1. 27 4月, 2013 4 次提交
    • R
      use atomic decrement rather than cas in pthread_exit thread count · c3a6839c
      Rich Felker 提交于
      now that blocking signals prevents any application code from running
      while the last thread is exiting, the cas logic is no longer needed to
      prevent decrementing below zero.
      c3a6839c
    • R
      add comments on some of the pthread_exit logic · 6e531f99
      Rich Felker 提交于
      6e531f99
    • R
      always block signals in pthread_exit before decrementing thread count · 23f21c30
      Rich Felker 提交于
      the thread count (1+libc.threads_minus_1) must always be greater than
      or equal to the number of threads which could have application code
      running, even in an async-signal-safe sense. there is at least one
      dangerous race condition if this invariant fails to hold: dlopen could
      allocate too little TLS for existing threads, and a signal handler
      running in the exiting thread could claim the allocated TLS for itself
      (via __tls_get_addr), leaving too little for the other threads it was
      allocated for and thereby causing out-of-bounds access.
      
      there may be other situations where it's dangerous for the thread
      count to be too low, particularly in the case where only one thread
      should be left, in which case locking may be omitted. however, all
      such code paths seem to arise from undefined behavior, since
      async-signal-unsafe functions are not permitted to be called from a
      signal handler that interrupts pthread_exit (which is itself
      async-signal-unsafe).
      
      this change may also simplify logic in __synccall and improve the
      chances of making __synccall async-signal-safe.
      23f21c30
    • R
      remove explicit locking to prevent __synccall setuid during posix_spawn · a0473a0c
      Rich Felker 提交于
      for the duration of the vm-sharing clone used by posix_spawn, all
      signals are blocked in the parent process, including
      implementation-internal signals. since __synccall cannot do anything
      until successfully signaling all threads, the fact that signals are
      blocked automatically yields the necessary safety.
      
      aside from debloating and general simplification, part of the
      motivation for removing the explicit lock is to simplify the
      synchronization logic of __synccall in hopes that it can be made
      async-signal-safe, which is needed to make setuid and setgid, which
      depend on __synccall, conform to the standard. whether this will be
      possible remains to be seen.
      a0473a0c
  2. 23 4月, 2013 1 次提交
  3. 22 4月, 2013 1 次提交
  4. 21 4月, 2013 4 次提交
  5. 20 4月, 2013 1 次提交
    • R
      make dynamic linker accept : or \n as path separator · 8c203eae
      Rich Felker 提交于
      this allows /etc/ld-musl-$(ARCH).path to contain one path per line,
      which is much more convenient for users than the :-delimited format,
      which was a source of repeated and unnecessary confusion. for
      simplicity, \n is also accepted in environment variables, though it
      should probably not be used there.
      
      at the same time, issues with overly long paths invoking UB or getting
      truncated have been fixed. such issues should not have arisen with the
      environment (which is size-limited) but could have been generated by a
      path file larger than 2**31 bytes in length.
      8c203eae
  6. 14 4月, 2013 1 次提交
  7. 11 4月, 2013 1 次提交
    • R
      make ifaddrs.h expose sys/socket.h · 4ba3ebdc
      Rich Felker 提交于
      the getifaddrs interface seems to have been invented by glibc, and
      they expose socket.h, so for us not to do so is just gratuitous
      incompatibility with the interface we're mimicing.
      4ba3ebdc
  8. 09 4月, 2013 5 次提交
    • R
      getifaddrs: implement proper ipv6 netmasks · 9947ed5c
      rofl0r 提交于
      9947ed5c
    • R
      mbrtowc: do not leave mbstate_t in permanent-fail state after EILSEQ · 23ab8c25
      Rich Felker 提交于
      the standard is clear that the old behavior is conforming: "In this
      case, [EILSEQ] shall be stored in errno and the conversion state is
      undefined."
      
      however, the specification of mbrtowc has one peculiarity when the
      source argument is a null pointer: in this case, it's required to
      behave as mbrtowc(NULL, "", 1, ps). no motivation is provided for this
      requirement, but the natural one that comes to mind is that the intent
      is to reset the mbstate_t object. for stateful encodings, such
      behavior is actually specified: "If the corresponding wide character
      is the null wide character, the resulting state described shall be the
      initial conversion state." but in the case of UTF-8 where the
      mbstate_t object contains a partially-decoded character rather than a
      shift state, a subsequent '\0' byte indicates that the previous
      partial character is incomplete and thus an illegal sequence.
      
      naturally, applications using their own mbstate_t object should clear
      it themselves after an error, but the standard presently provides no
      way to clear the builtin mbstate_t object used when the ps argument is
      a null pointer. I suspect this issue may be addressed in the future by
      specifying that a null source argument resets the state, as this seems
      to have been the intent all along.
      
      for what it's worth, this change also slightly reduces code size.
      23ab8c25
    • R
      implement mbtowc directly, not as a wrapper for mbrtowc · ea34b1b9
      Rich Felker 提交于
      the interface contract for mbtowc admits a much faster implementation
      than mbrtowc can achieve; wrapping mbrtowc with an extra call frame
      only made the situation worse.
      
      since the regex implementation uses mbtowc already, this change should
      improve regex performance too. it may be possible to improve
      performance in other places internally by switching from mbrtowc to
      mbtowc.
      ea34b1b9
    • R
      optimize mbrtowc · a49e038b
      Rich Felker 提交于
      this simple change, in my measurements, makes about a 7% performance
      improvement. at first glance this change would seem like a
      compiler-specific hack, since the modified code is not even used.
      however, I suspect the reason is that I'm eliminating a second path
      into the main body of the code, allowing the compiler more flexibility
      to optimize the normal (hot) path into the main body. so even if it
      weren't for the measurable (and quite notable) difference in
      performance, I think the change makes sense.
      a49e038b
    • R
      fix out-of-bounds access in UTF-8 decoding · 8f06ab0e
      Rich Felker 提交于
      SA and SB are used as the lowest and highest valid starter bytes, but
      the value of SB was one-past the last valid starter. this caused
      access past the end of the state table when the illegal byte '\xf5'
      was encountered in a starter position. the error did not show up in
      full-character decoding tests, since the bogus state read from just
      past the table was unlikely to admit any continuation bytes as valid,
      but would have shown up had we tested feeding '\xf5' to the
      byte-at-a-time decoding in mbrtowc: it would cause the funtion to
      wrongly return -2 rather than -1.
      
      I may eventually go back and remove all references to SA and SB,
      replacing them with the values; this would make the code more
      transparent, I think. the original motivation for using macros was to
      allow misguided users of the code to redefine them for the purpose of
      enlarging the set of accepted sequences past the end of Unicode...
      8f06ab0e
  9. 08 4月, 2013 1 次提交
    • R
      fix signalfd not to ignore flags · bcd93025
      Rich Felker 提交于
      also include fallback code for broken kernels that don't support the
      flags. as usual, the fallback has a race condition that can leak file
      descriptors.
      bcd93025
  10. 07 4月, 2013 3 次提交
  11. 06 4月, 2013 9 次提交
  12. 05 4月, 2013 9 次提交