More work towards getting bash to build.

Implemented some syscalls: dup(), dup2(), getdtablesize().
FileHandle is now a retainable, since that's needed for dup()'ed fd's.
I didn't really test any of this beyond a basic smoke check.

LibC/dirent.cpp

@@ -3,6 +3,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <errno.h>
 #include <Kernel/Syscall.h>
 
 extern "C" {
@@ -20,6 +21,16 @@ DIR* opendir(const char* name)
     return dirp;
 }
 
+int closedir(DIR* dirp)
+{
+    if (!dirp || dirp->fd == -1)
+        return -EBADF;
+    int rc = close(dirp->fd);
+    if (rc == 0)
+        dirp->fd = -1;
+    return rc;
+}
+
 struct sys_dirent {
     ino_t ino;
     byte file_type;

LibC/dirent.h

@@ -23,7 +23,8 @@ struct __DIR {
 typedef struct __DIR DIR;
 
 DIR* opendir(const char* name);
-struct dirent* readdir(DIR* dirp);
+int closedir(DIR*);
+struct dirent* readdir(DIR*);
 
 __END_DECLS
 

LibC/stdio.cpp

@@ -193,6 +193,17 @@ FILE* fopen(const char* pathname, const char* mode)
     return fp;
 }
 
+FILE* fdopen(int fd, const char* mode)
+{
+    assert(!strcmp(mode, "r") || !strcmp(mode, "rb"));
+    if (fd < 0)
+        return nullptr;
+    auto* fp = (FILE*)malloc(sizeof(FILE));
+    fp->fd = fd;
+    fp->eof = false;
+    return fp;
+}
+
 int fclose(FILE* stream)
 {
     int rc = close(stream->fd);

LibC/stdio.h

@@ -29,6 +29,7 @@ int fileno(FILE*);
 int fgetc(FILE*);
 int getc(FILE*);
 int getchar();
+FILE* fdopen(int fd, const char* mode);
 FILE* fopen(const char* pathname, const char* mode);
 int fclose(FILE*);
 void rewind(FILE*);

LibC/unistd.cpp

@@ -190,5 +190,22 @@ int isatty(int fd)
     __RETURN_WITH_ERRNO(rc, 1, 0);
 }
 
+int getdtablesize()
+{
+    int rc = Syscall::invoke(Syscall::Getdtablesize);
+    __RETURN_WITH_ERRNO(rc, 1, 0);
 }
 
+int dup(int old_fd)
+{
+    int rc = Syscall::invoke(Syscall::Dup, (dword)old_fd);
+    __RETURN_WITH_ERRNO(rc, rc, -1);
+}
+
+int dup2(int old_fd, int new_fd)
+{
+    int rc = Syscall::invoke(Syscall::Dup2, (dword)old_fd, (dword)new_fd);
+    __RETURN_WITH_ERRNO(rc, rc, -1);
+}
+
+}

LibC/unistd.h

@@ -39,6 +39,9 @@ int ttyname_r(int fd, char* buffer, size_t);
 off_t lseek(int fd, off_t, int whence);
 int link(const char* oldpath, const char* newpath);
 int unlink(const char* pathname);
+int getdtablesize();
+int dup(int old_fd);
+int dup2(int old_fd, int new_fd);
 
 #define WEXITSTATUS(status) (((status) & 0xff00) >> 8)
 #define WTERMSIG(status) ((status) & 0x7f)