the mode member of struct ipc_perm is specified by POSIX to have type
mode_t, which is uniformly defined as unsigned int. however, Linux
defines it with type __kernel_mode_t, and defines __kernel_mode_t as
unsigned short on some archs. since there is a subsequent padding
field, treating it as a 32-bit unsigned int works on little endian
archs, but the order is backwards on big endian archs with the
erroneous definition.

since multiple archs are affected, remedy the situation with fixup
code in the affected functions (shmctl, semctl, and msgctl) rather
than repeating the same shims in syscall_arch.h for every affected
arch.

new in linux commit 71406883fd35794d573b3085433c41d0a3bf6c21

new in linux commit 256211f2b0b251e532d1899b115e374feb16fa7a

hwcaps for armv8.4, new in linux commit
7206dc93a58fb76421c4411eefa3c003337bcb2d

add pkey_mprotect, pkey_alloc, pkey_free syscall numbers,
new in linux commits 3350eb2ea127978319ced883523d828046af4045
and 9499ec1b5e82321829e1c1510bcc37edc20b6f38

armv8.4 fp mul instructions.
added in commit 3b3b681097fae73b7f5dcdd42db6cfdf32943d4c

three ABIs are supported: the default with 68881 80-bit fpu format and
results returned in floating point registers, softfloat-only with the
same format, and coldfire fpu with IEEE single/double only. only the
first is tested at all, and only under qemu which has fpu emulation
bugs.

basic functionality smoke tests have been performed for the most
common arch-specific breakage via libc-test and qemu user-level
emulation. some sysvipc failures remain, but are shared with other big
endian archs and will be fixed separately.

In TLS variant I the TLS is above TP (or above a fixed offset from TP)
but on some targets there is a reserved gap above TP before TLS starts.

This matters for the local-exec tls access model when the offsets of
TLS variables from the TP are hard coded by the linker into the
executable, so the libc must compute these offsets the same way as the
linker.  The tls offset of the main module has to be

	alignup(GAP_ABOVE_TP, main_tls_align).

If there is no TLS in the main module then the gap can be ignored
since musl does not use it and the tls access models of shared
libraries are not affected.

The previous setup only worked if (tls_align & -GAP_ABOVE_TP) == 0
(i.e. TLS did not require large alignment) because the gap was
treated as a fixed offset from TP.  Now the TP points at the end
of the pthread struct (which is aligned) and there is a gap above
it (which may also need alignment).

The fix required changing TP_ADJ and __pthread_self on affected
targets (aarch64, arm and sh) and in the tlsdesc asm the offset to
access the dtv changed too.

in thumb mode, r7 is the ABI frame pointer register, and unless frame
pointer is disabled, gcc insists on treating it as a fixed register,
refusing to spill it to satisfy constraints. unfortunately, r7 is also
used in the syscall ABI for passing the syscall number.

up til now we just treated this as a requirement to disable frame
pointer when generating code as thumb, but it turns out gcc forcibly
enables frame pointer, and the fixed register constraint that goes
with it, for functions which contain VLAs. this produces an
unacceptable arch-specific constraint that (non-arm-specific) source
files making syscalls cannot use VLAs.

as a workaround, avoid r7 register constraints when producing thumb
code and instead save/restore r7 in a temp register as part of the asm
block. at some point we may want/need to support armv6-m/thumb1, so
the asm has been tweaked to be thumb1-compatible while also
near-optimal for thumb2: it allows the temp and/or syscall number to
be in high registers (necessary since r0-r5 may all be used for
syscalll args) and in thumb2 mode allows the syscall number to be an
8-bit immediate.

ARMv6 cores with support for Thumb2 can take advantage of the "ldrex"
and "strex" based implementations of a_ll and a_sc.

__ARM_ARCH_6ZK__ is a gcc specific historical typo which may not be
defined by other compilers.

  https://gcc.gnu.org/ml/gcc-patches/2015-07/msg02237.html

To avoid unexpected results when building for ARMv6KZ with clang, the
correct form of the macro (ie 6KZ) needs to be tested. The incorrect
form of the macro (ie 6ZK) still needs to be tested for compatibility
with pre-2015 versions of gcc.

Provide an ARM specific a_ctz_32 helper function for architecture
versions for which it can be implemented efficiently via the "rbit"
instruction (ie all Thumb-2 capable versions of ARM v6 and above).

Update atomic.h to provide a_ctz_l in all cases (atomic_arch.h should
now only provide a_ctz_32 and/or a_ctz_64).

The generic version of a_ctz_32 now takes advantage of a_clz_32 if
available and the generic a_ctz_64 now makes use of a_ctz_32.

the output delay features (NL*, CR*, TAB*, BS*, and VT*) are
XSI-shaded. VT* is in the V* namespace reservation but the rest need
to be suppressed in base POSIX namespace.

unfortunately this change introduces feature test macro checks into
another bits header. at some point these checks should be simplified
by having features.h handle the "FTM X implies Y" relationships.

align with commit c9c2cd3e.

PAGESIZE is actually the version defined in POSIX base, with PAGE_SIZE
being in the XSI option. use PAGESIZE as the underlying definition to
facilitate making exposure of PAGE_SIZE conditional.

signal context definitions for scalable vector extension new in commit
d0b8cd3187889476144bd9b13bf36a932c3e7952

HWCAP_SVE is new in linux commit 43994d824e8443263dc98b151e6326bf677be52e
HWCAP_SHA3, HWCAP_SM3, HWCAP_SM4, HWCAP_ASIMDDP and HWCAP_SHA512 are new in
f5e035f8694c3bdddc66ea46ecda965ee6853718

for systems without tp register or kuser helper, new in linux commit
8fcd6c45f5a65621ec809b7866a3623e9a01d4ed

PPC_FEATURE2_HTM_NO_SUSPEND is new in linux commit
cba6ac4869e45cc93ac5497024d1d49576e82666
PPC_FEATURE2_DARN and PPC_FEATURE2_SCV were new in v4.12 in commit
a4700a26107241cc7b9ac8528b2c6714ff99983d

to store hypervisor information, added in linux commit
3d8757b87d7fc15a87928bc970f060bc9c6dc618

for synchronous page faults, new in linux commit
1c9725974074a047f6080eecc62c50a8e840d050 and
b6fb293f2497a9841d94f6b57bd2bb2cd222da43
note that only targets that use asm-generic/mman.h have this new
flag defined, so undef it on other targets (mips*, powerpc*).

use the same token to define TIOCSER_TEMT as is used in ioctl.h
so when both headers are included there are no redefinition warnings
during musl build.

indicates ARMv8.2-DCPoP persistent memory support extension.
new in linux commit 7aac405ebb3224037efd56b73d82d181111cdac3

s390 can use the generic ioctls definitions other than FIOQSIZE (like arm).

this fixes some missing ioctls and two incorrect ones:
TIOCTTYGSTRUCT and TIOCM_MODEM_BITS seem to be defined on frv
target only in linux.

statx number is allocated for microblaze in linux commit
f5ef419630e85e80284cd0256cb5a13a66bbd6c5

allows expanding the signal frame beyond the 4k reserved space.
new in linux commit 33f082614c3443d937f50fe936f284f62bbb4a1b

added for safe opening of peer end of pty in a mount namespace.
new in linux commit c6325179238f1d4683edbec53d8322575d76d7e2

new syscall in linux commit 916cda1aa1b412d7cf2991c3af7479544942d121

syscall for i386 compat mode on x86_64 for non-x86_64 prctls.
new in linux commit 79170fda313ed5be2394f87aa2a00d597f8ed4a1

hwcap bits for armv8.3 extensions, added in linux commits
c8c3798d2369e4285da44b244638eafe446a8f8a
cb567e79fa504575cb97fb2f866d2040ed1c92e7
c651aae5a7732287c1c9bc974ece4ed798780544

statx was added in linux commit a528d35e8bfcc521d7cb70aaf03e1bd296c8493f
(there is no libc wrapper yet and microblaze and sh misses the number).

new hwcap bits were added in kernel commits
77c97b4ee21290f5f083173d957843b615abbff2
f92f5ce01ee6a6a86cbfc4e3b0d18529c302b1ea

added in linux commit 80f60e509a03ff9ff2bdbf9cd1e935c6360b8bd9

missing syscalls got allocated on microblaze.

commit 06fbefd1 (first included in
release 1.1.17) introduced this regression.

patch by Adrian Bunk. it fixes the regression in all cases, but
spuriously prevents use of the clz instruction on very old compiler
versions that don't define __ARM_ARCH. this may be fixed in a more
general way at some point in the future. it also omits thumb1 logic
since building as thumb1 code is currently not supported.

MAP_{NORESERVE,LOCKED} have different values on powerpc than in generic.

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.