Kernel, libc: Add fstat()

kernel/include/sys/Syscall.h

@@ -22,6 +22,9 @@
 #define SYS_fork 17
 #define SYS_waitpid 18
 #define SYS_access 19
+#define SYS_fstat 20
+
+struct stat;
 
 namespace Syscall
 {
@@ -47,4 +50,5 @@ void sys_clock(Context* context);
 void sys_mkdir(Context* context, const char* filename);
 void sys_fork(Context* context);
 void sys_waitpid(Context* context, long pid, int* wstatus, int options);
-void sys_access(Context* context, const char* path, int amode);
+void sys_access(Context* context, const char* path, int amode);
+void sys_fstat(Context* context, int fd, struct stat* buf);

kernel/src/sys/Syscall.cpp

@@ -31,7 +31,8 @@ void Syscall::entry(Context* context)
     case SYS_fork: sys_fork(context); break;
     case SYS_waitpid: sys_waitpid(context, (long)context->rdi, (int*)context->rsi, (int)context->rdx); break;
     case SYS_access: sys_access(context, (const char*)context->rdi, (int)context->rsi); break;
+    case SYS_fstat: sys_fstat(context, (int)context->rdi, (struct stat*)context->rsi); break;
     default: context->rax = -ENOSYS; break;
     }
     VMM::exit_syscall_context();
-}
+}

kernel/src/sys/stat.cpp

@@ -0,0 +1,44 @@
+#include "fs/VFS.h"
+#include "interrupts/Context.h"
+#include "std/errno.h"
+#include "sys/UserMemory.h"
+#include "thread/Scheduler.h"
+
+typedef unsigned long off_t;
+typedef unsigned short mode_t;
+typedef unsigned long ino_t;
+
+struct stat // FIXME: This struct is quite stubbed out.
+{
+    ino_t st_ino;
+    mode_t st_mode;
+    off_t st_size;
+};
+
+void sys_fstat(Context* context, int fd, struct stat* buf)
+{
+    Task* current_task = Scheduler::current_task();
+    if (fd < 0 || fd >= TASK_MAX_FDS)
+    {
+        context->rax = -EBADF;
+        return;
+    }
+    Descriptor& file = current_task->files[fd];
+    if (!file.is_open())
+    {
+        context->rax = -EBADF;
+        return;
+    }
+    struct stat* kstat = obtain_user_ref(buf);
+    if (!kstat)
+    {
+        context->rax = -EFAULT; // FIXME: The manual doesn't say fstat can return EFAULT, but it seems logical here...
+        return;
+    }
+    VFS::Node* node = file.node();
+    kstat->st_ino = node->inode;
+    kstat->st_mode = (mode_t)node->type;
+    kstat->st_size = node->length;
+    release_user_ref(kstat);
+    context->rax = 0;
+}

libs/libc/include/luna/vfs.h

@@ -0,0 +1,8 @@
+#ifndef _LUNA_VFS_H
+#define _LUNA_VFS_H
+
+#define __VFS_FILE 0x0
+#define __VFS_DIRECTORY 0x1
+#define __VFS_DEVICE 0x2
+
+#endif

libs/libc/include/sys/stat.h

@@ -1,8 +1,18 @@
 #ifndef _SYS_STAT_H
 #define _SYS_STAT_H
 
+#include <luna/vfs.h>
 #include <sys/types.h>
 
+struct stat // FIXME: This struct is quite stubbed out.
+{
+    ino_t st_ino;
+    mode_t st_mode;
+    off_t st_size;
+};
+
+#define S_ISDIR(mode) (((mode)&0xf) == __VFS_DIRECTORY)
+
 #ifdef __cplusplus
 extern "C"
 {
@@ -11,6 +21,9 @@ extern "C"
     /* Creates a new directory at the path pathname. FIXME: For now, mode is ignored. */
     int mkdir(const char* pathname, mode_t mode);
 
+    /* Returns information about the file pointed to by fd in buf. */
+    int fstat(int fd, struct stat* buf);
+
 #ifdef __cplusplus
 }
 #endif

libs/libc/include/sys/syscall.h

@@ -21,5 +21,6 @@
 #define SYS_fork 17
 #define SYS_waitpid 18
 #define SYS_access 19
+#define SYS_fstat 20
 
 #endif

libs/libc/src/sys/stat.cpp

@@ -8,4 +8,9 @@ extern "C"
     {
         return (int)syscall(SYS_mkdir, pathname);
     }
+
+    int fstat(int fd, struct stat* buf)
+    {
+        return (int)syscall(SYS_fstat, fd, buf);
+    }
 }

libs/libc/src/syscall.cpp

@@ -23,6 +23,7 @@ extern "C" long syscall(long number, ...)
     case SYS_sleep: result = __luna_syscall1(number, va_arg(ap, arg)); break;
     case SYS_munmap:
     case SYS_access:
+    case SYS_fstat:
     case SYS_open: {
         arg arg0 = va_arg(ap, arg);
         arg arg1 = va_arg(ap, arg);