minix/lib/libsffs/lookup.c

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/* 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"
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static int get_mask(vfs_ucred_t *ucred);
static int access_as_dir(struct inode *ino, struct sffs_attr *attr, int
uid, int mask);
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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);
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static int go_down(char path[PATH_MAX], struct inode *ino, char *name,
struct inode **res_ino, struct sffs_attr *attr);
/*===========================================================================*
* get_mask *
*===========================================================================*/
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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 *
*===========================================================================*/
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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 *
*===========================================================================*/
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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 *
*===========================================================================*/
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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 *
*===========================================================================*/
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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 *
*===========================================================================*/
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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);
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);
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) {
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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;
}