Commit 821f7440 authored by Peter Griffin's avatar Peter Griffin Committed by Linus Torvalds
Browse files

scripts/gdb: add lx-fdtdump command 

lx-fdtdump dumps the flattened device tree passed to the kernel from the
bootloader to the filename specified as the command argument.  If no
argument is provided it defaults to fdtdump.dtb.  This then allows
further post processing on the machine running GDB.  The fdt header is
also also printed in the GDB console.  For example:

  (gdb) lx-fdtdump
  fdt_magic:         0xD00DFEED
  fdt_totalsize:     0xC108
  off_dt_struct:     0x38
  off_dt_strings:    0x3804
  off_mem_rsvmap:    0x28
  version:           17
  last_comp_version: 16
  Dumped fdt to fdtdump.dtb

  >fdtdump fdtdump.dtb | less

This command is useful as the bootloader can often re-write parts of the
device tree, and this can sometimes cause the kernel to not boot.

Link: http://lkml.kernel.org/r/1481280065-5336-2-git-send-email-kbingham@kernel.org


Signed-off-by: default avatarPeter Griffin <peter.griffin@linaro.org>
Signed-off-by: default avatarKieran Bingham <kbingham@kernel.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 59224ac1

scripts/gdb/linux/constants.py.in

+7 −0
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 


#include <linux/fs.h>

#include <linux/mount.h>

#include <linux/of_fdt.h>



/* We need to stringify expanded macros so that they can be parsed */
@@ -50,3 +51,9 @@ LX_VALUE(MNT_NOEXEC) 
LX_VALUE(MNT_NOATIME)

LX_VALUE(MNT_NODIRATIME)

LX_VALUE(MNT_RELATIME)



/* linux/of_fdt.h> */

LX_VALUE(OF_DT_HEADER)



/* Kernel Configs */

LX_CONFIG(CONFIG_OF)

scripts/gdb/linux/proc.py

+73 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ from linux import constants 
from linux import utils

from linux import tasks

from linux import lists

from struct import *





class LxCmdLine(gdb.Command):
@@ -195,3 +196,75 @@ values of that process namespace""" 
                        info_opts(MNT_INFO, m_flags)))



LxMounts()





class LxFdtDump(gdb.Command):

    """Output Flattened Device Tree header and dump FDT blob to the filename

       specified as the command argument. Equivalent to

       'cat /proc/fdt > fdtdump.dtb' on a running target"""



    def __init__(self):

        super(LxFdtDump, self).__init__("lx-fdtdump", gdb.COMMAND_DATA,

                                        gdb.COMPLETE_FILENAME)



    def fdthdr_to_cpu(self, fdt_header):



        fdt_header_be = ">IIIIIII"

        fdt_header_le = "<IIIIIII"



        if utils.get_target_endianness() == 1:

            output_fmt = fdt_header_le

        else:

            output_fmt = fdt_header_be



        return unpack(output_fmt, pack(fdt_header_be,

                                       fdt_header['magic'],

                                       fdt_header['totalsize'],

                                       fdt_header['off_dt_struct'],

                                       fdt_header['off_dt_strings'],

                                       fdt_header['off_mem_rsvmap'],

                                       fdt_header['version'],

                                       fdt_header['last_comp_version']))



    def invoke(self, arg, from_tty):



        if not constants.LX_CONFIG_OF:

            raise gdb.GdbError("Kernel not compiled with CONFIG_OF\n")



        if len(arg) == 0:

            filename = "fdtdump.dtb"

        else:

            filename = arg



        py_fdt_header_ptr = gdb.parse_and_eval(

            "(const struct fdt_header *) initial_boot_params")

        py_fdt_header = py_fdt_header_ptr.dereference()



        fdt_header = self.fdthdr_to_cpu(py_fdt_header)



        if fdt_header[0] != constants.LX_OF_DT_HEADER:

            raise gdb.GdbError("No flattened device tree magic found\n")



        gdb.write("fdt_magic:         0x{:02X}\n".format(fdt_header[0]))

        gdb.write("fdt_totalsize:     0x{:02X}\n".format(fdt_header[1]))

        gdb.write("off_dt_struct:     0x{:02X}\n".format(fdt_header[2]))

        gdb.write("off_dt_strings:    0x{:02X}\n".format(fdt_header[3]))

        gdb.write("off_mem_rsvmap:    0x{:02X}\n".format(fdt_header[4]))

        gdb.write("version:           {}\n".format(fdt_header[5]))

        gdb.write("last_comp_version: {}\n".format(fdt_header[6]))



        inf = gdb.inferiors()[0]

        fdt_buf = utils.read_memoryview(inf, py_fdt_header_ptr,

                                        fdt_header[1]).tobytes()



        try:

            f = open(filename, 'wb')

        except:

            raise gdb.GdbError("Could not open file to dump fdt")



        f.write(fdt_buf)

        f.close()



        gdb.write("Dumped fdt blob to " + filename + "\n")



LxFdtDump()

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