libc: Use the new write() syscall

The new one is write(fd, buf, count).
The old one was write(buf, count).

So the old one tries to pass buf as a file descriptor, and write() complains that 4000000 is too large of a file descriptor and throws EBADF.

We now use the new syscall, through the wrapper that fwrite() provides us.

kernel/include/fs/FileDescriptor.h

@@ -14,14 +14,20 @@ struct Descriptor
         return m_can_read && m_is_open;
     }
 
+    bool can_write()
+    {
+        return m_can_write && m_is_open;
+    }
+
     void close()
     {
         m_is_open = false;
     }
 
     ssize_t read(size_t size, char* buffer);
+    ssize_t write(size_t size, const char* buffer);
 
-    void open(VFS::Node* node, bool can_read);
+    void open(VFS::Node* node, bool can_read, bool can_write);
 
     Descriptor(const Descriptor& other);
     Descriptor();
@@ -29,6 +35,7 @@ struct Descriptor
   private:
     bool m_is_open;
     bool m_can_read;
+    bool m_can_write;
     VFS::Node* m_node;
     uint64_t m_offset;
 };

kernel/include/fs/VFS.h

@@ -14,6 +14,7 @@ namespace VFS
     struct Node;
 
     typedef ssize_t (*node_read)(Node*, size_t, size_t, char*);
+    typedef ssize_t (*node_write)(Node*, size_t, size_t, const char*);
     typedef Node* (*node_finddir)(Node*, const char*);
     typedef int (*node_mkdir)(Node*, const char*);
 
@@ -27,10 +28,12 @@ namespace VFS
         node_read read_func;
         node_finddir find_func;
         node_mkdir mkdir_func;
+        node_write write_func;
         Node* link;
     };
 
     ssize_t read(Node* node, size_t offset, size_t length, char* buffer);
+    ssize_t write(Node* node, size_t offset, size_t length, const char* buffer);
     int mkdir(const char* path, const char* name); // FIXME: Support deducing this via a single path.
 
     void mount_root(Node* root);

kernel/include/fs/devices/Console.h

@@ -0,0 +1,9 @@
+#pragma once
+#include "fs/VFS.h"
+
+namespace ConsoleDevice
+{
+    VFS::Node* create_new();
+
+    ssize_t write(VFS::Node* node, size_t offset, size_t size, const char* buffer);
+}

kernel/include/sys/Syscall.h

@@ -24,7 +24,7 @@ namespace Syscall
 void sys_exit(Context* context, int status);
 void sys_yield(Context* context);
 void sys_sleep(Context* context, uint64_t ms);
-void sys_write(Context* context, const char* addr, size_t size);
+void sys_write(Context* context, int fd, size_t size, const char* addr);
 void sys_paint(Context* context, uint64_t x, uint64_t y, uint64_t w, uint64_t h, uint64_t col);
 void sys_rand(Context* context);
 void sys_getversion(Context* context, char* buffer, size_t max);

kernel/src/fs/FileDescriptor.cpp

@@ -5,13 +5,15 @@ Descriptor::Descriptor() : m_is_open(false)
 }
 
 Descriptor::Descriptor(const Descriptor& other)
-    : m_is_open(other.m_is_open), m_can_read(other.m_can_read), m_node(other.m_node), m_offset(other.m_offset)
+    : m_is_open(other.m_is_open), m_can_read(other.m_can_read), m_can_write(other.m_can_write), m_node(other.m_node),
+      m_offset(other.m_offset)
 {
 }
 
-void Descriptor::open(VFS::Node* node, bool can_read)
+void Descriptor::open(VFS::Node* node, bool can_read, bool can_write)
 {
     m_can_read = can_read;
+    m_can_write = can_write;
     m_node = node;
     m_offset = 0;
     m_is_open = true;
@@ -22,4 +24,11 @@ ssize_t Descriptor::read(size_t size, char* buffer)
     ssize_t result = VFS::read(m_node, m_offset, size, buffer);
     m_offset += result;
     return result;
+}
+
+ssize_t Descriptor::write(size_t size, const char* buffer)
+{
+    ssize_t result = VFS::write(m_node, m_offset, size, buffer);
+    m_offset += result;
+    return result;
 }

kernel/src/fs/VFS.cpp

@@ -26,12 +26,30 @@ ssize_t VFS::read(Node* node, size_t offset, size_t length, char* buffer)
         return -1;
     }
 
-    kdbgln("read(): node %s (inode %ld), offset %zd, %zd bytes, into %p", node->name, node->inode, offset, length,
-           (void*)buffer);
-
     return node->read_func(node, offset, length, buffer);
 }
 
+ssize_t VFS::write(Node* node, size_t offset, size_t length, const char* buffer)
+{
+    if (!node)
+    {
+        kwarnln("write() failed: trying to write to nullptr");
+        return -1;
+    }
+    if (node->type == VFS_DIRECTORY)
+    {
+        kwarnln("write() failed: is a directory");
+        return -EISDIR;
+    }
+    if (!node->write_func)
+    {
+        kwarnln("write() failed: the chosen node doesn't support writing");
+        return -1;
+    }
+
+    return node->write_func(node, offset, length, buffer);
+}
+
 void VFS::mount_root(Node* root)
 {
     if (!root)
@@ -92,15 +110,12 @@ VFS::Node* VFS::resolve_path(const char* filename, Node* root)
             }
             if (child->flags & VFS_MOUNTPOINT)
             {
-                kdbgln("Current node (%s, inode=%ld) is a mountpoint, resolving actual node", child->name,
-                       child->inode);
                 if (!child->link)
                 {
                     kwarnln("Current node's link is null");
                     return 0;
                 }
                 child = child->link;
-                kdbgln("Resolved to %s (inode %ld)", child->name, child->inode);
             }
             current_node = child;
             kfree(buffer);

kernel/src/fs/devices/Console.cpp

@@ -0,0 +1,25 @@
+#include "fs/devices/Console.h"
+#include "config.h"
+#include "render/TextRenderer.h"
+#include "std/stdio.h"
+#include "std/stdlib.h"
+#include "std/string.h"
+
+VFS::Node* ConsoleDevice::create_new()
+{
+    VFS::Node* dev = new VFS::Node;
+    dev->write_func = ConsoleDevice::write;
+    dev->inode = 0;
+    dev->length = 0;
+    dev->type = VFS_FILE;
+    dev->flags = 0;
+    strncpy(dev->name, "console", sizeof(dev->name));
+    return dev;
+}
+
+ssize_t ConsoleDevice::write(VFS::Node* node, size_t, size_t size, const char* buffer)
+{
+    if (!node) return -1;
+    TextRenderer::write(buffer, size);
+    return (ssize_t)size;
+}

kernel/src/fs/devices/DeviceFS.cpp

@@ -1,4 +1,5 @@
 #include "fs/devices/DeviceFS.h"
+#include "fs/devices/Console.h"
 #include "fs/devices/Version.h"
 #include "std/stdlib.h"
 #include "std/string.h"
@@ -21,6 +22,7 @@ VFS::Node* DeviceFS::get()
     strncpy(devfs_root->name, "dev", sizeof(devfs_root->name));
 
     devfs_files[devfs_file_count++] = VersionDevice::create_new();
+    devfs_files[devfs_file_count++] = ConsoleDevice::create_new();
     return devfs_root;
 }
 

kernel/src/fs/devices/Version.cpp

@@ -11,6 +11,7 @@ VFS::Node* VersionDevice::create_new()
     dev->inode = 0;
     dev->length = strlen(moon_version()) + 5;
     dev->type = VFS_FILE;
+    dev->flags = 0;
     strncpy(dev->name, "version", sizeof(dev->name));
     return dev;
 }
@@ -20,7 +21,6 @@ ssize_t VersionDevice::read(VFS::Node* node, size_t offset, size_t size, char* b
     if (!node) return -1;
     if (offset > node->length) return -1;
     if (offset + size > node->length) { size = node->length - offset; }
-    if (offset > 0) return -1;
     snprintf(buffer, size + 1, "moon %s", moon_version()); // FIXME: Support offseting this read
     return (ssize_t)size;
 }

kernel/src/sys/Syscall.cpp

@@ -18,7 +18,7 @@ void Syscall::entry(Context* context)
         sys_sleep(context, context->rdi);
         break;
     case SYS_write: // sys_write
-        sys_write(context, (const char*)context->rdi, context->rsi);
+        sys_write(context, (int)context->rdi, context->rsi, (const char*)context->rdx);
         break;
     case SYS_paint: sys_paint(context, context->rdi, context->rsi, context->rdx, context->r10, context->r8); break;
     case SYS_rand: sys_rand(context); break;

kernel/src/sys/stdio.cpp

@@ -8,12 +8,44 @@
 #include "thread/Scheduler.h"
 #include "thread/Task.h"
 
+#define OPEN_READ 1
+#define OPEN_WRITE 2
+
 #define STDIO_FAIL(function, error) kwarnln("%s failed with %s", #function, #error)
 
-void sys_write(Context* context, const char* addr, size_t size)
+void sys_write(Context* context, int fd, size_t size, const char* addr)
 {
-    context->rax = size;
-    TextRenderer::write(addr, size);
+    if (!addr)
+    {
+        STDIO_FAIL(write, EINVAL);
+        context->rax = -EINVAL; // FIXME: This should probably return EFAULT.
+        return;
+    }
+    if (fd >= TASK_MAX_FDS || fd < 0)
+    {
+        kwarnln("file descriptor %d is outside the valid range", fd);
+        STDIO_FAIL(write, EBADF);
+        context->rax = -EBADF;
+        return;
+    }
+    Task* current_task = Scheduler::current_task();
+    if (!current_task->files[fd].is_open())
+    {
+        kwarnln("file descriptor %d is not open", fd);
+        STDIO_FAIL(write, EBADF);
+        context->rax = -EBADF;
+        return;
+    }
+    if (!current_task->files[fd].can_write())
+    {
+        kwarnln("file descriptor %d is not open for writing", fd);
+        STDIO_FAIL(write, EBADF);
+        context->rax = -EBADF;
+        return;
+    }
+    ssize_t result = current_task->files[fd].write(size, addr);
+    context->rax = (size_t)result;
+    return;
 }
 
 void sys_open(Context* context, const char* filename, int flags)
@@ -24,12 +56,14 @@ void sys_open(Context* context, const char* filename, int flags)
     {
         if (!current_task->files[fd].is_open()) break;
     }
+
     if (fd == TASK_MAX_FDS)
     {
         STDIO_FAIL(open, EMFILE);
         context->rax = -EMFILE;
         return;
     }
+
     VFS::Node* node = VFS::resolve_path(filename);
     if (!node)
     {
@@ -37,9 +71,23 @@ void sys_open(Context* context, const char* filename, int flags)
         context->rax = -ENOENT;
         return;
     }
-    kdbgln("open(): opening %s, allocated file descriptor %d", filename, fd);
-    current_task->files[fd].open(node,
-                                 (bool)flags); // FIXME: Implement more flags. (right now, 1 is can_read, 0 is not)
+
+    bool can_read = (flags & OPEN_READ) > 0;
+    bool can_write = (flags & OPEN_WRITE) > 0;
+    if (!can_read && !can_write)
+    {
+        STDIO_FAIL(open, EINVAL);
+        context->rax = -EINVAL;
+        return;
+    }
+
+    kdbgln("open(): opening %s %s, allocated file descriptor %d", filename,
+           (can_read && can_write) ? "rw"
+           : can_read              ? "r-"
+                                   : "-w",
+           fd);
+
+    current_task->files[fd].open(node, can_read, can_write);
     context->rax = fd;
     return;
 }

libs/libc/crt0.asm

@@ -3,6 +3,7 @@ section .text
 extern _init
 extern main
 extern _fini
+extern initialize_libc
 extern exit
 
 global _start
@@ -13,6 +14,8 @@ _start:
 	push rbp ; rbp=0
 	mov rbp, rsp
 
+	call initialize_libc
+
 	call _init
 
     mov rdi, 0 ; argc = 0

libs/libc/include/fcntl.h

@@ -2,6 +2,8 @@
 #define _FCNTL_H
 
 #define O_RDONLY 1
+#define O_WRONLY 2
+#define O_RDWR 3
 
 #ifdef __cplusplus
 extern "C"

libs/libc/include/stdio.h

@@ -13,13 +13,15 @@ typedef struct
     int f_err;
 } FILE;
 
+extern FILE* __stderr;
+extern FILE* __stdout;
+#define stderr __stderr
+#define stdout __stdout
+
 #ifdef __cplusplus
 extern "C"
 {
 #endif
-
-    extern FILE* stderr;
-#define stderr stderr
     int fclose(FILE*);
     int fflush(FILE*);
     FILE* fopen(const char*, const char*);

libs/libc/include/unistd.h

@@ -16,6 +16,7 @@ extern "C"
     unsigned int sleep(unsigned int);
 
     ssize_t read(int, void*, size_t);
+    ssize_t write(int, const void*, size_t);
     int close(int);
 
 #ifdef __cplusplus

libs/libc/src/file.cpp

@@ -5,6 +5,9 @@
 #include <stdlib.h>
 #include <unistd.h>
 
+FILE* __stderr;
+FILE* __stdout;
+
 extern "C"
 {
     int fclose(FILE* stream)
@@ -29,7 +32,7 @@ extern "C"
 
     FILE* fopen(const char* pathname, const char*)
     {
-        int fd = open(pathname, O_RDONLY); // FIXME: Use the mode string.
+        int fd = open(pathname, O_RDWR); // FIXME: Use the mode string.
         if (fd < 0) { return 0; }
         FILE* stream = (FILE*)malloc(sizeof(FILE));
         stream->f_fd = fd;
@@ -74,9 +77,16 @@ extern "C"
         NOT_IMPLEMENTED("ftell");
     }
 
-    size_t fwrite(const void*, size_t, size_t, FILE*)
+    size_t fwrite(const void* buf, size_t size, size_t nmemb, FILE* stream)
     {
-        NOT_IMPLEMENTED("fwrite");
+        ssize_t status = write(stream->f_fd, buf, size * nmemb);
+        if (status < 0)
+        {
+            stream->f_err = 1;
+            return 0;
+        }
+        if (status == 0) stream->f_eof = 1;
+        return (size_t)status;
     }
 
     void setbuf(FILE*, char*)

libs/libc/src/init.cpp

@@ -0,0 +1,14 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+extern "C" void initialize_libc()
+{
+    __stderr = fopen("/dev/console", "rw");
+    if (!stderr) exit(errno);
+    __stdout = fopen("/dev/console", "rw");
+    if (!stdout) exit(errno);
+    clearerr(__stderr);
+    clearerr(__stdout);
+}

libs/libc/src/luna.cpp

@@ -1,4 +1,5 @@
 #include <luna.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/syscall.h>
@@ -20,7 +21,7 @@ extern "C"
 
     noreturn void __luna_abort(const char* message)
     {
-        syscall(SYS_write, message, strlen(message));
+        fwrite(message, strlen(message), 1, stdout);
         abort();
     }
 }

libs/libc/src/printf.cpp

@@ -306,8 +306,7 @@ extern "C"
 {
     int vprintf(const char* format, va_list ap)
     {
-        return internal_printf(
-            format, [](const char* s) { syscall(SYS_write, s, strlen(s)); }, -1, ap);
+        return vfprintf(stdout, format, ap);
     }
 
     int vsprintf(char* str, const char* format, va_list ap)
@@ -352,23 +351,23 @@ extern "C"
     {
         va_list ap;
         va_start(ap, format);
-        int written = vprintf(format, ap);
+        int written = vfprintf(stdout, format, ap);
         va_end(ap);
         return written;
     }
 
-    int fprintf(FILE*, const char* format, ...) // FIXME: Make fprintf print to the selected file instead of stdout.
+    int fprintf(FILE* stream, const char* format, ...)
     {
         va_list ap;
         va_start(ap, format);
-        int written = vprintf(format, ap);
+        int written = vfprintf(stream, format, ap);
         va_end(ap);
         return written;
     }
 
-    int vfprintf(FILE*, const char* format,
-                 va_list ap) // FIXME: Make vfprintf print to the selected file instead of stdout.
+    int vfprintf(FILE* stream, const char* format, va_list ap)
     {
-        return vprintf(format, ap);
+        return internal_printf(
+            format, [&](const char* s) { fwrite(s, strlen(s), 1, stream); }, -1, ap);
     }
 }

libs/libc/src/stdio.cpp

@@ -10,9 +10,9 @@ extern "C"
 {
     int puts(const char* s)
     {
-        long nwritten = syscall(SYS_write, s, strlen(s));
+        long nwritten = fwrite(s, strlen(s), 1, stdout);
         if (nwritten < 0) return -1;
-        nwritten += syscall(SYS_write, "\n", 1);
+        nwritten += fwrite("\n", 1, 1, stdout);
         return (int)nwritten;
     }
     void perror(const char* s) // FIXME: Print to stderr, whenever we have an stderr.

libs/libc/src/unistd.cpp

@@ -37,7 +37,6 @@ extern "C"
         case SYS_exit:
         case SYS_close:
         case SYS_sleep: result = __luna_syscall1(number, va_arg(ap, arg)); break;
-        case SYS_write:
         case SYS_munmap:
         case SYS_open:
         case SYS_getversion: {
@@ -46,6 +45,7 @@ extern "C"
             result = __luna_syscall2(number, arg0, arg1);
             break;
         }
+        case SYS_write:
         case SYS_read:
         case SYS_mmap: {
             arg arg0 = va_arg(ap, arg);
@@ -80,6 +80,11 @@ extern "C"
         return syscall(SYS_read, fd, count, buf); // yes, our read() syscall is in the wrong order.
     }
 
+    ssize_t write(int fd, const void* buf, size_t count)
+    {
+        return syscall(SYS_write, fd, count, buf); // yes, our read() syscall is in the wrong order.
+    }
+
     int close(int fd)
     {
         return (int)syscall(SYS_close, fd);