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

under some conditions, the mmap syscall wrongly fails with EPERM
instead of ENOMEM when memory is exhausted; this is probably the
result of the kernel trying to fit the allocation somewhere that
crosses into the kernel range or below mmap_min_addr. in any case it's
a conformance bug, so work around it. for now, only handle the case of
anonymous mappings with no requested address; in other cases EPERM may
be a legitimate error.

this indirectly fixes the possibility of malloc failing with the wrong
errno value.

GLOB_PERIOD is a gnu extension, and GNU glob does not seem to honor it
except in the last path component. it's not clear whether this a bug
or intentional, but it seems reasonable that it should exclude the
special entries . and .. when walking.

changes based on report and analysis by Julien Ramseier.

some applications use getservbyport to find port numbers that are not
assigned to a service; if getservbyport always succeeds with a numeric
string as the result, they fail to find any available ports.

POSIX doesn't seem to mandate the behavior one way or another. it
specifies an abstract service database, which an implementation could
define to include numeric port strings, but it makes more sense to
align behavior with traditional implementations.

based on patch by A. Wilcox. the original patch only changed
getservbyport[_r]. to maintain a consistent view of the "service
database", I have also modified getservbyname[_r] to exclude numeric
port strings.

if the parent thread was able to set the new thread's priority before
it reached the check for 'startlock', the new thread failed to restore
its signal mask and thus ran with all signals blocked.

concept for patch by Sergei, who reported the issue; unnecessary
changes were removed and comments added since the whole 'startlock'
thing is non-idiomatic and confusing. eventually it should be replaced
with use of idiomatic synchronization primitives.

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.

this is mandated by C and POSIX standards and is in accordance with
glibc behavior.

Reported by Leah Neukirchen.

This aligns clearenv with the Linux man page by setting 'environ'
rather than '*environ' to NULL, and stops it from leaking entries
allocated by the libc.

Rewrite environment access functions to slim down code, fix bugs and
avoid invoking undefined behavior.

* avoid using int-typed iterators where size_t would be correct;
* use strncmp instead of memcmp consistently;
* tighten prologues by invoking __strchrnul;
* handle NULL environ.

putenv:
* handle "=value" input via unsetenv too (will return -1/EINVAL);
* rewrite and simplify __putenv; fix the leak caused by failure to
  deallocate entry added by preceding setenv when called from putenv.

setenv:
* move management of libc-allocated entries to this translation unit,
  and use no-op weak symbols in putenv/unsetenv;

unsetenv:
* rewrite; this fixes UB caused by testing a free'd pointer against
  NULL on entry to subsequent loops.

Not changed:
Failure to extend allocation tracking array (previously __env_map, now
env_alloced) is ignored rather than causing to report -1/ENOMEM to the
caller; the worst-case consequence is leaking this allocation when it
is removed or replaced in a subsequent environment access.

Initially UB in unsetenv was reported by Alexander Cherepanov.
Using a weak alias to avoid pulling in malloc via unsetenv was
suggested by Rich Felker.

the DFA table controlling accepted ranges for the f4 prefix used an
incorrect upper bound of 0xa0 where it should have been 0x90, allowing
such sequences to be accepted and decoded as non-Unicode-scalar values
0x110000 through 0x11ffff.

the value computed as an output limit that bounds the amount of input
consumed below the input limit was incorrectly being used as the
actual amount of input consumed. instead, compute the actual amount of
input consumed as a difference of pointers before and after the
conversion.

patch by Mikhail Kremnyov.

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.)

counts leading zero bits of a 64bit int, undefined on zero input.
(has nothing to do with atomics, added to atomic.h so target specific
helper functions are together.)

there is a logarithmic generic implementation and another in terms of
a 32bit a_clz_32 on targets where that's available.

aligned with linux arch/s390/include/asm/elf.h
(these macros should be exported into uapi, but they are not)

it's in the reserved namespace for the latter, where it seems it was
historically defined, and some programs expect to find it there.

patch by Pascal Cuoq.

It is possible for argv[0] to be a null pointer, but the __progname
variable is used to implement functions in src/legacy/err.c that do not
expect it to be null. It is also available to the user via the
program_invocation_name alias as a GNU extension, and the implementation
in Glibc initializes it to a pointer to empty string rather than NULL.

Since argv[0] is usually non-null and it's preferable to keep those
variables in BSS, implement the fallbacks in __init_libc, which also
allows to have an intermediate fallback to AT_EXECFN.

it is defined in linux asm/sockios.h since commit
ae40eb1ef30ab4120bd3c8b7e3da99ee53d27a23 (linux v2.6.22)
but was missing from musl by accident.

in musl the sockios macros are exposed in sys/ioctl.h together
with other ioctl requests instead of in sys/socket.h because of
namespace rules. (glibc has them in sys/socket.h under _GNU_SOURCE.)

commit c002668e inadvertently moved
the check for unflushed write buffer outside of the scope of the
existing lock.

Due to a missing ":" in an asm() statement, the "memory" clobber is
considered by gcc as an input operand and not a clobber, which causes a
build failure.

passing to pthread_join the id of a thread which is not joinable
results in undefined behavior.

in principle the check to trap does not necessarily work if
pthread_detach was called after thread creation, since no effort is
made here to synchronize access to t->detached, but the check is
well-defined and harmless for callers which did not invoke UB, and
likely to help catch erroneous code that would otherwise mysteriously
hang.

patch by William Pitcock.

The TOC pointer is constant within a single dso, but needs to be saved
and restored around cross-dso calls.  The PLT stub saves it to the
caller's stack frame, and the linker adds code to the caller to restore
it.

With a local call, as within a single dso or with static linking, this
doesn't happen and the TOC pointer is always in r2.  Therefore,
setjmp/longjmp need to save/restore the TOC pointer from/to different
locations depending on whether the call to setjmp was a local or non-local
call.

It is always safe for longjmp to restore to both r2 and the caller's stack.
If the call to setjmp was local, and only r2 matters and the stack location
will be ignored, but is required by the ABI to be reserved for the TOC
pointer.  If the call was non-local, then only the stack location matters,
and whatever is restored into r2 will be clobbered anyway when the caller
reloads r2 from the stack.

A little extra care is required for sigsetjmp, because it uses setjmp
internally.  After the second return from this setjmp call, r2 will contain
the caller's TOC pointer instead of libc's TOC pointer.  We need to save
and restore the correct libc pointer before we can tail call to
__sigsetjmp_tail.

neither current compilers nor linkers treat protected visibility the
way I expected, as having fixed source-level semantics rather than
being dependent on target-specific ABI details, and change seems
unlikely. while the use here does not actually depend on the specific
semantics, at least some versions of some linkers, especially lld,
refuse to allow linking to a libc.so where the symbols have protected
visibility. this cannot be detected at configure-time because linking
libc.so itself works fine, and because even if we could test linking
an application against libc.so successfully, we could not justifiably
assume that the same linker used to link libc.so would also be used
later to link applications.

disable the vis.h hack by default at the configure level, but add an
explicit "auto" option to request the old configure-time detection
rather than just removing it. this leaves it easy to evaluate whether
it actually resulted in significant size or performance benefits while
ensuring that out-of-the-box builds are not unlinkable for some users.

fortunately, preliminary evaluation suggests that at least x86_64,
arm, and aarch64 don't suffer at all from the change, and impact on
other archs is low. if low is not low enough, it should not be hard to
analyze where the significant PLT call ABI costs are present and
mitigate them without the hack.

since setlocale(cat, NULL) is required to return the setting for the
global locale, there is no standard mechanism to obtain the name of
the currently active thread-local locale set by uselocale. this makes
it impossible for application/library software to load appropriate
translations, etc. unless using the gettext implementation provided by
libc, which has privileged access to libc internals.

to fill this gap, glibc introduced the _NL_LOCALE_NAME macro which can
be used with nl_langinfo to obtain the name. GNU gettext/gnulib code
already use this functionality on glibc, and can easily be adapted to
make use of it on non-glibc systems if it's available; for other
systems they poke at locale implementation internals, which we want to
avoid. this patch provides a compatible interface to the one glibc
introduced.

The switch statement has no 'default:' case and the function ends
immediately following the switch, so the extra comparison did not
communicate any extra information to the compiler.

The flag 1<<7 is used in several places for different purposes that are
not always easy to distinguish. Mark those usages that correspond to the
flag that is used by the kernel for futexes.

commit 58e2396a missed that the same
code was duplicated in implementation of vfwprintf.

The two functions str{,n}casecmp_l are specified to be declared in
<strings.h> which is already included from <string.h> under _GNU_SOURCE.

previously, the pathname used to load the program was always used as
argv[0]. the default remains the same, but a new --argv0 option can be
used to provide a different value.

commit 4ff234f6 inadvertently removed
the logic to do this when changing the representation of global
status.

a null pointer for a library's deps list was ambiguous: it could
indicate either no dependencies or that the dependency list had not
yet been populated. inability to distinguish could lead to spurious
work when dlopen is called multiple times on a library with no deps,
and due to related bugs, could actually cause other libraries to
falsely appear as dependencies, translating into false positives for
dlsym.

avoid the problem by always initializing the deps pointer, pointing to
an empty list if there are no deps. rather than wasting memory and
introducing another failure path by allocating an empty list per
library, simply share a global dummy list.

further fixes will be needed for related bugs, and much of this code
may end up being replaced.

while the official elfv2 abi for "powerpc64le" sets power8 as the
baseline isa, we use it for both little and big endian powerpc64
targets and need to maintain compatibility with pre-power8 models. the
instructions for sqrt, fabs, and fma are in the baseline isa; support
for the rest is conditional via predefined isa-level macros.

patch by David Edelsohn.