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* add support for powerpc/powerpc64 unaligned relocationsSamuel Holland2019-08-111-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | R_PPC_UADDR32 (R_PPC64_UADDR64) has the same meaning as R_PPC_ADDR32 (R_PPC64_ADDR64), except that its address need not be aligned. For powerpc64, BFD ld(1) will automatically convert between ADDR<->UADDR relocations when the address is/isn't at its native alignment. This will happen if, for example, there is a pointer in a packed struct. gold and lld do not currently generate R_PPC64_UADDR64, but pass through misaligned R_PPC64_ADDR64 relocations from object files, possibly relaxing them to misaligned R_PPC64_RELATIVE. In both cases (relaxed or not) this violates the PSABI, which defines the relevant field type as "a 64-bit field occupying 8 bytes, the alignment of which is 8 bytes unless otherwise specified." All three linkers violate the PSABI on 32-bit powerpc, where the only difference is that the field is 32 bits wide, aligned to 4 bytes. Currently musl fails to load executables linked by BFD ld containing R_PPC64_UADDR64, with the error "unsupported relocation type 43". This change provides compatibility with BFD ld on powerpc64, and any static linker on either architecture that starts following the PSABI more closely.
* ioctl: add fallback for new time64 SIOCGSTAMP[NS]Rich Felker2019-07-311-0/+7
| | | | | | | | | | | without this, the SIOCGSTAMP and SIOCGSTAMPNS ioctl commands, for obtaining timestamps, would stop working on pre-5.1 kernels after time_t is switched to 64-bit and their values are changed to the new time64 versions. new code is written such that it's statically unreachable on 64-bit archs, and on existing 32-bit archs until the macro values are changed to activate 64-bit time_t.
* get/setsockopt: add fallback for new time64 SO_RCVTIMEO/SO_SNDTIMEORich Felker2019-07-311-0/+7
| | | | | | | | | | without this, the SO_RCVTIMEO and SO_SNDTIMEO socket options would stop working on pre-5.1 kernels after time_t is switched to 64-bit and their values are changed to the new time64 versions. new code is written such that it's statically unreachable on 64-bit archs, and on existing 32-bit archs until the macro values are changed to activate 64-bit time_t.
* make __socketcall analogous to __syscall, error-returningRich Felker2019-07-311-6/+6
| | | | | | | | | | | the __socketcall and __socketcall_cp macros are remnants from a really old version of the syscall-mechanism infrastructure, and don't follow the pattern that the "__" version of the macro returns the raw negated error number rather than setting errno and returning -1. for time64 purposes, some socket syscalls will need to operate on the error value rather than returning immediately, so fix this up so they can use it.
* internally, define plain syscalls, if missing, as their time64 variantsRich Felker2019-07-271-0/+83
| | | | | | | | | | | | | this commit has no effect whatsoever right now, but is in preparation for a future riscv32 port and other future 32-bit archs that will be "time64-only" from the start on the kernel side. together with the previous x32 changes, this commit ensures that syscall call points that don't care about time (passing null timeouts, etc.) can continue to do so without having to special-case time64-only archs, and allows code using the time64 syscalls to uniformly test for the need to fallback with SYS_foo != SYS_foo_time64, rather than needing to check defined(SYS_foo) && SYS_foo != SYS_foo_time64.
* do not use _Noreturn for a function pointer in dynamic linkerMatthew Maurer2019-06-211-1/+1
| | | | | _Noreturn is a C11 construct, and may only be used at the site of a function definition.
* allow archs to provide a 7-argument syscall if neededRich Felker2019-05-051-0/+1
| | | | | | | | commit 788d5e24ca19c6291cebd8d1ad5b5ed6abf42665 noted that we could add this if needed, and in fact it is needed, but not for one of the archs documented as having a 7th syscall arg register. rather, it's needed for mips (o32), where all but the first 4 arguments are passed on the stack, and the stack can accommodate a 7th.
* make new math code compatible with unused variable warning/errorRich Felker2019-04-201-3/+6
| | | | | | | | | | | | | | | | commit b50d315fd23f0fbc4c11e2583801dd123d933745 introduced fp_force_eval implemented by default with a dead store to a volatile variable. unfortunately introduces warnings with -Wunused-variable and breaks the ability to use -Werror with the default warning options set by configure when warnings are enabled. we could just call fp_barrier instead, but that results in a spurious load after the store due to volatile semantics. the fix committed here avoids the load. it will still produce warnings without -Wno-unused-but-set-variable, but that's part of our default warning profile, and there are already other locations in the source where an unused variable warning will occur without it.
* math: new powSzabolcs Nagy2019-04-171-0/+1
| | | | | | | | | | | | | | | | | | from https://github.com/ARM-software/optimized-routines, commit 04884bd04eac4b251da4026900010ea7d8850edc The underflow exception is signaled if the result is in the subnormal range even if the result is exact. code size change: +3421 bytes. benchmark on x86_64 before, after, speedup: -Os: pow rthruput: 102.96 ns/call 33.38 ns/call 3.08x pow latency: 144.37 ns/call 54.75 ns/call 2.64x -O3: pow rthruput: 98.91 ns/call 32.79 ns/call 3.02x pow latency: 138.74 ns/call 53.78 ns/call 2.58x
* math: new powfSzabolcs Nagy2019-04-171-0/+6
| | | | | | | | | | | | | | | | | | | | | from https://github.com/ARM-software/optimized-routines, commit 04884bd04eac4b251da4026900010ea7d8850edc POWF_SCALE != 1.0 case only matters if TOINT_INTRINSICS is set, which is currently not supported for any target. SNaN is not supported, it would require an issignalingf implementation. code size change: -816 bytes. benchmark on x86_64 before, after, speedup: -Os: powf rthruput: 95.14 ns/call 20.04 ns/call 4.75x powf latency: 137.00 ns/call 34.98 ns/call 3.92x -O3: powf rthruput: 92.48 ns/call 13.67 ns/call 6.77x powf latency: 131.11 ns/call 35.15 ns/call 3.73x
* math: new exp2f and expfSzabolcs Nagy2019-04-171-0/+16
| | | | | | | | | | | | | | | | | | | | | | from https://github.com/ARM-software/optimized-routines, commit 04884bd04eac4b251da4026900010ea7d8850edc In expf TOINT_INTRINSICS is kept, but is unused, it would require support for __builtin_round and __builtin_lround as single instruction. code size change: +94 bytes. benchmark on x86_64 before, after, speedup: -Os: expf rthruput: 9.19 ns/call 8.11 ns/call 1.13x expf latency: 34.19 ns/call 18.77 ns/call 1.82x exp2f rthruput: 5.59 ns/call 6.52 ns/call 0.86x exp2f latency: 17.93 ns/call 16.70 ns/call 1.07x -O3: expf rthruput: 9.12 ns/call 4.92 ns/call 1.85x expf latency: 34.44 ns/call 18.99 ns/call 1.81x exp2f rthruput: 5.58 ns/call 4.49 ns/call 1.24x exp2f latency: 17.95 ns/call 16.94 ns/call 1.06x
* math: add configuration macrosSzabolcs Nagy2019-04-171-0/+5
| | | | | | | Musl currently aims to support non-nearest rounding mode and does not support SNaNs. These macros allow marking relevant code paths in case these decisions are changed later (they also help documenting the corner cases involved).
* math: add macros for static branch prediction hintsSzabolcs Nagy2019-04-171-0/+9
| | | | | | | | These don't have an effectw with -Os so not useful with default settings other than documenting the expectation. With --enable-optimize=internal,malloc,string,math the libc.so code size increases by 18K on x86_64 and performance varies in -2% .. +10%.
* math: add double precision error handling functionsSzabolcs Nagy2019-04-171-0/+5
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* math: add single precision error handling functionsSzabolcs Nagy2019-04-171-0/+7
| | | | | | | | | | These are supposed to be used in tail call positions when handling special cases in new code. (fp exceptions may be raised "naturally" by the common code path if special casing is more effort.) This implements the error handling apis used in https://github.com/ARM-software/optimized-routines without errno setting.
* math: add eval_as_float and eval_as_doubleSzabolcs Nagy2019-04-171-0/+17
| | | | | | | | | | | | | | | | | | Previously type casts or assignments were used for handling excess precision, which assumed standard C99 semantics, but since it's a rarely needed obscure detail, it's better to use explicit helper functions to document where we rely on this. It also helps if the code is used outside of the libc in non-C99 compilation mode: with the default excess precision handling of gcc, explicit inline asm barriers are needed for narrowing on FLT_EVAL_METHOD!=0 targets. I plan to use this in new code with the existing style that uses double_t and float_t as much as possible. One ugliness is that it is required for almost every return statement since that does not drop excess precision (the standard changed this in C11 annex F, but that does not help in non-standard compilation modes or with old compilers).
* math: add fp_arch.h with fp_barrier and fp_force_evalSzabolcs Nagy2019-04-171-6/+65
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | C99 has ways to support fenv access, but compilers don't implement it and assume nearest rounding mode and no fp status flag access. (gcc has -frounding-math and then it does not assume nearest rounding mode, but it still assumes the compiled code itself does not change the mode. Even if the C99 mechanism was implemented it is not ideal: it requires all code in the library to be compiled with FENV_ACCESS "on" to make it usable in non-nearest rounding mode, but that limits optimizations more than necessary.) The math functions should give reasonable results in all rounding modes (but the quality may be degraded in non-nearest rounding modes) and the fp status flag settings should follow the spec, so fenv side-effects are important and code transformations that break them should be prevented. Unfortunately compilers don't give any help with this, the best we can do is to add fp barriers to the code using volatile local variables (they create a stack frame and undesirable memory accesses to it) or inline asm (gcc specific, requires target specific fp reg constraints, often creates unnecessary reg moves and multiple barriers are needed to express that an operation has side-effects) or extern call (only useful in tail-call position to avoid stack-frame creation and does not work with lto). We assume that in a math function if an operation depends on the input and the output depends on it, then the operation will be evaluated at runtime when the function is called, producing all the expected fenv side-effects (this is not true in case of lto and in case the operation is evaluated with excess precision that is not rounded away). So fp barriers are needed (1) to prevent the move of an operation within a function (in case it may be moved from an unevaluated code path into an evaluated one or if it may be moved across a fenv access), (2) force the evaluation of an operation for its side-effect when it has no input dependency (may be constant folded) or (3) when its output is unused. I belive that fp_barrier and fp_force_eval can take care of these and they should not be needed in hot code paths.
* math: remove sun copyright from libm.hSzabolcs Nagy2019-04-171-23/+0
| | | | | | | Nothing is left from the original fdlibm header nor from the bsd modifications to it other than some internal api declarations. Comments are dropped that may be copyrightable content.
* math: add asuint, asuint64, asfloat and asdoubleSzabolcs Nagy2019-04-171-33/+15
| | | | | Code generation for SET_HIGH_WORD slightly changes, but it only affects pow, otherwise the generated code is unchanged.
* math: move complex math out of libm.hSzabolcs Nagy2019-04-172-15/+22
| | | | | | This makes it easier to build musl math code with a compiler that does not support complex types (tcc) and in general more sensible factorization of the internal headers.
* remove external __syscall function and last remaining usersRich Felker2019-04-1017-263/+1
| | | | | | | | | | | | | | the weak version of __syscall_cp_c was using a tail call to __syscall to avoid duplicating the 6-argument syscall code inline in small static-linked programs, but now that __syscall no longer exists, the inline expansion is no longer duplication. the syscall.h machinery suppported up to 7 syscall arguments, only via an external __syscall function, but we presently have no syscall call points that actually make use of that many, and the kernel only defines 7-argument calling conventions for arm, powerpc (32-bit), and sh. if it turns out we need them in the future, they can easily be added.
* overhaul i386 syscall mechanism not to depend on external asm sourceRich Felker2019-04-104-70/+24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | this is the first part of a series of patches intended to make __syscall fully self-contained in the object file produced using syscall.h, which will make it possible for crt1 code to perform syscalls. the (confusingly named) i386 __vsyscall mechanism, which this commit removes, was introduced before the presence of a valid thread pointer was mandatory; back then the thread pointer was setup lazily only if threads were used. the intent was to be able to perform syscalls using the kernel's fast entry point in the VDSO, which can use the sysenter (Intel) or syscall (AMD) instruction instead of int $128, but without inlining an access to the __syscall global at the point of each syscall, which would incur a significant size cost from PIC setup everywhere. the mechanism also shuffled registers/calling convention around to avoid spills of call-saved registers, and to avoid allocating ebx or ebp via asm constraints, since there are plenty of broken-but-supported compiler versions which are incapable of allocating ebx with -fPIC or ebp with -fno-omit-frame-pointer. the new mechanism preserves the properties of avoiding spills and avoiding allocation of ebx/ebp in constraints, but does it inline, using some fairly simple register shuffling, and uses a field of the thread structure rather than global data for the vdso-provided syscall code address. for now, the external __syscall function is refactored not to use the old __vsyscall so it can be kept, but the intent is to remove it too.
* fix crash/out-of-bound read in sscanfRich Felker2019-03-142-2/+3
| | | | | | | | | | | | | | | | | | | | | commit d6c855caa88ddb1ab6e24e23a14b1e7baf4ba9c7 caused this "regression", though the behavior was undefined before, overlooking that f->shend=0 was being used as a sentinel for "EOF" status (actual EOF or hitting the scanf field width) of the stream helper (shgetc) functions. obviously the shgetc macro could be adjusted to check for a null pointer in addition to the != comparison, but it's the hot path, and adding extra code/branches to it begins to defeat the purpose. so instead of setting shend to a null pointer to block further reads, which no longer works, set it to the current position (rpos). this makes the shgetc macro work with no change, but it breaks shunget, which can no longer look at the value of shend to determine whether to back up. Szabolcs Nagy suggested a solution which I'm using here: setting shlim to a negative value is inexpensive to test at shunget time, and automatically re-trips the cnt>=shlim stop condition in __shgetc no matter what the original limit was.
* add membarrier syscall wrapper, refactor dynamic tls install to use itRich Felker2019-02-221-1/+1
| | | | | | | | | | the motivation for this change is twofold. first, it gets the fallback logic out of the dynamic linker, improving code readability and organization. second, it provides application code that wants to use the membarrier syscall, which depends on preregistration of intent before the process becomes multithreaded unless unbounded latency is acceptable, with a symbol that, when linked, ensures that this registration happens.
* install dynamic tls synchronously at dlopen, streamline accessRich Felker2019-02-181-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | previously, dynamic loading of new libraries with thread-local storage allocated the storage needed for all existing threads at load-time, precluding late failure that can't be handled, but left installation in existing threads to take place lazily on first access. this imposed an additional memory access and branch on every dynamic tls access, and imposed a requirement, which was not actually met, that the dynamic tlsdesc asm functions preserve all call-clobbered registers before calling C code to to install new dynamic tls on first access. the x86[_64] versions of this code wrongly omitted saving and restoring of fpu/vector registers, assuming the compiler would not generate anything using them in the called C code. the arm and aarch64 versions saved known existing registers, but failed to be future-proof against expansion of the register file. now that we track live threads in a list, it's possible to install the new dynamic tls for each thread at dlopen time. for the most part, synchronization is not needed, because if a thread has not synchronized with completion of the dlopen, there is no way it can meaningfully request access to a slot past the end of the old dtv, which remains valid for accessing slots which already existed. however, it is necessary to ensure that, if a thread sees its new dtv pointer, it sees correct pointers in each of the slots that existed prior to the dlopen. my understanding is that, on most real-world coherency architectures including all the ones we presently support, a built-in consume order guarantees this; however, don't rely on that. instead, the SYS_membarrier syscall is used to ensure that all threads see the stores to the slots of their new dtv prior to the installation of the new dtv. if it is not supported, the same is implemented in userspace via signals, using the same mechanism as __synccall. the __tls_get_addr function, variants, and dynamic tlsdesc asm functions are all updated to remove the fallback paths for claiming new dynamic tls, and are now all branch-free.
* rewrite __synccall in terms of global thread listRich Felker2019-02-161-1/+0
| | | | | | | | | | | | | | | | the __synccall mechanism provides stop-the-world synchronous execution of a callback in all threads of the process. it is used to implement multi-threaded setuid/setgid operations, since Linux lacks them at the kernel level, and for some other less-critical purposes. this change eliminates dependency on /proc/self/task to determine the set of live threads, which in addition to being an unwanted dependency and a potential point of resource-exhaustion failure, turned out to be inaccurate. test cases provided by Alexey Izbyshev showed that it could fail to reflect newly created threads. due to how the presignaling phase worked, this usually yielded a deadlock if hit, but in the worst case it could also result in threads being silently missed (allowed to continue running without executing the callback).
* track all live threads in an AS-safe, fully-consistent linked listRich Felker2019-02-151-4/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | the hard problem here is unlinking threads from a list when they exit without creating a window of inconsistency where the kernel task for a thread still exists and is still executing instructions in userspace, but is not reflected in the list. the magic solution here is getting rid of per-thread exit futex addresses (set_tid_address), and instead using the exit futex to unlock the global thread list. since pthread_join can no longer see the thread enter a detach_state of EXITED (which depended on the exit futex address pointing to the detach_state), it must now observe the unlocking of the thread list lock before it can unmap the joined thread and return. it doesn't actually have to take the lock. for this, a __tl_sync primitive is offered, with a signature that will allow it to be enhanced for quick return even under contention on the lock, if needed. for now, the exiting thread always performs a futex wake on its detach_state. a future change could optimize this out except when there is already a joiner waiting. initial/dynamic variants of detached state no longer need to be tracked separately, since the futex address is always set to the global list lock, not a thread-local address that could become invalid on detached thread exit. all detached threads, however, must perform a second sigprocmask syscall to block implementation-internal signals, since locking the thread list with them already blocked is not permissible. the arch-independent C version of __unmapself no longer needs to take a lock or setup its own futex address to release the lock, since it must necessarily be called with the thread list lock already held, guaranteeing exclusive access to the temporary stack. changes to libc.threads_minus_1 no longer need to be atomic, since they are guarded by the thread list lock. it is largely vestigial at this point, and can be replaced with a cheaper boolean indicating whether the process is multithreaded at some point in the future.
* always block signals for starting new threads, refactor start argsRich Felker2019-02-151-11/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | whether signals need to be blocked at thread start, and whether unblocking is necessary in the entry point function, has historically depended on intricacies of the cancellation design and on whether there are scheduling operations to perform on the new thread before its successful creation can be committed. future changes to track an AS-safe list of live threads will require signals to be blocked whenever changes are made to the list, so ... prior to commits b8742f32602add243ee2ce74d804015463726899 and 40bae2d32fd6f3ffea437fa745ad38a1fe77b27e, a signal mask for the entry function to restore was part of the pthread structure. it was removed to trim down the size of the structure, which both saved a small amount of stack space and improved code generation on archs where small immediate displacements are less costly than arbitrary ones, by limiting the range of offsets between the base of the thread structure, its members, and the thread pointer. these commits moved the saved mask to a special structure used only when special scheduling was needed, in which case the pthread_create caller and new thread had to synchronize with each other and could use this memory to pass a mask. this commit partially reverts the above two commits, but instead of putting the mask back in the pthread structure, it moves all "start argument" members out of the pthread structure, trimming it down further, and puts them in a separate structure passed on the new thread's stack. the code path for explicit scheduling of the new thread is also changed to synchronize with the calling thread in such a way to avoid spurious futex wakes.
* add __timedwait backend workaround for old kernels where futex EINTRsRich Felker2018-12-181-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | prior to linux 2.6.22, futex wait could fail with EINTR even for non-interrupting (SA_RESTART) signals. this was no problem provided the caller simply restarted the wait, but sem_[timed]wait is required by POSIX to return when interrupted by a signal. commit a113434cd68ce30642c4995b1caadcd084be6f09 introduced this behavior, and commit c0ed5a201b2bdb6d1896064bec0020c9973db0a1 reverted it based on a mistaken belief that it was not required. this belief stems from a bug in the specification: the description requires the function to return when interrupted, but the errors section marks EINTR as a "may fail" condition rather than a "shall fail" one. since there does seem to be significant value in the change made in commit c0ed5a201b2bdb6d1896064bec0020c9973db0a1, making it so that programs that call sem_wait without checking for EINTR don't silently make forward progress without obtaining the semaphore or treat it as a fatal error and abort, add a behind-the-scenes mechanism in the __timedwait backend to suppress EINTR in programs that have never installed interrupting signal handlers, and have sigaction track and report this state. this way the semaphore code is not cluttered by workarounds and can be updated (to be done in next commit) to reflect the high-level logic for conforming behavior. these changes are based loosely on a patch by Markus Wichmann, with the main changes being atomic update to flag object and moving the workaround from sem_timedwait to the __timedwait futex backend.
* remove volatile qualification from category pointers in __locale_structRich Felker2018-10-201-1/+1
| | | | | | | | | | commit 63c188ec42e76ff768e81f6b65b11c68fc43351e missed making this change when switching from atomics to locking for modification of the global locale, leaving access to locale structures unnecessarily burdened with the restrictions of volatile. the volatile qualification was originally added in commit 56fbaa3bbe73f12af2bfbbcf2adb196e6f9fe264.
* adapt setlocale to support possibility of failureRich Felker2018-10-201-0/+2
| | | | | | | introduce a new LOC_MAP_FAILED sentinel for errors, since null pointers for a category's locale map indicate the C locale. at this time, __get_locale does not fail, so there should be no functional change by this commit.
* adjust types in FILE struct to make line buffering check less expensiveRich Felker2018-10-181-4/+2
| | | | | | | | | | | | | | | | | the choice of signed char for lbf was a theoretically space-saving hack that was not helping, and was unwantedly expensive. while comparing bytes against a byte-sized member sounds easy, the trick here was that the byte to be compared was unsigned while the lbf member was signed, making it possible to set lbf negative to disable line buffering. however, this imposed a requirement to promote both operands, zero-extending one and sign-extending the other, in order to compare them. to fix this, repurpose the waiters count slot (unused since commit c21f750727515602a9e84f2a190ee8a0a2aeb2a1). while we're at it, switch mode (orientation) from signed char to int as well. this makes no semantic difference (its only possible values are -1, 0, and 1) but it might help on archs where byte access is awkward.
* optimize internal putc_unlocked macro used in putcRich Felker2018-10-181-1/+2
| | | | | | | | to check whether flush due to line buffering is needed, the int-type character argument must be truncated to unsigned char for comparison. if the original value is subsequently passed to __overflow, it must be preserved, adding to register pressure. since it doesn't matter, truncate all uses so the original value is no longer live.
* fix wrong result for putc variants due to operator precedenceRich Felker2018-10-181-1/+1
| | | | | | | the internal putc_unlocked macro was wrongly returning a meaningless boolean result rather than the written character or EOF. bug was found by reading (very surprising) asm.
* move stdio locking MAYBE_WAITERS definition to stdio_impl.hRich Felker2018-10-161-0/+2
| | | | don't repeat definition in two places.
* combine arch ABI's DTP_OFFSET into DTV pointersRich Felker2018-10-121-2/+3
| | | | | | | | | | | | | | | | | | | | | | as explained in commit 6ba5517a460c6c438f64d69464fdfc3269a4c91a, some archs use an offset (typicaly -0x8000) with their DTPOFF relocations, which __tls_get_addr needs to invert. on affected archs, which lack direct support for large immediates, this can cost multiple extra instructions in the hot path. instead, incorporate the DTP_OFFSET into the DTV entries. this means they are no longer valid pointers, so store them as an array of uintptr_t rather than void *; this also makes it easier to access slot 0 as a valid slot count. commit e75b16cf93ebbc1ce758d3ea6b2923e8b2457c68 left behind cruft in two places, __reset_tls and __tls_get_new, from back when it was possible to have uninitialized gap slots indicated by a null pointer in the DTV. since the concept of null pointer is no longer meaningful with an offset applied, remove this cruft. presently there are no archs with both TLSDESC and nonzero DTP_OFFSET, but the dynamic TLSDESC relocation code is also updated to apply an inverted offset to its offset field, so that the offset DTV would not impose a runtime cost in TLSDESC resolver functions.
* increase default thread stack/guard sizeRich Felker2018-09-181-2/+2
| | | | | | | | | | | | stack size default is increased from 80k to 128k. this coincides with Linux's hard-coded default stack for the main thread (128k is initially committed; growth beyond that up to ulimit is contingent on additional allocation succeeding) and GNU ld's default PT_GNU_STACK size for FDPIC, at least on sh. guard size default is increased from 4k to 8k to reduce the risk of guard page jumping on overflow, since use of just over 4k of stack is common (PATH_MAX buffers, etc.).
* limit the configurable default stack/guard size for threadsRich Felker2018-09-181-2/+5
| | | | | | | | | | limit to 8MB/1MB, repectively. since the defaults cannot be reduced once increased, excessively large settings would lead to an unrecoverably broken state. this change is in preparation to allow defaults to be increased via program headers at the linker level. creation of threads that really need larger sizes needs to be done with an explicit attribute.
* fix deletion of pthread tsd keys that still have non-null values storedRich Felker2018-09-181-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | 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.
* fix null pointer subtraction and comparison in stdioRich Felker2018-09-161-2/+2
| | | | | | | | | | | | | | | | | | | | 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.
* fix undefined behavior in strto* via FILE buffer pointer abuseRich Felker2018-09-152-8/+40
| | | | | | | | | | | | | | | | | | | | | | | | | | | | 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.
* fix regression with compilers not incorporating C99 DR#289 resolutionRich Felker2018-09-131-1/+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.
* remove vis.h protected-visibility hackRich Felker2018-09-121-27/+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.
* split internal lock API out of libc.h, creating lock.hRich Felker2018-09-122-6/+9
| | | | | | | | | 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.
* move misplaced __fork_handler declarationRich Felker2018-09-122-1/+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.
* remove spurious inclusion of libc.h for LFS64 ABI aliasesRich Felker2018-09-121-6/+0
| | | | | | 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.
* reduce spurious inclusion of libc.hRich Felker2018-09-127-8/+7
| | | | | | | | | | | | | | | | | | | | | 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.
* remove unused __futex function and source fileRich Felker2018-09-121-2/+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.
* declare and make hidden additional internal init/exit symbolsRich Felker2018-09-121-0/+4
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* declare and make hidden additional internal stdio symbolsRich Felker2018-09-121-0/+5
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