mainly added to linux to allow a central process management service in
android to give MADV_COLD|PAGEOUT hints for other processes, see
linux commit ecb8ac8b1f146915aa6b96449b66dd48984caacc
mm/madvise: introduce process_madvise() syscall: an external memory
hinting API
see
linux commit 9b4feb630e8e9801603f3cab3a36369e3c1cf88d
arch: wire-up close_range()
linux commit 278a5fbaed89dacd04e9d052f4594ffd0e0585de
open: add close_range()
the linux faccessat syscall lacks a flag argument that is necessary
to implement the posix api, see
linux commit c8ffd8bcdd28296a198f237cc595148a8d4adfbe
vfs: add faccessat2 syscall
also added clone3 on sh and m68k, on sh it's still missing (not
yet wired up), but reserved so safe to add.
see
linux commit fddb5d430ad9fa91b49b1d34d0202ffe2fa0e179
open: introduce openat2(2) syscall
linux commit 9a2cef09c801de54feecd912303ace5c27237f12
arch: wire up pidfd_getfd syscall
linux commit 8649c322f75c96e7ced2fec201e123b2b073bf09
pid: Implement pidfd_getfd syscall
linux commit e8bb2a2a1d51511e6b3f7e08125d52ec73c11139
m68k: Wire up clone3() syscall
this extends commit 5a105f19b5, removing
timer[fd]_settime and timer[fd]_gettime. the timerfd ones are likely
to have been used in software that started using them before it could
rely on libc exposing functions.
some nontrivial number of applications have historically performed
direct syscalls for these operations rather than using the public
functions. such usage is invalid now that time_t is 64-bit and these
syscalls no longer match the types they are used with, and it was
already harmful before (by suppressing use of vdso).
since syscall() has no type safety, incorrect usage of these syscalls
can't be caught at compile-time. so, without manually inspecting or
running additional tools to check sources, the risk of such errors
slipping through is high.
this patch renames the syscalls on 32-bit archs to clock_gettime32 and
gettimeofday_time32, so that applications using the original names
will fail to build without being fixed.
note that there are a number of other syscalls that may also be unsafe
to use directly after the time64 switchover, but (1) these are the
main two that seem to be in widespread use, and (2) most of the others
continue to have valid usage with a null timeval/timespec argument, as
the argument is an optional timeout or similar.
the syscall number is reserved on all targets, but it is not wired up
on all targets, see
linux commit 8f6ccf6159aed1f04c6d179f61f6fb2691261e84
Merge tag 'clone3-v5.3' of ... brauner/linux
linux commit 8f3220a806545442f6f26195bc491520f5276e7c
arch: wire-up clone3() syscall
linux commit 7f192e3cd316ba58c88dfa26796cf77789dd9872
fork: add clone3
see
linux commit 7615d9e1780e26e0178c93c55b73309a5dc093d7
arch: wire-up pidfd_open()
linux commit 32fcb426ec001cb6d5a4a195091a8486ea77e2df
pid: add pidfd_open()
now that all 32-bit archs have 64-bit time_t (and suseconds_t), the
arch-provided _Int64 macro (long or long long, as appropriate) can be
used to define them, and arch-specific definitions are no longer
needed.
now that all 32-bit archs have 64-bit time types, the values for the
time-related ioctls can be shared. the mechanism for this is an
arch/generic version of the bits header. archs which don't use the
generic header still need to duplicate the definitions.
x32, which does not use the new time64 values of the macros, already
has its own overrides, so this commit does not affect it.
now that all 32-bit archs have 64-bit time types, the values for the
time-related socket option macros can be treated as universal for
32-bit archs. the sys/socket.h mechanism for this predates
arch/generic and is instead in the top-level header.
x32, which does not use the new time64 values of the macros, already
has its own overrides, so this commit does not affect it.
this commit preserves ABI fully for existing interface boundaries
between libc and libc consumers (applications or libraries), by
retaining existing symbol names for the legacy 32-bit interfaces and
redirecting sources compiled against the new headers to alternate
symbol names. this does not necessarily, however, preserve the
pairwise ABI of libc consumers with one another; where they use
time_t-derived types in their interfaces with one another, it may be
necessary to synchronize updates with each other.
the intent is that ABI resulting from this commit already be stable
and permanent, but it will not be officially so until a release is
made. changes to some header-defined types that do not play any role
in the ABI between libc and its consumers may still be subject to
change.
mechanically, the changes made by this commit for each 32-bit arch are
as follows:
- _REDIR_TIME64 is defined to activate the symbol redirections in
public headers
- COMPAT_SRC_DIRS is defined in arch.mak to activate build of ABI
compat shims to serve as definitions for the original symbol names
- time_t and suseconds_t definitions are changed to long long (64-bit)
- IPC_STAT definition is changed to add the IPC_TIME64 bit (0x100),
triggering conversion of semid_ds, shmid_ds, and msqid_ds split
low/high time bits into new time_t members
- structs semid_ds, shmid_ds, msqid_ds, and stat are modified to add
new 64-bit time_t/timespec members at the end, maintaining existing
layout of other members.
- socket options (SO_*) and ioctl (sockios) command macros are
redefined to use the kernel's "_NEW" values.
in addition, on archs where vdso clock_gettime is used, the
VDSO_CGT_SYM macro definition in syscall_arch.h is changed to use a
new time64 vdso function if available, and a new VDSO_CGT32_SYM macro
is added for use as fallback on kernels lacking time64.
policy has long been that these definitions are purely a function of
whether long/pointer is 32- or 64-bit, and that they are not allowed
to vary per-arch. move the definition to the shared alltypes.h.in
fragment, using integer constant expressions in terms of sizeof to
vary the array dimensions appropriately. I'm not sure whether this is
more or less ugly than using preprocessor conditionals and two sets of
definitions here, but either way is a lot less ugly than repeating the
same thing for every arch.
LLONG_MAX is uniform for all archs we support and plenty of header and
code level logic assumes it is, so it does not make sense for limits.h
bits mechanism to pretend it's variable.
LONG_BIT can be defined in terms of LONG_MAX; there's no reason to put
it in bits.
by moving LONG_MAX definition to __LONG_MAX in alltypes.h and moving
LLONG_MAX out of bits, there are now no plain-C limits that are
defined in the bits header, so the bits header only needs to be
included in the POSIX or extended profiles. this allows the feature
test macro logic to be removed from the bits header, facilitating a
long-term goal of getting such logic out of bits.
having __LONG_MAX in alltypes.h will allow further generalization of
headers.
archs without a constant PAGESIZE no longer need bits/limits.h at all.
this change is motivated by the intersection of several factors.
presently, despite being a nonstandard header, endian.h is exposing
the unprefixed byte order macros and functions only if _BSD_SOURCE or
_GNU_SOURCE is defined. this is to accommodate use of endian.h from
other headers, including bits headers, which need to define structure
layout in terms of endianness. with time64 switch-over, even more
headers will need to do this.
at the same time, the resolution of Austin Group issue 162 makes
endian.h a standard header for POSIX-future, requiring that it expose
the unprefixed macros and the functions even in standards-conforming
profiles. changes to meet this new requirement would break existing
internal usage of endian.h by causing it to violate namespace where
it's used.
instead, have the arch's alltypes.h define __BYTE_ORDER, either as a
fixed constant or depending on the right arch-specific predefined
macros for determining endianness. explicit literals 1234 and 4321 are
used instead of __LITTLE_ENDIAN and __BIG_ENDIAN so that there's no
danger of getting the wrong result if a macro is undefined and
implicitly evaluates to 0 at the preprocessor level.
the powerpc (32-bit) bits/endian.h being removed had logic for varying
endianness, but our powerpc arch has never supported that and has
always been big-endian-only. this logic is not carried over to the new
__BYTE_ORDER definition in alltypes.h.
now that commit f7f1079796 removed the
legacy i386 conditional definition, va_list is in no way
arch-specific, and has no reason to be in the future. move it to the
shared part of alltypes.h.in
new mount api syscalls were added, same numers on all targets, see
linux commit a07b20004793d8926f78d63eb5980559f7813404
vfs: syscall: Add open_tree(2) to reference or clone a mount
linux commit 2db154b3ea8e14b04fee23e3fdfd5e9d17fbc6ae
vfs: syscall: Add move_mount(2) to move mounts around
linux commit 24dcb3d90a1f67fe08c68a004af37df059d74005
vfs: syscall: Add fsopen() to prepare for superblock creation
linux commit ecdab150fddb42fe6a739335257949220033b782
vfs: syscall: Add fsconfig() for configuring and managing a context
linux commit 93766fbd2696c2c4453dd8e1070977e9cd4e6b6d
vfs: syscall: Add fsmount() to create a mount for a superblock
linux commit cf3cba4a429be43e5527a3f78859b1bfd9ebc5fb
vfs: syscall: Add fspick() to select a superblock for reconfiguration
linux commit 9c8ad7a2ff0bfe58f019ec0abc1fb965114dde7d
uapi, x86: Fix the syscall numbering of the mount API syscalls [ver #2]
linux commit d8076bdb56af5e5918376cd1573a6b0007fc1a89
uapi: Wire up the mount API syscalls on non-x86 arches [ver #2]
otherwise, 32-bit archs that could otherwise share the generic
bits/ipc.h would need to duplicate the struct ipc_perm definition,
obscuring the fact that it's the same. sysvipc is not widely used and
these headers are not commonly included, so there is no performance
gain to be had by limiting the number of indirectly included files
here.
files with the existing time32 definition of IPC_STAT are added to all
current 32-bit archs now, so that when it's changed the change will
show up as a change rather than addition of a new file where it's less
obvious that the value is changing vs the generic one that was used
before.
there are more archs sharing the generic 64-bit version of the struct,
which is uniform and much more reasonable, than sharing the current
"generic" one, and depending on how time64 sysvipc is done for 32-bit
archs, even more may be sharing the "64-bit version" in the future.
so, duplicate the current generic to all archs using it (arm, i386,
m68k, microblaze, or1k) so that the generic can be changed freely.
this is recorded as its own commit mainly as a hint to git tooling, to
assist in copy/move tracking.
syscall numbers are now synced up across targets (starting from 403 the
numbers are the same on all targets other than an arch specific offset)
IPC syscalls sem*, shm*, msg* got added where they were missing (except
for semop: only semtimedop got added), the new semctl, shmctl, msgctl
imply IPC_64, see
linux commit 0d6040d4681735dfc47565de288525de405a5c99
arch: add split IPC system calls where needed
new 64bit time_t syscall variants got added on 32bit targets, see
linux commit 48166e6ea47d23984f0b481ca199250e1ce0730a
y2038: add 64-bit time_t syscalls to all 32-bit architectures
new async io syscalls got added, see
linux commit 2b188cc1bb857a9d4701ae59aa7768b5124e262e
Add io_uring IO interface
linux commit edafccee56ff31678a091ddb7219aba9b28bc3cb
io_uring: add support for pre-mapped user IO buffers
a new syscall got added that uses the fd of /proc/<pid> as a stable
handle for processes: allows sending signals without pid reuse issues,
intended to eventually replace rt_sigqueueinfo, kill, tgkill and
rt_tgsigqueueinfo, see
linux commit 3eb39f47934f9d5a3027fe00d906a45fe3a15fad
signal: add pidfd_send_signal() syscall
on some targets (arm, m68k, s390x, sh) some previously missing syscall
numbers got added as well.
most of the found naming differences don't matter to musl, because
internally it unifies the syscall names that vary across targets,
but for external code the names should match the kernel uapi.
aarch64:
__NR_fstatat is called __NR_newfstatat in linux.
__NR_or1k_atomic got mistakenly copied from or1k.
arm:
__NR_arm_sync_file_range is an alias for __NR_sync_file_range2
__NR_fadvise64_64 is called __NR_arm_fadvise64_64 in linux,
the old non-arm name is kept too, it should not cause issues.
(powerpc has similar nonstandard fadvise and it uses the
normal name.)
i386:
__NR_madvise1 was removed from linux in commit
303395ac3bf3e2cb488435537d416bc840438fcb 2011-11-11
microblaze:
__NR_fadvise, __NR_fstatat, __NR_pread, __NR_pwrite
had different name in linux.
mips:
__NR_fadvise, __NR_fstatat, __NR_pread, __NR_pwrite, __NR_select
had different name in linux.
mipsn32:
__NR_fstatat is called __NR_newfstatat in linux.
or1k:
__NR__llseek is called __NR_llseek in linux.
the old name is kept too because that's the name musl uses
internally.
powerpc:
__NR_{get,set}res{gid,uid}32 was never present in powerpc linux.
__NR_timerfd was briefly defined in linux but then got renamed.
Glibc renamed the linux uapi HWCAP_* macros to HWCAP_ARM_*
so have both variants in case some code depends on it.
(The HWCAP2_ macros are not defined in glibc currently so those
only have the linux uapi variant.)
the ABI for arm was silently changed at some point to allow page sizes
other than 4k; traditional binaries built with only 4k-aligned offsets
between load segments cannot run on such systems, but newer binutils
versions use 64k offset alignment.
while larger page size is undesirable for various reasons, users have
encountered hardware and/or kernels that lock the page size to a
larger value, so follow the new ABI and allow it to vary.
aarch64, arm, mips, mips64, mipsn32, powerpc, powerpc64 and sh have
cpu feature bits defined in linux for AT_HWCAP auxv entry, so expose
those in sys/auxv.h
it seems the mips hwcaps were never exposed to userspace neither
by linux nor by glibc, but that's most likely an oversight.
placing the opening brace on the same line as the struct keyword/tag
is the style I prefer and seems to be the prevailing practice in more
recent additions.
these changes were generated by the command:
find include/ arch/*/bits -name '*.h' \
-exec sed -i '/^struct [^;{]*$/{N;s/\n/ /;}' {} +
and subsequently checked by hand to ensure that the regex did not pick
up any false positives.
the syscalls take an additional flag argument, they were added in commit
f17d8b35452cab31a70d224964cd583fb2845449 and a RWF_HIPRI priority hint
flag was added to linux/fs.h in 97be7ebe53915af504fb491fb99f064c7cf3cb09.
the syscall is not allocated for microblaze and sh yet.
it was introduced for offloading copying between regular files
in linux commit 29732938a6289a15e907da234d6692a2ead71855
(microblaze and sh does not yet have the syscall number.)
currently five targets use the same mman.h constants and the rest
share most constants too, so move them to sys/mman.h before the
bits/mman.h include where the differences can be corrected by
redefinition of the macros.
this fixes two minor bugs: POSIX_MADV_DONTNEED was wrong on most
targets (it should be the same as MADV_DONTNEED), and sh defined
the x86-only MAP_32BIT mmap flag.
all bits headers that were identical for a number of 'clean' archs are
moved to the new arch/generic tree. in addition, a few headers that
differed only cosmetically from the new generic version are removed.
additional deduplication may be possible in mman.h and in several
headers (limits.h, posix.h, stdint.h) that mostly depend on whether
the arch is 32- or 64-bit, but they are left alone for now because
greater gains are likely possible with more invasive changes to header
logic, which is beyond the scope of this commit.
they lock faulted pages into memory (useful when a small part of a
large mapped file needs efficient access), new in linux v4.4, commit
b0f205c2a3082dd9081f9a94e50658c5fa906ff1
MLOCK_* is not in the POSIX reserved namespace for sys/mman.h
this is mlock with a flags argument, new in linux commit
a8ca5d0ecbdde5cc3d7accacbd69968b0c98764e
as usual microblaze and sh don't have allocated syscall number yet.
new in linux v4.3 added for aarch64, arm, i386, mips, or1k, powerpc,
x32 and x86_64.
membarrier is a system wide memory barrier, moves most of the
synchronization cost to one side, new in kernel commit
5b25b13ab08f616efd566347d809b4ece54570d1
userfaultfd is useful for qemu and is new in kernel commit
8d2afd96c20316d112e04d935d9e09150e988397
switch_endian is powerpc only for switching endianness, new in commit
529d235a0e190ded1d21ccc80a73e625ebcad09b
while it's the same for all presently supported archs, it differs at
least on sparc, and conceptually it's no less arch-specific than the
other O_* macros. O_SEARCH and O_EXEC are still defined in terms of
O_PATH in the main fcntl.h.
the previous values (2k min and 8k default) were too small for some
archs. aarch64 reserves 4k in the signal context for future extensions
and requires about 4.5k total, and powerpc reportedly uses over 2k.
the new minimums are chosen to fit the saved context and also allow a
minimal signal handler to run.
since the default (SIGSTKSZ) has always been 6k larger than the
minimum, it is also increased to maintain the 6k usable by the signal
handler. this happens to be able to store one pathname buffer and
should be sufficient for calling any function in libc that doesn't
involve conversion between floating point and decimal representations.
x86 (both 32-bit and 64-bit variants) may also need a larger minimum
(around 2.5k) in the future to support avx-512, but the values on
these archs are left alone for now pending further analysis.
the value for PTHREAD_STACK_MIN is not increased to match MINSIGSTKSZ
at this time. this is so as not to preclude applications from using
extremely small thread stacks when they know they will not be handling
signals. unfortunately cancellation and multi-threaded set*id() use
signals as an implementation detail and therefore require a stack
large enough for a signal context, so applications which use extremely
small thread stacks may still need to avoid using these features.
these macros have the same distinct definition on blackfin, frv, m68k,
mips, sparc and xtensa kernels. POLLMSG and POLLRDHUP additionally
differ on sparc.
the memory model we use internally for atomics permits plain loads of
values which may be subject to concurrent modification without
requiring that a special load function be used. since a compiler is
free to make transformations that alter the number of loads or the way
in which loads are performed, the compiler is theoretically free to
break this usage. the most obvious concern is with atomic cas
constructs: something of the form tmp=*p;a_cas(p,tmp,f(tmp)); could be
transformed to a_cas(p,*p,f(*p)); where the latter is intended to show
multiple loads of *p whose resulting values might fail to be equal;
this would break the atomicity of the whole operation. but even more
fundamental breakage is possible.
with the changes being made now, objects that may be modified by
atomics are modeled as volatile, and the atomic operations performed
on them by other threads are modeled as asynchronous stores by
hardware which happens to be acting on the request of another thread.
such modeling of course does not itself address memory synchronization
between cores/cpus, but that aspect was already handled. this all
seems less than ideal, but it's the best we can do without mandating a
C11 compiler and using the C11 model for atomics.
in the case of pthread_once_t, the ABI type of the underlying object
is not volatile-qualified. so we are assuming that accessing the
object through a volatile-qualified lvalue via casts yields volatile
access semantics. the language of the C standard is somewhat unclear
on this matter, but this is an assumption the linux kernel also makes,
and seems to be the correct interpretation of the standard.
Szabolcs Nagy
Rich Felker
Bobby Bingham
Trutz Behn