From 28fd7590aad2ab4c0aae6b6674b15f103c492d64 Mon Sep 17 00:00:00 2001 From: Simon Glass Date: Mon, 2 Mar 2020 12:02:53 -0700 Subject: [PATCH] libfdt: Improve comments in some of the assumptions Add a little more detail in a few of these comments. Signed-off-by: Simon Glass Suggested-by: David Gibson Message-Id: <20200302190255.51426-2-sjg@chromium.org> Signed-off-by: David Gibson --- libfdt/libfdt_internal.h | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/libfdt/libfdt_internal.h b/libfdt/libfdt_internal.h index 3201678..7999f6a 100644 --- a/libfdt/libfdt_internal.h +++ b/libfdt/libfdt_internal.h @@ -91,7 +91,9 @@ enum { * * With this assumption enabled, normal device trees produced by libfdt * and the compiler should be handled safely. Malicious device trees and - * complete garbage may cause libfdt to behave badly or crash. + * complete garbage may cause libfdt to behave badly or crash. Truncated + * device trees (e.g. those only partially loaded) can also cause + * problems. * * Note: Only checks that relate exclusively to the device tree itself * (not the parameters passed to libfdt) are disabled by this @@ -130,8 +132,15 @@ enum { ASSUME_NO_ROLLBACK = 1 << 3, /* - * This assumes that the device tree components appear in the correct - * order. As such it disables a check in fdt_open_into() and removes the + * This assumes that the device tree components appear in a 'convenient' + * order, i.e. the memory reservation block first, then the structure + * block and finally the string block. + * + * This order is not specified by the device-tree specification, + * but is expected by libfdt. The device-tree compiler always created + * device trees with this order. + * + * This assumption disables a check in fdt_open_into() and removes the * ability to fix the problem there. This is safe if you know that the * device tree is correctly ordered. See fdt_blocks_misordered_(). */