this probably saves a few bytes, avoids duplicating the clunky
lseek/_llseek syscall convention in two places, and sets the stage for
fixing broken seeks on x32 and mipsn32.

these additions were made by scanning git log since the last major
update in commit 1366b3c5.

as before my aim was adding everyone with either substantial code
contributions or a pattern of ongoing simple patch submission; any
omissions are unintentional.

a fully thumb1 build is not supported because some asm files are
incompatible with thumb1, but apparently it works to compile the C
code as thumb1

commit 06fbefd1 caused this regression
but introducing use of the clz instruction, which is not supported in
arm mode prior to v5, and not supported in thumb prior to thumb2
(v6t2). commit 1b9406b0 fixed the
issue only for arm mode pre-v5 but left thumb1 broken.

In the public header, __errno_location is declared with the "const"
attribute, conditional on __GNUC__. Ensure that its internal alias has
the same attributes.

Maintainer's note: This change also fixes a regression in quality of
code generation -- multiple references to errno in a single function
started generating multiple calls again -- introduced by commit
e13063aa.

Commit 3517d74a changed the token in
sys/ioctl.h from 0x01 to 1, so bits/termios.h no longer matches. Revert
the bits/termios.h change to keep the headers in sync.

This reverts commit 9eda4dc6.

The old/new parameters to pthread_sigmask, sigprocmask, and setitimer
are marked restrict, so passing the same address to both is
prohibited. Modify callers of these functions to use a separate object
for each argument.

as reported by Tavian Barnes, a dup2 file action for the internal pipe
fd used by posix_spawn could cause it to remain open after execve and
allow the child to write an artificial error into it, confusing the
parent. POSIX allows internal use of file descriptors by the
implementation, with undefined behavior for poking at them, so this is
not a conformance problem, but it seems preferable to diagnose and
prevent the error when we can do so easily.

catch attempts to apply a dup2 action to the internal pipe fd and
emulate EBADF for it instead.

commit c8b49b2f introduced code that
checked bestsym to determine whether a matching symbol was found, but
bestsym is uninitialized if not. instead use best, consistent with use
in the rest of the function.

simplified from bug report and patch by Cheng Liu.

this was apparently copied from x86_64; it's not part of the kernel
API for riscv64. this change eliminates the need for a
riscv64-specific bits header and lets it use the generic one.

maintainer's note: these are not meaningful/correct/needed and the
clang integrated assembler errors out upon seeing them.

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.

Linux v5.1 introduced ipc syscalls on targets where previously only
SYS_ipc was available, change the logic such that the ipc code keeps
using SYS_ipc which works backward compatibly on older kernels.

This changes behaviour on microblaze which had both mechanisms, now
SYS_ipc will be used instead of separate syscalls.

the numbers added in

  commit d149e69c
  add io_pgetevents and rseq syscall numbers from linux v4.18

were incorrect.

to request or change pointer auth keys for criu via ptrace, new in

  linux commit d0a060be573bfbf8753a15dca35497db5e968bb0
  arm64: add ptrace regsets for ptrauth key management

RFC 4286: "The IPv4 multicast address for All-Snoopers is 224.0.0.106."
from

  linux commit 4effd28c1245303dce7fd290c501ac2c11052114
  bridge: join all-snoopers multicast address

SO_BINDTOIFINDEX behaves similar to SO_BINDTODEVICE, but takes a
network interface index as argument, rather than the network
interface name. see

  linux commit f5dd3d0c9638a9d9a02b5964c4ad636f06cf7e2c
  net: introduce SO_BINDTOIFINDEX sockopt

the s390x definitions matched the generic ones in sys/socket.h.

restricts router alert packets received by the socket to the
socket's namespace only. see

  linux commit 9036b2fe092a107856edd1a3bad48b83f2b45000
  net: ipv6: add socket option IPV6_ROUTER_ALERT_ISOLATE

allows specifying that the speculative store bypass disable bit should
be cleared on exec. see

  linux commit 71368af9027f18fe5d1c6f372cfdff7e4bde8b48
  x86/speculation: Add PR_SPEC_DISABLE_NOEXEC

needed for android so it can migrate from its ashmem to memfd.
allows making the memfd readonly for future users while keeping
a writable mmap of it. see

  linux commit ab3948f58ff841e51feb845720624665ef5b7ef3
  mm/memfd: add an F_SEAL_FUTURE_WRITE seal to memfd

includes changes from linux v5.1

  linux commit 235328d1fa4251c6dcb32351219bb553a58838d2
  fanotify: add support for create/attrib/move/delete events

  linux commit 5e469c830fdb5a1ebaa69b375b87f583326fd296
  fanotify: copy event fid info to user

  linux commit e9e0c8903009477b630e37a8b6364b26a00720da
  fanotify: encode file identifier for FAN_REPORT_FID

as well as earlier changes that were missed.

sys/statfs.h is included for fsid_t.

synccall may be called by AS-safe functions such as setuid/setgid after
fork. although fork() resets libc.threads_minus_one, causing synccall to
take the single-threaded path, synccall still takes the thread list
lock. This lock may be held by another thread if for example fork()
races with pthread_create(). After fork(), the value of the lock is
meaningless, so clear it.

maintainer's note: commit 8f11e612 and
e4235d70 introduced this regression.
the state protected by this lock is the linked list, which is entirely
replaced in the child path of fork (next=prev=self), so resetting it
is semantically sound.

the linux syscall treats this argument as having type int, so passing
extremely long buffer sizes would be misinterpreted by the kernel.
since "short reads" are always acceptable, just cap it down.

patch based on report and suggested change by Florian Weimer.

after commit a48ccc15 removed the use
of _Noreturn on the stage3_func type (which only worked due to it
being defined to the "GNU C" attribute in C99 mode), GCC could no
longer assume that the ends of __dls2 and __dls2b are unreachable, and
produced a warning that a function marked _Noreturn returns.

also, since commit 4390383b, the
_Noreturn declaration for __libc_start_main in crt1/rcrt1 has been not
only inconsistent with the definition, but wrong. formally,
__libc_start_main does return, via a (hopefully) tail call to a helper
function after the barrier. incorrect usage of _Noreturn in the
declaration was probably formal UB.

the _Noreturn specifiers were not useful in any of these places, so
remove them all. now, the only remaining usage of _Noreturn is in
public interfaces where _Noreturn is part of their contract.

previously, POSIX erroneously required this to fail with EINVAL
despite the traditional glibc implementation, on which the POSIX
interface was based, allowing it. the resolution of Austin Group issue
818 removes the requirement to fail.

_Noreturn is a C11 construct, and may only be used at the site of a
function definition.

this reverts commit f552c792, which
exposed the sysmacros.h macros (device major/minor calculations) for
BSD and GNU profiles to mimic an unintentional glibc behavior some
code depended on. glibc has deprecated and since removed them as the
resolution to bug #19239, so it makes no sense for us to keep this
behavior. affected code should all have been fixed by now, and if it's
not yet fixed it needs to be for use with modern glibc anyway.

Author: Alex Suykov <alex.suykov@gmail.com>
Author: Aric Belsito <lluixhi@gmail.com>
Author: Drew DeVault <sir@cmpwn.com>
Author: Michael Clark <mjc@sifive.com>
Author: Michael Forney <mforney@mforney.org>
Author: Stefan O'Rear <sorear2@gmail.com>

This port has involved the work of many people over several years. I
have tried to ensure that everyone with substantial contributions has
been credited above; if any omissions are found they will be noted
later in an update to the authors/contributors list in the COPYRIGHT
file.

The version committed here comes from the riscv/riscv-musl repo's
commit 3fe7e2c75df78eef42dcdc352a55757729f451e2, with minor changes by
me for issues found during final review:

- a_ll/a_sc atomics are removed (according to the ISA spec, lr/sc
  are not safe to use in separate inline asm fragments)

- a_cas[_p] is fixed to be a memory barrier

- the call from the _start assembly into the C part of crt1/ldso is
  changed to allow for the possibility that the linker does not place
  them nearby each other.

- DTP_OFFSET is defined correctly so that local-dynamic TLS works

- reloc.h LDSO_ARCH logic is simplified and made explicit.

- unused, non-functional crti/n asm files are removed.

- an empty .sdata section is added to crt1 so that the
  __global_pointer reference is resolvable.

- indentation style errors in some asm files are fixed.

with the glibc generation counter model for reusing dynamic tls slots
after dlclose, it's really not possible to get away with fewer than 4
working registers. for us however it's always been possible, but
tricky, and only became apparent after the switch to installing new
dynamic tls at dlopen time. by merging the negated thread pointer into
the addend early, the register holding the thread pointer can
immediately be reused, bringing the working register count down to
three. this allows saving/restoring via a single stp/ldp pair, since
the return register x0 does not need to be saved.

net reduction of 3 instructions, 2 of which were push/pop.

between v2 and v3 of the powerpc64 port patch, the change was made
from a 32x4 array of 32-bit unsigned ints for vrregs[] to a 32-element
array of __int128. this mismatches the API applications working with
mcontext_t expect from glibc, and seems to have been motivated by a
misinterpretation of a comment on how aarch64 did things as a
suggestion to do the same on powerpc64.

the mistaken layout seems to have been adapted from 32-bit powerpc,
where vscr and vrsave are packed into the same 128-bit slot in a way
that looks like it relies on non-overlapping-ness of the value bits in
big endian.

the powerpc64 port accounted for the fact that the 64-bit ABI puts
each in its own 128-bit slot, but ordered them incorrectly (matching
the bit order used on the 32-bit ABI), and failed to account for vscr
being padded according to endianness so that it can be accessed via
vector moves.

in addition to ABI layout, our definition used different logical
member layout/naming from glibc, where vscr is a structure to
facilitate access as a 32-bit word or a 128-bit vector. the
inconsistency here was unintentional, so fix it.

currently the bfd linker does not seem to create tls segments where
p_vaddr%p_align != 0, but this is valid in ELF and then the runtime
computed tls offset must satisfy

  offset%p_align == (base+p_vaddr)%p_align

and in case of local exec tls (main executable) the smallest such
offset must be used (otherwise it is incompatible with the offset
computed by the static linker). the !TLS_ABOVE_TP case is handled
correctly (the offset is negative then in the formula).

the ldso code for TLS_ABOVE_TP is changed so the static tls offset
of each module satisfies the formula.

tls_offset should always point to the end of the allocated static tls
area, but this was not handled correctly on "tls variant 1" targets
in the dynamic linker:

after application tls was allocated, tls_offset was aligned up,
potentially wasting tls space. (alignment may be needed at the
begining of the tls area, not at the end, but that will be fixed
separately as it is unlikely to affect real binaries.)

when static tls was allocated for a shared library, tls_offset was
only updated with the size of the tls segment which does not include
alignment gaps, which can easily happen if the tls size update for
one library leaves tls_offset misaligned for the next one. this can
cause oob access in __copy_tls or arbitrary breakage at tls access.
(the issue was observed on aarch64 with rust binaries)

commit 648c3b4e omitted this change,
which is needed to be able to use uid/gid values greater than INT_MAX
with these interfaces. it fixes alpine linux bug #10460.