lx-fdtdump dumps the flatenned device tree passed to the kernel
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:
(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@xxxxxxxxxx>
---
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"
+
+ 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")
+
+LxFdtDump()
--
1.9.1
--
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