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Message-ID: <a440581a-e28c-2f9f-8110-26203e0b3809@bingham.xyz>
Date: Tue, 18 Oct 2016 16:56:39 +0100
From: Kieran Bingham <kieran@...uared.org.uk>
To: Peter Griffin <peter.griffin@...aro.org>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
kernel@...inux.com, jan.kiszka@...mens.com
Cc: lee.jones@...aro.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 1/2] scripts/gdb: add lx-fdtdump command
Hi Pete,
Thanks for your patch.
On 18/10/16 16:07, Peter Griffin wrote:
> lx-fdtdump dumps the flatenned device tree passed to the kernel
s/flatenned/flattened/
> from the bootloader to a file called fdtdump.dtb to allow further
> post processing on the machine running GDB. The fdt header is also
> also printed in the GDB console. For example:
>
Excellent - I've been looking forward to this
General comment: It would be good to see the output filename
configurable as a parameter, defaulting to fdtdump.dtb if none provided.
Is this something you have time to add?
> (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.
>
> Signed-off-by: Peter Griffin <peter.griffin@...aro.org>
> ---
> scripts/gdb/linux/constants.py.in | 8 +++++
> scripts/gdb/linux/proc.py | 70 ++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 77 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/gdb/linux/constants.py.in b/scripts/gdb/linux/constants.py.in
> index 7986f4e..43c6241 100644
> --- a/scripts/gdb/linux/constants.py.in
> +++ b/scripts/gdb/linux/constants.py.in
> @@ -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 +51,10 @@ 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)
> +
> diff --git a/scripts/gdb/linux/proc.py b/scripts/gdb/linux/proc.py
> index 38b1f09..f20fcfa 100644
> --- a/scripts/gdb/linux/proc.py
> +++ b/scripts/gdb/linux/proc.py
> @@ -16,7 +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):
> """ Report the Linux Commandline used in the current kernel.
> @@ -195,3 +195,71 @@ 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 a file
> + Equivalent to 'cat /proc/fdt > fdtdump.dtb' on a running target"""
> +
> + def __init__(self):
> + super(LxFdtDump, self).__init__("lx-fdtdump", gdb.COMMAND_DATA)
> +
> + 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 constants.LX_CONFIG_OF:
> +
> + filename = "fdtdump.dtb"
> +
You could parse the arguments here to allow users to write to their own
file / path ... arg is just a string, so you can either parse it as such
or convert to argv with
argv = gdb.string_to_argv(arg)
Aha - I see Jan beat me to it :)
> + 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 to " + filename + "\n")
> +
> + else:
> + gdb.write("Kernel not compiled with CONFIG_OF\n")
Would it be cleaner to write
if not constants.LX_CONFIG_OF:
raise gdb.GdbError("Kernel not compiled with CONFIG_OF\n")
at the beginning, and reduce the indentation level required ?
> +
> +LxFdtDump()
>
--
Regards
Kieran Bingham
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