143 lines
3.2 KiB
C
143 lines
3.2 KiB
C
/* Code to mangle pathnames into those matching a given prefix.
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eg. open("/lib/foo.so") => open("/usr/gnemul/i386-linux/lib/foo.so");
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The assumption is that this area does not change.
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*/
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#include "qemu/osdep.h"
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#include <sys/param.h>
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#include <dirent.h>
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#include "qemu/cutils.h"
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#include "qemu/path.h"
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#include "qemu/thread.h"
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static const char *base;
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static GHashTable *hash;
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static QemuMutex lock;
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#ifdef CONFIG_LATX
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static bool path_is_proc_namespace(const char *name)
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{
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static const char proc_root[] = "/proc";
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const char *component;
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size_t length = sizeof(proc_root) - 1;
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if (strncmp(name, proc_root, length) ||
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(name[length] && name[length] != '/')) {
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return false;
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}
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component = name + length;
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while (*component) {
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component += strspn(component, "/");
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if (component[0] == '.' && component[1] == '.' &&
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(component[2] == '\0' || component[2] == '/')) {
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return false;
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}
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component += strcspn(component, "/");
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}
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return true;
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}
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#endif
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void init_paths(const char *prefix)
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{
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if (prefix[0] == '\0' || !strcmp(prefix, "/")) {
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return;
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}
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if (prefix[0] == '/') {
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base = g_strdup(prefix);
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} else {
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char *cwd = g_get_current_dir();
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base = g_build_filename(cwd, prefix, NULL);
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g_free(cwd);
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}
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hash = g_hash_table_new(g_str_hash, g_str_equal);
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qemu_mutex_init(&lock);
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}
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static bool path_has_prefix(const char *name)
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{
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if (!base || !name || name[0] != '/' || name[1] == '\0') {
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return false;
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}
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#ifdef CONFIG_LATX
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/* Keep live procfs visible even when the runtime contains /proc. */
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if (path_is_proc_namespace(name)) {
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return false;
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}
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#endif
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return true;
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}
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char *path_get_prefixed(const char *name)
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{
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if (!path_has_prefix(name)) {
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return g_strdup(name);
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}
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return g_build_filename(base, name, NULL);
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}
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/* Look for path in emulation dir, otherwise return name. */
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const char *path(const char *name)
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{
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gpointer key, value;
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const char *ret;
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/* Only do absolute paths: quick and dirty, but should mostly be OK. */
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if (!path_has_prefix(name)) {
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return name;
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}
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qemu_mutex_lock(&lock);
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/* Have we looked up this file before? */
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if (g_hash_table_lookup_extended(hash, name, &key, &value)) {
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ret = value ? value : name;
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} else {
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char *save = g_strdup(name);
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char *full = path_get_prefixed(name);
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/* Look for the path; record the result, pass or fail. */
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if (access(full, F_OK) == 0) {
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/* Exists. */
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g_hash_table_insert(hash, save, full);
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ret = full;
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} else {
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/* Does not exist. */
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g_free(full);
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g_hash_table_insert(hash, save, NULL);
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ret = name;
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}
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}
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qemu_mutex_unlock(&lock);
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return ret;
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}
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/* Keep a child from inheriting a path-cache lock held by another thread. */
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void path_fork_start(void)
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{
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if (base) {
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qemu_mutex_lock(&lock);
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}
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}
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void path_fork_end(int child)
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{
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if (!base) {
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return;
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}
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if (child) {
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qemu_mutex_init(&lock);
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} else {
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qemu_mutex_unlock(&lock);
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}
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}
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