minix/lib/libsffs/lookup.c
David van Moolenbroek ef7b484e5c Create SFFS library out of HGFS
This Shared Folders File System library (libsffs) now contains all the
file system logic originally in HGFS. The actual HGFS server code is
now a stub that passes on all the work to libsffs. The libhgfs library
is changed accordingly.
2012-04-09 18:08:26 +02:00

332 lines
8.2 KiB
C

/* This file provides path-to-inode lookup functionality.
*
* The entry points into this file are:
* do_lookup perform the LOOKUP file system call
*
* Created:
* April 2009 (D.C. van Moolenbroek)
*/
#include "inc.h"
static int get_mask(vfs_ucred_t *ucred);
static int access_as_dir(struct inode *ino, struct sffs_attr *attr, int
uid, int mask);
static int next_name(char **ptr, char **start, char name[NAME_MAX+1]);
static int go_up(char path[PATH_MAX], struct inode *ino, struct inode
**res_ino, struct sffs_attr *attr);
static int go_down(char path[PATH_MAX], struct inode *ino, char *name,
struct inode **res_ino, struct sffs_attr *attr);
/*===========================================================================*
* get_mask *
*===========================================================================*/
static int get_mask(ucred)
vfs_ucred_t *ucred; /* credentials of the caller */
{
/* Given the caller's credentials, precompute a search access mask to test
* against directory modes.
*/
int i;
if (ucred->vu_uid == sffs_params->p_uid) return S_IXUSR;
if (ucred->vu_gid == sffs_params->p_gid) return S_IXGRP;
for (i = 0; i < ucred->vu_ngroups; i++)
if (ucred->vu_sgroups[i] == sffs_params->p_gid) return S_IXGRP;
return S_IXOTH;
}
/*===========================================================================*
* access_as_dir *
*===========================================================================*/
static int access_as_dir(ino, attr, uid, mask)
struct inode *ino; /* the inode to test */
struct sffs_attr *attr; /* attributes of the inode */
int uid; /* UID of the caller */
int mask; /* search access mask of the caller */
{
/* Check whether the given inode may be accessed as directory.
* Return OK or an appropriate error code.
*/
mode_t mode;
assert(attr->a_mask & SFFS_ATTR_MODE);
/* The inode must be a directory to begin with. */
if (!IS_DIR(ino)) return ENOTDIR;
/* The caller must have search access to the directory. Root always does. */
if (uid == 0) return OK;
mode = get_mode(ino, attr->a_mode);
return (mode & mask) ? OK : EACCES;
}
/*===========================================================================*
* next_name *
*===========================================================================*/
static int next_name(ptr, start, name)
char **ptr; /* cursor pointer into path (in, out) */
char **start; /* place to store start of name */
char name[NAME_MAX+1]; /* place to store name */
{
/* Get the next path component from a path.
*/
char *p;
int i;
for (p = *ptr; *p == '/'; p++);
*start = p;
if (*p) {
for (i = 0; *p && *p != '/' && i <= NAME_MAX; p++, i++)
name[i] = *p;
if (i > NAME_MAX)
return ENAMETOOLONG;
name[i] = 0;
} else {
strcpy(name, ".");
}
*ptr = p;
return OK;
}
/*===========================================================================*
* go_up *
*===========================================================================*/
static int go_up(path, ino, res_ino, attr)
char path[PATH_MAX]; /* path to take the last part from */
struct inode *ino; /* inode of the current directory */
struct inode **res_ino; /* place to store resulting inode */
struct sffs_attr *attr; /* place to store inode attributes */
{
/* Given an inode, progress into the parent directory.
*/
struct inode *parent;
int r;
pop_path(path);
parent = ino->i_parent;
assert(parent != NULL);
if ((r = verify_path(path, parent, attr, NULL)) != OK)
return r;
get_inode(parent);
*res_ino = parent;
return r;
}
/*===========================================================================*
* go_down *
*===========================================================================*/
static int go_down(path, parent, name, res_ino, attr)
char path[PATH_MAX]; /* path to add the name to */
struct inode *parent; /* inode of the current directory */
char *name; /* name of the directory entry */
struct inode **res_ino; /* place to store resulting inode */
struct sffs_attr *attr; /* place to store inode attributes */
{
/* Given a directory inode and a name, progress into a directory entry.
*/
struct inode *ino;
int r, stale = 0;
if ((r = push_path(path, name)) != OK)
return r;
dprintf(("%s: go_down: name '%s', path now '%s'\n", sffs_name, name, path));
ino = lookup_dentry(parent, name);
dprintf(("%s: lookup_dentry('%s') returned %p\n", sffs_name, name, ino));
if (ino != NULL)
r = verify_path(path, ino, attr, &stale);
else
r = sffs_table->t_getattr(path, attr);
dprintf(("%s: path query returned %d\n", sffs_name, r));
if (r != OK) {
if (ino != NULL) {
put_inode(ino);
ino = NULL;
}
if (!stale)
return r;
}
dprintf(("%s: name '%s'\n", sffs_name, name));
if (ino == NULL) {
if ((ino = get_free_inode()) == NULL)
return ENFILE;
dprintf(("%s: inode %p ref %d\n", sffs_name, ino, ino->i_ref));
ino->i_flags = MODE_TO_DIRFLAG(attr->a_mode);
add_dentry(parent, name, ino);
}
*res_ino = ino;
return OK;
}
/*===========================================================================*
* do_lookup *
*===========================================================================*/
int do_lookup()
{
/* Resolve a path string to an inode.
*/
ino_t dir_ino_nr, root_ino_nr;
struct inode *cur_ino, *root_ino;
struct inode *next_ino = NULL;
struct sffs_attr attr;
char buf[PATH_MAX], path[PATH_MAX];
char name[NAME_MAX+1];
char *ptr, *last;
vfs_ucred_t ucred;
mode_t mask;
size_t len;
int r;
dir_ino_nr = m_in.REQ_DIR_INO;
root_ino_nr = m_in.REQ_ROOT_INO;
len = m_in.REQ_PATH_LEN;
/* Fetch the path name. */
if (len < 1 || len > PATH_MAX)
return EINVAL;
r = sys_safecopyfrom(m_in.m_source, m_in.REQ_GRANT, 0,
(vir_bytes) buf, len, D);
if (r != OK)
return r;
if (buf[len-1] != 0) {
printf("%s: VFS did not zero-terminate path!\n", sffs_name);
return EINVAL;
}
/* Fetch the credentials, and generate a search access mask to test against
* directory modes.
*/
if (m_in.REQ_FLAGS & PATH_GET_UCRED) {
if (m_in.REQ_UCRED_SIZE != sizeof(ucred)) {
printf("%s: bad credential structure size\n", sffs_name);
return EINVAL;
}
r = sys_safecopyfrom(m_in.m_source, m_in.REQ_GRANT2, 0,
(vir_bytes) &ucred, m_in.REQ_UCRED_SIZE, D);
if (r != OK)
return r;
}
else {
ucred.vu_uid = m_in.REQ_UID;
ucred.vu_gid = m_in.REQ_GID;
ucred.vu_ngroups = 0;
}
mask = get_mask(&ucred);
/* Start the actual lookup. */
dprintf(("%s: lookup: got query '%s'\n", sffs_name, buf));
if ((cur_ino = find_inode(dir_ino_nr)) == NULL)
return EINVAL;
attr.a_mask = SFFS_ATTR_MODE | SFFS_ATTR_SIZE;
if ((r = verify_inode(cur_ino, path, &attr)) != OK)
return r;
get_inode(cur_ino);
if (root_ino_nr > 0)
root_ino = find_inode(root_ino_nr);
else
root_ino = NULL;
/* One possible optimization would be to check a path only right before the
* first ".." in a row, and at the very end (if still necessary). This would
* have consequences for inode validation, though.
*/
for (ptr = last = buf; *ptr != 0; ) {
if ((r = access_as_dir(cur_ino, &attr, ucred.vu_uid, mask)) != OK)
break;
if ((r = next_name(&ptr, &last, name)) != OK)
break;
dprintf(("%s: lookup: next name '%s'\n", sffs_name, name));
if (!strcmp(name, ".") ||
(cur_ino == root_ino && !strcmp(name, "..")))
continue;
if (!strcmp(name, "..")) {
if (IS_ROOT(cur_ino))
r = ELEAVEMOUNT;
else
r = go_up(path, cur_ino, &next_ino, &attr);
} else {
r = go_down(path, cur_ino, name, &next_ino, &attr);
}
if (r != OK)
break;
assert(next_ino != NULL);
put_inode(cur_ino);
cur_ino = next_ino;
}
dprintf(("%s: lookup: result %d\n", sffs_name, r));
if (r != OK) {
put_inode(cur_ino);
/* We'd need support for these here. We don't have such support. */
assert(r != EENTERMOUNT && r != ESYMLINK);
if (r == ELEAVEMOUNT) {
m_out.RES_OFFSET = (int) (last - buf);
m_out.RES_SYMLOOP = 0;
}
return r;
}
m_out.RES_INODE_NR = INODE_NR(cur_ino);
m_out.RES_MODE = get_mode(cur_ino, attr.a_mode);
m_out.RES_FILE_SIZE_HI = ex64hi(attr.a_size);
m_out.RES_FILE_SIZE_LO = ex64lo(attr.a_size);
m_out.RES_UID = sffs_params->p_uid;
m_out.RES_GID = sffs_params->p_gid;
m_out.RES_DEV = NO_DEV;
return OK;
}