feat(select): poll/select and fd_set

src/select/poll.c

@@ -0,0 +1,32 @@
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <poll.h>
+
+#include "../internal/syscall.h"
+
+/*
+ * poll: plain POSIX poll over SYS_ppoll with a NULL sigmask (Linux has no
+ * separate poll syscall for >1024 fds; ppoll is the generic form). The
+ * millisecond timeout is converted to the struct timespec the kernel
+ * expects; a negative timeout means "block indefinitely" and stays NULL.
+ *
+ * The (nfds_t, int) parameter pair is the fixed POSIX signature, so the
+ * easily-swappable-parameters warning does not apply.
+ */
+int
+poll(struct pollfd *fds, nfds_t nfds, // NOLINT(bugprone-easily-swappable-parameters)
+     int timeout)
+{
+    struct timespec ts;
+    struct timespec *tsp = NULL;
+
+    if (timeout >= 0)
+    {
+        ts.tv_sec = timeout / 1000;
+        ts.tv_nsec = (long)(timeout % 1000) * 1000000L;
+        tsp = &ts;
+    }
+    return syscall_ret(__syscall5(SYS_ppoll, (long)fds, (long)nfds, (long)tsp, 0L, 0L));
+}

src/select/ppoll.c

@@ -0,0 +1,24 @@
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <poll.h>
+
+#include "../internal/syscall.h"
+
+#if VLIBC_LEVEL_GE(2)
+
+/*
+ * ppoll: Linux-specific poll over SYS_ppoll with a struct timespec timeout
+ * and an optional signal mask (the kernel takes the mask and its size as
+ * separate trailing arguments; the size is only announced — as the 8-byte
+ * kernel sigset size — when a mask is actually given).
+ */
+int
+ppoll(struct pollfd *fds, nfds_t nfds, const struct timespec *timeout, const sigset_t *sigmask)
+{
+    return syscall_ret(__syscall5(SYS_ppoll, (long)fds, (long)nfds, (long)timeout, (long)sigmask,
+                                  sigmask != NULL ? (long)sizeof(sigset_t) : 0L));
+}
+
+#endif /* VLIBC_LEVEL_GE(2) */

src/select/pselect.c

@@ -0,0 +1,27 @@
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <sys/select.h>
+
+#include "../internal/syscall.h"
+
+/*
+ * pselect: plain POSIX pselect over SYS_pselect6. Its 6th kernel argument is
+ * a pointer to a { sigset_t *, size_t } pair (the kernel reads two words);
+ * NULL means "leave the signal mask alone", so the pair is only supplied —
+ * and only the 8-byte kernel sigset size announced — when sigmask is given.
+ * The timeout passes through as a struct timespec (NULL = indefinite).
+ */
+int
+pselect(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
+        const struct timespec *timeout, const sigset_t *sigmask)
+{
+    long data[2];
+
+    data[0] = (long)sigmask;
+    data[1] = (long)sizeof(sigset_t);
+    return syscall_ret(__syscall6(SYS_pselect6, (long)nfds, (long)readfds, (long)writefds,
+                                  (long)exceptfds, (long)timeout,
+                                  sigmask != NULL ? (long)data : 0L));
+}

src/select/select.c

@@ -0,0 +1,38 @@
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <sys/select.h>
+
+#include <errno.h>
+
+#include "../internal/syscall.h"
+
+/*
+ * select: plain POSIX select over SYS_pselect6. The kernel wants a struct
+ * timespec, so the struct timeval timeout is converted here (NULL passes
+ * through as "block indefinitely") and the sigset pair stays NULL: select
+ * never changes the signal mask. select() and pselect() share this syscall
+ * on Linux; the 6th argument of pselect6 is a { sigset_t *, size_t } pair
+ * pointer that is NULL when the mask is left alone.
+ */
+int
+select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout)
+{
+    struct timespec ts;
+    struct timespec *tsp = NULL;
+
+    if (timeout != NULL)
+    {
+        if (timeout->tv_sec < 0 || timeout->tv_usec < 0 || timeout->tv_usec >= 1000000L)
+        {
+            errno = EINVAL;
+            return -1;
+        }
+        ts.tv_sec = timeout->tv_sec;
+        ts.tv_nsec = (long)timeout->tv_usec * 1000;
+        tsp = &ts;
+    }
+    return syscall_ret(__syscall6(SYS_pselect6, (long)nfds, (long)readfds, (long)writefds,
+                                  (long)exceptfds, (long)tsp, 0L));
+}