diff options
Diffstat (limited to 'libc/sysdeps/linux/common')
| -rw-r--r-- | libc/sysdeps/linux/common/pselect.c | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/common/pselect.c b/libc/sysdeps/linux/common/pselect.c index bf19ce3d7..3f1dd28a2 100644 --- a/libc/sysdeps/linux/common/pselect.c +++ b/libc/sysdeps/linux/common/pselect.c @@ -30,6 +30,57 @@ static int __NC(pselect)(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, const struct timespec *timeout, const sigset_t *sigmask) { +#ifdef __NR_pselect6 +#define NSEC_PER_SEC 1000000000L + struct timespec _ts, *ts = 0; + if (timeout) { + /* The Linux kernel can in some situations update the timeout value. + * We do not want that so use a local variable. + */ + _ts = *timeout; + + /* GNU extension: allow for timespec values where the sub-sec + * field is equal to or more than 1 second. The kernel will + * reject this on us, so take care of the time shift ourself. + * Some applications (like readline and linphone) do this. + * See 'clarification on select() type calls and invalid timeouts' + * on the POSIX general list for more information. + */ + if (_ts.tv_nsec >= NSEC_PER_SEC) { + _ts.tv_sec += _ts.tv_nsec / NSEC_PER_SEC; + _ts.tv_nsec %= NSEC_PER_SEC; + } + + ts = &_ts; + } + + /* The pselect6 syscall API is strange. It wants a 7th arg to be + * the sizeof(*sigmask). However syscalls with > 6 arguments aren't + * supported on linux. So arguments 6 and 7 are stuffed in a struct + * and a pointer to that struct is passed as the 6th argument to + * the syscall. + * Glibc stuffs arguments 6 and 7 in a ulong[2]. Linux reads + * them as if there were a struct { sigset_t*; size_t } in + * userspace. There woudl be trouble if userspace and the kernel are + * compiled differently enough that size_t isn't the same as ulong, + * but not enough to trigger the compat layer in linux. I can't + * think of such a case, so I'm using linux's struct. + * Furthermore Glibc sets the sigsetsize to _NSIG/8. However linux + * checks for sizeof(sigset_t), which internally is a ulong array. + * This means that if _NSIG isn't a multiple of BITS_PER_LONG then + * linux will refuse glibc's value. So I prefer sizeof(sigset_t) for + * the value of sigsetsize. + */ + struct { + const sigset_t *sigmask; + size_t sigsetsize; + } args67 = { + sigmask, + sizeof(sigset_t), + }; + + return INLINE_SYSCALL(pselect6, 6, nfds, readfds, writefds, exceptfds, ts, &args67); +#else struct timeval tval; int retval; sigset_t savemask; @@ -57,6 +108,7 @@ static int __NC(pselect)(int nfds, fd_set *readfds, fd_set *writefds, sigprocmask (SIG_SETMASK, &savemask, NULL); return retval; +#endif } CANCELLABLE_SYSCALL(int, pselect, (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, const struct timespec *timeout, const sigset_t *sigmask), |