path: root/arch/sh/bits
AgeCommit message (Collapse)AuthorLines
2021-02-15bits/syscall.h: add process_madvise from linux v5.10Szabolcs Nagy-0/+1
mainly added to linux to allow a central process management service in android to give MADV_COLD|PAGEOUT hints for other processes, see linux commit ecb8ac8b1f146915aa6b96449b66dd48984caacc mm/madvise: introduce process_madvise() syscall: an external memory hinting API
2020-12-12sh: fix incorrect mcontext_t member namingAriadne Conill-2/+11
while the layouts match, the member member naming expected by software using mcontext_t omits the sc_ prefix.
2020-11-29bits/syscall.h: add __NR_close_range from linux v5.9Szabolcs Nagy-0/+1
see linux commit 9b4feb630e8e9801603f3cab3a36369e3c1cf88d arch: wire-up close_range() linux commit 278a5fbaed89dacd04e9d052f4594ffd0e0585de open: add close_range()
2020-09-09bits/syscall.h: add __NR_faccessat2 from linux v5.8Szabolcs Nagy-0/+1
the linux faccessat syscall lacks a flag argument that is necessary to implement the posix api, see linux commit c8ffd8bcdd28296a198f237cc595148a8d4adfbe vfs: add faccessat2 syscall
2020-09-09add pidfd_getfd and openat2 syscall numbers from linux v5.6Szabolcs Nagy-0/+3
also added clone3 on sh and m68k, on sh it's still missing (not yet wired up), but reserved so safe to add. see linux commit fddb5d430ad9fa91b49b1d34d0202ffe2fa0e179 open: introduce openat2(2) syscall linux commit 9a2cef09c801de54feecd912303ace5c27237f12 arch: wire up pidfd_getfd syscall linux commit 8649c322f75c96e7ced2fec201e123b2b073bf09 pid: Implement pidfd_getfd syscall linux commit e8bb2a2a1d51511e6b3f7e08125d52ec73c11139 m68k: Wire up clone3() syscall
2020-02-05remove legacy time32 timer[fd] syscalls from public syscall.hRich Felker-4/+4
this extends commit 5a105f19b5aae79dd302899e634b6b18b3dcd0d6, removing timer[fd]_settime and timer[fd]_gettime. the timerfd ones are likely to have been used in software that started using them before it could rely on libc exposing functions.
2020-02-05remove further legacy time32 clock syscalls from public syscall.hRich Felker-4/+4
this extends commit 5a105f19b5aae79dd302899e634b6b18b3dcd0d6, removing clock_settime, clock_getres, clock_nanosleep, and settimeofday.
2020-01-30remove legacy clock_gettime and gettimeofday from public syscall.hRich Felker-2/+2
some nontrivial number of applications have historically performed direct syscalls for these operations rather than using the public functions. such usage is invalid now that time_t is 64-bit and these syscalls no longer match the types they are used with, and it was already harmful before (by suppressing use of vdso). since syscall() has no type safety, incorrect usage of these syscalls can't be caught at compile-time. so, without manually inspecting or running additional tools to check sources, the risk of such errors slipping through is high. this patch renames the syscalls on 32-bit archs to clock_gettime32 and gettimeofday_time32, so that applications using the original names will fail to build without being fixed. note that there are a number of other syscalls that may also be unsafe to use directly after the time64 switchover, but (1) these are the main two that seem to be in widespread use, and (2) most of the others continue to have valid usage with a null timeval/timespec argument, as the argument is an optional timeout or similar.
2019-12-30add pidfd_open syscall number from linux v5.3Szabolcs Nagy-0/+1
see linux commit 7615d9e1780e26e0178c93c55b73309a5dc093d7 arch: wire-up pidfd_open() linux commit 32fcb426ec001cb6d5a4a195091a8486ea77e2df pid: add pidfd_open()
2019-11-02move time_t and suseconds_t definitions to common alltypes.h.inRich Felker-3/+0
now that all 32-bit archs have 64-bit time_t (and suseconds_t), the arch-provided _Int64 macro (long or long long, as appropriate) can be used to define them, and arch-specific definitions are no longer needed.
2019-11-02move time64 socket options from arch bits to top-level sys/socket.hRich Felker-5/+0
now that all 32-bit archs have 64-bit time types, the values for the time-related socket option macros can be treated as universal for 32-bit archs. the sys/socket.h mechanism for this predates arch/generic and is instead in the top-level header. x32, which does not use the new time64 values of the macros, already has its own overrides, so this commit does not affect it.
2019-11-02switch all existing 32-bit archs to 64-bit time_tRich Felker-22/+41
this commit preserves ABI fully for existing interface boundaries between libc and libc consumers (applications or libraries), by retaining existing symbol names for the legacy 32-bit interfaces and redirecting sources compiled against the new headers to alternate symbol names. this does not necessarily, however, preserve the pairwise ABI of libc consumers with one another; where they use time_t-derived types in their interfaces with one another, it may be necessary to synchronize updates with each other. the intent is that ABI resulting from this commit already be stable and permanent, but it will not be officially so until a release is made. changes to some header-defined types that do not play any role in the ABI between libc and its consumers may still be subject to change. mechanically, the changes made by this commit for each 32-bit arch are as follows: - _REDIR_TIME64 is defined to activate the symbol redirections in public headers - COMPAT_SRC_DIRS is defined in arch.mak to activate build of ABI compat shims to serve as definitions for the original symbol names - time_t and suseconds_t definitions are changed to long long (64-bit) - IPC_STAT definition is changed to add the IPC_TIME64 bit (0x100), triggering conversion of semid_ds, shmid_ds, and msqid_ds split low/high time bits into new time_t members - structs semid_ds, shmid_ds, msqid_ds, and stat are modified to add new 64-bit time_t/timespec members at the end, maintaining existing layout of other members. - socket options (SO_*) and ioctl (sockios) command macros are redefined to use the kernel's "_NEW" values. in addition, on archs where vdso clock_gettime is used, the VDSO_CGT_SYM macro definition in syscall_arch.h is changed to use a new time64 vdso function if available, and a new VDSO_CGT32_SYM macro is added for use as fallback on kernels lacking time64.
2019-10-17move pthread types out of per-arch alltypes.hRich Felker-8/+0
policy has long been that these definitions are purely a function of whether long/pointer is 32- or 64-bit, and that they are not allowed to vary per-arch. move the definition to the shared fragment, using integer constant expressions in terms of sizeof to vary the array dimensions appropriately. I'm not sure whether this is more or less ugly than using preprocessor conditionals and two sets of definitions here, but either way is a lot less ugly than repeating the same thing for every arch.
2019-10-17define LONG_MAX via arch alltypes.h, strip down bits/limits.hRich Felker-7/+2
LLONG_MAX is uniform for all archs we support and plenty of header and code level logic assumes it is, so it does not make sense for limits.h bits mechanism to pretend it's variable. LONG_BIT can be defined in terms of LONG_MAX; there's no reason to put it in bits. by moving LONG_MAX definition to __LONG_MAX in alltypes.h and moving LLONG_MAX out of bits, there are now no plain-C limits that are defined in the bits header, so the bits header only needs to be included in the POSIX or extended profiles. this allows the feature test macro logic to be removed from the bits header, facilitating a long-term goal of getting such logic out of bits. having __LONG_MAX in alltypes.h will allow further generalization of headers. archs without a constant PAGESIZE no longer need bits/limits.h at all.
2019-10-17move __BYTE_ORDER definition to alltypes.hRich Felker-5/+6
this change is motivated by the intersection of several factors. presently, despite being a nonstandard header, endian.h is exposing the unprefixed byte order macros and functions only if _BSD_SOURCE or _GNU_SOURCE is defined. this is to accommodate use of endian.h from other headers, including bits headers, which need to define structure layout in terms of endianness. with time64 switch-over, even more headers will need to do this. at the same time, the resolution of Austin Group issue 162 makes endian.h a standard header for POSIX-future, requiring that it expose the unprefixed macros and the functions even in standards-conforming profiles. changes to meet this new requirement would break existing internal usage of endian.h by causing it to violate namespace where it's used. instead, have the arch's alltypes.h define __BYTE_ORDER, either as a fixed constant or depending on the right arch-specific predefined macros for determining endianness. explicit literals 1234 and 4321 are used instead of __LITTLE_ENDIAN and __BIG_ENDIAN so that there's no danger of getting the wrong result if a macro is undefined and implicitly evaluates to 0 at the preprocessor level. the powerpc (32-bit) bits/endian.h being removed had logic for varying endianness, but our powerpc arch has never supported that and has always been big-endian-only. this logic is not carried over to the new __BYTE_ORDER definition in alltypes.h.
2019-10-17remove per-arch definitions for va_listRich Felker-3/+0
now that commit f7f1079796abc6f97c69521d2334e9c7d3945dd8 removed the legacy i386 conditional definition, va_list is in no way arch-specific, and has no reason to be in the future. move it to the shared part of
2019-09-11add new syscall numbers from linux v5.2Szabolcs Nagy-0/+6
new mount api syscalls were added, same numers on all targets, see linux commit a07b20004793d8926f78d63eb5980559f7813404 vfs: syscall: Add open_tree(2) to reference or clone a mount linux commit 2db154b3ea8e14b04fee23e3fdfd5e9d17fbc6ae vfs: syscall: Add move_mount(2) to move mounts around linux commit 24dcb3d90a1f67fe08c68a004af37df059d74005 vfs: syscall: Add fsopen() to prepare for superblock creation linux commit ecdab150fddb42fe6a739335257949220033b782 vfs: syscall: Add fsconfig() for configuring and managing a context linux commit 93766fbd2696c2c4453dd8e1070977e9cd4e6b6d vfs: syscall: Add fsmount() to create a mount for a superblock linux commit cf3cba4a429be43e5527a3f78859b1bfd9ebc5fb vfs: syscall: Add fspick() to select a superblock for reconfiguration linux commit 9c8ad7a2ff0bfe58f019ec0abc1fb965114dde7d uapi, x86: Fix the syscall numbering of the mount API syscalls [ver #2] linux commit d8076bdb56af5e5918376cd1573a6b0007fc1a89 uapi: Wire up the mount API syscalls on non-x86 arches [ver #2]
2019-09-08honor __WCHAR_TYPE__ on archs with legacy long definition of wchar_tRich Felker-0/+4
historically, a number of 32-bit archs used long rather than int for wchar_t, for no good reason. GCC still uses the historical types, but clang replaced them all with int, and it seems PCC uses int too. mismatching the compiler's type for wchar_t is not an option due to wide string literals. note that the mismatch does not affect C++ ABI since wchar_t is its own builtin type/keyword in C++, distinct from both int and long, not a typedef. i386 already worked around this by honoring __WCHAR_TYPE__ if defined by the compiler, and only using the official legacy ABI type if not. add the same to the other affected archs. it might make sense at some point to switch to using int as the default if __WCHAR_TYPE__ is not defined, if the expectations is that new compilers will treat int as the correct choice, but it's unlikely that the case where __WCHAR_TYPE__ is undefined will ever be used anyway. I actually wanted to move the definition of wchar_t to the top-level shared, using __WCHAR_TYPE__ and falling back to int if not defined, but that can't be done without assuming all compilers define __WCHAR_TYPE__ thanks to some pathological archs where the ABI has wchar_t as an unsigned type.
2019-08-19fix clash between sys/user.h and kernel ptrace.h on powerpc[64], shRich Felker-29/+5
due to historical accident/sloppiness in glibc, the powerpc, powerpc64, and sh versions of struct user, defined by sys/user.h, used struct pt_regs from the kernel asm/ptrace.h for their regs member. this made it impossible to define the type in an API-compatible manner without either including asm/ptrace.h like glibc does (contrary to our policy of not depending on kernel headers), or clashing with asm/ptrace.h's definition of struct pt_regs if both headers are included (which is almost always the case in software using sys/user.h). for a long time I viewed this problem as having no reasonable fix. I even explored the possibility of having the powerpc[64] and sh versions of user.h just include the kernel header (breaking with policy), but that looked like it might introduce new clashes with sys/ptrace.h. and it would also bring in a lot of additional cruft that makes no sense for sys/user.h to expose. glibc goes out of its way to suppress some of that with #undef, possibly leading to different problems. this is a rabbit-hole that should be explored no further. as it turns out, however, nothing actually uses struct user sufficiently to care about the type of the regs member; most software including sys/user.h does not even use struct user at all. so, the problem can be fixed just by doing away with the insistence on strict glibc API compatibility for the struct tag of the regs member. rather than renaming the tag, which might lead to the new name entering use as API, simply use an untagged structure inside struct user with the same members/layout as struct pt_regs. for sh, struct pt_dspregs is just removed entirely since it was not used.
2019-08-02move IPC_STAT definition to a new bits/ipcstat.h fileRich Felker-0/+1
otherwise, 32-bit archs that could otherwise share the generic bits/ipc.h would need to duplicate the struct ipc_perm definition, obscuring the fact that it's the same. sysvipc is not widely used and these headers are not commonly included, so there is no performance gain to be had by limiting the number of indirectly included files here. files with the existing time32 definition of IPC_STAT are added to all current 32-bit archs now, so that when it's changed the change will show up as a change rather than addition of a new file where it's less obvious that the value is changing vs the generic one that was used before.
2019-07-29duplicate generic bits/msg.h for each arch using it, in prep to changeRich Felker-0/+15
2019-07-29duplicate generic bits/sem.h for each arch using it, in prep to changeRich Felker-0/+16
2019-07-01add new syscall numbers from linux v5.1Szabolcs Nagy-0/+39
syscall numbers are now synced up across targets (starting from 403 the numbers are the same on all targets other than an arch specific offset) IPC syscalls sem*, shm*, msg* got added where they were missing (except for semop: only semtimedop got added), the new semctl, shmctl, msgctl imply IPC_64, see linux commit 0d6040d4681735dfc47565de288525de405a5c99 arch: add split IPC system calls where needed new 64bit time_t syscall variants got added on 32bit targets, see linux commit 48166e6ea47d23984f0b481ca199250e1ce0730a y2038: add 64-bit time_t syscalls to all 32-bit architectures new async io syscalls got added, see linux commit 2b188cc1bb857a9d4701ae59aa7768b5124e262e Add io_uring IO interface linux commit edafccee56ff31678a091ddb7219aba9b28bc3cb io_uring: add support for pre-mapped user IO buffers a new syscall got added that uses the fd of /proc/<pid> as a stable handle for processes: allows sending signals without pid reuse issues, intended to eventually replace rt_sigqueueinfo, kill, tgkill and rt_tgsigqueueinfo, see linux commit 3eb39f47934f9d5a3027fe00d906a45fe3a15fad signal: add pidfd_send_signal() syscall on some targets (arm, m68k, s390x, sh) some previously missing syscall numbers got added as well.
2019-02-07move arch-invariant definitions out of bits/ioctl.hBobby Bingham-96/+0
2018-09-20add arm and sh bits/ptrace.hSzabolcs Nagy-0/+5
These should have been added in commit df6d9450ea19fd71e52cf5cdb4c85beb73066394 that added target specific PTRACE_ macros, but somehow got missed.
2018-03-10reverse definition dependency between PAGESIZE and PAGE_SIZERich Felker-1/+1
PAGESIZE is actually the version defined in POSIX base, with PAGE_SIZE being in the XSI option. use PAGESIZE as the underlying definition to facilitate making exposure of PAGE_SIZE conditional.
2017-11-05ioctl TIOCGPTPEER from linux v4.13Szabolcs Nagy-0/+1
added for safe opening of peer end of pty in a mount namespace. new in linux commit c6325179238f1d4683edbec53d8322575d76d7e2
2017-08-29add SIOCGSTAMPNS socket ioctl macro to ioctl.hSzabolcs Nagy-0/+1
it is defined in linux asm/sockios.h since commit ae40eb1ef30ab4120bd3c8b7e3da99ee53d27a23 (linux v2.6.22) but was missing from musl by accident. in musl the sockios macros are exposed in sys/ioctl.h together with other ioctl requests instead of in sys/socket.h because of namespace rules. (glibc has them in sys/socket.h under _GNU_SOURCE.)
2016-10-20add bits/hwcap.h and include it in sys/auxv.hSzabolcs Nagy-0/+11
aarch64, arm, mips, mips64, mipsn32, powerpc, powerpc64 and sh have cpu feature bits defined in linux for AT_HWCAP auxv entry, so expose those in sys/auxv.h it seems the mips hwcaps were never exposed to userspace neither by linux nor by glibc, but that's most likely an oversight.
2016-10-20add sh syscall numbers from linux v4.8Szabolcs Nagy-0/+14
sh was updated in linux commit 74bdaa611fa69368fb4032ad437af073d31116bd to have numbers for new syscalls.
2016-07-03make brace placement in public header struct definitions consistentRich Felker-4/+2
placing the opening brace on the same line as the struct keyword/tag is the style I prefer and seems to be the prevailing practice in more recent additions. these changes were generated by the command: find include/ arch/*/bits -name '*.h' \ -exec sed -i '/^struct [^;{]*$/{N;s/\n/ /;}' {} + and subsequently checked by hand to ensure that the regex did not pick up any false positives.
2016-07-03remove termios2 related ioctls from sh ioctl.hSzabolcs Nagy-4/+0
musl does not define these on other targets either.
2016-07-03add missing TIOC* macros to ioctl.hSzabolcs Nagy-0/+2
these are defined in linux asm/ioctls.h. (powerpc64 and powerpc bits/ioctl.h are now identical)
2016-07-03add missing SIOCSIFNAME from linux/sockios.h to ioctl.hSzabolcs Nagy-0/+1
glibc ioctl.h has it too.
2016-07-03remove ioctl macros that were removed from linux uapiSzabolcs Nagy-2/+0
TIOCTTYGSTRUCT, TIOCGHAYESESP, TIOCSHAYESESP and TIOCM_MODEM_BITS were removed from the linux uapi and not present in glibc ioctl.h
2016-05-12deduplicate __NR_* and SYS_* syscall number definitionsBobby Bingham-684/+341
2016-03-18deduplicate bits/mman.hSzabolcs Nagy-60/+0
currently five targets use the same mman.h constants and the rest share most constants too, so move them to sys/mman.h before the bits/mman.h include where the differences can be corrected by redefinition of the macros. this fixes two minor bugs: POSIX_MADV_DONTNEED was wrong on most targets (it should be the same as MADV_DONTNEED), and sh defined the x86-only MAP_32BIT mmap flag.
2016-01-27deduplicate the bulk of the arch bits headersRich Felker-408/+0
all bits headers that were identical for a number of 'clean' archs are moved to the new arch/generic tree. in addition, a few headers that differed only cosmetically from the new generic version are removed. additional deduplication may be possible in mman.h and in several headers (limits.h, posix.h, stdint.h) that mostly depend on whether the arch is 32- or 64-bit, but they are left alone for now because greater gains are likely possible with more invasive changes to header logic, which is beyond the scope of this commit.
2016-01-26add MCL_ONFAULT and MLOCK_ONFAULT mlockall and mlock2 flagsSzabolcs Nagy-0/+1
they lock faulted pages into memory (useful when a small part of a large mapped file needs efficient access), new in linux v4.4, commit b0f205c2a3082dd9081f9a94e50658c5fa906ff1 MLOCK_* is not in the POSIX reserved namespace for sys/mman.h
2015-04-27fix sh jmp_buf size to match ABIRich Felker-1/+1
while the sh port is still experimental and subject to ABI instability, this is not actually an application/libc boundary ABI change. it only affects third-party APIs where jmp_buf is used in a shared structure at the ABI boundary, because nothing anywhere near the end of the jmp_buf object (which includes the oversized sigset_t) is accessed by libc. both glibc and uclibc have 15-slot jmp_buf for sh. presumably the smaller version was used in musl because the slots for fpu status register and thread pointer register (gbr) were incorrect and must not be restored by longjmp, but the size should have been preserved, as it's generally treated as a libc-agnostic ABI property for the arch, and having extra slots free in case we ever need them for something is useful anyway.
2015-04-01move O_PATH definition back to arch bitsRich Felker-0/+1
while it's the same for all presently supported archs, it differs at least on sparc, and conceptually it's no less arch-specific than the other O_* macros. O_SEARCH and O_EXEC are still defined in terms of O_PATH in the main fcntl.h.
2015-03-18fix MINSIGSTKSZ values for archs with large signal contextsRich Felker-0/+5
the previous values (2k min and 8k default) were too small for some archs. aarch64 reserves 4k in the signal context for future extensions and requires about 4.5k total, and powerpc reportedly uses over 2k. the new minimums are chosen to fit the saved context and also allow a minimal signal handler to run. since the default (SIGSTKSZ) has always been 6k larger than the minimum, it is also increased to maintain the 6k usable by the signal handler. this happens to be able to store one pathname buffer and should be sufficient for calling any function in libc that doesn't involve conversion between floating point and decimal representations. x86 (both 32-bit and 64-bit variants) may also need a larger minimum (around 2.5k) in the future to support avx-512, but the values on these archs are left alone for now pending further analysis. the value for PTHREAD_STACK_MIN is not increased to match MINSIGSTKSZ at this time. this is so as not to preclude applications from using extremely small thread stacks when they know they will not be handling signals. unfortunately cancellation and multi-threaded set*id() use signals as an implementation detail and therefore require a stack large enough for a signal context, so applications which use extremely small thread stacks may still need to avoid using these features.
2015-03-07fix FLT_ROUNDS to reflect the current rounding modeSzabolcs Nagy-1/+0
Implemented as a wrapper around fegetround introducing a new function to the ABI: __flt_rounds. (fegetround cannot be used directly from float.h)
2015-03-04fix POLLWRNORM and POLLWRBAND on mipsTrutz Behn-0/+0
these macros have the same distinct definition on blackfin, frv, m68k, mips, sparc and xtensa kernels. POLLMSG and POLLRDHUP additionally differ on sparc.
2015-03-03make all objects used with atomic operations volatileRich Felker-7/+7
the memory model we use internally for atomics permits plain loads of values which may be subject to concurrent modification without requiring that a special load function be used. since a compiler is free to make transformations that alter the number of loads or the way in which loads are performed, the compiler is theoretically free to break this usage. the most obvious concern is with atomic cas constructs: something of the form tmp=*p;a_cas(p,tmp,f(tmp)); could be transformed to a_cas(p,*p,f(*p)); where the latter is intended to show multiple loads of *p whose resulting values might fail to be equal; this would break the atomicity of the whole operation. but even more fundamental breakage is possible. with the changes being made now, objects that may be modified by atomics are modeled as volatile, and the atomic operations performed on them by other threads are modeled as asynchronous stores by hardware which happens to be acting on the request of another thread. such modeling of course does not itself address memory synchronization between cores/cpus, but that aspect was already handled. this all seems less than ideal, but it's the best we can do without mandating a C11 compiler and using the C11 model for atomics. in the case of pthread_once_t, the ABI type of the underlying object is not volatile-qualified. so we are assuming that accessing the object through a volatile-qualified lvalue via casts yields volatile access semantics. the language of the C standard is somewhat unclear on this matter, but this is an assumption the linux kernel also makes, and seems to be the correct interpretation of the standard.
2015-01-30move MREMAP_MAYMOVE and MREMAP_FIXED out of bitsTrutz Behn-3/+0
the definitions are generic for all kernel archs. exposure of these macros now only occurs on the same feature test as for the function accepting them, which is believed to be more correct.
2014-12-21move wint_t definition to the shared part of alltypes.h.inRich Felker-1/+0
2014-09-06add threads.h and needed per-arch types for mtx_t and cnd_tRich Felker-0/+2
based on patch by Jens Gustedt. mtx_t and cnd_t are defined in such a way that they are formally "compatible types" with pthread_mutex_t and pthread_cond_t, respectively, when accessed from a different translation unit. this makes it possible to implement the C11 functions using the pthread functions (which will dereference them with the pthread types) without having to use the same types, which would necessitate either namespace violations (exposing pthread type names in threads.h) or incompatible changes to the C++ name mangling ABI for the pthread types. for the rest of the types, things are much simpler; using identical types is possible without any namespace considerations.
2014-08-20add max_align_t definition for C11 and C++11Rich Felker-0/+2
unfortunately this needs to be able to vary by arch, because of a huge mess GCC made: the GCC definition, which became the ABI, depends on quirks in GCC's definition of __alignof__, which does not match the formal alignment of the type. GCC's __alignof__ unexpectedly exposes the an implementation detail, its "preferred alignment" for the type, rather than the formal/ABI alignment of the type, which it only actually uses in structures. on most archs the two values are the same, but on some (at least i386) the preferred alignment is greater than the ABI alignment. I considered using _Alignas(8) unconditionally, but on at least one arch (or1k), the alignment of max_align_t with GCC's definition is only 4 (even the "preferred alignment" for these types is only 4).
2014-08-17make pointers used in robust list volatileRich Felker-1/+1
when manipulating the robust list, the order of stores matters, because the code may be asynchronously interrupted by a fatal signal and the kernel will then access the robust list in what is essentially an async-signal context. previously, aliasing considerations made it seem unlikely that a compiler could reorder the stores, but proving that they could not be reordered incorrectly would have been extremely difficult. instead I've opted to make all the pointers used as part of the robust list, including those in the robust list head and in the individual mutexes, volatile. in addition, the format of the robust list has been changed to point back to the head at the end, rather than ending with a null pointer. this is to match the documented kernel robust list ABI. the null pointer, which was previously used, only worked because faults during access terminate the robust list processing.