Fix "pselect: Use linux pselect6 syscall when available"

Commit e3c3bf2b58 introduce use of pselect6, but has following disadvantages:

* Use of userspace types in args67 structure - it breaks, for example,
  configs when 32-bit uClibc-ng compiled against 64-bit kernel. Syscall
  will always return EINVAL. We must use __kernel_* types and
  __SYSCALL_SIGSET_T_SIZE.

* It have excess checks for NSEC_PER_SEC. Original code from select()
  implementation has struct timeval => struct timespec conversion,
  kernel select() syscall implementation do the same.
  But none of libc versions (glibc, eglibc, musl) I know, perform similar
  checks for pselect() - there is no structure fields conversions,
  just struct timespec through all the calls.
  To have such checks in uClibc-ng we need one example, at least.

* It is possible to avoid extra userspace reads from kernel code if
  sigmask == NULL. I suggest to do it, for a few bytes cost.

* Commit didn't add test case to testsuite.

Signed-off-by: Leonid Lisovskiy <lly.dev@gmail.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/test/unistd/tst-pselect.c b/test/unistd/tst-pselect.c
new file mode 100644
index 000000000..cab945119
--- /dev/null
+++ b/test/unistd/tst-pselect.c
@@ -0,0 +1,51 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <signal.h>
+#include <sys/types.h>
+#include <sys/select.h>
+
+// our SIGALRM handler
+void handler(int signum) {
+	(void)signum;
+	puts("got signal\n");
+}
+
+static int
+do_test (void)
+{
+	int rc;
+	sigset_t wait_mask, mask_sigchld;
+	struct sigaction act;
+
+	// block SIGALRM. We want to handle it only when we're ready
+	sigemptyset(&mask_sigchld);
+	sigaddset(&mask_sigchld, SIGALRM);
+	sigprocmask(SIG_BLOCK,  &mask_sigchld, &wait_mask);
+	sigdelset(&wait_mask, SIGALRM);
+
+	// register a signal handler so we can see when the signal arrives
+	memset(&act, 0, sizeof(act));
+	sigemptyset(&act.sa_mask); // just in case an empty set isn't all 0's (total paranoia)
+	act.sa_handler = handler;
+	sigaction(SIGALRM, &act, NULL);
+
+	// send ourselves a SIGARLM. It will pend until we unblock that signal in pselect()
+	printf("sending ourselves a signal\n");
+	kill(getpid(), SIGALRM);
+
+	printf("signal is pending; calling pselect()\n");
+	rc = pselect(0, NULL, NULL, NULL, NULL, &wait_mask);
+	if (rc != -1 || errno != EINTR) {
+		int e = errno;
+		printf("pselect() returned %d, errno %d (%s)\n", rc, e, strerror(e));
+		exit(1);
+	}
+
+	return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include <test-skeleton.c>