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2018-09-18fix deletion of pthread tsd keys that still have non-null values storedRich Felker-18/+104
per POSIX, deletion of a key for which some threads still have values stored is permitted, and newly created keys must initially hold the null value in all threads. these properties were not met by our implementation; if a key was deleted with values left and a new key was created in the same slot, the old values were still visible. moreover, due to lack of any synchronization in pthread_key_delete, there was a TOCTOU race whereby a concurrent pthread_exit could attempt to call a null destructor pointer for the newly orphaned value. this commit introduces a solution based on __synccall, stopping the world to zero out the values for deleted keys, but only does so lazily when all key slots have been exhausted. pthread_key_delete is split off into a separate translation unit so that static-linked programs which only create keys but never delete them will not pull in the __synccall machinery. a global rwlock is added to synchronize creation and deletion of keys with dtor execution. since the dtor execution loop now has to release and retake the lock around its call to each dtor, checks are made not to call the nodtor dummy function for keys which lack a dtor.
2018-09-18fix race condition in file lockingKaarle Ritvanen-6/+6
The condition occurs when - thread #1 is holding the lock - thread #2 is waiting for it on __futexwait - thread #1 is about to release the lock and performs a_swap - thread #3 enters the __lockfile function and manages to grab the lock before thread #1 calls __wake, resetting the MAYBE_WAITERS flag - thread #1 calls __wake - thread #2 wakes up but goes again to __futexwait as the lock is held by thread #3 - thread #3 releases the lock but does not call __wake as the MAYBE_WAITERS flag is not set This condition results in thread #2 not being woken up. This patch fixes the problem by making the woken up thread ensure that the flag is properly set before going to sleep again. Mainainer's note: This fixes a regression introduced in commit c21f750727515602a9e84f2a190ee8a0a2aeb2a1.
2018-09-16getdelim: only grow buffer when necessary, improve OOM behaviorRich Felker-10/+17
commit b114190b29417fff6f701eea3a3b3b6030338280 introduced spurious realloc of the output buffer in cases where the result would exactly fit in the caller-provided buffer. this is contrary to a strict reading of the spec, which only allows realloc when the provided buffer is "of insufficient size". revert the adjustment of the realloc threshold, and instead push the byte read by getc_unlocked (for which the adjustment was made) back into the stdio buffer if it does not fit in the output buffer, to be read in the next loop iteration. in order not to leave a pushed-back byte in the stdio buffer if realloc fails (which would violate the invariant that logical FILE position and underlying open file description offset match for unbuffered FILEs), the OOM code path must be changed. it would suffice move just one byte in this case, but from a QoI perspective, in the event of ENOMEM the entire output buffer (up to the allocated length reported via *n) should contain bytes read from the FILE stream. otherwise the caller has no way to distinguish trunated data from uninitialized buffer space. the SIZE_MAX/2 check is removed since the sum of disjoint object sizes is assumed not to be able to overflow, leaving just one OOM code path.
2018-09-16fix null pointer subtraction and comparison in stdioRich Felker-31/+41
morally, for null pointers a and b, a-b, a<b, and a>b should all be defined as 0; however, C does not define any of them. the stdio implementation makes heavy use of such pointer comparison and subtraction for buffer logic, and also uses null pos/base/end pointers to indicate that the FILE is not in the corresponding (read or write) mode ready for accesses through the buffer. all of the comparisons are fixed trivially by using != in place of the relational operators, since the opposite relation (e.g. pos>end) is logically impossible. the subtractions have been reviewed to check that they are conditional the stream being in the appropriate reading- or writing-through-buffer mode, with checks added where needed. in fgets and getdelim, the checks added should improve performance for unbuffered streams by avoiding a do-nothing call to memchr, and should be negligible for buffered streams.
2018-09-16fix failure of getdelim to set stream orientation on errorRich Felker-0/+2
if EINVAL or ENOMEM happened before the first getc_unlocked, it was possible that the stream orientation had not yet been set.
2018-09-15check for kernel support before allowing robust mutex creationRich Felker-1/+17
on some archs, linux support for futex operations (including robust_list processing) that depend on kernelspace CAS is conditional on a runtime check. as of linux 4.18, this check fails unconditionally on nommu archs that perform it, and spurious failure on powerpc64 was observed but not explained. it's also possible that futex support is omitted entirely, or that the kernel is older than 2.6.17. for most futex ops, ENOSYS does not yield hard breakage; userspace will just spin at 100% cpu load. but for robust mutexes, correct behavior depends on the kernel functionality. use the get_robust_list syscall to probe for support at the first call to pthread_mutexattr_setrobust, and block creation of robust mutexes with a reportable error if they can't be supported.
2018-09-15always reset DST rules during tzsetBenjamin Peterson-1/+2
do_tzset() did't always reset the DST transition rules r0 and r1. That means the rules from older TZ settings could leak into newer ones.
2018-09-15fix undefined behavior in strto* via FILE buffer pointer abuseRich Felker-20/+43
in order to produce FILE objects to pass to the intscan/floatscan backends without any (prohibitively costly) extra buffering layer, the strto* functions set the FILE's rend (read end) buffer pointer to an invalid value at the end of the address space, or SIZE_MAX/2 past the beginning of the string. this led to undefined behavior comparing and subtracting the end pointer with the buffer position pointer (rpos). the comparison issue is easily eliminated by using != instead of <. however the subtractions require nontrivial changes: previously, f->shcnt stored the count that would have been read if consuming the whole buffer, which required an end pointer for the buffer. the purpose for this was that it allowed reading it and adding rpos-rend at any time to get the actual count so far, and required no adjustment at the time of __shgetc (actual function call) since the call would only happen when reaching the end of the buffer. to get rid of the dependency on rend, instead offset shcnt by buf-rpos (start of buffer) at the time of last __shlim/__shgetc call. this makes for slightly more work in __shgetc the function, but for the inline macro it's still just as easy to compute the current count. since the scan helper interfaces used here are a big hack, comments are added to document their contracts and what's going on with their implementations.
2018-09-15improve error handling of ttyname_r and isattyBenjamin Peterson-2/+6
POSIX allows ttyname(_r) and isatty to return EBADF if passed file descriptor is invalid. maintainer's note: these are optional ("may fail") errors, but it's non-conforming for ttyname_r to return ENOTTY when it failed for a different reason.
2018-09-14add hidden version of &errno accessor functionRich Felker-0/+13
this significantly improves codegen in functions that need to access errno but otherwise have no need for a GOT pointer. we could probably improve it much more by including an inline version of the &errno accessor function, but that depends on having the definitions of struct __pthread and __pthread_self(), which at present would expose a lot more than is appropriate. moving them to a small tls.h later might make this more reasonable.
2018-09-14fix build regression in sysconf for archs with variable page sizeRich Felker-0/+1
commit 5ce3737931bb411a8d167356d4d0287b53b0cbdc removed the inclusion of libc.h from this file as spurious, but it's needed to get PAGE_SIZE on archs where PAGE_SIZE is not a constant defined by limits.h.
2018-09-14drop lazy plural forms init in dcngettextRich Felker-18/+17
there is no good reason to wait to find and process the plural rules for a translated message file until a gettext form requesting plural rule processing is used. it just imposes additional synchronization, here in the form of clunky use of atomics. it looks like there may also have been a race condition where nplurals could be seen without plural_rule being seen, possibly leading to null pointer dereference. if so, this commit fixes it.
2018-09-14fix broken atomic store on powerpc[64]Rich Felker-16/+0
in our memory model, all atomics are supposed to be full barriers; stores are not release-only. this is important because store is used as an unlock operation in places where it needs to acquire the waiter count to determine if a futex wake is needed. at least in the malloc-internal locks, but possibly elsewhere, soft deadlocks from missing futex wake (breakable by poking the threads to restart the syscall, e.g. by attaching a tracer) were reported to occur. once the malloc lock is replaced with Jens Gustedt's new lock implementation (see commit 47d0bcd4762f223364e5b58d5a381aaa0cbd7c38), malloc will not be affected by the issue, but it's not clear that other uses won't be. reducing the strength of the ordering properties required from a_store would require a thorough analysis of how it's used. to fix the problem, I'm removing the powerpc[64]-specific a_store definition; now, the top-level atomic.h will implement a_store using a_barrier on both sides of the store. it's not clear to me yet whether there might be issues with the other atomics. it's possible that a_post_llsc needs to be replaced with a full barrier to guarantee the formal semanics we want, but either way I think the difference is unlikely to impact the way we use them.
2018-09-13define MAX_HANDLE_SZ for use with name_to_handle_atKhem Raj-0/+1
MAX_HANDLE_SZ is described in name_to_handle_at() to contain maximum expected size for a file handle
2018-09-13fix regression with compilers not incorporating C99 DR#289 resolutionRich Felker-1/+1
as originally published, the C99 syntax only allowed static index parameter declarators when a gratuitous parameter name was included. gcc 3, which some projects use for bootstrapping, is a supported C99 compiler, but does not have the fix to the standard incorporated, so edit the affected declaration to conform to the earlier buggy C99 syntax.
2018-09-12configure: only try -Qunused-arguments for clangRich Felker-1/+1
other compilers don't need this option, but gcc 3 and perhaps others accept it despite not understanding it, then print warnings about it at build time. omitting it when not needed will also help shorten the command lines.
2018-09-12wireup linux/name_to_handle_at and name_to_handle_at syscallsKhem Raj-0/+25
2018-09-12remove vis.h protected-visibility hackRich Felker-65/+0
since commit dc2f368e565c37728b0d620380b849c3a1ddd78f this has been disabled by default, but was left available in case users unhappy with the resulting size or performance regressions wanted to try to make it work. now that we make widespread use of hidden visibility for internal interfaces, this no longer makes sense. if any costly calls remain they can be fixed with hidden aliases.
2018-09-12split internal lock API out of libc.h, creating lock.hRich Felker-17/+32
this further reduces the number of source files which need to include libc.h and thereby be potentially exposed to libc global state and internals. this will also facilitate further improvements like adding an inline fast-path, if we want to do so later.
2018-09-12move misplaced __fork_handler declarationRich Felker-1/+1
pthread_atfork.c does not actually include pthread_impl.h and has no reason to, so it wasn't getting the declaration. move it to libc.h which is already included by both fork.c and pthread_atfork.c. this makes more sense anyway since the function has little to do with pthreads anyway aside from the name.
2018-09-12remove spurious inclusion of libc.h for LFS64 ABI aliasesRich Felker-107/+59
the LFS64 macro was not self-documenting and barely saved any characters. simply use weak_alias directly so that it's clear what's being done, and doesn't depend on a header to provide a strange macro.
2018-09-12reduce spurious inclusion of libc.hRich Felker-177/+43
libc.h was intended to be a header for access to global libc state and related interfaces, but ended up included all over the place because it was the way to get the weak_alias macro. most of the inclusions removed here are places where weak_alias was needed. a few were recently introduced for hidden. some go all the way back to when libc.h defined CANCELPT_BEGIN and _END, and all (wrongly implemented) cancellation points had to include it. remaining spurious users are mostly callers of the LOCK/UNLOCK macros and files that use the LFS64 macro to define the awful *64 aliases. in a few places, new inclusion of libc.h is added because several internal headers no longer implicitly include libc.h. declarations for __lockfile and __unlockfile are moved from libc.h to stdio_impl.h so that the latter does not need libc.h. putting them in libc.h made no sense at all, since the macros in stdio_impl.h are needed to use them correctly anyway.
2018-09-12use wrapper headers to hide most namespaced/internally-public symbolsRich Felker-60/+64
not all prefixed symbols can be made hidden. some are part of ABI-compat (e.g. __nl_langinfo_l) and others are ABI as a consequence of the way copy relocations for weak aliases work in ELF shared libraries. most, however, can be made hidden. with this commit, there should be no remaining unintentionally visible symbols exported from libc.so.
2018-09-12remove __vfork aliasRich Felker-28/+7
this was added so that posix_spawn and possibly other functionality could be implemented in terms of vfork, but that turned out to be unsafe. any such usage needs __clone with proper handling of stack lifetime.
2018-09-12hide purely dependency-triggering functions in stdio __toread & __towriteRich Felker-2/+2
2018-09-12declare __env_rm_add in wrapper stdlib.hRich Felker-0/+1
this is perhaps not the ideal place, but no better alternatives stand out.
2018-09-12hide dependency-triggering pointer object in malloc_usable_size.cRich Felker-2/+2
2018-09-12rework malloc_usable_size to use malloc_impl.hRich Felker-9/+1
2018-09-12remove unused __futex function and source fileRich Felker-9/+0
the direct syscall or various thin and mostly-inline wrappers around it are used instead internally. at some point a public futex function should be added, but it's not yet clear what the signature should be, and in the mean time this file is not useful.
2018-09-12hide __pthread_once_full symbolRich Felker-1/+1
this is a special case that does not need a declaration, because it's not even a libc-internal interface between translation units. instead it's a poor hack around compilers' inability to shrink-wrap critical code paths. after vis.h was disabled, it became more of a pessimization on many archs due to the extra layer of machinery to support a call through the PLT, but now it should be efficient again.
2018-09-12declare and make hidden additional internal init/exit symbolsRich Felker-0/+4
2018-09-12declare and make hidden additional internal stdio symbolsRich Felker-0/+5
2018-09-12move declaration and apply hidden visibility to __utc stringRich Felker-4/+1
2018-09-12declare and make hidden more internal locale functionsRich Felker-0/+2
2018-09-12remove unused __getdents, rename and move fileRich Felker-4/+1
the __-prefixed filename does not make sense when the only purpose of this file is implementing a public function that's not used as a backend for implementing the standard dirent functions.
2018-09-12remove or make static various unused __-prefixed symbolsRich Felker-17/+10
2018-09-12move additional pthread internal declarations to pthread_impl.h, hideRich Felker-2/+15
these were overlooked for various reasons in earlier stages.
2018-09-12apply hidden visibility to various remaining internal interfacesRich Felker-46/+52
2018-09-12apply hidden visibility to sigreturn code fragmentsRich Felker-9/+49
these were overlooked in the declarations overhaul work because they are not properly declared, and the current framework even allows their declared types to vary by arch. at some point this should be cleaned up, but I'm not sure what the right way would be.
2018-09-12apply hidden visibility to pthread internalsRich Felker-11/+11
2018-09-12apply hidden visibility to stdio internalsRich Felker-26/+26
2018-09-12apply hidden visibility to internal time[zone] implementation functionsRich Felker-8/+8
2018-09-12apply hidden visibility to internal math functionsRich Felker-26/+26
this makes significant differences to codegen on archs with an expensive PLT-calling ABI; on i386 and gcc 7.3 for example, the sin and sinf functions no longer touch call-saved registers or the stack except for pushing outgoing arguments. performance is likely improved too, but no measurements were taken.
2018-09-12overhaul internally-public declarations using wrapper headersRich Felker-192/+200
commits leading up to this one have moved the vast majority of libc-internal interface declarations to appropriate internal headers, allowing them to be type-checked and setting the stage to limit their visibility. the ones that have not yet been moved are mostly namespace-protected aliases for standard/public interfaces, which exist to facilitate implementing plain C functions in terms of POSIX functionality, or C or POSIX functionality in terms of extensions that are not standardized. some don't quite fit this description, but are "internally public" interfacs between subsystems of libc. rather than create a number of newly-named headers to declare these functions, and having to add explicit include directives for them to every source file where they're needed, I have introduced a method of wrapping the corresponding public headers. parallel to the public headers in $(srcdir)/include, we now have wrappers in $(srcdir)/src/include that come earlier in the include path order. they include the public header they're wrapping, then add declarations for namespace-protected versions of the same interfaces and any "internally public" interfaces for the subsystem they correspond to. along these lines, the wrapper for features.h is now responsible for the definition of the hidden, weak, and weak_alias macros. this means source files will no longer need to include any special headers to access these features. over time, it is my expectation that the scope of what is "internally public" will expand, reducing the number of source files which need to include *_impl.h and related headers down to those which are actually implementing the corresponding subsystems, not just using them.
2018-09-12declare __getopt_msg in stdio_impl.hRich Felker-2/+3
it's not ideal, but the function is essentially an extended stdio function specialized to getopt's needs. the only reason it exists is avoiding pulling printf code into every program using getopt.
2018-09-12use lighter internal stdio lock in getopt error printingRich Felker-2/+3
the public flockfile interface is significantly heavier because it has to handle the possibility of caller returning or thread exiting while holding the lock.
2018-09-12add crypt_des header for declarations shared with encrypt functionRich Felker-12/+16
2018-09-12make mkostemps source file include the header for its declarationRich Felker-0/+1
2018-09-12move __memalign declaration to malloc_impl.hRich Felker-4/+4
the malloc-implementation-private header is the only right place for this, because, being in the reserved namespace, __memalign is not interposable and thus not valid to use anywhere else. anything outside of the malloc implementation must call an appropriate-namespace public function (aligned_alloc or posix_memalign).
2018-09-12use hidden visibility for sh __unmapself backendsRich Felker-2/+3