel.org/r/20200616030734.87257-1-nixiaoming@huawei.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Pull networking updates from David Miller:
1) Support 6Ghz band in ath11k driver, from Rajkumar Manoharan.
2) Support UDP segmentation in code TSO code, from Eric Dumazet.
3) Allow flashing different flash images in cxgb4 driver, from Vishal
Kulkarni.
4) Add drop frames counter and flow status to tc flower offloading,
from Po Liu.
5) Support n-tuple filters in cxgb4, from Vishal Kulkarni.
6) Various new indirect call avoidance, from Eric Dumazet and Brian
Vazquez.
7) Fix BPF verifier failures on 32-bit pointer arithmetic, from
Yonghong Song.
8) Support querying and setting hardware address of a port function via
devlink, use this in mlx5, from Parav Pandit.
9) Support hw ipsec offload on bonding slaves, from Jarod Wilson.
10) Switch qca8k driver over to phylink, from Jonathan McDowell.
11) In bpftool, show list of processes holding BPF FD references to
maps, programs, links, and btf objects. From Andrii Nakryiko.
12) Several conversions over to generic power management, from Vaibhav
Gupta.
13) Add support for SO_KEEPALIVE et al. to bpf_setsockopt(), from Dmitry
Yakunin.
14) Various https url conversions, from Alexander A. Klimov.
15) Timestamping and PHC support for mscc PHY driver, from Antoine
Tenart.
16) Support bpf iterating over tcp and udp sockets, from Yonghong Song.
17) Support 5GBASE-T i40e NICs, from Aleksandr Loktionov.
18) Add kTLS RX HW offload support to mlx5e, from Tariq Toukan.
19) Fix the ->ndo_start_xmit() return type to be netdev_tx_t in several
drivers. From Luc Van Oostenryck.
20) XDP support for xen-netfront, from Denis Kirjanov.
21) Support receive buffer autotuning in MPTCP, from Florian Westphal.
22) Support EF100 chip in sfc driver, from Edward Cree.
23) Add XDP support to mvpp2 driver, from Matteo Croce.
24) Support MPTCP in sock_diag, from Paolo Abeni.
25) Commonize UDP tunnel offloading code by creating udp_tunnel_nic
infrastructure, from Jakub Kicinski.
26) Several pci_ --> dma_ API conversions, from Christophe JAILLET.
27) Add FLOW_ACTION_POLICE support to mlxsw, from Ido Schimmel.
28) Add SK_LOOKUP bpf program type, from Jakub Sitnicki.
29) Refactor a lot of networking socket option handling code in order to
avoid set_fs() calls, from Christoph Hellwig.
30) Add rfc4884 support to icmp code, from Willem de Bruijn.
31) Support TBF offload in dpaa2-eth driver, from Ioana Ciornei.
32) Support XDP_REDIRECT in qede driver, from Alexander Lobakin.
33) Support PCI relaxed ordering in mlx5 driver, from Aya Levin.
34) Support TCP syncookies in MPTCP, from Flowian Westphal.
35) Fix several tricky cases of PMTU handling wrt. briding, from Stefano
Brivio.
* git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (2056 commits)
net: thunderx: initialize VF's mailbox mutex before first usage
usb: hso: remove bogus check for EINPROGRESS
usb: hso: no complaint about kmalloc failure
hso: fix bailout in error case of probe
ip_tunnel_core: Fix build for archs without _HAVE_ARCH_IPV6_CSUM
selftests/net: relax cpu affinity requirement in msg_zerocopy test
mptcp: be careful on subflow creation
selftests: rtnetlink: make kci_test_encap() return sub-test result
selftests: rtnetlink: correct the final return value for the test
net: dsa: sja1105: use detected device id instead of DT one on mismatch
tipc: set ub->ifindex for local ipv6 address
ipv6: add ipv6_dev_find()
net: openvswitch: silence suspicious RCU usage warning
Revert "vxlan: fix tos value before xmit"
ptp: only allow phase values lower than 1 period
farsync: switch from 'pci_' to 'dma_' API
wan: wanxl: switch from 'pci_' to 'dma_' API
hv_netvsc: do not use VF device if link is down
dpaa2-eth: Fix passing zero to 'PTR_ERR' warning
net: macb: Properly handle phylink on at91sam9x
...
|
|
Now that the ->compat_{get,set}sockopt proto_ops methods are gone
there is no good reason left to keep the compat syscalls separate.
This fixes the odd use of unsigned int for the compat_setsockopt
optlen and the missing sock_use_custom_sol_socket.
It would also easily allow running the eBPF hooks for the compat
syscalls, but such a large change in behavior does not belong into
a consolidation patch like this one.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
|
|
This wires up the close_range() syscall into all arches at once.
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Cc: Jann Horn <jannh@google.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Dmitry V. Levin <ldv@altlinux.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: linux-api@vger.kernel.org
Cc: linux-alpha@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-m68k@lists.linux-m68k.org
Cc: linux-mips@vger.kernel.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: sparclinux@vger.kernel.org
Cc: linux-xtensa@linux-xtensa.org
Cc: linux-arch@vger.kernel.org
Cc: x86@kernel.org
|
|
POSIX defines faccessat() as having a fourth "flags" argument, while the
linux syscall doesn't have it. Glibc tries to emulate AT_EACCESS and
AT_SYMLINK_NOFOLLOW, but AT_EACCESS emulation is broken.
Add a new faccessat(2) syscall with the added flags argument and implement
both flags.
The value of AT_EACCESS is defined in glibc headers to be the same as
AT_REMOVEDIR. Use this value for the kernel interface as well, together
with the explanatory comment.
Also add AT_EMPTY_PATH support, which is not documented by POSIX, but can
be useful and is trivial to implement.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
For the 32-bit syscall interface, 64-bit arguments (loff_t) are passed via
a pair of 32-bit registers. These register pairs end up in consecutive stack
slots, which matches the C ABI for 64-bit arguments. But when accessing the
registers directly from pt_regs, the wrapper needs to manually reassemble the
64-bit value. These wrappers already exist for 32-bit compat, so make them
available to 32-bit native in preparation for enabling pt_regs-based syscalls.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Link: https://lkml.kernel.org/r/20200313195144.164260-16-brgerst@gmail.com
|
|
Rename the syscalls that only exist for 32-bit from x86_* to ia32_* to make it
clear they are for 32-bit only. Also rename the functions to match the syscall
name.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Link: https://lkml.kernel.org/r/20200313195144.164260-15-brgerst@gmail.com
|
|
After removal of the __ia32_ prefix, remove compat entries that are now
identical to the native entry.
Converted with this script and fixing up whitespace:
while read nr abi name entry compat; do
if [ "${nr:0:1}" = "#" ]; then
echo $nr $abi $name $entry $compat
continue
fi
if [ "$entry" = "$compat" ]; then
compat=""
fi
echo "$nr $abi $name $entry $compat"
done
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200313195144.164260-14-brgerst@gmail.com
|
|
Move the ABI prefixes to the __SYSCALL_[abi]() macros. This allows removal
of the need to strip the prefix for UML.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200313195144.164260-13-brgerst@gmail.com
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull thread management updates from Christian Brauner:
"Sargun Dhillon over the last cycle has worked on the pidfd_getfd()
syscall.
This syscall allows for the retrieval of file descriptors of a process
based on its pidfd. A task needs to have ptrace_may_access()
permissions with PTRACE_MODE_ATTACH_REALCREDS (suggested by Oleg and
Andy) on the target.
One of the main use-cases is in combination with seccomp's user
notification feature. As a reminder, seccomp's user notification
feature was made available in v5.0. It allows a task to retrieve a
file descriptor for its seccomp filter. The file descriptor is usually
handed of to a more privileged supervising process. The supervisor can
then listen for syscall events caught by the seccomp filter of the
supervisee and perform actions in lieu of the supervisee, usually
emulating syscalls. pidfd_getfd() is needed to expand its uses.
There are currently two major users that wait on pidfd_getfd() and one
future user:
- Netflix, Sargun said, is working on a service mesh where users
should be able to connect to a dns-based VIP. When a user connects
to e.g. 1.2.3.4:80 that runs e.g. service "foo" they will be
redirected to an envoy process. This service mesh uses seccomp user
notifications and pidfd to intercept all connect calls and instead
of connecting them to 1.2.3.4:80 connects them to e.g.
127.0.0.1:8080.
- LXD uses the seccomp notifier heavily to intercept and emulate
mknod() and mount() syscalls for unprivileged containers/processes.
With pidfd_getfd() more uses-cases e.g. bridging socket connections
will be possible.
- The patchset has also seen some interest from the browser corner.
Right now, Firefox is using a SECCOMP_RET_TRAP sandbox managed by a
broker process. In the future glibc will start blocking all signals
during dlopen() rendering this type of sandbox impossible. Hence,
in the future Firefox will switch to a seccomp-user-nofication
based sandbox which also makes use of file descriptor retrieval.
The thread for this can be found at
https://sourceware.org/ml/libc-alpha/2019-12/msg00079.html
With pidfd_getfd() it is e.g. possible to bridge socket connections
for the supervisee (binding to a privileged port) and taking actions
on file descriptors on behalf of the supervisee in general.
Sargun's first version was using an ioctl on pidfds but various people
pushed for it to be a proper syscall which he duely implemented as
well over various review cycles. Selftests are of course included.
I've also added instructions how to deal with merge conflicts below.
There's also a small fix coming from the kernel mentee project to
correctly annotate struct sighand_struct with __rcu to fix various
sparse warnings. We've received a few more such fixes and even though
they are mostly trivial I've decided to postpone them until after -rc1
since they came in rather late and I don't want to risk introducing
build warnings.
Finally, there's a new prctl() command PR_{G,S}ET_IO_FLUSHER which is
needed to avoid allocation recursions triggerable by storage drivers
that have userspace parts that run in the IO path (e.g. dm-multipath,
iscsi, etc). These allocation recursions deadlock the device.
The new prctl() allows such privileged userspace components to avoid
allocation recursions by setting the PF_MEMALLOC_NOIO and
PF_LESS_THROTTLE flags. The patch carries the necessary acks from the
relevant maintainers and is routed here as part of prctl()
thread-management."
* tag 'threads-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
prctl: PR_{G,S}ET_IO_FLUSHER to support controlling memory reclaim
sched.h: Annotate sighand_struct with __rcu
test: Add test for pidfd getfd
arch: wire up pidfd_getfd syscall
pid: Implement pidfd_getfd syscall
vfs, fdtable: Add fget_task helper
|
|
/* Background. */
For a very long time, extending openat(2) with new features has been
incredibly frustrating. This stems from the fact that openat(2) is
possibly the most famous counter-example to the mantra "don't silently
accept garbage from userspace" -- it doesn't check whether unknown flags
are present[1].
This means that (generally) the addition of new flags to openat(2) has
been fraught with backwards-compatibility issues (O_TMPFILE has to be
defined as __O_TMPFILE|O_DIRECTORY|[O_RDWR or O_WRONLY] to ensure old
kernels gave errors, since it's insecure to silently ignore the
flag[2]). All new security-related flags therefore have a tough road to
being added to openat(2).
Userspace also has a hard time figuring out whether a particular flag is
supported on a particular kernel. While it is now possible with
contemporary kernels (thanks to [3]), older kernels will expose unknown
flag bits through fcntl(F_GETFL). Giving a clear -EINVAL during
openat(2) time matches modern syscall designs and is far more
fool-proof.
In addition, the newly-added path resolution restriction LOOKUP flags
(which we would like to expose to user-space) don't feel related to the
pre-existing O_* flag set -- they affect all components of path lookup.
We'd therefore like to add a new flag argument.
Adding a new syscall allows us to finally fix the flag-ignoring problem,
and we can make it extensible enough so that we will hopefully never
need an openat3(2).
/* Syscall Prototype. */
/*
* open_how is an extensible structure (similar in interface to
* clone3(2) or sched_setattr(2)). The size parameter must be set to
* sizeof(struct open_how), to allow for future extensions. All future
* extensions will be appended to open_how, with their zero value
* acting as a no-op default.
*/
struct open_how { /* ... */ };
int openat2(int dfd, const char *pathname,
struct open_how *how, size_t size);
/* Description. */
The initial version of 'struct open_how' contains the following fields:
flags
Used to specify openat(2)-style flags. However, any unknown flag
bits or otherwise incorrect flag combinations (like O_PATH|O_RDWR)
will result in -EINVAL. In addition, this field is 64-bits wide to
allow for more O_ flags than currently permitted with openat(2).
mode
The file mode for O_CREAT or O_TMPFILE.
Must be set to zero if flags does not contain O_CREAT or O_TMPFILE.
resolve
Restrict path resolution (in contrast to O_* flags they affect all
path components). The current set of flags are as follows (at the
moment, all of the RESOLVE_ flags are implemented as just passing
the corresponding LOOKUP_ flag).
RESOLVE_NO_XDEV => LOOKUP_NO_XDEV
RESOLVE_NO_SYMLINKS => LOOKUP_NO_SYMLINKS
RESOLVE_NO_MAGICLINKS => LOOKUP_NO_MAGICLINKS
RESOLVE_BENEATH => LOOKUP_BENEATH
RESOLVE_IN_ROOT => LOOKUP_IN_ROOT
open_how does not contain an embedded size field, because it is of
little benefit (userspace can figure out the kernel open_how size at
runtime fairly easily without it). It also only contains u64s (even
though ->mode arguably should be a u16) to avoid having padding fields
which are never used in the future.
Note that as a result of the new how->flags handling, O_PATH|O_TMPFILE
is no longer permitted for openat(2). As far as I can tell, this has
always been a bug and appears to not be used by userspace (and I've not
seen any problems on my machines by disallowing it). If it turns out
this breaks something, we can special-case it and only permit it for
openat(2) but not openat2(2).
After input from Florian Weimer, the new open_how and flag definitions
are inside a separate header from uapi/linux/fcntl.h, to avoid problems
that glibc has with importing that header.
/* Testing. */
In a follow-up patch there are over 200 selftests which ensure that this
syscall has the correct semantics and will correctly handle several
attack scenarios.
In addition, I've written a userspace library[4] which provides
convenient wrappers around openat2(RESOLVE_IN_ROOT) (this is necessary
because no other syscalls support RESOLVE_IN_ROOT, and thus lots of care
must be taken when using RESOLVE_IN_ROOT'd file descriptors with other
syscalls). During the development of this patch, I've run numerous
verification tests using libpathrs (showing that the API is reasonably
usable by userspace).
/* Future Work. */
Additional RESOLVE_ flags have been suggested during the review period.
These can be easily implemented separately (such as blocking auto-mount
during resolution).
Furthermore, there are some other proposed changes to the openat(2)
interface (the most obvious example is magic-link hardening[5]) which
would be a good opportunity to add a way for userspace to restrict how
O_PATH file descriptors can be re-opened.
Another possible avenue of future work would be some kind of
CHECK_FIELDS[6] flag which causes the kernel to indicate to userspace
which openat2(2) flags and fields are supported by the current kernel
(to avoid userspace having to go through several guesses to figure it
out).
[1]: https://lwn.net/Articles/588444/
[2]: https://lore.kernel.org/lkml/CA+55aFyyxJL1LyXZeBsf2ypriraj5ut1XkNDsunRBqgVjZU_6Q@mail.gmail.com
[3]: commit 629e014bb834 ("fs: completely ignore unknown open flags")
[4]: https://sourceware.org/bugzilla/show_bug.cgi?id=17523
[5]: https://lore.kernel.org/lkml/20190930183316.10190-2-cyphar@cyphar.com/
[6]: https://youtu.be/ggD-eb3yPVs
Suggested-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
This wires up the pidfd_getfd syscall for all architectures.
Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200107175927.4558-4-sargun@sargun.me
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
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|
Use the correct function type for sys_ni_syscall() in system
call tables to fix indirect call mismatches with Control-Flow
Integrity (CFI) checking.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H . Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191008224049.115427-5-samitolvanen@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
Use COMPAT_SYSCALL_DEFINE0 to define (rt_)sigreturn() syscalls to
replace sys32_sigreturn() and sys32_rt_sigreturn(). This fixes indirect
call mismatches with Control-Flow Integrity (CFI) checking.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H . Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191008224049.115427-4-samitolvanen@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
I'm working on some code that detects at build time if there's a
COMPAT_SYSCALL_DEFINE() that is not referenced in the x86 syscall tables.
It catches three offenders: rt_sigsuspend(), rt_sigprocmask(), and
sendfile64().
For rt_sigsuspend() and rt_sigprocmask(), the only potential difference
between the native and compat versions is that the compat version converts
the sigset_t, but, on little endian architectures, the conversion is a
no-op. This is why they both currently work on x86.
To make the code more consistent, and to make the upcoming patches work,
rewire x86 to use the compat vesions.
sendfile64() is more complicated, and will be addressed separately.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/51643ac3157b5921eae0e172a8a0b1d953e68ebb.1562185330.git.luto@kernel.org
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull clone3 system call from Christian Brauner:
"This adds the clone3 syscall which is an extensible successor to clone
after we snagged the last flag with CLONE_PIDFD during the 5.2 merge
window for clone(). It cleanly supports all of the flags from clone()
and thus all legacy workloads.
There are few user visible differences between clone3 and clone.
First, CLONE_DETACHED will cause EINVAL with clone3 so we can reuse
this flag. Second, the CSIGNAL flag is deprecated and will cause
EINVAL to be reported. It is superseeded by a dedicated "exit_signal"
argument in struct clone_args thus freeing up even more flags. And
third, clone3 gives CLONE_PIDFD a dedicated return argument in struct
clone_args instead of abusing CLONE_PARENT_SETTID's parent_tidptr
argument.
The clone3 uapi is designed to be easy to handle on 32- and 64 bit:
/* uapi */
struct clone_args {
__aligned_u64 flags;
__aligned_u64 pidfd;
__aligned_u64 child_tid;
__aligned_u64 parent_tid;
__aligned_u64 exit_signal;
__aligned_u64 stack;
__aligned_u64 stack_size;
__aligned_u64 tls;
};
and a separate kernel struct is used that uses proper kernel typing:
/* kernel internal */
struct kernel_clone_args {
u64 flags;
int __user *pidfd;
int __user *child_tid;
int __user *parent_tid;
int exit_signal;
unsigned long stack;
unsigned long stack_size;
unsigned long tls;
};
The system call comes with a size argument which enables the kernel to
detect what version of clone_args userspace is passing in. clone3
validates that any additional bytes a given kernel does not know about
are set to zero and that the size never exceeds a page.
A nice feature is that this patchset allowed us to cleanup and
simplify various core kernel codepaths in kernel/fork.c by making the
internal _do_fork() function take struct kernel_clone_args even for
legacy clone().
This patch also unblocks the time namespace patchset which wants to
introduce a new CLONE_TIMENS flag.
Note, that clone3 has only been wired up for x86{_32,64}, arm{64}, and
xtensa. These were the architectures that did not require special
massaging.
Other architectures treat fork-like system calls individually and
after some back and forth neither Arnd nor I felt confident that we
dared to add clone3 unconditionally to all architectures. We agreed to
leave this up to individual architecture maintainers. This is why
there's an additional patch that introduces __ARCH_WANT_SYS_CLONE3
which any architecture can set once it has implemented support for
clone3. The patch also adds a cond_syscall(clone3) for architectures
such as nios2 or h8300 that generate their syscall table by simply
including asm-generic/unistd.h. The hope is to get rid of
__ARCH_WANT_SYS_CLONE3 and cond_syscall() rather soon"
* tag 'clone3-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
arch: handle arches who do not yet define clone3
arch: wire-up clone3() syscall
fork: add clone3
|
|
This wires up the pidfd_open() syscall into all arches at once.
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jann Horn <jannh@google.com>
Cc: Andy Lutomirsky <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-api@vger.kernel.org
Cc: linux-alpha@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-m68k@lists.linux-m68k.org
Cc: linux-mips@vger.kernel.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: sparclinux@vger.kernel.org
Cc: linux-xtensa@linux-xtensa.org
Cc: linux-arch@vger.kernel.org
Cc: x86@kernel.org
|
|
Wire up the clone3() call on all arches that don't require hand-rolled
assembly.
Some of the arches look like they need special assembly massaging and it is
probably smarter if the appropriate arch maintainers would do the actual
wiring. Arches that are wired-up are:
- x86{_32,64}
- arm{64}
- xtensa
Signed-off-by: Christian Brauner <christian@brauner.io>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Adrian Reber <adrian@lisas.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: linux-api@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: x86@kernel.org
|
|
Fix the syscall numbering of the mount API syscalls so that the numbers
match between i386 and x86_64 and that they're in the common numbering
scheme space.
Fixes: a07b20004793 ("vfs: syscall: Add open_tree(2) to reference or clone a mount")
Fixes: 2db154b3ea8e ("vfs: syscall: Add move_mount(2) to move mounts around")
Fixes: 24dcb3d90a1f ("vfs: syscall: Add fsopen() to prepare for superblock creation")
Fixes: ecdab150fddb ("vfs: syscall: Add fsconfig() for configuring and managing a context")
Fixes: 93766fbd2696 ("vfs: syscall: Add fsmount() to create a mount for a superblock")
Fixes: cf3cba4a429b ("vfs: syscall: Add fspick() to select a superblock for reconfiguration")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Provide an fspick() system call that can be used to pick an existing
mountpoint into an fs_context which can thereafter be used to reconfigure a
superblock (equivalent of the superblock side of -o remount).
This looks like:
int fd = fspick(AT_FDCWD, "/mnt",
FSPICK_CLOEXEC | FSPICK_NO_AUTOMOUNT);
fsconfig(fd, FSCONFIG_SET_FLAG, "intr", NULL, 0);
fsconfig(fd, FSCONFIG_SET_FLAG, "noac", NULL, 0);
fsconfig(fd, FSCONFIG_CMD_RECONFIGURE, NULL, NULL, 0);
At the point of fspick being called, the file descriptor referring to the
filesystem context is in exactly the same state as the one that was created
by fsopen() after fsmount() has been successfully called.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-api@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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|
Provide a system call by which a filesystem opened with fsopen() and
configured by a series of fsconfig() calls can have a detached mount object
created for it. This mount object can then be attached to the VFS mount
hierarchy using move_mount() by passing the returned file descriptor as the
from directory fd.
The system call looks like:
int mfd = fsmount(int fsfd, unsigned int flags,
unsigned int attr_flags);
where fsfd is the file descriptor returned by fsopen(). flags can be 0 or
FSMOUNT_CLOEXEC. attr_flags is a bitwise-OR of the following flags:
MOUNT_ATTR_RDONLY Mount read-only
MOUNT_ATTR_NOSUID Ignore suid and sgid bits
MOUNT_ATTR_NODEV Disallow access to device special files
MOUNT_ATTR_NOEXEC Disallow program execution
MOUNT_ATTR__ATIME Setting on how atime should be updated
MOUNT_ATTR_RELATIME - Update atime relative to mtime/ctime
MOUNT_ATTR_NOATIME - Do not update access times
MOUNT_ATTR_STRICTATIME - Always perform atime updates
MOUNT_ATTR_NODIRATIME Do not update directory access times
In the event that fsmount() fails, it may be possible to get an error
message by calling read() on fsfd. If no message is available, ENODATA
will be reported.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-api@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Add a syscall for configuring a filesystem creation context and triggering
actions upon it, to be used in conjunction with fsopen, fspick and fsmount.
long fsconfig(int fs_fd, unsigned int cmd, const char *key,
const void *value, int aux);
Where fs_fd indicates the context, cmd indicates the action to take, key
indicates the parameter name for parameter-setting actions and, if needed,
value points to a buffer containing the value and aux can give more
information for the value.
The following command IDs are proposed:
(*) FSCONFIG_SET_FLAG: No value is specified. The parameter must be
boolean in nature. The key may be prefixed with "no" to invert the
setting. value must be NULL and aux must be 0.
(*) FSCONFIG_SET_STRING: A string value is specified. The parameter can
be expecting boolean, integer, string or take a path. A conversion to
an appropriate type will be attempted (which may include looking up as
a path). value points to a NUL-terminated string and aux must be 0.
(*) FSCONFIG_SET_BINARY: A binary blob is specified. value points to
the blob and aux indicates its size. The parameter must be expecting
a blob.
(*) FSCONFIG_SET_PATH: A non-empty path is specified. The parameter must
be expecting a path object. value points to a NUL-terminated string
that is the path and aux is a file descriptor at which to start a
relative lookup or AT_FDCWD.
(*) FSCONFIG_SET_PATH_EMPTY: As fsconfig_set_path, but with AT_EMPTY_PATH
implied.
(*) FSCONFIG_SET_FD: An open file descriptor is specified. value must
be NULL and aux indicates the file descriptor.
(*) FSCONFIG_CMD_CREATE: Trigger superblock creation.
(*) FSCONFIG_CMD_RECONFIGURE: Trigger superblock reconfiguration.
For the "set" command IDs, the idea is that the file_system_type will point
to a list of parameters and the types of value that those parameters expect
to take. The core code can then do the parse and argument conversion and
then give the LSM and FS a cooked option or array of options to use.
Source specification is also done the same way same way, using special keys
"source", "source1", "source2", etc..
[!] Note that, for the moment, the key and value are just glued back
together and handed to the filesystem. Every filesystem that uses options
uses match_token() and co. to do this, and this will need to be changed -
but not all at once.
Example usage:
fd = fsopen("ext4", FSOPEN_CLOEXEC);
fsconfig(fd, fsconfig_set_path, "source", "/dev/sda1", AT_FDCWD);
fsconfig(fd, fsconfig_set_path_empty, "journal_path", "", journal_fd);
fsconfig(fd, fsconfig_set_fd, "journal_fd", "", journal_fd);
fsconfig(fd, fsconfig_set_flag, "user_xattr", NULL, 0);
fsconfig(fd, fsconfig_set_flag, "noacl", NULL, 0);
fsconfig(fd, fsconfig_set_string, "sb", "1", 0);
fsconfig(fd, fsconfig_set_string, "errors", "continue", 0);
fsconfig(fd, fsconfig_set_string, "data", "journal", 0);
fsconfig(fd, fsconfig_set_string, "context", "unconfined_u:...", 0);
fsconfig(fd, fsconfig_cmd_create, NULL, NULL, 0);
mfd = fsmount(fd, FSMOUNT_CLOEXEC, MS_NOEXEC);
or:
fd = fsopen("ext4", FSOPEN_CLOEXEC);
fsconfig(fd, fsconfig_set_string, "source", "/dev/sda1", 0);
fsconfig(fd, fsconfig_cmd_create, NULL, NULL, 0);
mfd = fsmount(fd, FSMOUNT_CLOEXEC, MS_NOEXEC);
or:
fd = fsopen("afs", FSOPEN_CLOEXEC);
fsconfig(fd, fsconfig_set_string, "source", "#grand.central.org:root.cell", 0);
fsconfig(fd, fsconfig_cmd_create, NULL, NULL, 0);
mfd = fsmount(fd, FSMOUNT_CLOEXEC, MS_NOEXEC);
or:
fd = fsopen("jffs2", FSOPEN_CLOEXEC);
fsconfig(fd, fsconfig_set_string, "source", "mtd0", 0);
fsconfig(fd, fsconfig_cmd_create, NULL, NULL, 0);
mfd = fsmount(fd, FSMOUNT_CLOEXEC, MS_NOEXEC);
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-api@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Provide an fsopen() system call that starts the process of preparing to
create a superblock that will then be mountable, using an fd as a context
handle. fsopen() is given the name of the filesystem that will be used:
int mfd = fsopen(const char *fsname, unsigned int flags);
where flags can be 0 or FSOPEN_CLOEXEC.
For example:
sfd = fsopen("ext4", FSOPEN_CLOEXEC);
fsconfig(sfd, FSCONFIG_SET_PATH, "source", "/dev/sda1", AT_FDCWD);
fsconfig(sfd, FSCONFIG_SET_FLAG, "noatime", NULL, 0);
fsconfig(sfd, FSCONFIG_SET_FLAG, "acl", NULL, 0);
fsconfig(sfd, FSCONFIG_SET_FLAG, "user_xattr", NULL, 0);
fsconfig(sfd, FSCONFIG_SET_STRING, "sb", "1", 0);
fsconfig(sfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
fsinfo(sfd, NULL, ...); // query new superblock attributes
mfd = fsmount(sfd, FSMOUNT_CLOEXEC, MS_RELATIME);
move_mount(mfd, "", sfd, AT_FDCWD, "/mnt", MOVE_MOUNT_F_EMPTY_PATH);
sfd = fsopen("afs", -1);
fsconfig(fd, FSCONFIG_SET_STRING, "source",
"#grand.central.org:root.cell", 0);
fsconfig(fd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
mfd = fsmount(sfd, 0, MS_NODEV);
move_mount(mfd, "", sfd, AT_FDCWD, "/mnt", MOVE_MOUNT_F_EMPTY_PATH);
If an error is reported at any step, an error message may be available to be
read() back (ENODATA will be reported if there isn't an error available) in
the form:
"e <subsys>:<problem>"
"e SELinux:Mount on mountpoint not permitted"
Once fsmount() has been called, further fsconfig() calls will incur EBUSY,
even if the fsmount() fails. read() is still possible to retrieve error
information.
The fsopen() syscall creates a mount context and hangs it of the fd that it
returns.
Netlink is not used because it is optional and would make the core VFS
dependent on the networking layer and also potentially add network
namespace issues.
Note that, for the moment, the caller must have SYS_CAP_ADMIN to use
fsopen().
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-api@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Add a move_mount() system call that will move a mount from one place to
another and, in the next commit, allow to attach an unattached mount tree.
The new system call looks like the following:
int move_mount(int from_dfd, const char *from_path,
int to_dfd, const char *to_path,
unsigned int flags);
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-api@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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open_tree(dfd, pathname, flags)
Returns an O_PATH-opened file descriptor or an error.
dfd and pathname specify the location to open, in usual
fashion (see e.g. fstatat(2)). flags should be an OR of
some of the following:
* AT_PATH_EMPTY, AT_NO_AUTOMOUNT, AT_SYMLINK_NOFOLLOW -
same meanings as usual
* OPEN_TREE_CLOEXEC - make the resulting descriptor
close-on-exec
* OPEN_TREE_CLONE or OPEN_TREE_CLONE | AT_RECURSIVE -
instead of opening the location in question, create a detached
mount tree matching the subtree rooted at location specified by
dfd/pathname. With AT_RECURSIVE the entire subtree is cloned,
without it - only the part within in the mount containing the
location in question. In other words, the same as mount --rbind
or mount --bind would've taken. The detached tree will be
dissolved on the final close of obtained file. Creation of such
detached trees requires the same capabilities as doing mount --bind.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-api@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull pidfd system call from Christian Brauner:
"This introduces the ability to use file descriptors from /proc/<pid>/
as stable handles on struct pid. Even if a pid is recycled the handle
will not change. For a start these fds can be used to send signals to
the processes they refer to.
With the ability to use /proc/<pid> fds as stable handles on struct
pid we can fix a long-standing issue where after a process has exited
its pid can be reused by another process. If a caller sends a signal
to a reused pid it will end up signaling the wrong process.
With this patchset we enable a variety of use cases. One obvious
example is that we can now safely delegate an important part of
process management - sending signals - to processes other than the
parent of a given process by sending file descriptors around via scm
rights and not fearing that the given process will have been recycled
in the meantime. It also allows for easy testing whether a given
process is still alive or not by sending signal 0 to a pidfd which is
quite handy.
There has been some interest in this feature e.g. from systems
management (systemd, glibc) and container managers. I have requested
and gotten comments from glibc to make sure that this syscall is
suitable for their needs as well. In the future I expect it to take on
most other pid-based signal syscalls. But such features are left for
the future once they are needed.
This has been sitting in linux-next for quite a while and has not
caused any issues. It comes with selftests which verify basic
functionality and also test that a recycled pid cannot be signaled via
a pidfd.
Jon has written about a prior version of this patchset. It should
cover the basic functionality since not a lot has changed since then:
https://lwn.net/Articles/773459/
The commit message for the syscall itself is extensively documenting
the syscall, including it's functionality and extensibility"
* tag 'pidfd-v5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
selftests: add tests for pidfd_send_signal()
signal: add pidfd_send_signal() syscall
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Pull io_uring IO interface from Jens Axboe:
"Second attempt at adding the io_uring interface.
Since the first one, we've added basic unit testing of the three
system calls, that resides in liburing like the other unit tests that
we have so far. It'll take a while to get full coverage of it, but
we're working towards it. I've also added two basic test programs to
tools/io_uring. One uses the raw interface and has support for all the
various features that io_uring supports outside of standard IO, like
fixed files, fixed IO buffers, and polled IO. The other uses the
liburing API, and is a simplified version of cp(1).
This adds support for a new IO interface, io_uring.
io_uring allows an application to communicate with the kernel through
two rings, the submission queue (SQ) and completion queue (CQ) ring.
This allows for very efficient handling of IOs, see the v5 posting for
some basic numbers:
https://lore.kernel.org/linux-block/20190116175003.17880-1-axboe@kernel.dk/
Outside of just efficiency, the interface is also flexible and
extendable, and allows for future use cases like the upcoming NVMe
key-value store API, networked IO, and so on. It also supports async
buffered IO, something that we've always failed to support in the
kernel.
Outside of basic IO features, it supports async polled IO as well.
This particular feature has already been tested at Facebook months ago
for flash storage boxes, with 25-33% improvements. It makes polled IO
actually useful for real world use cases, where even basic flash sees
a nice win in terms of efficiency, latency, and performance. These
boxes were IOPS bound before, now they are not.
This series adds three new system calls. One for setting up an
io_uring instance (io_uring_setup(2)), one for submitting/completing
IO (io_uring_enter(2)), and one for aux functions like registrating
file sets, buffers, etc (io_uring_register(2)). Through the help of
Arnd, I've coordinated the syscall numbers so merge on that front
should be painless.
Jon did a writeup of the interface a while back, which (except for
minor details that have been tweaked) is still accurate. Find that
here:
https://lwn.net/Articles/776703/
Huge thanks to Al Viro for helping getting the reference cycle code
correct, and to Jann Horn for his extensive reviews focused on both
security and bugs in general.
There's a userspace library that provides basic functionality for
applications that don't need or want to care about how to fiddle with
the rings directly. It has helpers to allow applications to easily set
up an io_uring instance, and submit/complete IO through it without
knowing about the intricacies of the rings. It also includes man pages
(thanks to Jeff Moyer), and will continue to grow support helper
functions and features as time progresses. Find it here:
git://git.kernel.dk/liburing
Fio has full support for the raw interface, both in the form of an IO
engine (io_uring), but also with a small test application (t/io_uring)
that can exercise and benchmark the interface"
* tag 'io_uring-2019-03-06' of git://git.kernel.dk/linux-block:
io_uring: add a few test tools
io_uring: allow workqueue item to handle multiple buffered requests
io_uring: add support for IORING_OP_POLL
io_uring: add io_kiocb ref count
io_uring: add submission polling
io_uring: add file set registration
net: split out functions related to registering inflight socket files
io_uring: add support for pre-mapped user IO buffers
block: implement bio helper to add iter bvec pages to bio
io_uring: batch io_kiocb allocation
io_uring: use fget/fput_many() for file references
fs: add fget_many() and fput_many()
io_uring: support for IO polling
io_uring: add fsync support
Add io_uring IO interface
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