this extends commit 5a105f19, 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.

this extends commit 5a105f19, removing
clock_settime, clock_getres, clock_nanosleep, and settimeofday.

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.

this is not necessary for linux but is a simple, inexpensive change to
make that facilitates ports to systems where NAME_MAX needs to be
longer.

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.

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

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()

commit 4d3a162d overlooked that the
mips64 reloc.h dependent on endian.h not only for setting the ABI ldso
name to match the byte order, but also for use of the byte swapping
macros. they are needed to override R_TYPE, R_SYM, and R_INFO, to
compensate for a mips "quirk" of always using big endian order for
symbol references in relocations.

part of that commit canot be reverted because the original code was
wrong: it's invalid to define _GNU_SOURCE or any feature test macro
in reloc.h, or anywhere except at the top of a source file. however,
thanks to commit 316730cd, the feature
test macro is no longer needed to access the endian-swapping macros,
so simply bringing back the #include directive suffices.

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.

these definitions are copied from generic bits/ioctl.h, so that x32
keeps the "_OLD" versions (which are already time64 on x32) when
32-bit archs switch to 64-bit time_t.

these definitions are merely copied from the top-level sys/socket.h,
so there is no functional change at this time. however, the top-level
definitions will change to use the time64 "_NEW" versions on 32-bit
archs when time_t is switched over to 64-bit. this commit ensures that
change will be suppressed on x32.

these structures can now be defined generically in terms of endianness
and long size. previously, the 32-bit archs all shared a common
definition from the generic bits header, and each 64-bit arch had to
repeat the 64-bit version, with endian conditionals if the arch had
variants of each endianness.

I would prefer getting rid of the preprocessor conditionals for
padding and instead using unnamed bitfield members, like commit
9b2921be did for struct timespec.
however, at present sendmsg, recvmsg, and recvmmsg need access to the
padding members by name to zero them. this could perhaps be cleaned up
in the future.

being that it contains pointers and (from the kernel perspective,
which is wrong) size_t members, x32 uses the 32-bit version of the
structure, not a half-32-bit, half-64-bit layout like we had here. the
x86_64 definition was inadvertently copied when x32 was first added.

unlike errors in the opposite direction (missing padding), this error
was not easily detected breakage, because the layout of the commonly
used initial subset of members still matched. breakage could only be
observed in the presence of control messages or flags.

this is analogous to commit 40aa18d5.
so far, there are not any actual time64 versions of the rusage
syscalls (getrusage and wait4) and might never be. however, the
existing x32 ones behave the way time64 versions would if they
existed: using 64-bit slots in place of all longs.

presently, wait4 and getrusage are broken on x32, storing the timevals
correctly but messing up everything else due to the long/kernel-long
mismatch. this would be a huge buffer overflow if not for the 16
reserved slots we left long ago, which suffice to prevent 14
double-sized longs from overflowing into unrelated memory. this commit
will make it possible to fix them.

this is to match the kernel and glibc interfaces. here, struct pt_regs
is an incomplete type, but that's harmless, and if it's completed by
inclusion of another header then members of the struct pointed to by
the regs member can be accessed directly without going through a cast
or intermediate pointer object.

the userspace ucontext API has this as an array rather than a
structure.

commit 3c59a868 fixed the
corresponding mistake for vrregset_t, namely that the original
powerpc64 port used a mix of types from 32-bit powerpc and powerpc64
rather than matching the 64-bit types.

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.

building on commit 97d35a55,
__BYTE_ORDER is now available wherever alltypes.h is included. since
reloc.h is only used from src/internal/dynlink.h, it can be assumed
that __BYTE_ORDER is exposed. reloc.h is not permitted to be included
in other contexts, and generally, like most arch headers, lacks
inclusion guards that would allow such usage. the mips64 version
mistakenly included such guards; they are removed for consistency.

building on commit 97d35a55,
__BYTE_ORDER is now available wherever alltypes.h is included.
endian.h should not be used since, in the future, it will expose
identifiers that are not in the reserved namespace for the headers
which were previously using it.

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 f7f10797 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

commit ffaaa6d2 removed the
corresponding stdarg.h support for compilers without va_list builtins,
but failed to remove the alternate type definition, leaving incorrect
va_list definitions in place with compilers that don't define __GNUC__
with a value >= 3.

commit ab3eb89a removed it as part of
correcting the mcontext_t definition, but there is still code using
struct sigcontext and expecting the member names present in it, most
notably libgcc_eh. almost all such usage is incorrect, but bring back
struct sigcontext at least for now so as not to introduce regressions.

in order for sys/procfs.h (provided by sys/user.h) to be useful, it
needs to match the API its consumers (gdb, etc.) expect, including the
member names established by glibc.

this partly reverts commit 29e8737f,
which partly reverted d493206d,
eliminating struct user_fpregs_struct which seems to have had no
precedent and using union __riscv_mc_fp_state for elf_fpregset_t. this
requires indirect inclusion of signal.h to make union
__riscv_mc_fp_state visible, but being that these are nonstandard
"junk" headers with no official restrictions on what they can pull in,
that's no big deal.

split off and expanded from patch by Khem Raj.

the top-level mcontext_t member names were namespace-violating in
standards profiles before, and nested-level member names (some of them
single-letter) were egregiously bad namespace impositions even in
non-strict profiles. moreover, they mismatched those used in the
public API first defined in glibc, breaking any code making use of
them.

unlike most archs, the public API used in glibc for riscv mcontext_t
members was designed to be namespace-safe, so we can and should expose
the members regardless of feature test macros. only the typedefs for
greg_t, gregset_t, and fpregset_t need to be protected behind FTMs.

the struct tags for mcontext_t and ucontext_t are also changed. for
mcontext_t this is necessary to make the common definition across
profiles namespace-safe. for ucontext_t, it's just a matter of
matching the tag from the glibc-defined API.

these changes are split off and expanded from a patch by Khem Raj.

analogous to commit ddc7c4f9 for
mips64 and n32, remove the hack to load the syscall number into $2 via
asm, and use a constraint to let the compiler load it instead.

now, only $4, $5, and $6 are potential input-only registers. $2 is
always input and output, and $7 is both when it's an argument,
otherwise output-only. previously, $7 was treated as an input (with a
"1" constraint matching its output position) even when it was not an
input, which was arguably undefined behavior (asm input from
indeterminate value). this is corrected.

as before, $8, $9, and $10 are conditionally input-output registers
for 5-, 6-, and 7-argument syscalls. their role in input is carrying
in the values that will be stored on the stack for arguments 5-7.
their role in output is carrying back whatever the kernel has
clobbered them with, so that the compiler cannot assume they still
contain the input values.

mips r6 (an incompatible isa from traditional mips) removes the hi and
lo registers used for mul/div results. older gcc versions accepted
them in the clobber list for asm, but their presence is incorrect and
breaks on later versions.

in the process of fixing this, the clobber list for 32-bit mips
syscalls has been deduplicated via a macro like on mips64 and n32.

The operand sepcifiers in a_cas and a_cas_p for riscv64 were incorrect:
there's a backwards branch in the routine, so despite tmp being written
at the end of the assembly fragment it cannot be allocated in one of the
input registers because the input values may be needed for another trip
around the loop.

For code that follows the guaranteed forward progress requirements, the
backwards branch is rarely taken: SiFive's hardware only fails a store
conditional on execptional cases (ie, instruction cache misses inside
the loop), and until recently a bug in QEMU allowed back-to-back
store conditionals to succeed.  The bug has been fixed in the latest
QEMU release, but it turns out that the fix caused this latent bug in
musl to manifest.

AT_HWCAP2 flags, see

  linux commit 671db581815faf17cbedd7fcbc48823a247d90b1
  arm64: Expose DC CVADP to userspace

  linux commit 06a916feca2b262ab0c1a2aeb68882f4b1108a07
  arm64: Expose SVE2 features for userspace

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]

historically, a number of 32-bit archs used long rather than int for
wchar_t, for no good reason. GCC still uses the historical types, but
clang replaced them all with int, and it seems PCC uses int too.
mismatching the compiler's type for wchar_t is not an option due to
wide string literals.

note that the mismatch does not affect C++ ABI since wchar_t is its
own builtin type/keyword in C++, distinct from both int and long, not
a typedef.

i386 already worked around this by honoring __WCHAR_TYPE__ if defined
by the compiler, and only using the official legacy ABI type if not.
add the same to the other affected archs.

it might make sense at some point to switch to using int as the
default if __WCHAR_TYPE__ is not defined, if the expectations is that
new compilers will treat int as the correct choice, but it's unlikely
that the case where __WCHAR_TYPE__ is undefined will ever be used
anyway. I actually wanted to move the definition of wchar_t to the
top-level shared alltypes.h.in, using __WCHAR_TYPE__ and falling back
to int if not defined, but that can't be done without assuming all
compilers define __WCHAR_TYPE__ thanks to some pathological archs
where the ABI has wchar_t as an unsigned type.