Linux 2.6.33 64bit xen domU and CONFIG_DEBUG_RODATA

By cormander

So I setup new jobs in my Hudson server to track the “latest” kernel. It pulls in the latest changes, builds the kernel image, and with the -xenU ones, does a test boot. The current latest as of today is linux version 2.6.33.

It works on 32bit:

http://build.cormander.com/job/linux-2.6.latest-i686-vanilla-xenU/2/console

It does not work on 64bit:

http://build.cormander.com/job/linux-2.6.latest-x86_64-vanilla-xenU/2/console

But works on 64bit with grsecurity:

http://build.cormander.com/job/linux-2.6.latest-x86_64-grsec-xenU/1/console

Here is the output of the fail:

[    0.370394] EXT3-fs (xvda2): warning: maximal mount count reached, running e2fsck is recommended
[    0.372607] EXT3-fs (xvda2): using internal journal
[    0.372632] EXT3-fs (xvda2): mounted filesystem with writeback data mode
[    0.372670] VFS: Mounted root (ext3 filesystem) on device 202:2.
[    0.372771] Freeing unused kernel memory: 668k freed
[    0.373202] Write protecting the kernel read-only data: 10240k
[    0.379890] Freeing unused kernel memory: 648k freed
[    0.379910] BUG: unable to handle kernel paging request at ffff88000155e000
[    0.379922] IP: [] free_init_pages+0xb1/0xda
[    0.379939] PGD 1a2a067 PUD 1a2e067 PMD 1d38067 PTE 1000000155e025
[    0.379955] Oops: 0003 [#1] SMP
[    0.379965] last sysfs file:
[    0.379973] CPU 0
[    0.379984] Pid: 1, comm: swapper Not tainted 2.6.33 #1 /
[    0.379992] RIP: e030:[]  [] free_init_pages+0xb1/0xda
[    0.380005] RSP: e02b:ffff880007c5fea0  EFLAGS: 00010286
[    0.380005] RAX: 00000000cccccccc RBX: ffff88000155e000 RCX: 0000000000000400
[    0.380005] RDX: ffffea000004ac91 RSI: 0000000000000000 RDI: ffff88000155e000
[    0.380005] RBP: ffff880007c5fed0 R08: 0000000000000000 R09: ffff880007c08000
[    0.380005] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000400
[    0.380005] R13: ffff880001600000 R14: ffffea0000000000 R15: 00000000cccccccc
[    0.380005] FS:  0000000000000000(0000) GS:ffff880001d45000(0000) knlGS:0000000000000000
[    0.380005] CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
[    0.380005] CR2: ffff88000155e000 CR3: 0000000001a29000 CR4: 0000000000000660
[    0.380005] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    0.380005] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000000
[    0.380005] Process swapper (pid: 1, threadinfo ffff880007c5e000, task ffff880007c60000)
[    0.380005] Stack:
[    0.380005]  0000000000000000 6db6db6db6db6db7 0000000000000400 ffff880000000000
[    0.380005] <0> ffffffff81600000 0000000000000000 ffff880007c5ff00 ffffffff8102c9c4
[    0.380005] <0> ffffffff81b9d960 0000000000000040 ffffffff81afbc60 ffffffff81afbc68
[    0.380005] Call Trace:
[    0.380005]  [] mark_rodata_ro+0xe0/0x146
[    0.380005]  [] init_post+0x2b/0x19d
[    0.380005]  [] kernel_init+0x19f/0x1aa
[    0.380005]  [] kernel_thread_helper+0x4/0x10
[    0.380005]  [] ? int_ret_from_sys_call+0x7/0x1b
[    0.380005]  [] ? retint_restore_args+0x5/0x6
[    0.380005]  [] ? kernel_thread_helper+0x0/0x10
[    0.380005] Code: 89 df e8 27 49 00 00 48 c1 e8 0c 48 89 df 4c 89 e1 48 6b c0 38 48 81 e7 00 f0 ff ff 31 f6 4c 01 f0 c7 40 08 01 00 00 00 44 89 f8  ab 48 89 df 48 81 c3 00 10 00 00 e8 93 a3 08 00 48 ff 05 33
[    0.380005] RIP  [] free_init_pages+0xb1/0xda
[    0.380005]  RSP
[    0.380005] CR2: ffff88000155e000
[    0.380005] ---[ end trace 39c6a8b0e7165bad ]---
[    0.394371] swapper used greatest stack depth: 5160 bytes left
[    0.394385] Kernel panic - not syncing: Attempted to kill init!
[    0.394395] Pid: 1, comm: swapper Tainted: G      D    2.6.33 #1
[    0.394403] Call Trace:
[    0.394413]  [] panic+0x75/0x137
[    0.394425]  [] ? exit_ptrace+0xb1/0x131
[    0.394436]  [] do_exit+0x77/0x777
[    0.394446]  [] ? xen_restore_fl_direct_end+0x0/0x1
[    0.394458]  [] ? kmsg_dump+0x126/0x140
[    0.394470]  [] ? __acpi_nmi_disable+0x14/0x1d
[    0.394480]  [] oops_end+0xb9/0xc1
[    0.394490]  [] no_context+0x1f3/0x202
[    0.394500]  [] ? __acpi_nmi_disable+0x14/0x1d
[    0.394511]  [] ? atomic_notifier_call_chain+0x13/0x15
[    0.394522]  [] __bad_area_nosemaphore+0x1c0/0x1e6
[    0.394533]  [] ? xen_force_evtchn_callback+0xd/0xf
[    0.394544]  [] ? check_events+0x12/0x20
[    0.394554]  [] ? xen_force_evtchn_callback+0xd/0xf
[    0.395349]  [] ? check_events+0x12/0x20
[    0.395349]  [] ? __raw_callee_save_xen_pmd_val+0x11/0x1e
[    0.395349]  [] bad_area_nosemaphore+0xe/0x10
[    0.395349]  [] do_page_fault+0x1a0/0x2dd
[    0.395349]  [] page_fault+0x25/0x30
[    0.395349]  [] ? free_init_pages+0xb1/0xda
[    0.395349]  [] mark_rodata_ro+0xe0/0x146
[    0.395349]  [] init_post+0x2b/0x19d
[    0.395349]  [] kernel_init+0x19f/0x1aa
[    0.395349]  [] kernel_thread_helper+0x4/0x10
[    0.395349]  [] ? int_ret_from_sys_call+0x7/0x1b
[    0.395349]  [] ? retint_restore_args+0x5/0x6
[    0.395349]  [] ? kernel_thread_helper+0x0/0x10

A little digging and I unset CONFIG_DEBUG_RODATA in the vanilla configuration (it gets unset by the grsecurity patch) and rebuilt it. It works! Okay, so we have a regression in xen pv_ops when RODATA is enabled, because linux-2.6.32.9 (and other 2.6.32 kernels before it) boot just fine with DEBUG_RODATA enabled.

I don’t even know who to report this to. Then again, I don’t use vanilla xen domU kernels.. I just use them as a reference point when testing vanilla vs. grsecurity. I only actually use the grsecurity xen domU kernels, and those work. So I guess I’ll just sit back and wait for someone else to notice, and fix it.

A break from school has come to an end

By cormander

So today I have to start class again in order to retain student status; you can only take so long of a break. I’d rather start after my wife has the baby, which should be any day now, but alas I don’t get that choice.

So I login this afternoon to check how this next course is going to look; MATH/212 – Finite Mathematics. Read the syllabus, posted by bio… then thought:

“Hey wait a minute, I need a book for this class?”

This is my 10th class at University of Phoenix Online, and have so far never even had mention of having to have a book. It’s all been online. Turns out, without the book, I can’t do any of the assignments!

“Maybe I can rush delivery one, then”, or so I thought. I call and get transferred over to the book store, and guess what is out of stock? The book for that class. I get the ISBN number and google it; no results. I go to amazon and search it there; no results. I search the book title; no results. So I call my academic adviser and it lands in her voicemail; on vacation.

So at this point I’m starting to freak out a little. I manage to get ahold of another academic adviser and explain the situation. After 20 minutes and a little luck, I get put in a different class. Whew!

So I check in this evening and can see the new course on my dashboard; NTC/360 – Network and Telecommunications Concepts. <sarcasm>Boy, I sure am going to learn a lot in this class.</sarcasm> (not that I would have learned anything in a Math course either).

Oh, and to top it all off; the teacher for this course hasn’t posted a syllabus yet.

*facepalm*

Iditos text while they drive

By cormander

Well, it doesn’t take a rocket scientist to tell you that texting while driving increases your risk of an automobile accident. But in this case, I will refuse to call it an automobile accident, and instead, only refer to it as an automobile crash. In my opinion, a crash caused by stupidity isn’t an accident.

I read this article: Texting Raises Crash Risk 23 Times, Study Finds. Well, 23 times more likely, wow. I don’t know what else to say other than, don’t text while you drive, period.

An interview quote from the above article: “I’m pretty sure that someday it’s going to come back to bite me”

No, it won’t come back to bite you. It’s going to come back and KILL you, and probably someone else as well.

A linux release fail (2.6.27)

By cormander

2.6.27.1 came out today, with only one patch:

http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.27.y.git;a=commitdiff;h=d23d43386311fde5f11e06c16d4185e94a8d6d06

It’s quite small, see below:

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 263e9e6..aa53fdd 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -103,7 +103,8 @@ config CONTEXT_SWITCH_TRACER
 	  all switching of tasks.

 config DYNAMIC_FTRACE
-	bool "enable/disable ftrace tracepoints dynamically"
+	bool "enable/disable ftrace tracepoints dynamically (BROKEN)"
+	depends on BROKEN
 	depends on FTRACE
 	depends on HAVE_DYNAMIC_FTRACE
 	default y

As I recall this was supposed to be fixed for 2.6.27. Now they’re just turning it off again?

Well, glad they did come out and turn it off. But still, this is a big fail!