On Thu, Feb 20, 2020 at 02:45:49PM -0700, Simon Glass wrote: > > Since v1.4.6 libfdt has gained a number of checks for incorrect > device-tree input and incorrect parameters. These are valuable and should > be enabled by default. Some are basic sanity checks and some are designed > to avoid security risks with carefully crafted device-tree input. > > However the checks have added to code size to such an extent that many > U-Boot boards can no-longer build/boot in SPL. This has prevented recent > versions of libfdt from being used by U-Boot. > > U-Boot SPL generally reads a device tree which has been set up by the > build system and is known to be correct (e.g. it may be cryptographically > signed by the build system). Therefore sanity checks in SPL should never > fail, and just contribute to longer run-time and larger code size. > > During review of those patches[1] the code-size impact was discussed and > a possible solution was suggested. > > This series adds a new ASSUME_MASK option, which allows for some control > over the checks used in libfdt. With all assumptions enabled, libfdt > assumes that the input data and parameters are all correct and that > internal errors cannot happen. This allows U-Boot SPL to continue to use > later versions of libfdt. > > Within the code, preprocessor macros and an inline function are used which > resolve to true or false to control the use of checks in the code. This > seems better than using '#ifdefs' throughout the code. It also ensures > that all code is compiled regardless of which checks are enabled (useful > for build coverage). > > This series reduces the size of libfdt by about 3KB on 64-bit x86 > (about 6%) when all assumptions are enabled. Future work is planned to > reduce this further, but this is a good start. It enables U-Boot to move > to the latest libfdt. > > Note: libfdt includes a number of assignments in conditional statements. > I have only changed these where necessary. It might be desirable to remove > them all, to reduce the output from checkpatch.pl. > > Series available at https://github.com/sglass68/dtc/tree/small6 I've applied this series to my tree. There are some things I'd still like polished - comments on the individual patches - but those can be done as followups, they're not fundamental enough for me to request another spin. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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