Implement sys$chdir() and teach sh+ls to cd around and browse different dirs.

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/2749e7f1c2b

Kernel/Syscall.cpp

@@ -110,6 +110,8 @@ DWORD handle(DWORD function, DWORD arg1, DWORD arg2, DWORD arg3)
         return 0;
     case Syscall::GetArguments:
         return current->sys$get_arguments((int*)arg1, (char***)arg2);
+    case Syscall::PosixChdir:
+        return current->sys$chdir((const char*)arg1);
     default:
         kprintf("int0x80: Unknown function %x requested {%x, %x, %x}\n", function, arg1, arg2, arg3);
         break;

Kernel/Syscall.h

@@ -32,6 +32,7 @@ enum Function {
     PosixGettimeofday = 0x2000,
     PosixGethostname = 0x2001,
     GetArguments = 0x2002,
+    PosixChdir = 0x2003,
 };
 
 void initialize();

Kernel/Task.cpp

@@ -205,7 +205,14 @@ Task* Task::createUserTask(const String& path, uid_t uid, gid_t gid, pid_t paren
         return nullptr;
     }
 
-    auto handle = VirtualFileSystem::the().open(path);
+    RetainPtr<VirtualFileSystem::Node> cwd;
+    {
+        InterruptDisabler disabler;
+        if (auto* parentTask = Task::fromPID(parentPID))
+            cwd = parentTask->m_cwd.copyRef();
+    }
+
+    auto handle = VirtualFileSystem::the().open(path, cwd.ptr());
     if (!handle) {
         error = -ENOENT; // FIXME: Get a more detailed error from VFS.
         return nullptr;
@@ -327,9 +334,9 @@ Task::Task(String&& name, uid_t uid, gid_t gid, pid_t parentPID, RingLevel ring)
 
     auto* parentTask = Task::fromPID(parentPID);
     if (parentTask)
-        m_cwd = parentTask->m_cwd;
+        m_cwd = parentTask->m_cwd.copyRef();
     else
-        m_cwd = "/";
+        m_cwd = nullptr;
 
     m_nextRegion = LinearAddress(0x600000);
 
@@ -712,22 +719,29 @@ int Task::sys$close(int fd)
 
 int Task::sys$lstat(const char* path, void* statbuf)
 {
-    auto handle = VirtualFileSystem::the().open(move(path));
+    auto handle = VirtualFileSystem::the().open(move(path), m_cwd.ptr());
     if (!handle)
         return -1;
     handle->stat((Unix::stat*)statbuf);
     return 0;
 }
 
+int Task::sys$chdir(const char* path)
+{
+    auto handle = VirtualFileSystem::the().open(path, m_cwd.ptr());
+    if (!handle)
+        return -ENOENT; // FIXME: More detailed error.
+    if (!handle->isDirectory())
+        return -ENOTDIR;
+    m_cwd = handle->vnode();
+    kprintf("m_cwd <- %p (%u)\n", m_cwd.ptr(), handle->vnode()->inode.index());
+    return 0;
+}
+
 int Task::sys$getcwd(char* buffer, size_t size)
 {
-    if (size < m_cwd.length() + 1) {
-        // FIXME: return -ERANGE;
-        return -1;
-    }
-    memcpy(buffer, m_cwd.characters(), m_cwd.length());
-    buffer[m_cwd.length()] = '\0';
-    return 0;
+    // FIXME: Implement!
+    return -ENOTIMPL;
 }
 
 int Task::sys$open(const char* path, size_t pathLength)
@@ -744,7 +758,7 @@ int Task::sys$open(const char* path, size_t pathLength)
 
 FileHandle* Task::openFile(String&& path)
 {
-    auto handle = VirtualFileSystem::the().open(move(path));
+    auto handle = VirtualFileSystem::the().open(move(path), m_cwd.ptr());
     if (!handle) {
 #ifdef DEBUG_IO
         kprintf("vfs::open() failed\n");

Kernel/Task.h

@@ -6,6 +6,7 @@
 #include "TSS.h"
 #include <AK/Vector.h>
 #include "i386.h"
+#include <VirtualFileSystem/VirtualFileSystem.h>
 
 //#define TASK_SANITY_CHECKS
 
@@ -98,6 +99,7 @@ public:
     int sys$munmap(void*, size_t size);
     int sys$get_dir_entries(int fd, void*, size_t);
     int sys$getcwd(char*, size_t);
+    int sys$chdir(const char*);
     int sys$sleep(unsigned seconds);
     int sys$gettimeofday(timeval*);
     int sys$gethostname(char* name, size_t length);
@@ -150,7 +152,7 @@ private:
     pid_t m_waitee { -1 };
     int m_fdBlockedOnRead { -1 };
 
-    String m_cwd;
+    RetainPtr<VirtualFileSystem::Node> m_cwd;
 
     struct Region {
         Region(LinearAddress, size_t, RetainPtr<Zone>&&, String&&);

Kernel/errno.h

@@ -37,3 +37,5 @@
 #define ENAMETOOLONG 36 // Name too long
 
 #define EOVERFLOW 75    // Value too large for defined data type
+
+#define ENOTIMPL 999    // Not implemented

LibC/dirent.cpp

@@ -46,7 +46,7 @@ dirent* readdir(DIR* dirp)
         dirp->nextptr = dirp->buffer;
     }
 
-    if (dirp->nextptr > (dirp->buffer + dirp->buffer_size))
+    if (dirp->nextptr >= (dirp->buffer + dirp->buffer_size))
         return nullptr;
 
     auto* sys_ent = (sys_dirent*)dirp->nextptr;

LibC/string.cpp

@@ -69,6 +69,7 @@ const char* strerror(int errnum)
     case ERANGE: return "Math result not representable";
     case ENAMETOOLONG: return "Name too long";
     case EOVERFLOW: return "Value too large for data type";
+    case ENOTIMPL: return "Not implemented";
     }
     printf("strerror() missing string for errnum=%d\n", errnum);
     return "Unknown error";

LibC/unistd.cpp

@@ -51,6 +51,12 @@ int lstat(const char* path, stat* statbuf)
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
+int chdir(const char* path)
+{
+    int rc = Syscall::invoke(Syscall::PosixChdir, (dword)path);
+    __RETURN_WITH_ERRNO(rc, rc, -1);
+}
+
 char* getcwd(char* buffer, size_t size)
 {
     int rc = Syscall::invoke(Syscall::PosixGetcwd, (dword)buffer, (dword)size);

LibC/unistd.h

@@ -11,6 +11,7 @@ int open(const char* path);
 ssize_t read(int fd, void* buf, size_t count);
 int close(int fd);
 pid_t waitpid(pid_t);
+int chdir(const char* path);
 char* getcwd(char* buffer, size_t size);
 int lstat(const char* path, stat* statbuf);
 int sleep(unsigned seconds);

Userland/ls.cpp

@@ -4,14 +4,14 @@
 
 int main(int c, char** v)
 {
-    DIR* dirp = opendir("/");
+    DIR* dirp = opendir(".");
     if (!dirp) {
         printf("opendir failed :(\n");
         return 1;
     }
     char pathbuf[256];
     while (auto* de = readdir(dirp)) {
-        sprintf(pathbuf, "/%s", de->d_name);
+        sprintf(pathbuf, "%s", de->d_name);
         stat st;
         int rc = lstat(pathbuf, &st);
         if (rc == -1) {

Userland/sh.cpp

@@ -3,6 +3,9 @@
 #include <LibC/process.h>
 #include <LibC/errno.h>
 #include <LibC/string.h>
+#include <LibC/stdlib.h>
+
+char* g_cwd = nullptr;
 
 static void prompt()
 {
@@ -12,12 +15,63 @@ static void prompt()
         printf("$ ");
 }
 
+static int sh_pwd(int, const char**)
+{
+    printf("cwd: %s\n", g_cwd);
+}
+
+static int sh_cd(int argc, const char** argv)
+{
+    if (argc == 1) {
+        printf("usage: cd <path>\n");
+        return 0;
+    }
+
+    char pathbuf[128];
+    if (argv[1][1] == '/')
+        memcpy(pathbuf, argv[1], strlen(argv[1]));
+    else
+        sprintf(pathbuf, "%s/%s", g_cwd, argv[1]);
+    struct stat st;
+    int rc = lstat(pathbuf, &st);
+    if (rc < 0) {
+        printf("lstat(%s) failed: %s\n", pathbuf, strerror(errno));
+        return 1;
+    }
+    if (!S_ISDIR(st.st_mode)) {
+        printf("Not a directory: %s\n", pathbuf);
+        return 1;
+    }
+    rc = chdir(pathbuf);
+    if (rc < 0) {
+        printf("chdir(%s) failed: %s\n", pathbuf, strerror(errno));
+        return 1;
+    }
+    memcpy(g_cwd, pathbuf, strlen(pathbuf));
+    return 0;
+}
+
+static bool handle_builtin(int argc, const char** argv, int& retval)
+{
+    if (argc == 0)
+        return false;
+    if (!strcmp(argv[0], "cd")) {
+        retval = sh_cd(argc, argv);
+        return true;
+    }
+    if (!strcmp(argv[0], "pwd")) {
+        retval = sh_pwd(argc, argv);
+        return true;
+    }
+    return false;
+}
+
 static int runcmd(char* cmd)
 {
     if (cmd[0] == 0)
         return 0;
     char buf[128];
-    sprintf(buf, "/bin/%s", cmd);
+    memcpy(buf, cmd, 128);
 
     const char* argv[32];
     size_t argi = 1;
@@ -30,16 +84,27 @@ static int runcmd(char* cmd)
         }
     }
     argv[argi + 1] = nullptr;
-    int ret = spawn(argv[0], argv);
+
+    int retval = 0;
+    if (handle_builtin(argi, argv, retval)) {
+        return 0;
+    }
+
+    const char* search_path = "/bin";
+
+    char pathbuf[128];
+    sprintf(pathbuf, "%s/%s", search_path, argv[0]);
+    int ret = spawn(pathbuf, argv);
     if (ret == -1) {
         printf("spawn failed: %s (%s)\n", cmd, strerror(errno));
         return 1;
     }
+    // FIXME: waitpid should give us the spawned process's exit status
     waitpid(ret);
-    return 0;
+    return retval;
 }
 
-int main(int c, char** v)
+int main(int, char**)
 {
     char linebuf[128];
     int linedx = 0;
@@ -50,6 +115,9 @@ int main(int c, char** v)
         printf("failed to open /dev/keyboard :(\n");
         return 1;
     }
+    g_cwd = (char*)malloc(1024);
+    g_cwd[0] = '/';
+    g_cwd[1] = '\0';
     prompt();
     for (;;) {
         char keybuf[16];

VirtualFileSystem/FileHandle.cpp

@@ -128,6 +128,11 @@ ByteBuffer FileHandle::readEntireFile()
     return m_vnode->fileSystem()->readEntireInode(m_vnode->inode);
 }
 
+bool FileHandle::isDirectory() const
+{
+    return m_vnode->metadata().isDirectory();
+}
+
 ssize_t FileHandle::get_dir_entries(byte* buffer, size_t size)
 {
     Locker locker(VirtualFileSystem::lock());

VirtualFileSystem/FileHandle.h

@@ -20,6 +20,10 @@ public:
 
     String absolutePath() const;
 
+    bool isDirectory() const;
+
+    VirtualFileSystem::Node* vnode() { return m_vnode.ptr(); }
+
 #ifdef SERENITY
     int fd() const { return m_fd; }
     void setFD(int fd) { m_fd = fd; }

VirtualFileSystem/VirtualFileSystem.cpp

@@ -168,9 +168,9 @@ void VirtualFileSystem::freeNode(Node* node)
     m_nodeFreeList.append(move(node));
 }
 
-bool VirtualFileSystem::isDirectory(const String& path)
+bool VirtualFileSystem::isDirectory(const String& path, Node* base)
 {
-    auto inode = resolvePath(path);
+    auto inode = resolvePath(path, base);
     if (!inode.isValid())
         return false;
 
@@ -355,11 +355,11 @@ bool VirtualFileSystem::touch(const String& path)
     return inode.fileSystem()->setModificationTime(inode, ktime(nullptr));
 }
 
-OwnPtr<FileHandle> VirtualFileSystem::open(const String& path)
+OwnPtr<FileHandle> VirtualFileSystem::open(const String& path, Node* base)
 {
     Locker locker(VirtualFileSystem::lock());
 
-    auto inode = resolvePath(path);
+    auto inode = resolvePath(path, base);
     if (!inode.isValid())
         return nullptr;
     auto vnode = getOrCreateNode(inode);
@@ -368,7 +368,7 @@ OwnPtr<FileHandle> VirtualFileSystem::open(const String& path)
     return make<FileHandle>(move(vnode));
 }
 
-OwnPtr<FileHandle> VirtualFileSystem::create(const String& path)
+OwnPtr<FileHandle> VirtualFileSystem::create(const String& path, Node* base)
 {
     Locker locker(VirtualFileSystem::lock());
 
@@ -378,7 +378,7 @@ OwnPtr<FileHandle> VirtualFileSystem::create(const String& path)
     return nullptr;
 }
 
-OwnPtr<FileHandle> VirtualFileSystem::mkdir(const String& path)
+OwnPtr<FileHandle> VirtualFileSystem::mkdir(const String& path, Node* base)
 {
     Locker locker(VirtualFileSystem::lock());
 
@@ -398,10 +398,18 @@ InodeIdentifier VirtualFileSystem::resolveSymbolicLink(const String& basePath, I
     return resolvePath(buf);
 }
 
-InodeIdentifier VirtualFileSystem::resolvePath(const String& path)
+InodeIdentifier VirtualFileSystem::resolvePath(const String& path, Node* base)
 {
+    if (path.isEmpty())
+        return { };
+
     auto parts = path.split('/');
-    InodeIdentifier inode = m_rootNode->inode;
+    InodeIdentifier inode;
+
+    if (path[0] == '/')
+        inode = m_rootNode->inode;
+    else
+        inode = base ? base->inode : m_rootNode->inode;
 
     for (unsigned i = 0; i < parts.size(); ++i) {
         auto& part = parts[i];

VirtualFileSystem/VirtualFileSystem.h

@@ -51,7 +51,7 @@ public:
     VirtualFileSystem();
     ~VirtualFileSystem();
 
-    bool isDirectory(const String& path);
+    bool isDirectory(const String& path, Node* base = nullptr);
     void listDirectory(const String& path);
     void listDirectoryRecursively(const String& path);
 
@@ -64,9 +64,9 @@ public:
     bool mountRoot(RetainPtr<FileSystem>&&);
     bool mount(RetainPtr<FileSystem>&&, const String& path);
 
-    OwnPtr<FileHandle> open(const String& path);
-    OwnPtr<FileHandle> create(const String& path);
-    OwnPtr<FileHandle> mkdir(const String& path);
+    OwnPtr<FileHandle> open(const String& path, Node* base = nullptr);
+    OwnPtr<FileHandle> create(const String& path, Node* base = nullptr);
+    OwnPtr<FileHandle> mkdir(const String& path, Node* base = nullptr);
 
     bool isRoot(InodeIdentifier) const;
 
@@ -79,7 +79,7 @@ private:
 
     void enumerateDirectoryInode(InodeIdentifier, Function<bool(const FileSystem::DirectoryEntry&)>);
     String absolutePath(InodeIdentifier);
-    InodeIdentifier resolvePath(const String& path);
+    InodeIdentifier resolvePath(const String& path, Node* base = nullptr);
     InodeIdentifier resolveSymbolicLink(const String& basePath, InodeIdentifier symlinkInode);
 
     RetainPtr<Node> allocateNode();