Problem Description:
I have face an error on RHEL6.2 Kernel, where our Kernel module was dumping core. The stack was:
=============================================================
Call Trace:
<NMI> [<ffffffff814ed254>] ? panic+0x78/0x143
[<ffffffff810d90ed>] ? watchdog_overflow_callback+0xcd/0xd0
[<ffffffff8110a9fd>] ? __perf_event_overflow+0x9d/0x230
[<ffffffff8110afb4>] ? perf_event_overflow+0x14/0x20
[<ffffffff8101ced9>] ? p4_pmu_handle_irq+0x209/0x2e0
[<ffffffff814f2e76>] ? kprobe_exceptions_notify+0x16/0x430
[<ffffffff814f1959>] ? perf_event_nmi_handler+0x39/0xb0
[<ffffffff814f34a5>] ? notifier_call_chain+0x55/0x80
[<ffffffff814f350a>] ? atomic_notifier_call_chain+0x1a/0x20
[<ffffffff81096cde>] ? notify_die+0x2e/0x30
[<ffffffff814f1123>] ? do_nmi+0x173/0x2b0
[<ffffffff814f0a30>] ? nmi+0x20/0x30
[<ffffffff814f029e>] ? _spin_lock+0x1e/0x30
<<EOE>> [<ffffffff81042a0c>] ? vmalloc_sync_all+0x10c/0x180
[<ffffffff81097226>] ? register_die_notifier+0x16/0x30
[<ffffffff81029881>] ? nmi_shootdown_cpus+0x51/0xc0
[<ffffffff810333a1>] ? native_machine_crash_shutdown+0x51/0x200
[<ffffffff8106a36f>] ? release_console_sem+0x1cf/0x220
[<ffffffff810b8cab>] ? append_elf_note+0x8b/0xb0
[<ffffffff8102970f>] ? machine_crash_shutdown+0xf/0x20
[<ffffffff810b90c6>] ? crash_kexec+0x66/0x110
[<ffffffff810121b8>] ? apply_alternatives+0x328/0x3b0
[<ffffffff814f1410>] ? oops_end+0xc0/0x100
[<ffffffff8100f2bb>] ? die+0x5b/0x90
[<ffffffff814f0d04>] ? do_trap+0xc4/0x160
[<ffffffff8100ce75>] ? do_invalid_op+0x95/0xb0
[<ffffffff810121b8>] ? apply_alternatives+0x328/0x3b0
[<ffffffff8126c0b0>] ? idr_get_empty_slot+0x110/0x2c0
[<ffffffff81133229>] ? zone_statistics+0x99/0xc0
[<ffffffff8100bf1b>] ? invalid_op+0x1b/0x20
[<ffffffff810121b8>] ? apply_alternatives+0x328/0x3b0
[<ffffffff81096a5f>] ? up+0x2f/0x50
[<ffffffff8106a36f>] ? release_console_sem+0x1cf/0x220
[<ffffffff810aca32>] ? each_symbol+0xa2/0x1f0
[<ffffffff8106a931>] ? vprintk+0x1d1/0x4f0
[<ffffffff814ed360>] ? printk+0x41/0x49
[<ffffffff810339ac>] ? module_finalize+0x10c/0x1b0
[<ffffffff810af1a2>] ? load_module+0x17c2/0x1ca0
[<ffffffff810ac0e0>] ? setup_modinfo_srcversion+0x0/0x30
[<ffffffff810af6fb>] ? sys_init_module+0x7b/0x250
[<ffffffff8100b132>] ? system_call_fastpath+0x16/0x1b
===========================================================
Scenarios:
- You have your custom Build environment where you don't use Make environment for building your Kernel Module.
- You are using "arch" and "include" Kernel Header. We use modpost, in case of weak module support.
- You wanted to compile it "not in Weak Module Support". Therefore, you use only Kernel Headers.
====================================================
Root cause:
You compiled your Kernel Module with the set of Header you got from Kernel Source. It will miss the ELF segment (.rheldata), which is processed by modpost.
====================================================
Solution:
Use modpost with your Kernel Headers to compile your Kernel Module.
objdump Output:
XYZ-fs.ko misses the .rheldata segment.
-bash-4.1$ objdump -h /lib/modules/2.6.32-220.4.1.el6.620g0000.x86_64/extra/XYZfs/XYZfs.ko
/lib/modules/2.6.32-220.4.1.el6.620g0000.x86_64/extra/XYZfs/XYZfs.ko: file format elf64-x86-64
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 00351e10 0000000000000000 0000000000000000 00000040 2**4
CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
1 .altinstr_replacement 0000112e 0000000000000000 0000000000000000 005f3ba8 2**0
CONTENTS, ALLOC, LOAD, READONLY, CODE
2 .fixup 00000060 0000000000000000 0000000000000000 005f4cd6 2**0
CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
3 .init.text 000001b8 0000000000000000 0000000000000000 005f4df8 2**0
CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
4 .exit.text 0000009b 0000000000000000 0000000000000000 005f5358 2**0
CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
5 .rodata 00035ca0 0000000000000000 0000000000000000 005f5580 2**5
CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
6 .rodata.str1.8 000605ba 0000000000000000 0000000000000000 006b2b20 2**3
CONTENTS, ALLOC, LOAD, READONLY, DATA
7 .rodata.str1.1 000111d9 0000000000000000 0000000000000000 007130da 2**0
CONTENTS, ALLOC, LOAD, READONLY, DATA
8 .altinstructions 000044b4 0000000000000000 0000000000000000 007242b8 2**3
CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
9 .smp_locks 00000110 0000000000000000 0000000000000000 007310e0 2**3
CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
10 __bug_table 00000018 0000000000000000 0000000000000000 00731520 2**0
CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
11 __ex_table 00000080 0000000000000000 0000000000000000 00731598 2**3
CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
12 .modinfo 000001d1 0000000000000000 0000000000000000 007317a0 2**5
CONTENTS, ALLOC, LOAD, READONLY, DATA
13 __param 00000050 0000000000000000 0000000000000000 00731978 2**3
CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
14 .data 00010420 0000000000000000 0000000000000000 00731aa0 2**5
CONTENTS, ALLOC, LOAD, RELOC, DATA
15 .discard 000002dd 0000000000000000 0000000000000000 0074aef0 2**0
CONTENTS, ALLOC, LOAD, DATA
16 .gnu.linkonce.this_module 00000230 0000000000000000 0000000000000000 0074b1e0 2**5
CONTENTS, ALLOC, LOAD, RELOC, DATA, LINK_ONCE_DISCARD
17 .bss 000bc648 0000000000000000 0000000000000000 0074b440 2**5
ALLOC
18 .comment 00003392 0000000000000000 0000000000000000 0074b440 2**0
CONTENTS, READONLY
19 .gnu_debuglink 00000014 0000000000000000 0000000000000000 007f3580 2**2
CONTENTS, READONLY
Hello-Worl Kernel Module have a proof of presence of .rheldata Segment.
-bash-4.1$ grep -i .rheldata hello-1.objdump XYZfs.objdump
hello-1.objdump:Disassembly of section .rheldata:
hello-1.objdump:0000000000000000 <_rheldata>:
-bash-4.1$
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