path: root/src/thread
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2016-06-30pthread: implement try/timed join variantsBobby Bingham-3/+17
2016-06-27fix failure to obtain EOWNERDEAD status for process-shared robust mutexesRich Felker-3/+3
Linux's documentation (robust-futex-ABI.txt) claims that, when a process dies with a futex on the robust list, bit 30 (0x40000000) is set to indicate the status. however, what actually happens is that bits 0-30 are replaced with the value 0x40000000, i.e. bits 0-29 (containing the old owner tid) are cleared at the same time bit 30 is set. our userspace-side code for robust mutexes was written based on that documentation, assuming that kernel would never produce a futex value of 0x40000000, since the low (owner) bits would always be non-zero. commit d338b506e39b1e2c68366b12be90704c635602ce introduced this assumption explicitly while fixing another bug in how non-recoverable status for robust mutexes was tracked. presumably the tests conducted at that time only checked non-process-shared robust mutexes, which are handled in pthread_exit (which implemented the documented kernel protocol, not the actual one) rather than by the kernel. change pthread_exit robust list processing to match the kernel behavior, clearing bits 0-29 while setting bit 30, and use the value 0x7fffffff instead of 0x40000000 to encode non-recoverable status. the choice of value here is arbitrary; any value with at least one of bits 0-29 set should work just as well,
2016-05-08add powerpc64 portBobby Bingham-0/+101
2016-04-25fix thread structure/dtv-pointer corruption on powerpcRich Felker-0/+5
per the powerpc psabi, offset 4 of the stack at call time belongs to the callee and is used for spilling lr (return address). in addition, offset 0 on the stack must contain a pointer to the previous stack frame, or a null pointer for the initial stack frame of a thread. __clone failed to setup any stack frame on the new thread's stack, thereby allowing the start function it called to clobber offset 4 of the new thread's struct __pthread, which contains the dtv pointer. add code to setup a proper stack frame and align the stack pointer to a multiple of 16 (also an abi requirement) if it was not already aligned.
2016-04-18add mips n32 port (ILP32 ABI for mips64)Rich Felker-0/+90
based on patch submitted by Jaydeep Patil, with minor changes.
2016-03-06add mips64 portRich Felker-0/+91
patch by Mahesh Bodapati and Jaydeep Patil of Imagination Technologies.
2016-02-08remove workaround for broken mips assemblersRich Felker-5/+1
the workaround was for a bug that botched .gpword references to local labels, applying a nonsensical random offset of -0x4000 to them. this reverses commit 5e396fb996a80b035d0f6ecf7fed50f68aa3ebb7 and a removes a similar hack that was added to syscall_cp.s in the later commit 756c8af8589265e99e454fe3adcda1d0bc5e1963. it turns out one additional instance of the same idiom, the GETFUNCSYM macro in arch/mips/reloc.h, was still affected by the assembler bug and does not admit an easy workaround without making assumptions about how the macro is used. the previous workarounds made static linking work but left the early-stage dynamic linker broken and thus had limited usefulness. instead, affected users (using binutils versions older than 2.20) will need to fix the bug on the binutils side; the trivial patch is commit 453f5985b13e35161984bf1bf657bbab11515aa4 in the binutils-gdb repository.
2016-02-04in mips cancellable syscall asm, don't assume gp register is validRich Felker-2/+13
the old __cp_cancel code path loaded the address of __cancel from the GOT using the $gp register, which happened to be set to point to the correct GOT by the calling C function, but there is no ABI requirement that this happen. instead, go the roundabout way and compute the address of __cancel via pc-relative and gp-relative addressing starting with a fake return address generated by a bal instruction, which is the same trick crt1 uses to bootstrap.
2016-02-04avoid using signals when a thread attempts to cancel itselfRich Felker-0/+1
not only is pthread_kill expensive in this case; it also breaks testing under qemu app-level emulation.
2016-01-30fix misaligned pointer-like objects in arm atomics asm source fileRich Felker-0/+2
this file's .data section was not aligned, and just happened to get the correct alignment with past builds. it's likely that the move of atomic.s from arch/arm/src to src/thread/arm caused the change in alignment, which broke the atomic and thread-pointer access fragments on actual armv5 hardware.
2016-01-22move sh __unmapself code from arch/sh/src to main src treeRich Felker-0/+24
2016-01-22move x32 sysinfo impl and syscall fixup code out of arch/x32/srcRich Felker-0/+38
all such arch-specific translation units are being moved to appropriate arch dirs under the main src tree.
2016-01-22move arm-specific translation units out of arch/arm/src, to src/*/armRich Felker-1/+160
this is possible with the new build system that allows src/*/$(ARCH)/* files which do not shadow a file in the parent directory, and yields a more logical organization. eventually it will be possible to remove arch/*/src from the build system.
2016-01-21overhaul sh atomics for new atomics framework, add j-core cas.l backendRich Felker-0/+105
sh needs runtime-selected atomic backends since there are a number of supported models that use non-forwards-compatible (non-smp-compatible) atomic mechanisms. previously, the code paths for this were highly inefficient since they involved C function calls with multiple branches in the callee and heavy spills in the caller. the new code performs calls the runtime-selected asm fragment from inline asm with extremely minimal clobbers, rather than using a function call. for the sh4a case where the atomic mechanism is known and there is no forward-compatibility issue, the movli.l and movco.l instructions are provided as a_ll and a_sc, allowing the new shared atomic.h to generate efficient inline versions of all the basic atomic operations without needing a cas loop.
2015-11-11eliminate use of SHARED macro in __tls_get_addrRich Felker-6/+6
this was only a tiny optimization, and static-linked binaries should not be calling __tls_get_addr anyway since the linker is supposed to perform relaxation, resulting in use of the local-exec TLS model.
2015-11-11eliminate use of SHARED macro to suppress visibility attributesRich Felker-6/+0
this is the first and simplest stage of removal of the SHARED macro, which will eventually allow libc.a and to be produced from the same object files. the original motivation for these #ifdefs which are now being removed was to allow building a static-only libc using a compiler that does not support visibility. however, SHARED was the wrong condition to test for this anyway; various assembly-language sources refer to hidden symbols and declare them with the .hidden directive, making it wrong to define the referenced symbols as non-hidden. if there is a need in the future to build libc using compilers that lack visibility, support could be moved to the build system or perhaps the __PIC__ macro could be checked instead of SHARED.
2015-11-10explicitly assemble all arm asm sources as UALRich Felker-0/+3
these files are all accepted as legacy arm syntax when producing arm code, but legacy syntax cannot be used for producing thumb2 with access to the full ISA. even after switching to UAL, some asm source files contain instructions which are not valid in thumb mode, so these will need to be addressed separately.
2015-11-09remove non-working pre-armv4t support from arm asmRich Felker-4/+0
the idea of the three-instruction sequence being removed was to be able to return to thumb code when used on armv4t+ from a thumb caller, but also to be able to run on armv4 without the bx instruction available (in which case the low bit of lr would always be 0). however, without compiler support for generating such a sequence from C code, which does not exist and which there is unlikely to be interest in implementing, there is little point in having it in the asm, and it would likely be easier to add pre-armv4t support via enhanced linker handling of R_ARM_V4BX than at the compiler level. removing this code simplifies adding support for building libc in thumb2-only form (for cortex-m).
2015-11-02use explicit __cp_cancel label in cancellable syscall asm for all archsRich Felker-28/+32
previously, only archs that needed to do stack cleanup defined a __cp_cancel label for acting on cancellation in their syscall asm, and a default definition was provided by a weak alias to __cancel, the C function. this resulted in wrong codegen for arm on gcc versions affected by pr 68178 and possibly similar issues (like pr 66609) on other archs, and also created an inconsistency where the __cp_begin and __cp_end labels were treated as const data but __cp_cancel was treated as a function. this in turn caused incorrect code generation on archs where function pointers point to function descriptors rather than code (for now, only sh/fdpic).
2015-11-02properly access mcontext_t program counter in cancellation handlerRich Felker-3/+4
using the actual mcontext_t definition rather than an overlaid pointer array both improves correctness/readability and eliminates some ugly hacks for archs with 64-bit registers bit 32-bit program counter. also fix UB due to comparison of pointers not in a common array object.
2015-10-15add missing memory barrier to pthread_joinBobby Bingham-0/+1
POSIX requires pthread_join to synchronize memory on success. The futex wait inside __timedwait_cp cannot handle this because it's not called in all cases. Also, in the case of a spurious wake, tid can become zero between the wake and when the joining thread checks it.
2015-09-12make sh clone asm fdpic-compatibleRich Felker-3/+9
clone calls back to a function pointer provided by the caller, which will actually be a pointer to a function descriptor on fdpic. the obvious solution is to have a separate version of clone for fdpic, but I have taken a simpler approach to go around the problem. instead of calling the pointed-to function from asm, a direct call is made to an internal C function which then calls the pointed-to function. this lets the C compiler generate the appropriate calling convention for an indirect call with no need for ABI-specific assembly.
2015-06-25fix local-dynamic model TLS on mips and powerpcRich Felker-2/+2
the TLS ABI spec for mips, powerpc, and some other (presently unsupported) RISC archs has the return value of __tls_get_addr offset by +0x8000 and the result of DTPOFF relocations offset by -0x8000. I had previously assumed this part of the ABI was actually just an implementation detail, since the adjustments cancel out. however, when the local dynamic model is used for accessing TLS that's known to be in the same DSO, either of the following may happen: 1. the -0x8000 offset may already be applied to the argument structure passed to __tls_get_addr at ld time, without any opportunity for runtime relocations. 2. __tls_get_addr may be used with a zero offset argument to obtain a base address for the module's TLS, to which the caller then applies immediate offsets for individual objects accessed using the local dynamic model. since the immediate offsets have the -0x8000 adjustment applied to them, the base address they use needs to include the +0x8000 offset. it would be possible, but more complex, to store the pointers in the dtv[] array with the +0x8000 offset pre-applied, to avoid the runtime cost of adding 0x8000 on each call to __tls_get_addr. this change could be made later if measurements show that it would help.
2015-06-20work around mips detached thread exit breakage due to kernel regressionRich Felker-0/+1
linux kernel commit 46e12c07b3b9603c60fc1d421ff18618241cb081 caused the mips syscall mechanism to fail with EFAULT when the userspace stack pointer is invalid, breaking __unmapself used for detached thread exit. the workaround is to set $sp to a known-valid, readable address, and the simplest one to obtain is the address of the current function, which is available (per o32 calling convention) in $25.
2015-06-17ignore ENOSYS error from mprotect in pthread_create and dynamic linkerRich Felker-1/+2
this error simply indicated a system without memory protection (NOMMU) and should not cause failure in the caller.
2015-06-16switch to using trap number 31 for syscalls on shRich Felker-5/+5
nominally the low bits of the trap number on sh are the number of syscall arguments, but they have never been used by the kernel, and some code making syscalls does not even know the number of arguments and needs to pass an arbitrary high number anyway. sh3/sh4 traditionally used the trap range 16-31 for syscalls, but part of this range overlapped with hardware exceptions/interrupts on sh2 hardware, so an incompatible range 32-47 was chosen for sh2. using trap number 31 everywhere, since it's in the existing sh3/sh4 range and does not conflict with sh2 hardware, is a proposed unification of the kernel syscall convention that will allow binaries to be shared between sh2 and sh3/sh4. if this is not accepted into the kernel, we can refit the sh2 target with runtime selection mechanisms for the trap number, but doing so would be invasive and would entail non-trivial overhead.
2015-06-16switch sh port's __unmapself to generic version when running on sh2/nommuRich Felker-3/+3
due to the way the interrupt and syscall trap mechanism works, userspace on sh2 must never set the stack pointer to an invalid value. thus, the approach used on most archs, where __unmapself executes with no stack for the interval between SYS_munmap and SYS_exit, is not viable on sh2. in order not to pessimize sh3/sh4, the sh asm version of __unmapself is not removed. instead it's renamed and redirected through code that calls either the generic (safe) __unmapself or the sh3/sh4 asm, depending on compile-time and run-time conditions.
2015-06-16add support for sh2 interrupt-masking-based atomics to sh portRich Felker-6/+0
the sh2 target is being considered an ISA subset of sh3/sh4, in the sense that binaries built for sh2 are intended to be usable on later cpu models/kernels with mmu support. so rather than hard-coding sh2-specific atomics, the runtime atomic selection mechanisms that was already in place has been extended to add sh2 atomics. at this time, the sh2 atomics are not SMP-compatible; since the ISA lacks actual atomic operations, the new code instead masks interrupts for the duration of the atomic operation, producing an atomic result on single-core. this is only possible because the kernel/hardware does not impose protections against userspace doing so. additional changes will be needed to support future SMP systems. care has been taken to avoid producing significant additional code size in the case where it's known at compile-time that the target is not sh2 and does not need sh2-specific code.
2015-06-16refactor stdio open file list handling, move it out of global libc structRich Felker-1/+2
functions which open in-memory FILE stream variants all shared a tail with __fdopen, adding the FILE structure to stdio's open file list. replacing this common tail with a function call reduces code size and duplication of logic. the list is also partially encapsulated now. function signatures were chosen to facilitate tail call optimization and reduce the need for additional accessor functions. with these changes, static linked programs that do not use stdio no longer have an open file list at all.
2015-06-10implement arch-generic version of __unmapselfRich Felker-0/+29
this can be used to put off writing an asm version of __unmapself for new archs, or as a permanent solution on archs where it's not practical or even possible to run momentarily with no stack. the concept here is simple: the caller takes a lock on a global shared stack and uses it to make the munmap and exit syscalls. the only trick is unlocking, which must be done after the thread exits, and this is achieved by using the set_tid_address syscall to have the kernel zero and futex-wake the lock word as part of the exit syscall.
2015-05-25mark mips cancellable syscall code as codeRich Felker-0/+3
otherwise disassemblers treat it as data.
2015-05-16eliminate costly tricks to avoid TLS access for current locale stateRich Felker-6/+0
the code being removed used atomics to track whether any threads might be using a locale other than the current global locale, and whether any threads might have abstract 8-bit (non-UTF-8) LC_CTYPE active, a feature which was never committed (still pending). the motivations were to support early execution prior to setup of the thread pointer, to partially support systems (ancient kernels) where thread pointer setup is not possible, and to avoid high performance cost on archs where accessing the thread pointer may be very slow. since commit 19a1fe670acb3ab9ead0fe31859ca7d4fe40dd54, the thread pointer is always available, so these hacks are no longer needed. removing them greatly simplifies the affected code.
2015-05-16in i386 __set_thread_area, don't assume %gs register is initially zeroRich Felker-4/+9
commit f630df09b1fd954eda16e2f779da0b5ecc9d80d3 added logic to handle the case where __set_thread_area is called more than once by reusing the GDT slot already in the %gs register, and only setting up a new GDT slot when %gs is zero. this created a hidden assumption that %gs is zero when a new process image starts, which is true in practice on Linux, but does not seem to be documented ABI, and fails to hold under qemu app-level emulation. while it would in theory be possible to zero %gs in the entry point code, this code is shared between static and dynamic binaries, and dynamic binaries must not clobber the value of %gs already setup by the dynamic linker. the alternative solution implemented in this commit simply uses global data to store the GDT index that's selected. __set_thread_area should only be called in the initial thread anyway (subsequent threads get their thread pointer setup by __clone), but even if it were called by another thread, it would simply read and write back the same GDT index that was already assigned to the initial thread, and thus (in the x86 memory model) there is no data race.
2015-05-06fix stack protector crashes on x32 & powerpc due to misplaced TLS canaryRich Felker-1/+1
i386, x86_64, x32, and powerpc all use TLS for stack protector canary values in the default stack protector ABI, but the location only matched the ABI on i386 and x86_64. on x32, the expected location for the canary contained the tid, thus producing spurious mismatches (resulting in process termination) upon fork. on powerpc, the expected location contained the stdio_locks list head, so returning from a function after calling flockfile produced spurious mismatches. in both cases, the random canary was not present, and a predictable value was used instead, making the stack protector hardening much less effective than it should be. in the current fix, the thread structure has been expanded to have canary fields at all three possible locations, and archs that use a non-default location must define a macro in pthread_arch.h to choose which location is used. for most archs (which lack TLS canary ABI) the choice does not matter.
2015-05-02fix x32 __set_thread_area failure due to junk in upper bitsRich Felker-1/+1
the kernel does not properly clear the upper bits of the syscall argument, so we have to do it before the syscall.
2015-04-22minor optimization to pthread_spin_trylockRich Felker-2/+4
use CAS instead of swap since it's lighter for most archs, and keep EBUSY in the lock value so that the old value obtained by CAS can be used directly as the return value for pthread_spin_trylock.
2015-04-22optimize spin lock not to dirty cache line while spinningRich Felker-1/+1
2015-04-21fix mmap leak in sem_open failure path for link callRich Felker-0/+1
the leak was found by static analysis (reported by Alexander Monakov), not tested/observed, but seems to have occured both when failing due to O_EXCL, and in a race condition with O_CREAT but not O_EXCL where a semaphore by the same name was created concurrently.
2015-04-18make dlerror state and message thread-local and dynamically-allocatedRich Felker-0/+2
this fixes truncation of error messages containing long pathnames or symbol names. the dlerror state was previously required by POSIX to be global. the resolution of bug 97 relaxed the requirements to allow thread-safe implementations of dlerror with thread-local state and message buffer.
2015-04-17fix sh build regressions in asmRich Felker-1/+1
even hidden functions need @PLT symbol references; otherwise an absolute address is produced instead of a PC-relative one.
2015-04-17fix sh __set_thread_area uninitialized return valueRich Felker-1/+2
this caused the dynamic linker/startup code to abort when r0 happened to contain a negative value.
2015-04-14use hidden __tls_get_new for tls/tlsdesc lookup fallback casesRich Felker-1/+3
previously, the dynamic tlsdesc lookup functions and the i386 special-ABI ___tls_get_addr (3 underscores) function called __tls_get_addr when the slot they wanted was not already setup; __tls_get_addr would then in turn also see that it's not setup and call __tls_get_new. calling __tls_get_new directly is both more efficient and avoids the issue of calling a non-hidden (public API/ABI) function from asm. for the special i386 function, a weak reference to __tls_get_new is used since this function is not defined when static linking (the code path that needs it is unreachable in static-linked programs).
2015-04-14cleanup use of visibility attributes in pthread_cancel.cRich Felker-8/+9
applying the attribute to a weak_alias macro was a hack. instead use a separate declaration to apply the visibility, and consolidate declarations together to avoid having visibility mess all over the file.
2015-04-14fix inconsistent visibility for internal syscall symbolsRich Felker-0/+5
2015-04-14consistently use hidden visibility for cancellable syscall internalsRich Felker-30/+96
in a few places, non-hidden symbols were referenced from asm in ways that assumed ld-time binding. while these is no semantic reason these symbols need to be hidden, fixing the references without making them hidden was going to be ugly, and hidden reduces some bloat anyway. in the asm files, .global/.hidden directives have been moved to the top to unclutter the actual code.
2015-04-14fix inconsistent visibility for internal __tls_get_new functionRich Felker-3/+2
at the point of call it was declared hidden, but the definition was not hidden. for some toolchains this inconsistency produced textrels without ld-time binding.
2015-04-13remove remnants of support for running in no-thread-pointer modeRich Felker-11/+5
since 1.1.0, musl has nominally required a thread pointer to be setup. most of the remaining code that was checking for its availability was doing so for the sake of being usable by the dynamic linker. as of commit 71f099cb7db821c51d8f39dfac622c61e54d794c, this is no longer necessary; the thread pointer is now valid before any libc code (outside of dynamic linker bootstrap functions) runs. this commit essentially concludes "phase 3" of the "transition path for removing lazy init of thread pointer" project that began during the 1.1.0 release cycle.
2015-04-13allow i386 __set_thread_area to be called more than onceRich Felker-1/+5
previously a new GDT slot was requested, even if one had already been obtained by a previous call. instead extract the old slot number from GS and reuse it if it was already set. the formula (GS-3)/8 for the slot number automatically yields -1 (request for new slot) if GS is zero (unset).
2015-04-11remove mismatched arguments from vmlock function definitionsRich Felker-2/+2
commit f08ab9e61a147630497198fe3239149275c0a3f4 introduced these accidentally as remnants of some work I tried that did not work out.
2015-04-10apply vmlock wait to __unmapself in pthread_exitRich Felker-0/+4