libfdt: Add support for disabling dtb checks

Support ASSUME_VALID_DTB to disable some sanity checks

If we assume that the DTB itself is valid then we can skip some checks and
save code space. Add various conditions to handle this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Message-Id: <20200220214557.176528-4-sjg@chromium.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

4 files changed, 45 insertions, 29 deletions

diff --git a/libfdt/fdt.c b/libfdt/fdt.c
index 3e37a4b..d4daf60 100644
--- a/libfdt/fdt.c
+++ b/libfdt/fdt.c
@@ -19,6 +19,9 @@ int32_t fdt_ro_probe_(const void *fdt)
 {
 	uint32_t totalsize = fdt_totalsize(fdt);
 
+	if (can_assume(VALID_DTB))
+		return totalsize;
+
 	if (fdt_magic(fdt) == FDT_MAGIC) {
 		/* Complete tree */
 		if (fdt_version(fdt) < FDT_FIRST_SUPPORTED_VERSION)
@@ -81,38 +84,44 @@ int fdt_check_header(const void *fdt)
 
 	if (fdt_magic(fdt) != FDT_MAGIC)
 		return -FDT_ERR_BADMAGIC;
-	hdrsize = fdt_header_size(fdt);
 	if ((fdt_version(fdt) < FDT_FIRST_SUPPORTED_VERSION)
 	    || (fdt_last_comp_version(fdt) > FDT_LAST_SUPPORTED_VERSION))
 		return -FDT_ERR_BADVERSION;
 	if (fdt_version(fdt) < fdt_last_comp_version(fdt))
 		return -FDT_ERR_BADVERSION;
+	hdrsize = fdt_header_size(fdt);
+	if (!can_assume(VALID_DTB)) {
 
-	if ((fdt_totalsize(fdt) < hdrsize)
-	    || (fdt_totalsize(fdt) > INT_MAX))
-		return -FDT_ERR_TRUNCATED;
-
-	/* Bounds check memrsv block */
-	if (!check_off_(hdrsize, fdt_totalsize(fdt), fdt_off_mem_rsvmap(fdt)))
-		return -FDT_ERR_TRUNCATED;
+		if ((fdt_totalsize(fdt) < hdrsize)
+		    || (fdt_totalsize(fdt) > INT_MAX))
+			return -FDT_ERR_TRUNCATED;
 
-	/* Bounds check structure block */
-	if (fdt_version(fdt) < 17) {
+		/* Bounds check memrsv block */
 		if (!check_off_(hdrsize, fdt_totalsize(fdt),
-				fdt_off_dt_struct(fdt)))
+				fdt_off_mem_rsvmap(fdt)))
 			return -FDT_ERR_TRUNCATED;
-	} else {
+	}
+
+	if (!can_assume(VALID_DTB)) {
+		/* Bounds check structure block */
+		if (fdt_version(fdt) < 17) {
+			if (!check_off_(hdrsize, fdt_totalsize(fdt),
+					fdt_off_dt_struct(fdt)))
+				return -FDT_ERR_TRUNCATED;
+		} else {
+			if (!check_block_(hdrsize, fdt_totalsize(fdt),
+					  fdt_off_dt_struct(fdt),
+					  fdt_size_dt_struct(fdt)))
+				return -FDT_ERR_TRUNCATED;
+		}
+
+		/* Bounds check strings block */
 		if (!check_block_(hdrsize, fdt_totalsize(fdt),
-				  fdt_off_dt_struct(fdt),
-				  fdt_size_dt_struct(fdt)))
+				  fdt_off_dt_strings(fdt),
+				  fdt_size_dt_strings(fdt)))
 			return -FDT_ERR_TRUNCATED;
 	}
 
-	/* Bounds check strings block */
-	if (!check_block_(hdrsize, fdt_totalsize(fdt),
-			  fdt_off_dt_strings(fdt), fdt_size_dt_strings(fdt)))
-		return -FDT_ERR_TRUNCATED;
-
 	return 0;
 }
 
@@ -142,7 +151,7 @@ uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
 
 	*nextoffset = -FDT_ERR_TRUNCATED;
 	tagp = fdt_offset_ptr(fdt, offset, FDT_TAGSIZE);
-	if (!tagp)
+	if (!can_assume(VALID_DTB) && !tagp)
 		return FDT_END; /* premature end */
 	tag = fdt32_to_cpu(*tagp);
 	offset += FDT_TAGSIZE;
@@ -154,13 +163,13 @@ uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
 		do {
 			p = fdt_offset_ptr(fdt, offset++, 1);
 		} while (p && (*p != '\0'));
-		if (!p)
+		if (!can_assume(VALID_DTB) && !p)
 			return FDT_END; /* premature end */
 		break;
 
 	case FDT_PROP:
 		lenp = fdt_offset_ptr(fdt, offset, sizeof(*lenp));
-		if (!lenp)
+		if (!can_assume(VALID_DTB) && !lenp)
 			return FDT_END; /* premature end */
 		/* skip-name offset, length and value */
 		offset += sizeof(struct fdt_property) - FDT_TAGSIZE
diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index a5c2797..4c26fbe 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -388,7 +388,8 @@ static const struct fdt_property *fdt_get_property_namelen_(const void *fdt,
 	     (offset = fdt_next_property_offset(fdt, offset))) {
 		const struct fdt_property *prop;
 
-		if (!(prop = fdt_get_property_by_offset_(fdt, offset, lenp))) {
+		prop = fdt_get_property_by_offset_(fdt, offset, lenp);
+		if (!can_assume(VALID_DTB) && !prop) {
 			offset = -FDT_ERR_INTERNAL;
 			break;
 		}
diff --git a/libfdt/fdt_rw.c b/libfdt/fdt_rw.c
index 8795947..707c00a 100644
--- a/libfdt/fdt_rw.c
+++ b/libfdt/fdt_rw.c
@@ -24,6 +24,8 @@ static int fdt_blocks_misordered_(const void *fdt,
 
 static int fdt_rw_probe_(void *fdt)
 {
+	if (can_assume(VALID_DTB))
+		return 0;
 	FDT_RO_PROBE(fdt);
 
 	if (fdt_version(fdt) < 17)
diff --git a/libfdt/fdt_sw.c b/libfdt/fdt_sw.c
index 76bea22..352193c 100644
--- a/libfdt/fdt_sw.c
+++ b/libfdt/fdt_sw.c
@@ -12,10 +12,13 @@
 
 static int fdt_sw_probe_(void *fdt)
 {
-	if (fdt_magic(fdt) == FDT_MAGIC)
-		return -FDT_ERR_BADSTATE;
-	else if (fdt_magic(fdt) != FDT_SW_MAGIC)
-		return -FDT_ERR_BADMAGIC;
+	if (!can_assume(VALID_DTB)) {
+		if (fdt_magic(fdt) == FDT_MAGIC)
+			return -FDT_ERR_BADSTATE;
+		else if (fdt_magic(fdt) != FDT_SW_MAGIC)
+			return -FDT_ERR_BADMAGIC;
+	}
+
 	return 0;
 }
 
@@ -38,7 +41,7 @@ static int fdt_sw_probe_memrsv_(void *fdt)
 	if (err)
 		return err;
 
-	if (fdt_off_dt_strings(fdt) != 0)
+	if (!can_assume(VALID_DTB) && fdt_off_dt_strings(fdt) != 0)
 		return -FDT_ERR_BADSTATE;
 	return 0;
 }
@@ -151,7 +154,8 @@ int fdt_resize(void *fdt, void *buf, int bufsize)
 	headsize = fdt_off_dt_struct(fdt) + fdt_size_dt_struct(fdt);
 	tailsize = fdt_size_dt_strings(fdt);
 
-	if ((headsize + tailsize) > fdt_totalsize(fdt))
+	if (!can_assume(VALID_DTB) &&
+	    headsize + tailsize > fdt_totalsize(fdt))
 		return -FDT_ERR_INTERNAL;
 
 	if ((headsize + tailsize) > bufsize)