pselect: Use linux pselect syscall when available

[uclinux-h8/uclibc-ng.git] / libc / sysdeps / linux / common / pselect.c

diff --git a/libc/sysdeps/linux/common/pselect.c b/libc/sysdeps/linux/common/pselect.c
index bf19ce3..3f1dd28 100644 (file)
--- 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),