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* system is a cancellation pointRich Felker2012-10-281-0/+3
| | | | | | | | | | ideally, system would also be cancellable while running the external command, but I cannot find any way to make that work without either leaking zombie processes or introducing behavior that is far outside what the standard specifies. glibc handles cancellation by killing the child process with SIGKILL, but this could be unsafe in that it could leave the data being manipulated by the command in an inconsistent state.
* fix usage of locks with vforkRich Felker2012-10-192-2/+3
| | | | | | __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 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 Felker2012-10-182-29/+49
| | | | | | | | | | | | | | | | 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.
* 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.
* use vfork if possible in posix_spawnRich Felker2012-09-141-1/+3
| | | | | | vfork is implemented as the fork syscall (with no atfork handlers run) on archs where it is not available, so this change does not introduce any change in behavior or regression for such archs.
* use restrict everywhere it's required by c99 and/or posix 2008Rich Felker2012-09-069-18/+18
| | | | | | | | to deal with the fact that the public headers may be used with pre-c99 compilers, __restrict is used in place of restrict, and defined appropriately for any supported compiler. we also avoid the form [restrict] since older versions of gcc rejected it due to a bug in the original c99 standard, and instead use the form *restrict.
* x86_64 vfork implementationRich Felker2012-02-061-0/+12
| | | | untested; should work.
* support vfork on i386Rich Felker2011-10-141-0/+14
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* make available a namespace-safe vfork, if supportedRich Felker2011-10-141-1/+4
| | | | this may be useful to posix_spawn..?
* fix various bugs in path and error handling in execvp/fexecveRich Felker2011-09-292-18/+29
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* fix various errors in function signatures/prototypes found by nszRich Felker2011-09-132-5/+8
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* add missing posix_spawnattr_init/destroy functionsRich Felker2011-09-132-0/+13
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* use weak aliases rather than function pointers to simplify some codeRich Felker2011-08-061-2/+8
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* ensure in fork that child gets its own new robust mutex listRich Felker2011-07-161-0/+1
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* fix backwards posix_spawn file action orderRich Felker2011-05-295-6/+10
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* add accidentally-omitted file needed for posix_spawn file actionsRich Felker2011-05-281-0/+10
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* add file actions support to posix_spawnRich Felker2011-05-285-2/+85
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* posix_spawn: honor POSIX_SPAWN_SETSIGDEF flagRich Felker2011-05-281-1/+3
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* initial implementation of posix_spawnRich Felker2011-05-2812-0/+151
| | | | | file actions are not yet implemented, but everything else should be mostly complete and roughly correct.
* correct variadic prototypes for execl* familyRich Felker2011-04-273-15/+18
| | | | | the old versions worked, but conflicted with programs which declared their own prototypes and generated warnings with some versions of gcc.
* fix minor bugs due to incorrect threaded-predicate semanticsRich Felker2011-04-201-1/+2
| | | | | | | | | | | | some functions that should have been testing whether pthread_self() had been called and initialized the thread pointer were instead testing whether pthread_create() had been called and actually made the program "threaded". while it's unlikely any mismatch would occur in real-world problems, this could have introduced subtle bugs. now, we store the address of the main thread's thread descriptor in the libc structure and use its presence as a flag that the thread register is initialized. note that after fork, the calling thread (not necessarily the original main thread) is the new main thread.
* clean up handling of thread/nothread mode, lockingRich Felker2011-04-171-1/+1
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* overhaul pthread cancellationRich Felker2011-04-172-12/+2
| | | | | | | | | | | | | | | | | | | | | | this patch improves the correctness, simplicity, and size of cancellation-related code. modulo any small errors, it should now be completely conformant, safe, and resource-leak free. the notion of entering and exiting cancellation-point context has been completely eliminated and replaced with alternative syscall assembly code for cancellable syscalls. the assembly is responsible for setting up execution context information (stack pointer and address of the syscall instruction) which the cancellation signal handler can use to determine whether the interrupted code was in a cancellable state. these changes eliminate race conditions in the previous generation of cancellation handling code (whereby a cancellation request received just prior to the syscall would not be processed, leaving the syscall to block, potentially indefinitely), and remedy an issue where non-cancellable syscalls made from signal handlers became cancellable if the signal handler interrupted a cancellation point. x86_64 asm is untested and may need a second try to get it right.
* speed up threaded forkRich Felker2011-04-121-2/+1
| | | | | | after fork, we have a new process and the pid is equal to the tid of the new main thread. there is no need to make two separate syscalls to obtain the same number.
* overhaul cancellation to fix resource leaks and dangerous behavior with signalsRich Felker2011-03-242-2/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | this commit addresses two issues: 1. a race condition, whereby a cancellation request occurring after a syscall returned from kernelspace but before the subsequent CANCELPT_END would cause cancellable resource-allocating syscalls (like open) to leak resources. 2. signal handlers invoked while the thread was blocked at a cancellation point behaved as if asynchronous cancellation mode wer in effect, resulting in potentially dangerous state corruption if a cancellation request occurs. the glibc/nptl implementation of threads shares both of these issues. with this commit, both are fixed. however, cancellation points encountered in a signal handler will not be acted upon if the signal was received while the thread was already at a cancellation point. they will of course be acted upon after the signal handler returns, so in real-world usage where signal handlers quickly return, it should not be a problem. it's possible to solve this problem too by having sigaction() wrap all signal handlers with a function that uses a pthread_cleanup handler to catch cancellation, patch up the saved context, and return into the cancellable function that will catch and act upon the cancellation. however that would be a lot of complexity for minimal if any benefit...
* global cleanup to use the new syscall interfaceRich Felker2011-03-205-7/+7
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* make fork properly initialize the main thread in the child processRich Felker2011-03-091-0/+7
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* implement fexecveRich Felker2011-02-271-0/+10
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* add pthread_atfork interfaceRich Felker2011-02-181-3/+6
| | | | | | | | | note that this presently does not handle consistency of the libc's own global state during forking. as per POSIX 2008, if the parent process was threaded, the child process may only call async-signal-safe functions until one of the exec-family functions is called, so the current behavior is believed to be conformant even if non-ideal. it may be improved at some later time.
* initial check-in, version 0.5.0 v0.5.0Rich Felker2011-02-1212-0/+194