libfdt: Add support for disabling sanity checks

Allow enabling ASSUME_VALID_INPUT to disable sanity checks on the device
tree and the parameters to libfdt. This assumption covers that cases where
the problem could be with either.

Signed-off-by: Simon Glass <sjg@chromium.org>
Message-Id: <20200220214557.176528-5-sjg@chromium.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

libfdt/fdt.c

@@ -129,10 +129,11 @@ const void *fdt_offset_ptr(const void *fdt, int offset, unsigned int len)
 {
 	unsigned absoffset = offset + fdt_off_dt_struct(fdt);
 
-	if ((absoffset < offset)
-	    || ((absoffset + len) < absoffset)
-	    || (absoffset + len) > fdt_totalsize(fdt))
-		return NULL;
+	if (!can_assume(VALID_INPUT))
+		if ((absoffset < offset)
+		    || ((absoffset + len) < absoffset)
+		    || (absoffset + len) > fdt_totalsize(fdt))
+			return NULL;
 
 	if (fdt_version(fdt) >= 0x11)
 		if (((offset + len) < offset)
@@ -197,6 +198,8 @@ uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
 
 int fdt_check_node_offset_(const void *fdt, int offset)
 {
+	if (can_assume(VALID_INPUT))
+		return offset;
 	if ((offset < 0) || (offset % FDT_TAGSIZE)
 	    || (fdt_next_tag(fdt, offset, &offset) != FDT_BEGIN_NODE))
 		return -FDT_ERR_BADOFFSET;

libfdt/fdt_ro.c

@@ -33,17 +33,26 @@ static int fdt_nodename_eq_(const void *fdt, int offset,
 
 const char *fdt_get_string(const void *fdt, int stroffset, int *lenp)
 {
-	int32_t totalsize = fdt_ro_probe_(fdt);
-	uint32_t absoffset = stroffset + fdt_off_dt_strings(fdt);
+	int32_t totalsize;
+	uint32_t absoffset;
 	size_t len;
 	int err;
 	const char *s, *n;
 
+	if (can_assume(VALID_INPUT)) {
+		s = (const char *)fdt + fdt_off_dt_strings(fdt) + stroffset;
+
+		if (lenp)
+			*lenp = strlen(s);
+		return s;
+	}
+	totalsize = fdt_ro_probe_(fdt);
 	err = totalsize;
 	if (totalsize < 0)
 		goto fail;
 
 	err = -FDT_ERR_BADOFFSET;
+	absoffset = stroffset + fdt_off_dt_strings(fdt);
 	if (absoffset >= totalsize)
 		goto fail;
 	len = totalsize - absoffset;
@@ -151,10 +160,13 @@ static const struct fdt_reserve_entry *fdt_mem_rsv(const void *fdt, int n)
 	int offset = n * sizeof(struct fdt_reserve_entry);
 	int absoffset = fdt_off_mem_rsvmap(fdt) + offset;
 
-	if (absoffset < fdt_off_mem_rsvmap(fdt))
-		return NULL;
-	if (absoffset > fdt_totalsize(fdt) - sizeof(struct fdt_reserve_entry))
-		return NULL;
+	if (!can_assume(VALID_INPUT)) {
+		if (absoffset < fdt_off_mem_rsvmap(fdt))
+			return NULL;
+		if (absoffset > fdt_totalsize(fdt) -
+		    sizeof(struct fdt_reserve_entry))
+			return NULL;
+	}
 	return fdt_mem_rsv_(fdt, n);
 }
 
@@ -164,7 +176,7 @@ int fdt_get_mem_rsv(const void *fdt, int n, uint64_t *address, uint64_t *size)
 
 	FDT_RO_PROBE(fdt);
 	re = fdt_mem_rsv(fdt, n);
-	if (!re)
+	if (!can_assume(VALID_INPUT) && !re)
 		return -FDT_ERR_BADOFFSET;
 
 	*address = fdt64_ld(&re->address);
@@ -346,7 +358,8 @@ static const struct fdt_property *fdt_get_property_by_offset_(const void *fdt,
 	int err;
 	const struct fdt_property *prop;
 
-	if ((err = fdt_check_prop_offset_(fdt, offset)) < 0) {
+	if (!can_assume(VALID_INPUT) &&
+	    (err = fdt_check_prop_offset_(fdt, offset)) < 0) {
 		if (lenp)
 			*lenp = err;
 		return NULL;
@@ -462,14 +475,19 @@ const void *fdt_getprop_by_offset(const void *fdt, int offset,
 	if (namep) {
 		const char *name;
 		int namelen;
-		name = fdt_get_string(fdt, fdt32_ld(&prop->nameoff),
-				      &namelen);
-		if (!name) {
-			if (lenp)
-				*lenp = namelen;
-			return NULL;
+
+		if (!can_assume(VALID_INPUT)) {
+			name = fdt_get_string(fdt, fdt32_ld(&prop->nameoff),
+					      &namelen);
+			if (!name) {
+				if (lenp)
+					*lenp = namelen;
+				return NULL;
+			}
+			*namep = name;
+		} else {
+			*namep = fdt_string(fdt, fdt32_ld(&prop->nameoff));
 		}
-		*namep = name;
 	}
 
 	/* Handle realignment */
@@ -599,10 +617,12 @@ int fdt_supernode_atdepth_offset(const void *fdt, int nodeoffset,
 		}
 	}
 
-	if ((offset == -FDT_ERR_NOTFOUND) || (offset >= 0))
-		return -FDT_ERR_BADOFFSET;
-	else if (offset == -FDT_ERR_BADOFFSET)
-		return -FDT_ERR_BADSTRUCTURE;
+	if (!can_assume(VALID_INPUT)) {
+		if ((offset == -FDT_ERR_NOTFOUND) || (offset >= 0))
+			return -FDT_ERR_BADOFFSET;
+		else if (offset == -FDT_ERR_BADOFFSET)
+			return -FDT_ERR_BADSTRUCTURE;
+	}
 
 	return offset; /* error from fdt_next_node() */
 }
@@ -614,7 +634,8 @@ int fdt_node_depth(const void *fdt, int nodeoffset)
 
 	err = fdt_supernode_atdepth_offset(fdt, nodeoffset, 0, &nodedepth);
 	if (err)
-		return (err < 0) ? err : -FDT_ERR_INTERNAL;
+		return (can_assume(VALID_INPUT) || err < 0) ? err :
+			-FDT_ERR_INTERNAL;
 	return nodedepth;
 }