2 files changed, 75 insertions, 4 deletions

diff --git a/cpukit/dtc/libfdt/fdt_ro.c b/cpukit/dtc/libfdt/fdt_ro.c
index 4f4ef44a3a..347aa7bc8d 100644
--- a/cpukit/dtc/libfdt/fdt_ro.c
+++ b/cpukit/dtc/libfdt/fdt_ro.c
@@ -76,17 +76,72 @@ static int fdt_nodename_eq_(const void *fdt, int offset,
 		return 0;
 }
 
+const char *fdt_get_string(const void *fdt, int stroffset, int *lenp)
+{
+	uint32_t absoffset = stroffset + fdt_off_dt_strings(fdt);
+	size_t len;
+	int err;
+	const char *s, *n;
+
+	err = fdt_ro_probe_(fdt);
+	if (err != 0)
+		goto fail;
+
+	err = -FDT_ERR_BADOFFSET;
+	if (absoffset >= fdt_totalsize(fdt))
+		goto fail;
+	len = fdt_totalsize(fdt) - absoffset;
+
+	if (fdt_magic(fdt) == FDT_MAGIC) {
+		if (stroffset < 0)
+			goto fail;
+		if (fdt_version(fdt) >= 17) {
+			if (stroffset >= fdt_size_dt_strings(fdt))
+				goto fail;
+			if ((fdt_size_dt_strings(fdt) - stroffset) < len)
+				len = fdt_size_dt_strings(fdt) - stroffset;
+		}
+	} else if (fdt_magic(fdt) == FDT_SW_MAGIC) {
+		if ((stroffset >= 0)
+		    || (stroffset < -fdt_size_dt_strings(fdt)))
+			goto fail;
+		if ((-stroffset) < len)
+			len = -stroffset;
+	} else {
+		err = -FDT_ERR_INTERNAL;
+		goto fail;
+	}
+
+	s = (const char *)fdt + absoffset;
+	n = memchr(s, '\0', len);
+	if (!n) {
+		/* missing terminating NULL */
+		err = -FDT_ERR_TRUNCATED;
+		goto fail;
+	}
+
+	if (lenp)
+		*lenp = n - s;
+	return s;
+
+fail:
+	if (lenp)
+		*lenp = err;
+	return NULL;
+}
+
 const char *fdt_string(const void *fdt, int stroffset)
 {
-	return (const char *)fdt + fdt_off_dt_strings(fdt) + stroffset;
+	return fdt_get_string(fdt, stroffset, NULL);
 }
 
 static int fdt_string_eq_(const void *fdt, int stroffset,
 			  const char *s, int len)
 {
-	const char *p = fdt_string(fdt, stroffset);
+	int slen;
+	const char *p = fdt_get_string(fdt, stroffset, &slen);
 
-	return (strlen(p) == len) && (memcmp(p, s, len) == 0);
+	return p && (slen == len) && (memcmp(p, s, len) == 0);
 }
 
 uint32_t fdt_get_max_phandle(const void *fdt)
diff --git a/cpukit/include/libfdt.h b/cpukit/include/libfdt.h
index 837c5e27ee..b50af54296 100644
--- a/cpukit/include/libfdt.h
+++ b/cpukit/include/libfdt.h
@@ -288,6 +288,22 @@ int fdt_move(const void *fdt, void *buf, int bufsize);
 /**********************************************************************/
 
 /**
+ * fdt_get_string - retrieve a string from the strings block of a device tree
+ * @fdt: pointer to the device tree blob
+ * @stroffset: offset of the string within the strings block (native endian)
+ * @lenp: optional pointer to return the string's length
+ *
+ * fdt_get_string() retrieves a pointer to a single string from the
+ * strings block of the device tree blob at fdt, and optionally also
+ * returns the string's length in *lenp.
+ *
+ * returns:
+ *     a pointer to the string, on success
+ *     NULL, if stroffset is out of bounds, or doesn't point to a valid string
+ */
+const char *fdt_get_string(const void *fdt, int stroffset, int *lenp);
+
+/**
  * fdt_string - retrieve a string from the strings block of a device tree
  * @fdt: pointer to the device tree blob
  * @stroffset: offset of the string within the strings block (native endian)
@@ -297,7 +313,7 @@ int fdt_move(const void *fdt, void *buf, int bufsize);
  *
  * returns:
  *     a pointer to the string, on success
- *     NULL, if stroffset is out of bounds
+ *     NULL, if stroffset is out of bounds, or doesn't point to a valid string
  */
 const char *fdt_string(const void *fdt, int stroffset);