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* greatly improve freopen behaviorRich Felker2012-10-245-17/+41
| | | | | | | | | | | | | 1. don't open /dev/null just as a basis to copy flags; use shared __fmodeflags function to get the right file flags for the mode. 2. handle the case (probably invalid, but whatever) case where the original stream's file descriptor was closed; previously, the logic re-closed it. 3. accept the "e" mode flag for close-on-exec; update dup3 to fallback to using dup2 so we can simply call __dup3 instead of putting fallback logic in freopen itself.
* remove useless failure-check from freopen (can't happen)Rich Felker2012-10-241-2/+2
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* simplify logic in stpcpy; avoid copying first aligned byte twiceRich Felker2012-10-221-4/+4
| | | | | gcc seems to be generating identical or near-identical code for both versions, but the newer code is more expressive of what it's doing.
* as an extension, have putenv("VAR") behave as unsetenv("VAR")Rich Felker2012-10-211-5/+5
| | | | | | the behavior of putenv is left undefined if the argument does not contain an equal sign, but traditional implementations behave this way and gnulib replaces putenv if it doesn't do this.
* accept "nan(n-char-sequence)" in strtod/scanf functionsRich Felker2012-10-211-1/+19
| | | | | this will prevent gnulib from wrapping our strtod to handle this useless feature.
* fix copy/paste error in popen changes that broke signalsRich Felker2012-10-211-1/+1
| | | | signal mask was not being restored after fork, but instead blocked again.
* support looking up thread-local objects with dlsymRich Felker2012-10-191-0/+6
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* fix breakage in dlsym for looking up RTLD_DEFAULT, etc.Rich Felker2012-10-191-2/+5
| | | | | this was broken during the early dynamic-linked TLS commits, which rearranged some of the code for handling new relocation types.
* fix usage of locks with vforkRich Felker2012-10-193-3/+4
| | | | | | __release_ptc() is only valid in the parent; if it's performed in the child, the lock will be unlocked early then double-unlocked later, corrupting the lock state.
* fix crashes in static-linked multithreaded programs without TLSRich Felker2012-10-191-0/+2
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* fix order of syscall args for microblaze clone syscallRich Felker2012-10-191-3/+2
| | | | | with this commit, based on testing with patches to qemu which are not yet upstream,
* ensure microblaze __set_thread_area returns successRich Felker2012-10-181-1/+2
| | | | | since it did not set the return-value register, the caller could wrongly interpret this as failure.
* avoid raising spurious division-by-zero exception in printfRich Felker2012-10-181-1/+1
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* floating point environment/exceptions support for mipsRich Felker2012-10-181-0/+60
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* fix parent-memory-clobber in posix_spawn (environ)Rich Felker2012-10-183-9/+17
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* overhaul system() and popen() to use vfork; fix various related bugsRich Felker2012-10-184-56/+110
| | | | | | | | | | | | | | | | since we target systems without overcommit, special care should be taken that system() and popen(), like posix_spawn(), do not fail in processes whose commit charges are too high to allow ordinary forking. this in turn requires special precautions to ensure that the parent process's signal handlers do not end up running in the shared-memory child, where they could corrupt the state of the parent process. popen has also been updated to use pipe2, so it does not have a fd-leak race in multi-threaded programs. since pipe2 is missing on older kernels, (non-atomic) emulation has been added. some silly bugs in the old code should be gone too.
* fix (hopefully; untested) completely broken/incomplete microblaze sigsetjmpRich Felker2012-10-181-3/+12
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* fix microblaze asm relocations for shared libcRich Felker2012-10-174-6/+6
| | | | | | only @PLT relocations are considered functions for purposes of -Bsymbolic-functions, so always use @PLT. it should not hurt in the static-linked case.
* add memmem function (gnu extension)Rich Felker2012-10-151-0/+148
| | | | based on strstr. passes gnulib tests and a few quick checks of my own.
* add support for TLS variant I, presently needed for arm and mipsRich Felker2012-10-155-6/+46
| | | | | | | | | | | | | | | | | | | | | | despite documentation that makes it sound a lot different, the only ABI-constraint difference between TLS variants II and I seems to be that variant II stores the initial TLS segment immediately below the thread pointer (i.e. the thread pointer points to the end of it) and variant I stores the initial TLS segment above the thread pointer, requiring the thread descriptor to be stored below. the actual value stored in the thread pointer register also tends to have per-arch random offsets applied to it for silly micro-optimization purposes. with these changes applied, TLS should be basically working on all supported archs except microblaze. I'm still working on getting the necessary information and a working toolchain that can build TLS binaries for microblaze, but in theory, static-linked programs with TLS and dynamic-linked programs where only the main executable uses TLS should already work on microblaze. alignment constraints have not yet been heavily tested, so it's possible that this code does not always align TLS segments correctly on archs that need TLS variant I.
* block uid/gid changes during posix_spawnRich Felker2012-10-151-0/+10
| | | | | | | | | | | | | | | | | | usage of vfork creates a situation where a process of lower privilege may momentarily have write access to the memory of a process of higher privilege. consider the case of a multi-threaded suid program which is calling posix_spawn in one thread while another thread drops the elevated privileges then runs untrusted (relative to the elevated privilege) code as the original invoking user. this untrusted code can then potentially modify the data the child process will use before calling exec, for example changing the pathname or arguments that will be passed to exec. note that if vfork is implemented as fork, the lock will not be held until the child execs, but since memory is not shared it does not matter.
* fix overlap of thread stacks with thread tls segmentsRich Felker2012-10-141-2/+1
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* fix main program TLS alignment for dynamic-linked programsRich Felker2012-10-141-6/+5
| | | | | this change brings the behavior in line with the static-linked code, which seems to be correct.
* workaround broken hidden-visibility handling in pccRich Felker2012-10-131-1/+1
| | | | | | | | | | | | | with this change, pcc-built musl libc.so seems to work correctly. the problem is that pcc generates GOT lookups for external-linkage symbols even if they are hidden, rather than using GOT-relative addressing. the entire reason we're using hidden visibility on the __libc object is to make it accessible prior to relocations -- not to mention inexpensive to access. unfortunately, the workaround makes it even more expensive on pcc. when the pcc issue is fixed, an appropriate version test should be added so new pcc can use the much more efficient variant.
* fix namespace clash (libc) in dynlink.cRich Felker2012-10-131-14/+13
| | | | | | | this makes it so the #undef libc and __libc name are no longer needed, which were problematic because the "accessor function" mode for accessing the libc struct could not be used, breaking build on any compiler without (working) visibility.
* remove dead code from dynamic linkerRich Felker2012-10-131-10/+0
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* comment possibly-confusing i386 vsyscall asmRich Felker2012-10-111-1/+13
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* avoid the thread-ptr-init behavior of sigaction when not installing handlerRich Felker2012-10-111-1/+2
| | | | | | this is necessary because posix_spawn calls sigaction after vfork, and if the thread pointer is not already initialized, initializing it in the child corrupts the parent process's state.
* i386 vsyscall support (vdso-provided sysenter/syscall instruction based)Rich Felker2012-10-113-16/+62
| | | | | | this doubles the performance of the fastest syscalls on the atom I tested it on; improvement is reportedly much more dramatic on worst-case cpus. cannot be used for cancellable syscalls.
* ensure that buffer for decoding auxv at startup is initially zeroRich Felker2012-10-081-1/+1
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* clean up and refactor program initializationRich Felker2012-10-076-34/+33
| | | | | | | | | | | | | | | the code in __libc_start_main is now responsible for parsing auxv, rather than duplicating the parsing all over the place. this should shave off a few cycles and some code size. __init_libc is left as an external-linkage function despite the fact that it could be static, to prevent it from being inlined and permanently wasting stack space when main is called. a few other minor changes are included, like eliminating per-thread ssp canaries (they were likely broken when combined with certain dlopen usages, and completely unnecessary) and some other unnecessary checks. since this code gets linked into every program, it should be as small and simple as possible.
* fix breakage due to initializing thread pointer when loading libsRich Felker2012-10-071-1/+1
| | | | | | at initial program load, all libraries must be loaded before the thread pointer can be setup, since the TP-relative addresses of all initial TLS objects must be constant.
* make new TLS setup block even implementation-internals signalsRich Felker2012-10-061-2/+1
| | | | | | | | | | this is needed to ensure async-cancel-safety, i.e. to make it safe to access TLS objects when async cancellation is enabled. otherwise, if cancellation were acter upon after the atomic fetch/add but before the thread saved the obtained memory, another access to the same TLS in the cancellation handler could end up performing the atomic fetch/add again, consuming more memory than is actually available and overflowing into other objects on the heap.
* don't crash if TLS library is loaded into process with no thread pointerRich Felker2012-10-061-0/+5
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* fix buggy TLS size/alignment computations in static-linked TLSRich Felker2012-10-061-5/+22
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* fix symbol acceptance/rejection rules for TLSRich Felker2012-10-061-8/+14
| | | | | | | | symbol value of 0 is not "undefined" for TLS; it's the address of the first symbol in the TLS segment. however, non-definition TLS references also have values of 0, so check the section. hopefully the new logic is more clear, too.
* TLS fixes, mainly alignment handlingRich Felker2012-10-061-39/+48
| | | | | | | | | | | | | compute offsets from the thread pointer statically when loading the library, rather than repeating the logic on each thread creation. not only is the latter less efficient at runtime; it also fails to provide solid guarantees that the offsets will remain the same when the initial alignment of memory is different. the new alignment handling is both more rigorous and simpler. the old code was also clobbering TLS bss with random image data in some cases due to using tls_size (size of TLS segment) instead of tls_len (length of the TLS data image).
* fix/improve shared library ctor/dtor handling, allow recursive dlopenRich Felker2012-10-051-7/+29
| | | | | | | | | | | | | | | | | | | | some libraries call dlopen from their constructors, resulting in recursive calls to dlopen. previously, this resulted in deadlock. I'm now unlocking the dlopen lock before running constructors (this is especially important since the lock also blocked pthread_create and was being held while application code runs!) and using a separate recursive mutex protecting the ctor/dtor state instead. in order to prevent the same ctor from being called more than once, a module is considered "constructed" just before the ctor runs. also, switch from using atexit to register each dtor to using a single atexit call to register the dynamic linker's dtor processing as just one handler. this is necessary because atexit performs allocation and may fail, but the library has already been loaded and cannot be backed-out at the time dtor registration is performed. this change also ensures that all dtors run after all atexit functions, rather than in mixed order.
* small dynamic linker module search fixRich Felker2012-10-051-1/+2
| | | | | | libraries loaded more than once by pathname should not get shortnames that would cause them to later be used to satisfy non-pathname load requests.
* support for TLS in dynamic-loaded (dlopen) modulesRich Felker2012-10-057-47/+115
| | | | | | | | | | | | | | | | | | | | | unlike other implementations, this one reserves memory for new TLS in all pre-existing threads at dlopen-time, and dlopen will fail with no resources consumed and no new libraries loaded if memory is not available. memory is not immediately distributed to running threads; that would be too complex and too costly. instead, assurances are made that threads needing the new TLS can obtain it in an async-signal-safe way from a buffer belonging to the dynamic linker/new module (via atomic fetch-and-add based allocator). I've re-appropriated the lock that was previously used for __synccall (synchronizing set*id() syscalls between threads) as a general pthread_create lock. it's a "backwards" rwlock where the "read" operation is safe atomic modification of the live thread count, which multiple threads can perform at the same time, and the "write" operation is making sure the count does not increase during an operation that depends on it remaining bounded (__synccall or dlopen). in static-linked programs that don't use __synccall, this lock is a no-op and has no cost.
* fix race condition in dlopenRich Felker2012-10-051-1/+3
| | | | | orig_tail was being saved before the lock was obtained, allowing dlopen failure to roll-back other dlopens that had succeeded.
* dynamic-linked TLS support for everything but dlopen'd libsRich Felker2012-10-041-38/+58
| | | | | | | | currently, only i386 is tested. x86_64 and arm should probably work. the necessary relocation types for mips and microblaze have not been added because I don't understand how they're supposed to work, and I'm not even sure if it's defined yet on microblaze. I may be able to reverse engineer the requirements out of gcc/binutils output.
* remove freeing of dynamic linker data when dlopen/dlsym are not usedRich Felker2012-10-041-11/+0
| | | | | | | | | | | | | | | | this was an optimization to save/recover a minimal amount of extra memory for use by malloc, that's becoming increasingly costly to keep around. freeing this data: 1. breaks debugging with gdb (it can't find library symbols) 2. breaks thread-local storage in shared libraries it would be possible to disable freeing when TLS is used, but in addition to the above breakages, tracking whether dlopen/dlsym is used adds a cost to every symbol lookup, possibly making program startup slower for large programs. combined with the complexity, it's not worth it. we already save/recover plenty of memory in the dynamic linker with reclaim_gaps.
* beginnings of full TLS support in shared librariesRich Felker2012-10-044-1/+19
| | | | | | this code will not work yet because the necessary relocations are not supported, and cannot be supported without some internal changes to how relocation processing works (coming soon).
* partial TLS support for dynamic-linked programsRich Felker2012-10-042-27/+77
| | | | | only TLS in the main program is supported so far; TLS defined in shared libraries will not work yet.
* TLS (GNU/C11 thread-local storage) support for static-linked programsRich Felker2012-10-046-14/+117
| | | | | | | | | | | | | the design for TLS in dynamic-linked programs is mostly complete too, but I have not yet implemented it. cost is nonzero but still low for programs which do not use TLS and/or do not use threads (a few hundred bytes of new code, plus dependency on memcpy). i believe it can be made smaller at some point by merging __init_tls and __init_security into __libc_start_main and avoiding duplicate auxv-parsing code. at the same time, I've also slightly changed the logic pthread_create uses to allocate guard pages to ensure that guard pages are not counted towards commit charge.
* add getopt reset supportRich Felker2012-09-302-2/+18
| | | | | | | based on proposed patches by Daniel Cegiełka, with minor changes: - use a weak symbol for optreset so it doesn't clash with namespace - also reset optpos (position in multi-option arg like -lR) - also make getopt_long support reset
* protect sem_open against cancellationRich Felker2012-09-301-13/+19
| | | | | also fix one minor bug: failure to free the early-reserved slot when the semaphore later found to already be mapped.
* overhaul sem_openRich Felker2012-09-302-108/+99
| | | | | | | | | | | this function was overly complicated and not even obviously correct. avoid using openat/linkat just like in shm_open, and instead expand pathname using code shared with shm_open. remove bogus (and dangerous, with priorities) use of spinlocks. this commit also heavily streamlines the code and ensures there are no failure cases that can happen after a new semaphore has been created in the filesystem, since that case is unreportable.
* clean up, bugfixes, and general improvement for shm_open/shm_unlinkRich Felker2012-09-302-30/+28
| | | | | | | 1. don't make non-cloexec file descriptors 2. cancellation safety (cleanup handlers were missing, now unneeded) 3. share name validation/mapping code between open/unlink functions 4. avoid wasteful/slow syscalls