kernel+libc: Add the poll() syscall

kernel/CMakeLists.txt

@@ -42,6 +42,7 @@ set(SOURCES
     src/sys/resource.cpp
     src/sys/signal.cpp
     src/sys/socket.cpp
+    src/sys/poll.cpp
     src/fs/VFS.cpp
     src/fs/Pipe.cpp
     src/fs/Mount.cpp

kernel/src/sys/poll.cpp

@@ -0,0 +1,70 @@
+#include "fs/VFS.h"
+#include "memory/MemoryManager.h"
+#include "sys/Syscall.h"
+#include "thread/Scheduler.h"
+#include <bits/poll.h>
+
+Result<u64> sys_poll(Registers* regs, SyscallArgs args)
+{
+    struct pollfd* fds = (struct pollfd*)args[0];
+    nfds_t nfds = (nfds_t)args[1];
+    int timeout = (int)args[2];
+
+    struct pollfd* kfds = (struct pollfd*)TRY(malloc_impl(nfds * sizeof(pollfd)));
+    auto guard = make_scope_guard([kfds] { free_impl(kfds); });
+
+    if (!MemoryManager::copy_from_user(fds, kfds, nfds * sizeof(pollfd))) return err(EFAULT);
+
+    Vector<SharedPtr<VFS::Inode>> inodes;
+    auto* current = Scheduler::current();
+
+    for (nfds_t i = 0; i < nfds; i++)
+    {
+        int fd = kfds[i].fd;
+        auto maybe_inode = current->resolve_fd(fd);
+        if (maybe_inode.has_error())
+        {
+            kfds[i].revents |= POLLNVAL;
+            TRY(inodes.try_append({}));
+        }
+        else
+            TRY(inodes.try_append(maybe_inode.release_value()->description->inode));
+    }
+
+    bool infinite = timeout < 0;
+    int fds_with_events;
+
+    do {
+        fds_with_events = 0;
+        for (nfds_t i = 0; i < nfds; i++)
+        {
+            auto& inode = inodes[i];
+            if (!inode) continue;
+
+            if (kfds[i].events & POLLIN && !inode->will_block_if_read())
+            {
+                fds_with_events++;
+                kfds[i].revents |= POLLIN;
+            }
+        }
+
+        if (!fds_with_events && (timeout > 0 || infinite))
+        {
+            kernel_sleep(10);
+            timeout -= (int)current->sleep_ticks_left;
+            if (current->interrupted)
+            {
+                guard.deactivate();
+                free_impl(kfds);
+                if (current->will_invoke_signal_handler()) return err(EINTR);
+                current->process_pending_signals(regs);
+                return err(EINTR);
+            }
+            continue;
+        }
+    } while (false);
+
+    MemoryManager::copy_to_user(fds, kfds, nfds * sizeof(pollfd));
+
+    return fds_with_events;
+}

libc/include/bits/fixed-size-types.h

@@ -3,7 +3,8 @@
 #ifndef _BITS_FIXED_SIZE_TYPES_H
 #define _BITS_FIXED_SIZE_TYPES_H
 
-#if !defined(_SYS_TYPES_H) && !defined(_BITS_SETJMP_TYPES_H) && !defined(_BITS_MAKEDEV_H) && !defined(_BITS_TERMIOS_H)
+#if !defined(_SYS_TYPES_H) && !defined(_BITS_SETJMP_TYPES_H) && !defined(_BITS_MAKEDEV_H) &&                           \
+    !defined(_BITS_TERMIOS_H) && !defined(_BITS_POLL_H)
 #error "Never include bits/fixed-size-types.h, use the standard <stdint.h> header instead."
 #endif
 

libc/include/bits/poll.h

@@ -0,0 +1,21 @@
+/* bits/poll.h: The pollfd data structure. */
+
+#ifndef _BITS_POLL_H
+#define _BITS_POLL_H
+
+#include <bits/fixed-size-types.h>
+
+#define POLLIN 0
+#define POLLERR 1
+#define POLLNVAL 2
+
+typedef __u64_t nfds_t;
+
+struct pollfd
+{
+    int fd;
+    short events;
+    short revents;
+};
+
+#endif

libluna/include/luna/Syscall.h

@@ -7,7 +7,7 @@
                 _e(fstatat) _e(chdir) _e(getcwd) _e(unlinkat) _e(uname) _e(sethostname) _e(dup2) _e(pipe) _e(mount)    \
                     _e(umount) _e(pstat) _e(getrusage) _e(symlinkat) _e(readlinkat) _e(umask) _e(linkat) _e(faccessat) \
                         _e(pivot_root) _e(sigreturn) _e(sigaction) _e(kill) _e(sigprocmask) _e(setpgid) _e(isatty)     \
-                            _e(getpgid) _e(socket) _e(bind) _e(connect) _e(listen) _e(accept)
+                            _e(getpgid) _e(socket) _e(bind) _e(connect) _e(listen) _e(accept) _e(poll)
 
 enum Syscalls
 {