drgn -c doesn't work: not an ELF file

[osandov]

drgn -c doesn't work: not an ELF file

[osandov]

For kdump support, you'll need to install libkdumpfile and rebuild drgn. There's a link in the readme, but let me know if you need help.

[osandov]

Actually, come to think of it, that should've reported an error indicating that drgn wasn't built with kdump support. Could you please share the output of xxd vmcore | head?

[mishuang2017]

$ xxd vmcore | head
00000000: 4b44 554d 5020 2020 0600 0000 4c69 6e75 KDUMP ....Linu
00000010: 7800 0000 0000 0000 0000 0000 0000 0000 x...............
00000020: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000030: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000040: 0000 0000 0000 0000 0000 0000 0064 6576 .............dev
00000050: 2d72 3633 302d 3034 2e6d 7462 632e 6c61 -r630-04.mtbc.la
00000060: 6273 2e6d 6c6e 7800 0000 0000 0000 0000 bs.mlnx.........
00000070: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000080: 0000 0000 0000 0000 0000 0000 0000 342e ..............4.
00000090: 3139 2e33 362b 0000 0000 0000 0000 0000 19.36+..........

[osandov]

That's really strange, it has the kdump signature. I don't see any obvious bugs in the code. I'll try to reproduce this tomorrow, thanks for the report.

[mishuang2017]

Thanks for quick reply.

[mishuang2017]

My drgn source code is a little old. After pulling the latest code and installing libkdumpfile, now it works.

$ drgn -c ./vmcore
drgn 0.0.1 (using Python 3.6.6)
For help, type help(drgn).

import drgn
from drgn import cast, container_of, execscript, NULL, Object, reinterpret
from drgn.helpers.linux import *
dev_base_head = prog['init_net'].dev_base_head.address_of_()
print(dev_base_head)
*(struct list_head *)0xffffffff933e6890 = {
.next = (struct list_head *)0xffff929c19f10050,
.prev = (struct list_head *)0xffff929b87fca050,
}