Linux defines MAP_SYNC on powerpc and powerpc64 as of commit
22fcea6f85f2 ("mm: move MAP_SYNC to asm-generic/mman-common.h"),
so we can stop undefining it on those architectures.
kernel commit 4693916846269d633a3664586650dbfac2c5562f (first included
in release v4.14) silently fixed a bug whereby the reserved space
(which was later used for high bits of time) in IPC_STAT structures
was left untouched rather than zeroed. this means that a caller that
wants to read the high bits needs to pre-zero the memory.
since it's not clear that these operations are permitted to modify the
destination buffer on failure, use a temp buffer and copy back to the
caller's buffer on success.
on all mips variants, Linux did (and maybe still does) have some
syscall return paths that wrongly return both the error flag in r7 and
a negated error code in r2. in particular this happened for at least
some causes of ENOSYS.
add an extra check to only negate the error code if it's positive to
begin with.
bug report and concept for patch by Andreas Dröscher.
commit 4221f154ff added the r7
constraint apparently out of a misunderstanding of the breakage it was
addressing, and did so because the asm was in a shared macro used by
all the __syscallN inline functions. now "+r" is used in the output
section for the forms 4-argument and up, so having it in input is
redundant, and the forms with 0-3 arguments don't need it as an input
at all.
the r2 constraint is kept because without it most gcc versions (seems
to be all prior to 9.x) fail to honor the output register binding for
r2. this seems to be a variant of gcc bug #87733.
both the r7 and r2 input constraints look useless, but the r2 one was
a quiet workaround for gcc bug 87733, which affects all modern
versions prior to 9.x, so it's kept and documented.
exactly revert commit 604f8d3d8b which
was wrong; it caused a major regression on Linux versions prior to
2.6.36. old kernels did not properly preserve r2 across syscall
restart, and instead restarted with the instruction right before
syscall, imposing a contract that the previous instruction must load
r2 from an immediate or a register (or memory) not clobbered by the
syscall.
effectivly revert commit ddc7c4f936
which was wrong; it caused a major regression on Linux versions prior
to 2.6.36. old kernels did not properly preserve r2 across syscall
restart, and instead restarted with the instruction right before
syscall, imposing a contract that the previous instruction must load
r2 from an immediate or a register (or memory) not clobbered by the
syscall.
since other changes were made since, including removal of the struct
stat conversion that was replaced by separate struct kstat, this is
not a direct revert, only a functional one.
the "0"(r2) input constraint added back seems useless/erroneous, but
without it most gcc versions (seems to be all prior to 9.x) fail to
honor the output register binding for r2. this seems to be a variant
of gcc bug #87733. further changes should be made later if a better
workaround is found, but this one has been working since 2012. it
seems this issue was encountered but misidentified then, when it
inspired commit 4221f154ff.
this is added for POSIX-future as the outcome of Austin Group issue
599. since it's in the reserved namespace for pthread.h, there are no
namespace considerations for adding it early.
commit 59324c8b09 added __socketcall
analogous to __syscall, returning the negated error rather than
setting errno. use it to simplify the fallback path of socket(),
avoiding extern calls and access to errno.
Author: Rich Felker <dalias@aerifal.cx>
Date: Tue Jul 30 17:51:16 2019 -0400
make __socketcall analogous to __syscall, error-returning
this reverts commit 4ee039f354, which
added the helper as a hack to make vdprintf usable before relocation,
contingent on strong assumptions about the arch and tooling, back when
the dynamic linker did not have a real staged model for
self-relocation. since commit f3ddd17380
this has been unnecessary and the function was just wasting size and
execution time.
The final rounding operation should be done with the correct sign
otherwise huge results may incorrectly get rounded to or away from
infinity in upward or downward rounding modes.
This affected sinh and sinhf which set the sign on the result after
a potentially overflowing mul. There may be other non-nearest rounding
issues, but this was a known long standing issue with large ulp error
(depending on how ulp is defined near infinity).
The fix should have no effect on sinh and sinhf performance but may
have a tiny effect on cosh and coshf.
Handle when after reduction |y| > pi/4+tiny. This happens in directed
rounding modes because the fast round to int code does not give the
nearest integer. In such cases the reduction may not be symmetric
between x and -x so e.g. cos(x)==cos(-x) may not hold (but polynomial
evaluation is not symmetric either with directed rounding so fixing
that would require more changes with bigger performance impact).
The fix only adds two predictable branches in nearest rounding mode,
simple ubenchmark does not show relevant performance regression in
nearest rounding mode.
The code could be improved: e.g reducing the medium size threshold
such that two step reduction is enough instead of three, and the
single precision case can avoid the issue by doing the round to int
differently, but this fix was kept minimal.
because struct stat is no longer assumed to correspond to the
structure used by the stat-family syscalls, it's not valid to make any
of these syscalls directly using a buffer of type struct stat.
commit 9493892021 moved all logic around
this change for stat-family functions into fstatat.c, making the
others wrappers for it. but a few other direct uses of the syscall
were overlooked. the ones in tmpnam/tempnam are harmless since the
syscalls are just used to test for file existence. however, the uses
in fchmodat and __map_file depend on getting accurate file properties,
and these functions may actually have been broken one or more mips
variants due to removal of conversion hacks from syscall_arch.h.
as a low-risk fix, simply use struct kstat in place of struct stat in
the affected places.
these did not truncate excess precision in the return value. fixing
them looks like considerable work, and the current C code seems to
outperform them significantly anyway.
long double functions are left in place because they are not subject
to excess precision issues and probably better than the C code.
for functions implemented in C, this is a requirement of C11 (F.6);
strictly speaking that text does not apply to standard library
functions, but it seems to be intended to apply to them, and C2x is
expected to make it a requirement.
failure to drop excess precision is particularly bad for inverse trig
functions, where a value with excess precision can be outside the
range of the function (entire range, or range for a particular
subdomain), breaking reasonable invariants a caller may expect.
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.
under _GNU_SOURCE for namespace cleanliness, analogous to other archs.
the original placement in sys/reg.h seems not to have been motivated;
such a header isn't even present on other implementations.
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.
_POSIX_VDISABLE is only visible if unistd.h has already been included,
so conditional use of it here makes no sense. the value is always 0
anyway; it does not vary.
This patch adds an explicit cast to the int arguments passed to the
inline asm used in the RISC-V's implementation of `a_cas`, to ensure
that they are properly sign extended to 64 bits. They aren't
automatically sign extended by Clang, and GCC technically also doesn't
guarantee that they will be sign extended.
For Thumb2 compatibility, replace two instances of a single
instruction "orr with a variable shift" with the two instruction
equivalent. Neither of the replacements are in a performance critical
loop.
the bug fixed in commit b82cd6c78d was
mostly masked on arm because __hwcap was zero at the point of the call
from the dynamic linker to __set_thread_area, causing the access to
libc.auxv to be skipped and kuser_helper versions of TLS access and
atomics to be used instead of the armv6 or v7 versions. however, on
kernels with kuser_helper removed for hardening it would crash.
since __set_thread_area potentially uses __hwcap, it must be
initialized before the function is called. move the AT_HWCAP lookup
from stage 3 to stage 2b.
This enables alternative compilers, which may not define __GNUC__,
to implement alloca, which is still fairly widely used.
This is similar to how stdarg.h already works in musl; compilers must
implement __builtin_va_arg, there is no fallback definition.
this change was discussed on the mailing list thread for the linux
uapi v5.3 patches, and submitted as a v2 patch, but overlooked when I
applied the patches much later.
revert commit f291c09ec9 and apply the
v2 as submitted; the net change is just padding.
notes by Szabolcs Nagy follow:
compared to the linux uapi (and glibc) a padding is used instead of
aligned attribute for keeping the layout the same across targets, this
means the alignment of the struct may be different on some targets
(e.g. m68k where uint64_t is 2 byte aligned) but that should not affect
syscalls and this way the abi does not depend on nonstandard extensions.
at least gcc 9 broke execution of DT_INIT/DT_FINI for fdpic archs
(presently only sh) by recognizing that the stores to the
compound-literal function descriptor constructed to call them were
dead stores. there's no way to make a "may_alias function", so instead
launder the descriptor through an asm-statement barrier. in practice
just making the compound literal volatile seemed to have worked too,
but this should be less of a hack and more accurately convey the
semantics of what transformations are not valid.
commit 1c84c99913 moved the call to
__init_tp above the initialization of libc.auxv, inadvertently
breaking archs where __set_thread_area examines auxv for the sake of
determining the TLS/atomic model needed at runtime. this broke armv6
and sh2.
the syscall numbers were reserved in v5.3 but not wired up on mips, see
linux commit 0671c5b84e9e0a6d42d22da9b5d093787ac1c5f3
MIPS: Wire up clone3 syscall
mips application specific isa extensions were previously not exported
in hwcaps so userspace could not apply optimized code at runtime.
linux commit 38dffe1e4dde1d3174fdce09d67370412843ebb5
MIPS: elf_hwcap: Export userspace ASEs
allows waiting on a pidfd, in the future it might allow retrieving the
exit status by a non-parent process, see
linux commit 3695eae5fee0605f316fbaad0b9e3de791d7dfaf
pidfd: add P_PIDFD to waitid()
tcpi_rcv_ooopack for tracking connection quality:
linux commit f9af2dbbfe01def62765a58af7fbc488351893c3
tcp: Add TCP_INFO counter for packets received out-of-order
tcpi_snd_wnd peer window size for diagnosing tcp performance problems:
linux commit 8f7baad7f03543451af27f5380fc816b008aa1f2
tcp: Add snd_wnd to TCP_INFO
per thread prctl commands to relax the syscall abi such that top bits
of user pointers are ignored in the kernel. this allows the use of
those bits by hwasan or by mte to color pointers and memory on aarch64:
linux commit 63f0c60379650d82250f22e4cf4137ef3dc4f43d
arm64: Introduce prctl() options to control the tagged user addresses ABI
These were mainly introduced so android can optimize the memory usage
of unused apps.
MADV_COLD hints that the memory range is currently not needed (unlike
with MADV_FREE the content is not garbage, it needs to be swapped):
linux commit 9c276cc65a58faf98be8e56962745ec99ab87636
mm: introduce MADV_COLD
MADV_PAGEOUT hints that the memory range is not needed for a long time
so it can be reclaimed immediately independently of memory pressure
(unlike with MADV_DONTNEED the content is not garbage):
linux commit 1a4e58cce84ee88129d5d49c064bd2852b481357
mm: introduce MADV_PAGEOUT
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()
