kernel+libc: Add the poll() syscall

Placement new on arrays is a bit unreliable and could cause out-of-bounds data accesses.

apps/login.cpp

@@ -26,11 +26,12 @@ Result<int> luna_main(int argc, char** argv)
 
     String name;
 
+    setpgid(0, 0);
+    signal(SIGTTOU, SIG_IGN);
+    if (isatty(STDIN_FILENO)) tcsetpgrp(STDIN_FILENO, getpgid(0));
+
     if (username.is_empty())
     {
-        signal(SIGTTOU, SIG_IGN);
-
-        if (isatty(STDIN_FILENO)) tcsetpgrp(STDIN_FILENO, getpgid(0));
 
         auto input = os::File::standard_input();
 

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/arch/x86_64/disk/ATA.cpp

@@ -754,8 +754,8 @@ Result<u64> ATADevice::read(u8* buf, usize offset, usize size) const
     ScopedKMutexLock<100> lock(m_drive->channel()->lock());
 
     // FIXME: Don't always allocate this if we don't need it.
-    auto* temp = TRY(make_array<u8>(block_size));
-    auto guard = make_scope_guard([temp] { delete[] temp; });
+    auto* temp = (u8*)TRY(malloc_impl(block_size));
+    auto guard = make_scope_guard([temp] { free_impl(temp); });
 
     if (offset % block_size)
     {

kernel/src/fs/GPT.cpp

@@ -41,8 +41,8 @@ namespace GPT
 
         u32 partition_index = 1;
 
-        auto* table = TRY(make_array<PartitionEntry>(header.num_partitions));
-        auto guard = make_scope_guard([table] { delete[] table; });
+        auto* table = (PartitionEntry*)TRY(calloc_impl(header.num_partitions, sizeof(PartitionEntry)));
+        auto guard = make_scope_guard([table] { free_impl(table); });
 
         nread = TRY(device->read((u8*)table, partition_table_start, sizeof(PartitionEntry) * header.num_partitions));
         check(nread == sizeof(PartitionEntry) * header.num_partitions);

kernel/src/fs/ext2/Inode.cpp

@@ -91,8 +91,8 @@ namespace Ext2
         const usize inode_size = m_metadata.size;
         const usize block_size = m_fs->m_block_size;
 
-        u8* const buf = TRY(make_array<u8>(block_size));
-        auto guard = make_scope_guard([buf] { delete[] buf; });
+        u8* const buf = (u8*)TRY(calloc_impl(block_size, 1));
+        auto guard = make_scope_guard([buf] { free_impl(buf); });
 
         m_entries.clear();
 

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

libc/src/stdio.cpp

@@ -432,7 +432,12 @@ extern "C"
     {
         u8 value;
         ssize_t rc = read_from_buffer(stream, &value, 1);
-        if (rc <= 0) return EOF;
+        if (rc < 0)
+        {
+            stream->_err = 1;
+            return EOF;
+        }
+        else if (rc == 0) { return EOF; }
         return value;
     }
 

libluna/include/luna/Alloc.h

@@ -10,19 +10,7 @@ template <typename T, class... Args> [[nodiscard]] Result<T*> make(Args... args)
     return result;
 }
 
-template <typename T> [[nodiscard]] Result<T*> make_array(usize count)
-{
-    T* const result = (T*)TRY(calloc_impl(count, sizeof(T)));
-    new (result) T[count];
-    return result;
-}
-
 template <typename T> void destroy(T* item)
 {
     delete item;
 }
-
-template <typename T> void destroy_array(T* item)
-{
-    delete[] item;
-}

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
 {

libos/src/File.cpp

@@ -149,9 +149,9 @@ namespace os
         int current;
         while (true)
         {
-            current = fgetc(m_file);
+            current = TRY(getchar());
 
-            if (current == -1) break;
+            if (current == EOF) break;
 
             TRY(data.try_append((char)current));
 
@@ -208,7 +208,9 @@ namespace os
 
     Result<int> File::getchar()
     {
-        return fgetc(m_file);
+        int rc = fgetc(m_file);
+        if (rc == EOF && ferror(m_file)) return err(errno);
+        return rc;
     }
 
     void File::set_close_on_exec()

libos/src/FileSystem.cpp

@@ -82,12 +82,11 @@ namespace os::FileSystem
         TRY(stat(path, st, false));
         if (!S_ISLNK(st.st_mode)) return String {};
 
-        char* buf = TRY(make_array<char>(st.st_size + 1));
-        auto guard = make_scope_guard([buf] { delete[] buf; });
+        char* buf = (char*)TRY(calloc_impl(st.st_size + 1, 1));
+        auto guard = make_scope_guard([buf] { free_impl(buf); });
         usize nread = TRY(
             Result<usize>::from_syscall(syscall(SYS_readlinkat, path.dirfd(), path.name().chars(), buf, st.st_size)));
 
-        buf[nread] = '\0';
         guard.deactivate();
 
         return String { buf, nread };