1 files changed, 172 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/common/getcwd.c b/libc/sysdeps/linux/common/getcwd.c
new file mode 100644
index 000000000..1ec00a36e
--- /dev/null
+++ b/libc/sysdeps/linux/common/getcwd.c
@@ -0,0 +1,172 @@
+/* These functions find the absolute path to the current working directory.  */
+
+#include <stdlib.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <dirent.h>
+#include <string.h>
+#include <sys/syscall.h>
+
+#ifdef __NR_getcwd
+#define __NR___getcwd __NR_getcwd
+static inline _syscall2(int, __getcwd, char *, buf, unsigned long, size);
+
+char *getcwd(char *buf, int size)
+{
+	int olderrno, ret;
+	char *allocbuf;
+	
+	if (size == 0) {
+		__set_errno(EINVAL);
+		return NULL;
+	}
+	if (size < 3) {
+		__set_errno(ERANGE);
+		return NULL;
+	}
+	allocbuf=NULL;
+	olderrno = errno;
+	if (buf == NULL) {
+		buf = allocbuf = malloc (size);
+		if (buf == NULL)
+			return NULL;
+	}
+	ret = __getcwd(buf, size);
+	if (ret < 0) {
+	    if (allocbuf) {
+		free(allocbuf);
+	    }
+	    return NULL;
+	} 
+	__set_errno(olderrno);
+	return buf;
+}
+#else
+
+/* If the syscall is not present, we have to walk up the
+ * directory tree till we hit the root.  Now we _could_
+ * use /proc/self/cwd if /proc is mounted... That approach
+ * is left an an exercise for the reader... */
+
+
+/* Seems a few broken filesystems (like coda) don't like this */
+/* #undef FAST_DIR_SEARCH_POSSIBLE on Linux */
+
+
+/* Routine to find the step back down */
+static char *search_dir(dev_t this_dev, ino_t this_ino, char *path_buf, int path_size)
+{
+	DIR *dp;
+	struct dirent *d;
+	char *ptr;
+	int slen;
+	struct stat st;
+
+#ifdef FAST_DIR_SEARCH_POSSIBLE
+	/* The test is for ELKS lib 0.0.9, this should be fixed in the real kernel */
+	int slow_search = (sizeof(ino_t) != sizeof(d->d_ino));
+#endif
+
+	if (stat(path_buf, &st) < 0)
+		return 0;
+#ifdef FAST_DIR_SEARCH_POSSIBLE
+	if (this_dev != st.st_dev)
+		slow_search = 1;
+#endif
+
+	slen = strlen(path_buf);
+	ptr = path_buf + slen - 1;
+	if (*ptr != '/') {
+		if (slen + 2 > path_size) {
+			__set_errno(ERANGE);
+			return 0;
+		}
+		strcpy(++ptr, "/");
+		slen++;
+	}
+	slen++;
+
+	dp = opendir(path_buf);
+	if (dp == 0)
+		return 0;
+
+	while ((d = readdir(dp)) != 0) {
+#ifdef FAST_DIR_SEARCH_POSSIBLE
+		if (slow_search || this_ino == d->d_ino) {
+#endif
+			if (slen + strlen(d->d_name) > path_size) {
+				__set_errno(ERANGE);
+				return 0;
+			}
+			strcpy(ptr + 1, d->d_name);
+			if (stat(path_buf, &st) < 0)
+				continue;
+			if (st.st_ino == this_ino && st.st_dev == this_dev) {
+				closedir(dp);
+				return path_buf;
+			}
+#ifdef FAST_DIR_SEARCH_POSSIBLE
+		}
+#endif
+	}
+
+	closedir(dp);
+	__set_errno(ENOENT);
+	return 0;
+}
+
+/* Routine to go up tree */
+static char *recurser(char *path_buf, int path_size, dev_t root_dev, ino_t root_ino)
+{
+	struct stat st;
+	dev_t this_dev;
+	ino_t this_ino;
+
+	if (stat(path_buf, &st) < 0)
+		return 0;
+	this_dev = st.st_dev;
+	this_ino = st.st_ino;
+	if (this_dev == root_dev && this_ino == root_ino) {
+		strcpy(path_buf, "/");
+		return path_buf;
+	}
+	if (strlen(path_buf) + 4 > path_size) {
+		__set_errno(ERANGE);
+		return 0;
+	}
+	strcat(path_buf, "/..");
+	if (recurser(path_buf, path_size, root_dev, root_ino) == 0)
+		return 0;
+
+	return search_dir(this_dev, this_ino, path_buf, path_size);
+}
+
+
+char *getcwd(char *buf, int size)
+{
+	struct stat st;
+
+	if (size == 0) {
+		__set_errno(EINVAL);
+		return NULL;
+	}
+	if (size < 3) {
+		__set_errno(ERANGE);
+		return NULL;
+	}
+
+	if (buf == NULL) {
+		buf = malloc (size);
+		if (buf == NULL)
+			return NULL;
+	}
+
+	strcpy(buf, ".");
+	if (stat("/", &st) < 0) {
+		return NULL;
+	}
+
+	return recurser(buf, size, st.st_dev, st.st_ino);
+}
+
+#endif