Hi, On 30 October 2013 14:15, Simon Glass <sjg@xxxxxxxxxxxx> wrote: > This series adds two new functions, fdt_first_region() and > fdt_next_regions() which map FDT parts such as nodes and properties to > their regions in the FDT binary. The function is then used to implement > a grep utility for FDTs. > > The core core is quite simple and small, but it grew a little due > to the need to make it iterative (first/next/next). Also this series adds > tests and a grep utility, so quite a bit of code is built on it. > > The use for this feature is twofold. Firstly it provides a convenient > way of performing a structure-aware grep of the tree. For example it is > possible to grep for a node and get all the properties associated with > that node. Trees can be subsetted easily, by specifying the nodes that > are required, and then writing out the regions returned by this function. > This is useful for small resource-constrained systems, such as boot > loaders, which want to use an FDT but do not need to know about all of > it. The full FDT can be grepped to pull out the few things that are > needed - this can be automatic and does not require the FDT source code. > > This first use makes it easy to implement an FDT grep. Options are > provided to search for matching nodes (by name or compatible string), > properties and also for any of the above. It is possible to search for > non-matches also (useful for excluding a particular property from the > FDT, for example). The output is like fdtdump, but only with the regions > selected by the grep. Options are also provided to print the string table, > memory reservation table, etc. The fdtgrep utility can output valid > source, which can be used by dtc, but it can also directly output a new > .dtb binary. > > Secondly it makes it easy to hash parts of the tree and detect changes. > The intent is to get a list of regions which will be invariant provided > those parts are invariant. For example, if you request a list of regions > for all nodes but exclude the property "data", then you will get the > same region contents regardless of any change to "data" properties. > An assumption is made here that the tree ordering remains the same. > > This second use is the subject of a recent series sent to the U-Boot > mailing list, to enhance FIT images to support verified boot. Briefly, > this works by signing configurations (consisting of particular kernel > and FDT combinations) so that the boot loader can verify that these > combinations are valid and permitted. Since a FIT image is in fact an > FDT, we need to be able to hash particular regions of the FDT for the > signing and verification process. This is done by using the region functions > to select the data that needs to be hashed for a particular configuration. > > The fdtgrep utility could be used to replace all of the functions of > fdtdump. However fdtdump is intended as a separate, simple way of > dumping the tree (for verifying against dtc output for example). So > fdtdump remains a separate program and this series leaves it alone. > > Note: a somewhat unfortunately feature of this implementation is that > a state structure needs to be kept around between calls of > fdt_next_region(). This is declared in libfdt.h but really should be > opaque. Any comments on this please, or should I resend? Regards, Simon > > Changes in v3: > - Add a feature to include all subnodes > - Adjust help and command line processing to follow new approach > - Rename -V to -I to avoid using -V for a different purpose to other tools > - Rename -s to -e since it only 'enters' the node and does not include it all > - Add -s option to include all subnodes > - Add -f option to display offset; make -a display an absolute file address > - Add documentation on fdtgrep > > Changes in v2: > - Move region code to separate fdt_region.c file > - Fix info->count <= info->max_regions in fdt_add_region() merge case > - Add new FDT_ERR_TOODEEP error type and use it > - Change returned error from BADLAYOUT to BADSTRUCTURE > - Return FDT_ERR_BADLAYOUT error if strings block is before structure block > - Add note that changes in node/property order can cause false hash misses > - Add more comments about the -1 return value from h_include > - Drop FDT_IS_COMPAT and pass node offset to h_include function > - Drop stale comment about names / wildcards > - Move to a model with fdt_first_region()/fdt_next_region() > - Add long comment explaining theory of operation > - Add local fdt_find_regions() function since libfdt no longer has it > > Simon Glass (3): > libfdt: Add function to find regions in an FDT > Add documentation for fdtget/put > Add fdtgrep to grep and subset FDTs > > .gitignore | 1 + > Documentation/manual.txt | 125 +++++++ > Makefile | 4 + > Makefile.utils | 7 + > fdtgrep.c | 873 +++++++++++++++++++++++++++++++++++++++++++++++ > libfdt/Makefile.libfdt | 3 +- > libfdt/fdt_region.c | 457 +++++++++++++++++++++++++ > libfdt/libfdt.h | 217 +++++++++++- > tests/.gitignore | 1 + > tests/Makefile.tests | 3 +- > tests/grep.dts | 23 ++ > tests/region_tree.c | 352 +++++++++++++++++++ > tests/run_tests.sh | 361 +++++++++++++++++++- > tests/tests.sh | 1 + > 14 files changed, 2424 insertions(+), 4 deletions(-) > create mode 100644 fdtgrep.c > create mode 100644 libfdt/fdt_region.c > create mode 100644 tests/grep.dts > create mode 100644 tests/region_tree.c > > -- > 1.8.4.1 > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
